AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SHREVEPORT LA 945 AM CST SAT FEB 12 2000 OVERCAST CONDITIONS COVER MY ENTIRE FOUR STATE REGION THIS MORNING WITH CURRENT FORECAST READING PARTLY CLOUDY FOR TODAY. LATEST RUC DATA SUGGESTS THAT STRATUS WILL BEGIN TO ERODE LATE MORNING/EARLY AFTERNOON FROM WEST TO EAST ALONG THE I-20 CORRIDOR. SO WILL WORD FCST AS BECOMING PARTLY CLOUDY. RUC POTENTIAL TEMPERATURE CROSS SECTIONS SUGGEST LOW CLOUDS MAY HAVE A MORE DIFFICULT TIME CLEARING OUT ACROSS MY SOUTHERN HALF OR CLOSER TO THE FRONT WHICH IS LOCATED SOUTH OF A KJAN...KPOE LINE. MAY WORD THESE SECTIONS AS DECREASING CLOUDINESS. TEMPS OF COURSE ALL DEPENDENT ON THE TIMING OF THE CLOUD COVER AND APPEAR O.K. AT THIS TIME. MAY HAVE TO UPDATE LATE MORNING/EARLY AFTERNOON TO ACCOUNT FOR TEMPS BUT AT THIS TIME WILL LEAVE TEMP FORECAST AS IS. 13 .SHV...NONE. la AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIDLAND TX 955 PM CST SAT FEB 12 2000 SFC OBS SHOW WINDS AT KGDP REFUSING TO QUIT...AND LATEST RUC/ETA ADVERTISING GRADIENTS TO FURTHER INCREASE THROUGH THE NIGHT. HAVE REISSUED NPW FOR KGDP AND TWEAKED WINDS IN OTHER ZONES. EVERYTHING ELSE LOOKS FINE. .MAF... TX...NONE. NM...NONE. 44 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN ANGELO TX 852 PM CST SAT FEB 12 2000 PACIFIC FRONT JUST EAST OF THE NM/TX BORDER IS MOVING RAPIDLY EASTWARD AT THIS TIME. SATELLITE IMAGERY REVEALS MOSTLY MID/UPPER LEVEL CLOUDINESS IN ASSOCIATION WITH THE FRONT AND THE UPPER LEVEL DISTURBANCE. LATEST RUC STILL SHOWS PVA OVER THE HEARTLAND AROUND 09Z. WITH DEWPOINTS IN THE 50S OVER THE SOUTHERN HALF OF THE CWA...WILL CONTINUE THE CHANCE OF A SHOWER OR THUNDERSTORM ACROSS FAR EASTERN AREAS. SYSTEM APPEARS TO BE MOVING RAPIDLY EASTWARD AS THE MODELS HAVE ADVERTISED. OTHERWISE...NO CHANGES NEEDED . 850 WINDS ARE STILL EXPECTED TO INCREASE AFTER MIDNIGHT SO WILL CONTINUE LAKE CAUTIONS ACROSS THE BIG COUNTRY. 21 tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE SAN ANGELO TX 955 AM CST SAT FEB 12 2000 DEPTH OF MOISTURE TRAPPED BENEATH INVERSION MORE PRONOUNCED THAT EARLIER THOUGHT. SO NEED TO BEEF UP CLOUD WORDING ACROSS THE SOUTH HALF TODAY. MOISTURE DEPICTION ON THE 12Z DRT RAOB AND 14Z RUC SUPPORT ABOVE THINKING. WE/LL ALSO LOWER TEMPERATURES ACCORDINGLY. HIGH CLOUDS OVER WESTERN NEW MEXICO WILL REACH THE BIG COUNTRY BY 2 PM. .SJT...NONE. 17 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PADUCAH KY 220 AM CST SUN FEB 13 2000 06Z SURFACE MAP INDICATED LOW PRESSURE CENTER VICINITY OF WRN OKLAHOMA/KANSAS BORDER...ABOUT 50 MILES NORTH OF ETA/AVN 6-HOUR PROG. FOR THIS ZONE PACKAGE...WILL USE A SURFACE LOW TRACK SLIGHTLY FASTER AND FURTHER NORTH THAN 00Z ETA...IN AGREEMENT WITH LATEST RUC AND NGM MODELS. THIS WOULD TAKE LOW CENTER TO NEAR MDH BY 00Z THIS EVENING. THIS PLACES MOST OF THE FA IN THE WARM SECTOR BY LATE AFTERNOON. SPC MODERATE RISK AREA CORRESPONDS ALMOST EXACTLY WITH THE EXPECTED WARM SECTOR AREA...WHERE THREAT OF SURFACE BASED SEVERE STORMS WILL BE GREATEST. ALTHOUGH SURFACE DEW POINTS WERE ONLY IN THE 30S OVER THE FA AT 06Z...STRONG SOUTHERLY LOW LEVEL JET WILL RAPIDLY TRANSPORT MID 50S DEW POINTS NORTHWARD INTO WRN KENTUCKY BY MID AFTERNOON. ETA/RUC HAVE A GOOD HANDLE ON SFC DEW POINTS AT 06Z...AND BOTH SUPPORT 55 DEGREE DEW POINTS INTO SW KENTUCKY THIS AFTN. THESE VALUES ARE MARGINAL FOR ORGANIZED SEVERE STORMS...BUT IN LIGHT OF THE STRENGTH OF ALL THE OTHER PARAMETERS...WILL MENTION SVR THREAT IN ZONES AND ISSUE MORNING SPS. WIDESPREAD ELEVATED CONVECTION SHOULD BLOSSOM OVER THE FA THIS MORNING UNDER THE INFLUENCE OF LOW LEVEL JET AND STRONG 850 THETA-E ADVECTION. LIT RADAR AND LIGHTNING NETWORK AT 08Z SHOWED DEVELOPMENT OF CONVECTION FROM SW ARKANSAS INTO S CENTRAL MISSOURI...MOVING RAPIDLY NE. WITH LOW WET BULB ZERO HEIGHTS...COULD NOT RULE OUT SOME LARGE HAIL IN ELEVATED STORMS OVER THE FA LATER THIS MORNING. MAIN THREAT FOR WIND DAMAGE AND SUPERCELLS APPEARS TO BE IN ASSOCIATION WITH THE SURFACE LOW AND COLD FRONT LATE TODAY AND EARLY THIS EVENING. THIS IS WHEN BEST SURFACE BASED INSTABILITY AND LOW LEVEL CONVERGENCE WILL BE IN PLACE. 700 MB DRY AIR MAY ENHANCE DOWNDRAFT POTENTIAL. FLASH FLOOD THREAT APPEARS RELATIVELY LOW GIVEN HIGH FF GUIDANCE VALUES AND RELATIVELY DRY AIR AT 700 MB. AFTER PASSAGE OF THE COLD FRONT THIS EVENING...IT APPEARS A RETURN TO DRY WEATHER AND MORE SEASONABLE TEMPERATURES IS IN STORE. NGM MOS TEMPS APPEAR REASONABLE. .PAH...NONE. MY ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 940 PM EST SAT FEB 12 2000 01Z SFC ANALYSIS SHOWS THE DEVELOPING LOW PRESSURE SYSTEM IN THE OK PANHANDLE...ROUGHLY 4-6 HRS AHEAD OF THE ETA POSITION. DESPITE BEING A BIT SLOW, THE ETA SEEMS TO BE DOING THE BEST JOB WITH THE LOW COMPARED WITH THE NGM AND AVN. IR/WV LOOP SHOW CLOUDY SKIES OVER THE CWA ATTM WITH MORE MOISTURE OVER THE MO VALLEY HEADING EAST. KGRR-88D HAS BEEN SHOWING ANEMIC RETURNS SO FAR THIS EVENING AND PCPN STILL APPEARS CONFINED TO AREAS NORTH OF THE CWA. THE MAIN PROBLEM TONIGHT IS TO DECIDE WHETHER IT WILL SNOW...AND IF SO, HOW MUCH. I/M NOT VERY IMPRESSED SO FAR WITH THIS SYSTEM. LATEST RUC HAS A PRETTY GOOD HANDLE ON THE SNOW WITH MOST OF THE SNOW FALLING W/I THE 10MB CPD. THIS AREA DOESN'T SINK SOUTH UNTIL SUNDAY, BUT THE AREA OF 10 MB CPD EXPANDS EWD OVERNIGHT. MIXING RATIOS INCREASE LATE TONIGHT THROUGH SUNDAY MORNING OVER THE MS VALLEY AND SPREAD NWD AS THE LOW IN THE OK PANHANDLE MOVES NE. UPR DIVERGENCE DOES INCREASE OVERNIGHT WHICH WILL HELP SNOWFALL CHANCES SO WILL KEEP AT LEAST LIKELY POPS BUT NOT GO FOR VERY MUCH IN THE WAY OF ACCUMS. AS FOR TEMPS WILL GO NEARLY STEADY TEMPS IN THE MID 20S. CAN/T SEE TEMPS FALLING MUCH WITH WAA UNDERWAY AND OVERCAST CLOUD COVER. .GRR...NONE. mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1240 PM EST SAT FEB 12 2000 STRATO-CU DECK HAS DEVELOPED AROUND METRO DETROIT. RUC PROGS 925 MB RH FIELD TO DIMINISH THROUGH THE AFTERNOON. HOWEVER...WITH DECK IN PLACE...NOT SURE IT WILL DISSIPATE THAT QUICKLY. DECK ADVECTING NORTH IN LIGHT SOUTH/SOUTHEAST FLOW. WILL UPDATE ALL ZONES FROM PTK...OZW...MTC SOUTH.../EX LENAWEE/ TO VARIABLE CLOUDINESS...AND FNT PHN TO PARTLY SUNNY. .DTX...NONE. OKEEFE mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON MS 320 AM CST SUN FEB 13 2000 ...QUICK HITTING SEVERE WEATHER SYSTEM NEXT 12-18 HOURS... A STRONG SHORTWAVE IN SOUTHERN BRANCH OF THE WESTERLYS HEADING OUT OF ROCKIES INTO THE CENTRAL AND SOUTHERN PLAINS. A DEVELOPING SURFACE LOW CENTER NEAR KICT SHOULD MOVE THROUGH THE OZARKS DURING MIDDAY AS WARM FRONT ALONG A KTYR-KESF-KMOB LINE LIFTS QUICKLY NWD. ONCE AGAIN THOSE CRITICAL SURFACE DEWPOINTS OF 62-66 ARE EDGING NWD FROM AN I-10 AXIS AND UNLESS THEY PUSH UP TO ABOUT KGLH-KCBM AXIS BY EARLY AFTERNOON...CAPES WILL BE A LITTLE ON THE LOW SIDE FOR A MAJOR SEVERE WEATHER EVENT. IF THESE VALUES ARE REALIZED...THEN WE'LL REALLY BE UNDER THE GUN FROM ABOUT 20Z-04Z WITH CAPES 1200-1800J/KG COMBINING WITH 0-3KM STORM RELATIVE HELICITIES 350-500 RANGE. SEVERAL OTHER PARAMETERS ARE PROGGED TO BE IN THE CLASSIC RANGE FOR MS SEVERE WEATHER WITH SWEAT INDEXES 380-450...LIFTED INDEXES -5 TO -7...WET BULB ZEROES 9500-10000FT...AND BULK RICHARDSONS 15-25. LACK OF HEATING IN THE WARM SECTOR COULD BE A SPOILER AND VIRTUALLY NO CAPPING INVERSIONS ARE LIMITING FACTORS WHICH COULD KEEP THE STRONGEST STORMS CONFINED TO A NARROW SQUALL LINE. HOWEVER... MODEL 850MB JET MAX OF 45-60KTS AND VEERED(BY 60DEGREES) 500MB FLOW 70-80KT TOPPED BY LEFT EXIT REGION OF 250MB 105KT CORE PUNCHING EWD THROUGH CENTRAL MS SHOULD BE ENOUGH FOR SOME SUPERCELL SPIN UPS. ALSO COUPLED UPPER JET STRUCTURE NOT AS IMPRESSIVE AS PREVIOUS FORECASTS. THESE FACTORS ALONG WITH FAST FORWARD MOTION OF THE SYSTEM SHOULD MAKE WIND DAMAGE THE GREATEST CONCERN. CURRENTLY...SPOTTY SHOWERS BREAKING OUT ALONG AND W OF MS RIVER WITH AN AXIS OF ELEVATED TSTMS FROM AROUND KLIT-KGGG. NGM HANDLING THE MOISTURE CONVERGENCE/HUMIDITY FIELDS WITH THIS FIRST BATCH OF PRECIPITATION AND LOOKS TO BE BEST 00Z MODEL OVERALL. 06Z RUC ALSO SUPPORTS IT'S SCENARIO. STRONG WARM ADVECTION TODAY PUSHES WARM FRONT N OF LOCAL FA WITH COLD FRONT SWEEPING THROUGH BY 06-09Z TONIGHT. UNFORTUNATELY...RAINFALL WILL BE QUITE LIMITED: 24HR QPF DISCUSSION: FROM 12 TO 18Z...A FEW SHOWERS MAY OCCUR...BUT DO NOT EXPECT SIGNIFICANT AMOUNTS. FOR SECOND AND THIRD SIX HOUR PERIODS...STRONG COLD FRONT WILL BE MOVING RAPIDLY ACROSS THE FORECAST AREA THIS EVENING. AHEAD OF THE FRONT...WIDESPREAD THUNDERSTORM ACTIVITY IS LIKELY WITH HEAVIEST AMOUNTS IN THE NORTHERN SECTIONS. WESTERN AREAS OF THE FA WILL HAVE MOST OF THEIR QPF BY 00Z. THE REST OF THE FA WILL HAVE MOST QPF BETWEEN 00 AND 06Z. OF COURSE...TIMING OF FRONT WILL HAVE BIG IMPACT ON WHEN THE HEAVIEST RAINFALL WILL OCCUR IN VARIOUS LOCATIONS. AM GENERALLY GOING ALONG WITH NCEP'S 24 HOUR AMOUNTS FOR PERIOD ENDING AT 12Z ON MONDAY. THIS FORECAST IS MOST IN LINE WITH AVN QPF AMOUNTS. THE NGM AND ETA SEEM TO BE TOO LIGHT ON QPF AMOUNTS FOR THIS EVENT. BY LAST SIX HOURS (06-12Z) EXPECT ONLY LIGHT AMOUNTS LEFT IN EXTREME SOUTHEASTERN AREAS. IN THE EXTENDED: A DRY DAY TUESDAY EXPECTED WITH A WEAK RETURN OF LOW LEVEL MOISTURE TUESDAY NIGHT AND WEDNESDAY. SOME HOPE FOR SHOWERS WEDNESDAY NIGHT/THURSDAY BUT BUILDING UPPER RIDGE OVER THE GULF OF MEXICO MAY BE THE DEATH KNELL FOR PRECIPITATION IN THE DAY 5 TO DAY 7 TIME FRAME. SINCE A LONG TERM MODERATE DRY SPELL CONTINUES SINCE LAST FALL...WILL LEAVE OUT RAIN CHANCES FOR NOW. PRELIM NUMBERS: JAN 75/50/68/46 67-0 MEI 76/53/68/44 5710 .JAN... MS...NONE. AR...NONE. LA...NONE. ms AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO 200 AM CST SUN FEB 13 2000 OVERLAY OF MODEL VORT ON WATRE VAPOR LOOP SHOWS EACH MOEDL SIMILAR BUT ETA AND AVN SEEM TO HAVE BEST HANDLE. THE 06Z ANALYSIS ALSO SHOWED THAT THE ETA WAS PERFORMING THE BEST AT THAT TIME. WITH THIS IN MIND WILL LEAN TOWARDS THE ETA/AVN SOLUTION. MAIN CONCERNS TODAY ARE PRECIP CHANCES AND TYPE THEN TEMPERATURES. UA ANALYSIS INDICATED THAT LOW AND MID LEVEL DRY SLOT HAS...AS USUAL...DESENDED UPON THE EAX CWA. MODEL FORECASTS PICK UP ON THIS AND HAVE TROUBLE SPITTING OUT MUCH PRECIP TODAY. AT THIS TIME THE EAX 88D AND SURROUNDING SITES INDICATE VERY LITTLE IN THE WAY OF PRECIP. WILL DECIDE CLOSER TO ISSUANCE TIME BUT MAY NEED TO DROP TO JUST CHANCE CATEGORY FOR THE DAY...MAINLY BASED ON RADAR TRENDS AT 330 AM. TEMEPRATURES WILL ALSO BE SLOW TO RISE AS STRATUS NOT GOING ANYWHERE SOON. WILL PROBABLY SHOOT FOR TEMPERATURES ABOUT 3 T0 5 DEGREES ABOVE WHAT THEY ARE AT THIS TIME. MORE OF A NORTHERLY WIND ALREADY DEVELOPING OVER SOUTHEAST NEBRASKA AND SOUTHWEST IOWA SO THIS SHOULD KEEP NORTHWEST MISSOURI AND EXTREME NORTHEAST KANSAS FROM RISING MUCH. RUC INDICATES THAT A NORTH TO NORTHEAST WIND SHOULD TAKE OVER ALL OF CWA BY EARLY AFTERNOON AND DEF ZONE WILL MOVE ACROSS CWA...STRONGEST OVER IOWA. FOR TONIGHT...GUIDANCE HAS DROPPED TEMPS AND WOULD TEND TO AGREE...ESPECIALLY WITH POTENTIAL FOR LITTLE RISE THIS AFTERNOON. WILL LOWER TEMPS A CATEGORY ACROSS CWA. BOTH ETA AND AVN INDICATE A SECOND VORT MAX DEVELOPING LATE TODAY TO OUR WEST BEHIND MAIN VORT MAX. LOW LEVEL FORCING GONE AND 700 VVEL ABSENT BUT WILL CONTINUE CHANCE POPS FOR SNOW THROUGH MIDNIGHT WEST AND JUST TONIGHT EAST UNTIL UPPER LEVEL TROF AND STRONG DOWNWARD MOTION SETS IN. MONDAY...ATMOSPHERE TRIES TO WARM UP BEHIND THIS SYSTEM AND UPPER LEVEL HEIGHTS INCREASE THROUGH 48 HOURS. FAN NUMBERS LOOK A LITTLE WARM...ESPECIALLY WITH POTENTIAL FOR MORNING LOW CLOUDS AND HIGH CLOUDS THROUGHOUT THE DAY. WILL CONTINUE WITH GOING FORECAST. MONDAY NIGHT...WITH A SOUTHERY WIND DEVELOPING DO NOT EXPECT TEMPERATURES TO BE AS COLD AS TONIGHT. MAY ALSO SEE A FEW HIGH CLODS AROUND DURING THE NIGHT. WILL AIM FOR ABOUT A 10 DEGREE DIURNAL DROP WHICH WOULD PUT US IN THE UPPER 20S TO AROUND 30. .EAX...NONE. 18 mo AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE COLUMBIA SC 305 PM EST SAT FEB 12 2000 .CURRENTLY... UPPR LVL DIST AND AREA OF UPPR DIVG...ALONG WITH MID/UPPR DRYING... MOVG INTO CWA. SFC FNT ACRS S CENT CWA...WITH WEDGE TO THE NORTH OF IT. TEMP CONTRAST FROM L70S S CST TO NR 40 NR NC BORDER. INTERACTION OF ABV PRODUCING SCT SH/TSRA...PUSHING TO THE EAST. .SHORT TERM... RUC CONT MOVG UPPR VORT ACRS LATE THIS AFT TO NR THE CST THIS EVE. N GA LOW TO DISSIPATE WHILE NEW LOW TO FORM OFFSHORE. WEDGE TO PUSH SOUTH ACRS CWA...AND HANG IN OVRNT. QUESTION INVOLVES WEDGE STATUS SUN. MDLS MV HIGH CENTER EAST OFFSHR NEW ENG...AND INCR LOW LVL S/SW WINDS CONSIDERABLY DURG THE DAY. ETA SUGGESTS WEDGE COULD BREAK ACRS THE SOUTH CWA...AND LOOKS REASONABLE. WEDGES USUALLY HANG TOUGH...AND WILL LIKELY REMAIN OVR THE NORTH. MDLS BRING WEAK VORT ACRS SUN WITH SOME ISEN LIFT...WILL GO 20 POPS FOR -RA. TEMPS TOUGH SUN AND DEPENDENT ON WEDGE BREAKING. WILL SPLIT CWA THREE WAYS AND UNDERCUT GUIDANCE IN VARYING DEGREES. NEXT UPPER SYS TO MV INTO MID MISS AND OHIO VLLYS SUN NT/MON...TO PRODUCE STG SFC LOW PRESS AREA. MDLS SHOW INCR IN SFC PRESS GRAD FOR US SUN NT...WITH STG SW 850 JET 50 TO 70 KTS DEVLPNG. IF WEDGE DOESNT ERODE BY SUN AFTN...IT WILL DO SO SUN NT...WITH STEADY OR SLOWLY RISING TEMPS. SPC HAS MDT RISK SVR ALA/MISS UP TO 12Z MON. MDLS BRING FNT THRU MON. WILL GENERALLY GO WITH MDL CONSENSUS. TOO EARLY TO BE SPECIFIC ABOUT SVR IN THE ZFP FOR LATE SUN NT/MON...BUT WILL MENTION TSRA. MDLS ARE INDICATING POTENTIAL FOR WINDY CONDITIONS MON...BUT WILL JUST GO WITH BREEZY WORDING FOR NOW SINCE IT IS FOURTH PERIOD. .EXTENDED... MDLS SUGGEST FAIR WX BEHIND FRONT FOR TUE/WED...WITH WEAK DRY FRONT COMING THRU WED NT...BRINGING COOLER TEMPS IN FOR THU. PRELIM CCF CAE CE 43/58/56/70 1354 AGS EE 46/64/54/71 1354 .CAE...NONE. sc NORTHEAST AND NORTH CENTRAL COLORADO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER COLORADO 350 AM MST SUNDAY FEBRUARY 13 2000 SHORT TERM DISCUSSION: LOWER ELVTNS OF CWA SHOULD SEE APPRECIABLE DRYING NEXT 12-18 HRS WHILE MTNS AND HIGH FTHLS CONT TO RECIEVE DIMINISHING AMTS OF SNOWFALL..BUT INCREASING WNDS. MID-LVL SUBSIDENCE AND STRENGTHENING NWLY FLOW ALOFT WILL BE RESPONSIBLE FOR THE DRYING NOTED ABV. ATTM...LOW CLOUDS AND FOG (WITH VSBYS BLO A 1/4 MI IN AREAS) BLANKET MOST OF NERN CO PLAINS AND LOWER FTHLS. VRY LGT E-SELY SFC WNDS ON THE PLAINS KPG LOW LVL MOISTURE PUSHED UP INTO LOWER FTHLS WHERE SFC TROF NOW RESIDES. W OF SFC TROF...SFC WNDS AT FTHLS RAWS...LDAD AND NIWOT RIDGE OB SITES WERE GENERALLY W-NWLY AT 10-25KTS. PLATTEVILLE PROFILER SHOWED NWLY FLOW UP TO 350 MBS...WITH 700-500 MB WNDS INCREASING PAST COUPLE OF HRS. RADAR ALSO SHOWED AN INCREASE IN SNOWFALL IN THE MTNS...PARTICULARLY ALG AND W OF THE CONT DVD. INCREASING SNOW COVERAGE AND INTENSITY COINCIDING WITH PASSAGE OF WK MID-LVL SHRTWV AND MID-LVL CAA. MDLS SHOW THIS SUBTLE FEATURE...WITH WATER VAPOR IMAGERY ALSO SHOWING DARK AREA (SINKING/DRYING) IN ITS WAKE OVR XTRM NWRN CO/SWRN WY. DARK AREA WAS RACING SEWRD AT APXMTLY 45KTS. BASED ON THIS TIMING AND ON 06Z ETA/RUC AND SFM...SHOULD SEE A DROP OFF IN SNOWFALL IN THE MTNS BY LATE MRNG WITH ONSET OF WAA...BUT AN INCREASE IN WINDS...ESPLY ON RIDGES AND PASSES. STILL SEE ANOTHER 2-4 INCHES OF SNOW IN MTN ZNS BEFORE MIDDAY...ALG WITH AREAS OF BLWG AND DRFTG SNOW. BLOWING SNOW WILL PROBABLY BE MAIN CONCERN THIS AFTN IN HIGH COUNTRY WHERE GUSTS TO 60 MPH PSBL ON RIDGES AND EXPOSED AREAS. ON THE PLAINS...SAME MDLS MENTIONED ABV SHOWED SFC TROF PUSHING OFF FTHLS ERLY THIS MRNG AND ACRS THE NERN PLNS THIS AFTN. SFC-700MB GRIDS SUGGEST GUSTY WLY (DOWNSLOPE) WNDS DVLPG IN LWR FTHLS AND ADJCNT PLAINS BY MIDDAY...RESULTING IN SIGNIFICANT DRYING AND MDT WARMING. DRYING NOT AS FAST FARTHER OUT ON THE PLAINS WHERE COLD... MOIST AIR WILL LKLY RETARD EWRD ADVANCE OF SFC TROF. MAY SEE LOW CLOUDS AND UPR 20S/LWR 30S TEMPS FOR MOST OF THE DAY IN THE FAR NERN CTYS. MOS TEMP GUIDANCE LOOKS REASONABLE...HWVR GUIDANCE UNABLE TO REFLECT WIDE RANGE OF TEMPS XPCTD ON PLAINS TODAY. BAKER LONG TERM DISCUSSION: APPEARS THE SAGA OF SNOW AND BLOW WILL CONT IN THE MOUNTAINS FOR THE REST OF THE WEEK ACCORDING TO ALL MODELS. BRISK W-SW FLOW TO BE THE RULE THRU TUES XCP TODAY AND THEN ON WED AND THURS WHEN UPR RDG PUSHES IN AHEAD OF TROF THAT IS EXPECTED TO MOVE ONSHORE FRI. WATER VAPOR AND IR SAT PIX SHOW GOOD PLUME MSTR FROM SUBTROPICS ENTRAINED IN THIS FLOW. THE LOW/TROF OVER ERN PAC WILL KICK A NUMBER OF FAST MVG RIPPLES EWD ACRS THE ROCKIES DURING THE WEEK BUT NEARLY IMPOSSIBLE TO TIME IN THIS PTRN. SINCE PLENTY OF MSTR AND ORGRPHC LIFT WILL BE AIDED BY DYNMCS AT TIMES FROM THE PASSING SHT WVS WILL DO A BROADBRUSH FCST WITH GOOD CHANCE OF SNOW IN MTNS EACH DAY THRU THURS. SNOW MODEL GIVES 1 TO 4 INCHES OMTNS TNGT AND MON HWVR WAA WILL HINDER ORGRPHC SNOW MACHINE AND WILL GO WITH LTL LESS ACCUM FOR TNGT. FOR PLAINS THE PTRN TO CHNG TNGT AS ALL MODELS SHOW LEE TROF AND DWNSLP FLOW DVLPG. THAT LOOKS LIKE A GOOD BET UNDER BRISK WLY FLOW ALF. THE DWNSLP FLOW SHUD CONT THRU WED BUT MRF INDCTS ANOTHER SURGE OF CANADIAN AIR INTO PLAINS THURS WHICH CUD PUSH CD FNT AND WEAK UPSLP FLOW INTO NERN CO THURS. FMR TEMPS AT DEN ABT 10 DEGS COOLER ON THURS THAN TUE AND WED WHICH IS CONSISTENT WITH SHIFT TO UPSLP PTRN. NOT SURE THIS CHANGE WILL BE STG ENUF TO GENERATE ANY PCPN. PRESENT ERN CO EFP IS DRY AND WILL LEAVE AS IS. IN MEANTIME TEMPS TO WARM FROM TODAYS READINGS SINCE COLD AIR SHUD BE SCOURED OUT BY DWNSLP FLOW TNGT AND TMW. DESPITE WAA AND DWNSLP FLOW I BELIEVE FAN AND FWC ARE TOO OPTIMISTIC ABOUT HIGH TEMPS EXCEEDING 50 DEGREES TMW SINCE H7 TEMP PROGS GENLY SHOW TEMPS REACHING UPPER 40S BUT PLENTY OF CLOUDS WILL HAMPER WARMING. GCF .DEN...NONE. co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SHREVEPORT LA 930 AM CST SUN FEB 13 2000 CURRENT SFC MAP SHOWING SFC LOW PRESSURE CENTERED NEAR KTUL WITH WARM FRONT JUST NORTH OF MY CWA FROM NEAR FSM AND HOT TO NORTH OF GREENWOOD MISS. SFC TROF EXTENDS JUST WEST OF A ADM...DFW...AUS LINE WITH DRY LINE FURTHER WEST OF THIS TROF. MORNING RAOBS SHOW STRONG CAP AT AROUND THE 800MB LEVEL WITH A WEAKER LOW LEVEL INVERSION AT ABOUT 950MB. CLOUDS ALREADY STARTING TO THIN SOMEWHAT TO MY WEST SO LOW LEVEL INVERSION NOT ANY CONCERN. THIS CAP AT 800MB MAY BE OUR SAVING GRACE AS WET BULB ZEROES NEAR 7K AND SRH VALUES NEAR 350 M2/S2. SPC REQUESTING 18Z RAOB SO THIS MAY BE THE TELLING TALE. CAP NOT QUITE AS STRONG AT KJAN THIS AM...HAVING SAID THIS AND PUTTING MY FAITH IN THE CAP...DISORGANIZED LINE OF CONVECTION TRYING TO GET GOING ACROSS MY SOUTH WITH RATHER INTERESTING LOOKING CELL PULSING UP AND DOWN IN NORTHERN POLK COUNTY. TAKING A LOOK AT THE LATEST RUC AS WELL AS THE 06Z MESOETA...WILL LOWER POPS SIGNIFICANTLY ACROSS THE NORTHWEST FOR THIS AFTN BUT WILL LEAVE POPS AS IS ACROSS THE EXTREME EAST. TEMPS LOOK OK SO NO CHANGES EXPECTED THERE. SYSTEM IS A FAST MOVER SO HOPE TO GET THIS ACTIVITY...IF ANY AT ALL OUT OF HERE THIS EVENING. UPDATE WILL BE OUT BY 1100 AM. COORD WELCOME...13 .SHV...NONE. la AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1100 AM EST SUN FEB 13 2000 HAVE ISSUED A SNOW ADVISORY FOR THE SOUTHERN TIER OF NRN LWR MI. PARAMETERS ARE IN PLACE FOR APPRECIABLE SNOWFALL RATES -- 1/2" TO 1" PER HOUR -- ACROSS CENTRAL LOWER MICHIGAN THROUGH AT LEAST MID AFTERNOON. CURRENT MOSAIC RADAR LOOPS SHOW DEFINITE...EAST-WEST BANDS OF HEAVIER SNOW (REFLECTIVITY OVER 28 DBZ). OVER THE LAST HOUR AREAS ALONG AND SOUTH OF M-55 HAVE BEEN OBSERVING MODERATE TO OCCASIONALLY HEAVY SNOW. THE BANDS OF HEAVIER SNOW DO SHOW CSI CHARACTERISTICS... WHICH WOULDN'T BE REAL SURPRISING GIVEN THE STRONG N-S BAROCLINICITY ACROSS THE STATE...700 MB FRONTOGENESIS...AND 300 MB DIVERGENCE MAXIMIZING ACROSS CENTRAL LOWER MI. SLOPES OF THETA AND MOMENTUM SURFACES AND SLIGHTLY NEGATIVE EQUIVALENT POTENTIAL VORTICITY ON ETA/RUC CROSS SECTIONS SHOW THE POTENTIAL OF CSI BETWEEN 700 AND 600 MB...THOUGH MORE SO ACROSS SOUTHERN LOWER MI. LATEST RUC MODEL INDICATIONS SHOW COLD CONVEYOR BELT...DEFORMATION SNOWS SHOULD GRADUALLY TAPER FROM NW TO SE DURING THE AFTERNOON... AS REGION OF FAVORABLE MID LEVEL FRONTOGENESIS...RRQ JET UPPER DIVERGENCE...AND LOW LEVEL CONVERGENCE SHIFTS SOUTH OF THE REGION. Q-VECTORS BECOME MOST DIVERGENT ACROSS EASTERN UPPER LATE IN THE DAY...WHERE PARTIAL CLEARING IS CURRENTLY WORDED IN THE ZONES. GOOD UPPER CONFLUENCE/RRQ JET FORCING WILL INCREASE THE NORTHERLY WIND COMPONENT AT LOW LEVELS AS THE AFTERNOON PROGRESSES. THIS WILL NOT ONLY GRADUALLY DRY OUT THE REGION FROM N TO S...BUT WILL LIKELY HOLD TEMPS DOWN AS WELL GIVEN THE NEUTRAL TO COLD ADVECTION BETWEEN 950 AND 900 MB. ANOTHER ZONE UPDATE IS ANTICIPATED BY EARLY AFTERNOON TO FRESHEN THE WORDING AND ACCOUNT FOR TRANSITIONAL WEATHER ELEMENTS. .APX...SNOW ADVISORY...TODAY...MIZ033>036-041-042. HURLEY mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTH PLATTE NE 1036 AM CST SUN FEB 13 2000 ...CANCELLED SNOW ADVISORY... HAVE CANCELLED SNOW ADVISORY THAT WAS IN EFFECT TODAY FOR NORTHERN AND EASTERN ZONES. SATELLITE IMAGERY SHOWS SHORTWAVE MOVING THROUGH EASTERN WYOMING. SURFACE REPORTS INDICATE LIGHT TO MODERATE SNOWFALL AHEAD OF THE SHORTWAVE UNDER ENHANCED CLOUDS MOVING THROUGH NORTHERN PANHANDLE INTO N CENTRAL NEB. 88D MOSAIC AND METARS SHOW BACK EDGE OF SNOW ABOUT TO REACH ROUGHLY KAIA TO KCDR LINE. 12Z ETA AND LATEST RUC INDICATE DECENT H7-H5 LAYER Q-VECTOR CONVERGENCE WITH THIS WAVE TO LAST INTO EARLY AFTERNOON OVER WESTERN ZONES...AND THEN RAPIDLY DECREASE BY MID AFTERNOON. NO ISENTROPIC LIFT IS INDICATED AND LOW TO MID LEVEL LAPSE RATES NOT IMPRESSIVE TO SUGGEST MUCH CONVECTIVE POTENTIAL. ALSO...88DS DO NOT SHOW BANDING THAT WAS INDICATED SATURDAY. SATELLITE IR IMAGERY SHOWS SLIGHT WARMING CLOUD TOP TREND WITH THIS NEXT WAVE. ETA AND RUC MODEL SNOW ACCUMULATOR GUIDANCE SUGGEST POTENTIAL FOR 1 TO 2 INCHES ACROSS NORTHERN ZONES AND THIS LOOKS REASONABLE. ZONES IN N CENTRAL AND NORTHEAST HAVE HAD ENOUGH OF A BREAK IN SNOWFALL BEFORE NEXT ROUND BEGINS AND REPORTS COMING IN DO NOT SUGGEST ENOUGH TO VERIFY CURRENT ADVISORY...SO HAVE CANCELLED IT. .LBF...NONE. SHEETS ne SOUTH CENTRAL NEBRASKA/NORTH CENTRAL KANSAS FORECAST DISCUSSION NATIONAL WEATHER SERVICE HASTINGS NE...UPDATE 913 PM CST SAT FEB 12 2000 SATELLITE IMAGERY SHOWS DRY SLOT CROSSING CWA. DEFORMATION ZONE HAS PRODUCED SWATH OF SNOW OVER NC NEBRASKA BUT NONE IN CWA THUS FAR. BACK SIDE OF COMMA SEEN ROTATING OUT OF WYOMING HEADING FOR AREA. SURFACE LOW IN SW KANSAS TRACKING EAST. 00Z RUC BRUSHES NORTH CWA WHERE ADVISORY IS IN EFFECT WITH A DUSTING OVERNIGHT. LATEST ETA IS A LITTLE MORE AGRESSIVE DISHING OUT A COUPLE INCHES OF SNOW BY 24 HOURS. BEST DIVERGENCE TO OCCUR EARLY TONIGHT IN RRQ OF GREAT LAKES JET MAX. DPVA SHOULD CONTINUE INTO SUNDAY WITH ETA NOW PROJECTING ANOTHER VORTICY MAXIMUM TO SLIDE INTO BACK SIDE OF MAIN WAVE AHEAD OF RAPIDLY EASTWARD SHIFTING JET MAX NOW OVER CALIFORNIA. WILL BACK OFF ON THE ONSET OF SNOW BUT KEEP ADVISORY GOING THROUGH SUNDAY MORNING. ASIDE FROM ADVSY AREA BEST CHANCE FOR SNOW APPEARS TO BE IN WESTERN CWA...VCNTY OF KLXN. UPPER AIR ANALYSIS SHOWS AIR WILL BE COLD ENOUGH TO KEEP PCPN SNOW EXCEPT IN EXTREME SOUTH WHERE CHANCES FOR PCPN APPEAR INCREASINGLY SLIM. WANT TO TAKE A QUICK LOOK AT NEW NGM BEFORE UPDATE. IN ADDITION TO TIMING/PCPN TYPE ADJUSTMENTS TONIGHT...IT IS POSSIBLE THAT A FEW ADJUSTMENTS WILL BE MADE TO SUNDAY SECTION OF ZONES CONCERNING SNOW TIMING/ACCUMULATIONS. .GID...SNOW ADVISORY TONIGHT AND SUNDAY MORNING NEZ039>041-046>049. DROZD ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE COLUMBIA SC 1000 AM EST SUN FEB 13 2000 LTST RUC/MESOETA SUGGEST WEDGE BNDRY COULD MV NORTH THRU S CWA LATE AFTN...BUT WOULD LIKELY HANG ON N AND CENT CWA ALL DAY. THEREFORE... WILL LOWER MAXES TOD SIGNIFICANTLY N/CENT...AND SLIGHTLY S. .CAE...NONE. sc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 317 AM CST SUN FEB 13 2000 MAIN CONCERNS THIS MRNG ARE SNW AMTS AND ADVYS. WATER VAPOR/IR STLT IMAGERY SHOW SHRT WV MOVG THRU CNTRL NE WITH ASSOCD DEF ZN INTO NRN IA. WEAK SHRT WV OVR ID MAY ALSO AFFECT FA TNGT. 07Z SFC ANLYS PLACES LOW ACRS S CNTRL KS WITH WRM FNT ACRS NRN MO TO BTWN KUIN/KSTL. SOME SEMBLANCE OF DRY SLOT APPARENT BTWN DEF ZN AND DEEPER MSTR FETCH FM OK INTO SERN IA SO ITS TAKING AWHILE TO SATURATE AND DVLP MUCH PCPN SWRN SXNS. MAINLY DRZL AND FRZG DRZL. FOR TDA WL LEAN HEAVILY TWRD NOWCASTING TOOLS...EXTRAPOLATION OF DEF ZN PER RADAR AND STLT TRENDS AS WELL AS 06Z RUC. RUC H7/H3 VORT CNTR LNS UP QUITE WELL WITH SHRT WV ON STLT IMAGERY AND RUC TAKES THIS FEATURE TO BTWN KMIW/KCID BY 18Z. RGNL RADAR TRENDS...AND 00Z MDL QPF POINT TWRD THIS AS WELL SO WL KEEP ADVY AND SGFNT SNWS ALG AND N OF THESE LOCATIONS...OR KAIO-KMIW-KALO LN. LOOK FOR ADDITIONAL ACCUMULATIONS OF 2 TO 3 INCHES THERE...WITH AN INCH OR TWO IN COUNTIES JUST TO THE S. OVR SRN IA FRZG DRZL MAY BE MORE OF A CONCERN. CALLS TO LCL LAW ENFORCEMENT INDCD NO REAL PROBLEMS WITH ONLY PATCHY DRZL AND FOG SO WL NOT ISSUE ADVY. PCPN SHOULD CHG TO LIGHT SNOW OR FLURRIES LATER TDA. IN LATER PDS FAVOR AVN/ETA SOLUTION BASED ON PAST HISTORY AND PLACEMENT OF CURRENT FEATURES. NICE COUPLED JET CIRCULATION AHD OF LG WV TROF SHOULD RMN WELL SE OF FA THRU OH VLY WHERE SVR CONVECTION MAY DVLP. H85/H5 Q-VECTOR CNVGNC EXITS ERN FA JUST AFT 18Z BUT DEF ZN EFFECTS MAY LINGER AFT THAT. MID LVL QG FRONTOGENETICAL FORCING ALSO PUSHES E BY 18Z. SCNDRY FORCING ASSOCD WITH ID SHRT WV MAY IMPACT FA TNGT SO WL MENTION LGT SNW WITH LTL ACCUMULATION. COULD SEE SIMILAR SITUATION MON NGT TOO. TEMP WISE XPC STEADY OR SLOWLY FALLING TEMPS TDA. TNGT AND LATER PDS WL LEAN TWRD WRMR END FOR MINS AND LOW END OF MAXES. AVN/ETA LOW LVL RH PROGS DEPICTS PLENTY OF MSTR SO WE MAY SEE LTL DIURNAL CHG. COORD W/FSD...OAX...ARX AND DVN. .DSM...SNW ADVY TDA ALG AND N OF KAIO-KMIW-KALO LN. SMALL ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOUISVILLE KY 300 PM EST SUN FEB 13 2000 MODELS IN OVERALL GOOD AGREEMENT IN HANDLING OF STORM SYSTEM FCST TO MOVE NEWD ACROSS LOWER OH VLY TNGT. HWVR...MESOSCALE DETAILS AND PRECIP AND TSTM EVOLUTION CREATES SHORT TERM FCST PROBLEMS. CURRENTLY...SFC OBS AND MSAS DATA SHOW E-W WARM FRT BECOMING BETTER DEFINED ACRS CNTRL KY. INITIAL AREA OF PRECIP NOW IS ELEVATED NORTH OF FNT ALG AND N OF OH RVR. LATEST RUC HAS NICE HANDLE ON PRECIP PTRN AT THIS TIME. JUST S OF BNDRY...TEMPS AT 19 UTC HV RISEN TO ARND 60 IN S-C KY WITH DEWPTS IN MID 50S. SFC BASED LI VALUES HAVE BEEN DECRSG IN RESPONSE. AT SAME TIME WTR VPR IMAGERY SHOWS DARKENING/SINKING INTO BASE OF UPR TROF ACRS SRN PLAINS INDICATIVE OF RESPONSIVE INCRSG ASCENT DOWNWIND. VIS IMAGERY SHOWS CNVCTN DEVELOPING ACRS LWR MS VLY TO SRN IL WITHIN THIS ASCENT REGION AND AREA OF INSTBLTY. MODEL DATA ALSO INDICATE THAT IMPRESSIVE ANTICYCLONICALLY CURVED RT ENTRANCE RGN OF JET STREAK WILL BE FAVORABLY POSITIONED TO ENHANCE UPR LVL DIVERGENCE ACRS KY THIS EVNG. LO-LVL AGEO WINDS RESPOND TO UPR JET WITH INCRSLY SLY FLOW. THUS... AS SHORTWAVE MOVS ENEWD...EXPECT SHWRS/TSTMS TO AGN INCRS IN COVERAGE AND INTENSITY TO OUR WEST THEN SPREAD RAPIDLY NEWD INTO CNTRL KY THIS EVNG. CONSIDERED ISSUING FFA...BUT WL NOT ISSUE AT THIS TIME DESPITE EXPCTD HVY RAIN POTNL...AS RAIN THIS MRNG WAS NOT LONG LASTING AND PRECIP TNGT...WHILE HVYT AT TIMES...SHLD ALSO MOVE AT FAST ENOUGH SPEED TO PRECLUDE WIDESPREAD VERY HEAVY RAIN AMTS. LOOKS LIKE S-C KY CERTAINLY STILL IN THREAT FOR SVR GIVEN DESTABILIZATION IN BNDRY LYR CURRENTLY UNDERWAY. DIFFICULT TO TELL HOW FAR N SVR THREAT WL BE...PROBABLY NOT MUCH FARTHER N THAN OH RVR GIVEN XPCTD WARM FNTRL POSN AND SFC LOW TRACK. NEVERTHELESS... ELEVATED CNVCTN STILL LIKELY N OF BNDRY TNGT. ONCE SYSTEM MOVS BY TNGT...TIME HT CROSS SECTIONS ALL SHOW RESIDUAL LOW LEVEL MSTR THRU MUCH OF MONDAY. THUS WL KEEP A CLDY SKY AND SCT LGT SHWRS OR SPRINKLES DESPITE PASSAGE OF DEEPER-LAYERED MSTR (ESPCLY N-C AND E-C KY AND S-C IN). LOOKS LIKE GRADUAL CLRG WL OCR LATE MONDAY AFTN ACRS SWRN PART OF CWA AND ACRS REST OF AREA MONDAY NGT AS SFC RIDGE BUILDS EWD. THEN ZONAL FLOW AND RENEWED WARM ADVCTN PTRN WL BRING SOME MID OR HI CLDS BACK INTO AREA ON TUES...THUS WL GO PT SNY. FWC/FAN TEMPS LOOK REASONABLE OVERALL. .SDF...NONE. FUNK ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO 221 PM CST SUN FEB 13 2000 VIS LOOP THRU 1925 UTC SHWS ST COVERING MOST OF CNTL U.S. SFC LO OVR SW MO HAS BNDRY LYR GRADIENT ALLIGNED ACR CWA WHERE WAA STILL OCCURING OVR SE ZNS AND CAA ALREADY IN PLACE ACR NW. TEMPS STILL SLOWLY CREEPING UP ACR SE BUT MAINLY STEADY ELSEHWERE. MEANWHILE UPSTAIRS WV LOOP AND AM UPR ANLYS SHW DRY SLOT SPIKED ACR ALL BUT XTRM NW CWA. RUC SHWS WEAK POT VORTICITY CNTR THRU H7-H3 LYR LIFTING TO NE BET 2100-2400 UTC. THIS SHLD ALLOW MID LVLS TO MOISTEN UP AGN THIS EVNG AND SET THE STAGE FOR A FEW -SHSN THIS EVNG ACR NRN ZNS AS WEAK TRAILING SHRT WV ACR CNTL NE DIVES INTO LONGER WAVE LENGTH ELRY TNGT. ALL MODELS SHW WEAK CNVGNC OF TOTAL Q-VECT AND QN TRACKING ACR NRN MO. BASED ON THIS FORCING MECHANISM AND CRNT RADAR LOOP FOR CNTL NE WILL LEAVE CHC POPS FOR -SN ELRY TNGT IN FAR NRN ZNS AND REMOVE POP ELSEWHERE AND INSERT CHC FOR FLURRIES. PLAN ON OPENING UP 5 DEG TEMP RANGE UPWARDS FM CRNT FCST AND GUIDANCE VALUES ALL ZNS TNGT. CONCERNED THAT ST WILL HOLD READINGS UP IN MANY LOCATIONS BUT WHERE CLD DECK BRKS TEMPS MAY FALL OFF AND LOCALLY DENSE FG A POSSIBILITY. WILL INSERT FG INTO BODY OF FCST ALL ZNS. MODELS SHW STG WAA IN BOTH LWR AND MID TROPOSPHERE ON MON BUT WITH LACK OF STG SUBSIDENCE PRODUCER AND ST TRENDS UPSTREAM OVR HI PLNS WILL PLAY CAUTIOUS HAND AND GO WITH SLOW CLRG TREND IN W AND MSTLY CLDY E. FOR TEMPS WILL STAY CLOSER TO COOLER FWC AND CRNT FCST. ANOTHER TASTE OF SPRING PSBL ON TUE PROVIDED SW FLW STG ENOUGH TO LIFT RESIDUAL ST FM RGN. WILL STAY WITH PTLY CLDY AND BOOST TEMPS HALF TO THREE QUARTERS OF WAY TO VRY WRM GUIDANCE NUMBERS BUT RMN CLOSER TO COOLER FWC. MED RANGE MODELS STILL SUGGEST DRY CD FNTL PASSAGE IN TUE NITE/WED TIME FRAME FOLLOWED BY TEMPS CLOSER TO SEASONAL LVLS REST OF WK. PLAN ON NO XTND FCST CHGS. .EAX...NONE. BODNER mo AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTH PLATTE NE 310 PM CST SUN FEB 13 2000 H5 SHORTWAVE THAT PRODUCED LIGHT SNOW ACROSS CWFA TODAY WAS MOVING INTO CENTRAL NEBRASKA AT 20Z ACCORDING TO SATELLITE WV IMAGERY... WHICH CORRELATES WELL WITH KLNX 88D RETURNS. INITIAL FORECAST CHALLENGE WILL BE AMOUNT OF CLEARING THIS EVENING AND POSSIBILITY OF FOG OR STRATUS FORMATION DUE TO HIGH LOW LEVEL RH FROM FRESH SNOWFALL AND LIGHT SURFACE WIND. EXPECT MOST OF LIGHT SNOW TO BE OVER BY FORECAST ISSUANCE AND WILL HAVE TO WAIT UNTIL LAST MINUTE TO ADJUST WORDING IN THE NORTHEAST. MAIN FORECAST CHALLENGE IS TEMPERATURES. ETA HAD BEST INITIALIZATION AT H850 THIS MORNING AND KEEPS TEMPS AT THAT LEVEL LOWER THROUGH 24 HOURS AND GENERALLY FOLLOWED. LITTLE DIFFERENCES IN MODELS OVER CWFA THROUGH PERIOD AT THE UPPER LEVELS WITH ZONAL FLOW DEVELOPING AND WEAK SHORTWAVES TO IMPACT REGION. AT SURFACE...LEE TROUGH DEVELOPS MONDAY AND MOVES ACROSS NEBRASKA WITH LOW DEVELOPING MONDAY NIGHT. SOME DISAGREEMENT EXISTS ON SURFACE LOW TRACK AND PLACEMENT OF COLD FRONT...BUT ALL TRACK MAIN LOW IN SRN SD/NRN NEB AREA TO KEEP FORECAST AREA ON WARM AND DRY SIDE. EXPECT LOW CLOUDS TO CLEAR OUT FROM SW TO NE THIS EVENING WITH TIMING OF HIGH CLOUDS NOT FAR BEHIND OVER WY/CO CRITICAL TO FORECAST LOWS AND POSSIBILITY OF FOG AND STRATUS FORMATION. ETA AND RUC MID AND UPPER LEVEL RH FIELDS HINT AT ENOUGH CLEARING BY 06Z TONIGHT FOR RADIATIONAL COOLING AND FOG FORMATION FROM S CENTRAL TO NE ZONES BEFORE CI MOVES IN AND HAVE MENTIONED FOG IN THESE AREAS. WENT CLOSE TO OR JUST BELOW COOLER MOS TEMPERATURES AS CI SHOULD COVER MOST OF FORECAST AREA BY SUNRISE AND LIMIT RADIATIONAL COOLING. H850 TEMPERATURES RISE TO 8 TO 14 DEG C ACROSS CWFA MONDAY...BUT SNOW FIELDS AND CI FILTERED SUNSHINE WILL WORK AGAINST THE LOW LEVEL WAA TO KEEP HIGHS BELOW GUIDANCE AND WILL CUT BACK BELOW COOLER FAN. FWC HAS RAISED MONDAY HIGHS 5 TO 10 DEG THE PAST 3 MODEL RUNS... WHILE FAN HAS BEEN MORE STABLE. PRESSURE GRADIENT FROM SURFACE LOW WILL KEEP LOWER LEVELS FROM DECOUPLING MONDAY NIGHT AND GUIDANCE LOWS ACCEPTABLE. WITH DECREASING SNOW COVER AND DOWNSLOPE WINDS TUESDAY...IT SHOULD BE A BIT WARMER...DESPITE TRAILING COLD FRONT MOVING SOUTH THROUGH AREA. IN EXTENDED...WENT ALONG WITH MRF AND ADDED CHANCE RAIN OR SNOW TO SOUTH WEDNESDAY AS LOW MOVES ACROSS KS. ALSO INTRODUCED CHANCE OF SNOW TO NORTH AND NORTHEAST THURSDAY AS NRN STREAM SHORTWAVE AND VORT MAX MOVES THROUGH DAKOTAS. .LBF...NONE. SHEETS ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 235 PM CDT SUN FEB 13 2000 THE PRIMARY SHORT TERM CONCERN IS THE EASTWARD SPREAD OF AN AREA OF LIGHT SNOW NOW OVER N CNTRL NE. MID LEVEL Q-VECTOR CONVERGENCE SEEMS TO HAVE THE BEST MATCH TO THIS FEATURE...AND HAD HINTS OF IT EVEN YESTERDAY. BOTH ETA AND RUC SUGGEST IT WILL MOVE EWD MAINLY ACROSS THE NORTHERN CWA THIS EVENING...WEAKENING AS IT COMES. WILL KEEP THE EVENING FLURRIES IN THE FCST BUT DO NOT EXPECT TO SEE ANY ACCUMULATIONS. IN THE LATER PERIODS...MOST FORECAST ELEMENTS COME INTO PLAY AS A SERIES OF FAST MOVG BUT WEAK SHORTWAVES STREAK IN FROM THE PACIFIC AT VARIOUS LATITUDES. MODELS LACK RUN-TO-RUN CONSISTENCY WITH THESE FEATURES SO CONFIDENCE IS NOT HIGH ON THE DETAILS. IF ANYTHING... THE MAJOR TENDENCY HAS BEEN TO GO TOO FAR NORTH WITH SFC FEATURES AND ADJUST SWD OVER TIME...WITH NGM THE WORST IN THIS REGARD AS USUAL. IN ADDITION...THE BROAD SCALE UPPER FLOW IS CONFLUENT OVER THE CENTRAL U.S. AS THE SPLIT FLOW OVER THE ERN PACIFIC COMES BACK TOGETHER. THIS SUPPORTS THE TENDENCY OF EACH SYSTEM TO WEAKEN AND SHEAR OUT AS IT MOVES INTO OUR AREA. CLOUDS AND TEMPS ARE THE CONCERNS TONIGHT THROUGH MONDAY NIGHT AS THE SFC HIGH MOVES SE ACROSS THE AREA FOLLOWED BY STRONG LOW LEVEL WARM ADVN BEGINNING BY MONDAY MORNING. THE MODELS HANG ONTO A LOT OF LOW LEVEL MOISTURE TONIGHT...BUT WOULD EXPECT AS LEAST SOME BREAKS AFTER THE TRAILING SHRTWV MOVES OUT EARLY TONIGHT AND MID LEVEL SUBSIDENCE TAKES OVER. BREAKS ARE ALREADY SHOWING UP ACROSS S CNTRL NE WITH A LARGE HOLE OVER ERN SD. TEMPS ARE VULNERABLE TO A FAST DROP WITH ANY BREAKS IN THE CLOUDS WITH AT LEAST SOME SNOW COVER OVER THE NRN AND ERN CWA. LIGHT WINDS COULD ALSO ALLOW FOG... BUT ENOUGH CLEARING TO ALLOW WIDESPREAD DEVELOPMENT IS QUITE CHANCY. WILL LEAVE OUT OF THE PUBLIC FORECAST FOR NOW. PREV FCST LOWS ARE GENERALLY BELOW GUIDANCE AND LOOK GOOD. AS WARM ADVN TAKES OVER MONDAY...LOW CLOUDS SHOULD BE THINNING OUT...BUT HIGH CLOUDS WILL TEND TO BE ON THE INCREASE. I WILL AGAIN BE CLOSER TO THE COOLER TEMPS OF THE OLD FCST THAN THE NEW GUIDANCE. TEMPS WILL START OUT COLD AND WINDS DO NOT LOOK STRONG ENOUGH FOR BEST MIXING. NORTHEAST NEB HAS AROUND 2 INCHES OF SNOW AND WILL BE PARTICULARLY HARD TO WARM UP. AS STRONG WARM ADVN CONTINUES...THE TEMPS SHOULD NOT BE DROPPING OFF A LOT MONDAY NIGHT. UNCERTAIN HOW THICK MID AND HIGH CLOUDS WILL BE...ALTHOUGH MODELS DEVELOP FAIRLY STRONG 850-700 MB Q-VECTOR CONVERGENCE AND MODEST LIFT LATE IN THE NIGHT BEFORE THE BEST WARM ADVECTION IN THAT LAYER MOVES NORTHEAST OF THE STATE. WILL GO A BIT BELOW GUIDANCE TEMPS BUT NOT AS MUCH AS DURING THE DAY. TUESDAY IS MORE TRICKY AS A SFC LOW TRACKS ACROSS THE REGION...PRECEDED BY VERY MILD AIR AND FOLLOWED BY WIND...STRONG COLD ADVN...AND A CHC OF LIGHT RAIN/SNOW NORTH OF THE TRACK. TEMPS COULD GO REALLY MILD IN POST FRONTAL MIXING ZONE BEFORE COOLER AIR TAKES OVER...AS HAS HAPPENED SEVERAL TIMES THIS SEASON. I WILL FAVOR THE SOUTHERN TRACK OF THE ETA ACROSS NRN NEBRASKA FOR NOW. WITH RECENT MODEL TRENDS ...WOULD NOT BE SURPRISED IF THE SYSTEM ENDS UP TRACKING EVEN FURTHER S. WILL ALSO HOLD BACK TEMPS ACROSS THE NORTH AND INTRODUCE A LOW POP FOR RAIN OR SNOW. WINDY CONDITIONS EXPECTED FOR THE WHOLE AREA AFTER THE LOW PASSES EAST. UNCERTAINTY ONLY GROWS LARGER IN THE EXTENDED. THE NEXT SYSTEM WILL LIKELY CROSS SOUTH OF THE AREA ON WED. FOR NOW...WILL CALL FOR MAINLY DRY CONDS. COLDER AIR FOLLOWS SYSTEM BUT NOT FOR LONG. ECMWF CALLS FOR ANOTHER SFC LOW OF MODERATE INTENSITY TO CROSS KS ON FRI WHILE MRF AND LATEST UKMO APPEAR TO LEAVE US DRY AND IN WARM ADVN. WILL STICK CLOSE TO GUIDANCE THIS FAR OUT UNTIL WE SEE WHICH MODEL IS WINNING...IF ANY. .OMA...NONE POLLACK ne DEEP SOUTH TEXAS FORECAST DISCUSSION NATIONAL WEATHER SERVICE BROWNSVILLE TX 300 AM CST SUN FEB 13 2000 PROGRESSIVE FLOW CONTINUES ACROSS THE CONTINENTAL U.S. WITH SHORT WAVE TROF MOVING EAST ACROSS THE SOUTHERN PLAINS AND SOUTHWEST TEXAS. WATER VAPOR LOOP AND LATEST RUC MODEL SHOWS S/W JUST EAST OF MAF IN WEST TEXAS. CONSIDERABLE DRYING BEHIND THE SYSTEM AS DOWNSLOPING WESTERLY WINDS PREVAIL ACROSS WEST TEXAS AND NORTHERN MEXICO BEHIND SURFACE TROF. JUDGING BY SATELLITE AND OBS...IT LOOKS LIKE SURFACE TROF IS JUST NORTH OF LAREDO. THIS GOES IN LINE FROM WHAT MODELS HAVE BEEN FORECASTING WITH TROF OVER OUR WESTERN ZONES BY 12Z THIS MORNING. AS THE SURFACE LOW MOVES ACROSS OKLAHOMA THIS AFTERNOON...DRY PUNCH WILL OCCUR OVER WEST AND SOUTHWEST TEXAS BRINGING IN HOT NORTHWESTERLY AND WESTERLY WINDS INTO OUR WESTERN CWA BY AFTERNOON. THIS DOWNSLOPING WIND WILL MAKE IT TO THE COAST BEFORE SEABREEZE COUNTERACTS THE GRADIENT BY LATE AFTERNOON. WITH SURFWATER STILL IN THE 60S...30 DEGREE GRADIENT WILL SET UP ACROSS THE CWA BY AFTERNOON. 06Z MESOETA IS STILL HINTING AT 90S FOR OUR CWA THIS AFTERNOON. THE 02/12 12Z RUN OF OUR 10KM WORKSTATION ETA MODEL HITS THE CENTRAL ZONES WITH 95-96 DEGREES BY AFTERNOON. AS LONG AS THE CLOUDS STAY AWAY...THIS SEEMS REASONABLE WITH THE FORECASTED WESTERLY AND NORTHWESTERLY WINDS AND DEWPOINTS IN THE 30S AND 40S. THE EASTERN ZONES WILL BE A LITTLE MORE CHALLENGING IN TRYING TO FORECAST THE TIMING OF THE SEABREEZE AND WHETHER OR NOT BRO WILL HIT THE RECORD OF 89 BEFORE THE SEABREEZE KICKS IN. WILL INPUT WORDING OF NEAR RECORD TEMPS FOR ALL ZONES. MONDAY WILL SEE A RETURN OF LIGHT SOUTHEASTERLY WINDS AS ANOTHER LEE SIDE TROF SETS UP WITH THE ZONAL FLOW OVER THE ROCKIES. AVN THEN SHOWS THIS LOW PRESSURE AREA MOVING EAST ON TUESDAY ALTHOUGH RIGHT NOW THEY DONT SHOW A TROF PASSAGE FOR SOUTH TEXAS. WITH THIS PATTERN OF ZONAL FLOW...EXPECT ABOVE NORMAL TEMPS THROUGH WEEKS END. NO FLAGS EXPECTED FOR THE COASTAL WATERS. SOUTH WINDS NEAR 15 KNOTS SHOULD PREVAIL THROUGH THIS MORNING BEFORE AN OFFSHORE FLOW DEVELOPS THIS AFTERNOON WITH THE SOUTHWESTERLY WINDS. SWAPS MODEL SHOWS SEAS TO REMAIN IN THE 2 TO 4 FOOT RANGE TONIGHT AND MONDAY. BRO UU 089/060 085/065 085 0/0/0/0 MFE UU 094/060 087/065 087 0/0/0/0 RGC UU 096/058 090/062 090 0/0/0/0 SPI UU 083/063 080/067 080 0/0/0/0 69 INTERNET ADDRESS...WWW.SRH.NOAA.GOV/BRO .BRO...NONE. tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SEATTLE WA 900 AM PST SUN FEB 13 2000 AT 12Z LCL E PAC ANALYSIS HAS SFC LO ARND 990MB AT ABT 42/130. THIS A LTL DEEPR THAN NEW ETA AND NGM. ALSO STLT PICS SHOW A SECOND APPARENTLY STRONGR S/WV WITH SFC WAVE NOW OUT NR 35/142. MORE CD AIR UPSTRM OF THIS SYS. MDLS DO INITLZ A FAIRLY STG VORT CNTR WITH THIS SECOND SYS. STG JET MAX ASSOCD WITH BOTH INITIAL SECONDARY SYS. MSTR FM FIRST S/WV MOVS MAINLY EWD S OF MOST OF WRN WA TDA THEN SECOND S/WV HELPS LIFT SFC LO NOW ALG S ORE CST NWD AND FILLS LO WITH CENTER OFF AST ARND 12Z MON...BOTH NGM AND ETA SIMILIAR ALTHO NGM DEEPR. RUC SHOVED THIS LO INLND OVR CNTRL ORE ARND 00Z MON WHCH BELIEVED TO BE IN ERROR. ANYWAY BELIEVE ETA AND NGM SFC TRND AS WELL AS ADVECTION OF MSTR NWD PROBABLY BEST. UPSHOT IS THAT MSTR SHLDNT LIFT NWD INTO WRN WA TOO MUCH BFR 06Z TNGT AND SPRD TO CNTRL PGTSND 12Z MON AND NOT REACHG EXTRM N NR BLI UNTIL AFT 18Z MON. COOL TEMPS OVRNGT WITH 850MB AND SFC ELY FLOW SO COULD SEE MIXTURE RAIN/SNOW AS PCPN STARTS IN FAVORED AREAS LK NR OLYMPICS IN HOOD CANAL AREA AND PSBLY EXTRM N WHERE NELY FLOW IN BLI AREA WL BE SLOW IN SHIFTG TO S. FIRST USABLE VSB STLT SHOWS LOTS OF CLEAR SKIES WRN WA EXCPT EXTRM S WHERE RAIN REPORTED IN VUO AREA. ALSO SOME ST/SC SAN JUANS AND IN STRAIT JDF NR CLM. WL INDC SUNNY MOST AREAS OF W TDA BUT THIS ONLY CHG FOR ZONES. ART UIL 125 SEA -26 OLM 137 .KATX...VCP21/CSR21...OPERATIONAL. .SEW...SCA W ENTRNCE TO STRAIT JDF. wa AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 331 AM CST SUN FEB 13 2000 FCST FOCUS ON FINAL SNOW TOTALS AND ENDING OF PCPN. IN THE SHORT SHORT TERM (MRNG HRS)...MESOETA/RUC PRETTY MUCH IN LINE WITH ETA/NGM/AVN PROGS WHICH HAVE ALL GOTTEN THEIR ACT TOGETHER IN THIS RUN. SNOW FALLING OVR CWA NOW A COMBO OF RIGHT REAR UPPER JET AND ISENTROPIC LIFT...LOOKS TO HAVE SET UP SHOP FOR THE NEXT SEVERAL HRS. ETA/NGM/AVN ISENTROP CHARTS MAINTAIN 2-3 G/KG MOISTR THRU 18Z WHEN ISENTROP LIFT ENDS AND RIGHT REAR JET EXITS RGN. WETZEL CHARTS NOT ZEROING IN ON ANY PARTICULAR AREA OF CWA FOR CONCENTRATED SNOWFALL...BUT 88D RETURNS CURRENTLY FAVORING NRN PTNS OF CWA WITH BEST DBZS. IN THE SHORT TERM (AFTN HRS)...MESOETA/RUC A LITTLE MORE EMPHATIC WITH APPCHG VORT AS SYSTEM SNOW TAKES OVER THIS AFTN. BOTH MODELS SLIDE CONCENTRATED 18 UNITS OF VORTICITY ALG WI/IL BORDER AS PROGRESSIVE H5 OPEN WAVE MOVES FEATURE EWD. THIS COULD LEAD TO A FEW HRS OF MOD SNOWBURST DURING THE AFTN ACRS SRN PTNS OF CWA BEFORE FEATURE EXITS AREA. CURRNT IR SATL CONFIRMS THAT MESOETA HAS GOOD HANDLE ON VORT POSITION ATTM AS WELL AS SPC MESO DISC #150. SO WILL HANG ONTO WNTR WX ADVSRY FOR TDA AND ADJUST ALL FCST SNOW AMTS TO TOP END OF CRITERIA. A FEW ISOLATED SPOTS MAY TOP CRITERIA BUT WITHOUT SYSTEM SLOWING DOWN...FEEL THIS IS WAY TO GO ATTM. TIMING OF SNOW TO DIMINISH IN WRN PTNS OF CWA LATER THIS AFTN ALSO ON THE MARK AS PER MESOETA/RUC TIME XSECTIONS. IN THE FAR TERM...WILL BEGIN TO TAPER LIGHT SNOW FROM WEST TO EAST TNGT AS SYSTEM PASSES THRU OHIO RVR VLY. WHILE SIG UPPER FEATURES NO LONGER A FACTOR...TRAILING TROF FROM H8 LOW REMAINS IN RGN THRU AT LEAST MON MRNG. SO WILL KEEP TREND OF SNOW CHCS DIMISHING WITH TIME BUT WILL END ALL PCPN BY LATE MON MRNG. LK MI CONTRIBUTION TO BE MINIMAL AT BEST AS SYSTEM EXITS RGN. ETA DRIVES COLDER AIR THAN NGM BUT AGAIN WINDOW OF OPPORTUNITY FOR LK EFFECT SNOW QUITE SMALL. HAVE UPDATED LCL EXTENDED TO INCLUDE LITE SNOW/FLURYS FOR TUE AS PER AVN RUN. COORD WITH LOT..GRB..ARX..DVN. THANKS. .UWNMS...NOT MUCH DIFFERENT WITH RESPECT TO ETA/NGM MODELS. .MKX...WNTR WX ADV TDA WIZ046-047-051-052-056>060-062>072 /..0../..0 $$ ZAJDEL wi