Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/10/20
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1015 PM EDT Sat May 9 2020
.SYNOPSIS...
Strong high pressure will maintain below-normal temperatures across
the region through the weekend as the cold Canadian airmass may cause
early morning frost and freeze conditions. A reinforcing dry cold
front will keep temperatures below-normal to begin the work week,
however temperatures will warm quickly during the remainder of the
week as strong and dry high pressure develops over the Atlantic.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 1000 PM EDT Saturday: No changes to the Freeze Warning or
Frost Advisory with this update. Temps are starting fall quickly as
expected with winds decoupling under clear skies. A patch of some
thicker cirrus can be seen across central KY/TN approaching NC. The
GFS 500 mb RH lines up with this feature and shows it crossing the
NC mountains overnight. But otherwise, skies should remain clear
save for some thin cirrus. With all that said, I think the min temps
look good.
A short wave ridge will dampen and move overhead overnight, pushing
the center of sfc high pressure across the region around daybreak
Sunday. The result will be light/variable wind and mostly clear
sky...for most of the night. Temps are expected to drop off well
below normal again. Charlotte and Asheville will flirt with record
lows (see Climate section below), but the record low at GSP, which
incidentally is the date of latest freeze, looks like it is out of
reach. Most of the mtns look like they will drop below freezing, as
do many places out across the I-40 corridor east of the mtns, so the
Freeze Warning will remain intact. However, it will not be expanded.
Our low temp forecast is already at the lower bound of the guidance,
and there is some indication that a thicker patch of cirrus may pass
overhead for a few hours before dawn, which would temporarily put a
halt to lowering temperatures. Even with that possibility, however,
still think areas outside the Freeze Warning have an excellent
opportunity to see areas/widespread frost, so all but the Lakelands
will be kept in the Frost Advisory.
Sunday should be another unseasonably cool day, but five degrees
warmer than Saturday, as high pressure moves off to the east. Think
any significant clouds or chances for precip will remain to the
west through sunset as a reinforcing cold front approaches late
in the day.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 225 PM EDT Saturday: the short-term fcst picks up at 00z
on Monday with broad upper trofing amplifying again over the
Eastern CONUS as steep upper ridging remains over the west. The
upper trof axis is expected to translate over the fcst area
Monday aftn and then lift off the Atlantic Coast by early Tues.
In its wake, heights recover and flat upper ridging builds
over the area for the rest of the period. At the surface, low
pressure will move across the Southern Great Lakes and push a
relatively dry cold front thru the CWFA early Monday. The front
is expected to be moving offshore by Monday evening as another
round of cool, Canadian high pressure spreads over the region.
On Tues, the high will steadily drift SE and is expected to be
centered over the SE Coast by the end of the period late Tues.
This will allow low-lvl flow to eventually become SLY to SWLY
as deeper moisture begins to spread over the fcst area from
the west. The period is expected to be mostly dry save for some
light showers possible over the northern NC mtns as the above
mentioned front moves thru the area early Monday. Patchy frost
cannot be ruled out in the mountains early Monday, however
post-frontal winds should help limit the extent to sheltered
valley locations. With lighter winds and well-below normal temps,
Tues morning looks more favorable for frost development across
the higher terrain and possibly into the Foothills. There also
could be some fire wx concerns on Monday aftn/evening as RH
values are fcst to fall below 30% over the lower terrain and
winds will be gusty. A Fire Danger Statement could be needed.
Otherwise, temps will remain well-below normal thru the period.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 215 PM EDT Saturday: the extended fcst picks up at 00z on
Wednesday with heights gradually rising across the region as the
very broad upper trof moves off the New England Coast. Broad upper
ridging spreads over the region on Wednesday and persists thru day
7. At the surface, high pressure will be centered over the Southeast
early Wednesday and will steadily drift offshore thru the day. This
will put the fcst area back under warming SLY low-lvl flow with
deeper moisture also increasing from the west. The Southeast will
remain under warm, southerly flow for the rest of the period as
sub-tropical high pressure remains in place over Bermuda. The
resultant SLY and SELY low-level flow will advect enough Atlantic
moisture into the region to result in isolated diurnal shower
development each afternoon across the mountains for Wed and Thurs.
PoPs increase to solid chance over the mtns and slight chance
elsewhere for Fri and Sat aftn/evening. Most of the guidance has
little in the way of instability outside of the higher terrain,
thus thunder appears unlikely outside of the higher terrain.
Otherwise, temperatures will warm thru the period starting out
below normal on Wednesday, and warming to above normal by Friday.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
At KCLT and Elsewhere: VFR at all TAF sites through the 00Z
TAF period, as the center of sfc high pressure builds in. Winds will
become light, and generally just a few wisps of cirrus will stream
by from time to time. There are some hints that VFR-level stratocu
may develop around daybreak across KCLT and the Upstate sites,
possibly producing some cigs around 4-5 kft. But only some of the
guidance has this. So confidence is still low. Will go with few045-
050 for Sunday morning. Also, there will likely be frost concerns on
aircraft late tonight, as temps fall into the 30s. Otherwise, winds
will pick up out of the SW by midday, with some low-end gusts for
the aftn hours.
Outlook: A brief MVFR ceiling is possible over the mtns Sunday night
and Monday morning as another cold front moves through, otherwise
VFR conditions will prevail through Thursday.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% High 100% High 100% High 100%
KHKY High 100% High 100% High 100% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 100% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:
www.weather.gov/gsp/aviation
&&
.CLIMATE...
RECORDS FOR 05-09
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 90 1889 48 1908 65 1979 34 1984
KCLT 94 1889 60 1923 69 1916 39 1984
1906
1893
KGSP 96 1916 58 1989 70 2003 35 1917
1985 1979
1917
RECORDS FOR 05-10
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 89 1936 53 1924 65 1927 32 1966
1896 1906
KCLT 94 1896 59 1966 70 1927 38 1906
1889
KGSP 96 1889 56 1924 71 1895 32 1906
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Frost Advisory until 10 AM EDT Sunday for GAZ010-017-018.
NC...Freeze Warning until 10 AM EDT Sunday for NCZ033-035>037-
048>053-056>059-062>065-501>506.
Frost Advisory until 10 AM EDT Sunday for NCZ068>072-082-
507>510.
SC...Frost Advisory until 10 AM EDT Sunday for SCZ001>010-012>014.
&&
$$
SYNOPSIS...JPT
NEAR TERM...ARK/PM
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...ARK
CLIMATE...GSP
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
900 PM PDT Sat May 9 2020
.SYNOPSIS...09/744 PM.
A cooling trend will continue through Tuesday, with expanding
clouds over coastal and valley sections and gusty southwest winds
over the interior. A weak front will pass through Monday night
into Tuesday bringing a chance of light showers mainly north of
Santa Barbara. Warming will follow Wednesday through the end of
the week, with gusty northerly winds.
&&
.SHORT TERM (SAT-TUE)...09/900 PM.
Upstream upper level trough developing off the California coast
tonight and will become predominant weather feature over our area
during the next few days. Onshore flow continues to increase, with
LAX-Daggett gradient peaking at +6.1 mb this evening. As a result,
the marine layer depth continues to increase. Current ACARS
sounding showing the marine layer depth around 1500 feet across
the LA Basin, but is expected to deepen to around 2000 feet by
Sunday morning.
The increased onshore flow has brought the typical ramp-up of
onshore winds across the mountains and deserts this afternoon and
evening, with the highest wind gust of 44 mph being reported at
Lake Palmdale as of 8 pm. Current satellite imagery showing low
clouds and fog rapidly spreading into coastal areas this evening,
and is expected to overspread most valley areas overnight into
Sunday morning. In evening update, also adding some patchy drizzle
late tonight into Sunday morning for coastal/valley areas south of
Pt. Conceptino.The most likely area for patchy drizzle would be
the San Gabriel Valley and adjacent foothills.
Cooling trend underway today, with warmest valleys only reaching
the upper 80s. Most coastal/valley areas should see another 3 to 7
degrees of cooling on Sunday, with low clouds likely lingering
near some of the immediate coastal areas into the afternoon hours.
Also of note, will be strengthening onshore flow pattern on
Sunday, with the LAX-Daggett gradient expected to peak around +8
mb by late afternoon. This will likely result in widespread wind
gusts of 30 to 40 mph across the mountains and Antelope Valley,
with local gusts as high as 50 mph near Lake Palmdale. Winds could
approach advisory levels by Monday across the Antelope Valley.
*** From previous discussion ***
Marine layer clouds will continue to affect the coast and vlys
Mon night into Tue morning, altho additional cloudiness
associated with the cold front will move in as well, especially
over SLO/SBA Counties into nrn VTU County. This front is also
expected to bring a slight chance to chance of light rain mainly
to SLO/SBA Counties Mon night into Tue morning, with any
measurable rain expected to be less the 0.10 inch. Skies should
then become partly cloudy for many areas Tue afternoon.
Temps on Sun are expected to cool more significantly back to near
seasonal norms for most areas with the warmest vlys and lower mtns
reaching the upper 70s to low 80s. However, the Antelope Vly will
continue to be several degrees above normal on Sun with highs in the
mid 80s to around 90. Temps on Mon will be near normal to slightly
cooler than normal in all areas with the warmest vlys and lower
mtns reaching the mid 70s, except mid 70s to around 80 in the
Antelope Vly. Tue will be the coolest day next week with temps a
few degrees below normal for most areas. Highs for the inland
coastal areas and vlys should only be in the mid 60s to around
70.
.LONG TERM (WED-SAT)...09/152 PM.
The EC and GFS are in generally good agreement thru the extended
period. A broad zonal flow aloft will be over srn CA on Wed, then
flat upper level ridging can be expected for the most part Thu
thru Fri, with slightly stronger upper ridging expected Sat.
Varying amounts of night and morning marine layer clouds will
affect the coast and vlys Wed into Thu. It looks like marine layer
clouds should affect the coast and vlys S of Point Conception Thu
night into Fri morning as northerly flow develops over SLO/SBA
Counties. Offshore northerly flow should increase over all of swrn
CA later Fri thru Sat, keeping any low clouds away from the area.
Otherwise, mostly clear skies with some hi level clouds at times
can be expected thru the period.
Temps are forecast to be near normal to slightly below normal for
many areas Wed, then warm back to near normal by Fri and to a few
degrees above normal for Sat. Highs in the warmest vlys and lower
mtns should be in the lower 70s on Wed, mid 70s to around 80 on
Thu, upper 70s to lower 80s on Fri, and low to mid 80s on Sat.
&&
.AVIATION...09/2341Z.
At 2330Z at KLAX, the marine layer was 1500 feet deep. The top of
the inversion was around 2500 feet at a temperature of 20 C.
Overall, low to moderate confidence in all TAFs except high
confidence for KPMD/KWJF. Low clouds will push into all the
coastal and valley terminals this evening, but low confidence in
timing which could occur +/- 2 hours of forecast. For sites north
of Point Conception, moderate confidence in IFR/LIFR conditions
tonight. There is a 40% chance of VLIFR cigs/vis after midnight.
For sites south of Point Conception, expecting mostly IFR and low
end MVFR cigs, with a 40 percent chance of LIFR cigs at KSBA
overnight. Deepening of marine layer expected to bring slower
clearing to most coastal/valley TAF sites on Sunday.
KLAX...Moderate confidence in TAF. IFR/MVFR cigs expected to
return this evening, with timing +/- 2 hours of forecast
arrival of 04z. Slower clearing expected on Sunday, with a 20
percent chance of MVFR cigs lingering through the afternoon
hours.
KBUR...Moderate confidence in TAF. IFR/MVFR cigs expected to
return overnight, with timing +/- 2 hours of forecast arrival of
04z. Slower clearing expected on Sunday,
&&
.MARINE...09/809 PM.
Overall, moderate to high confidence in forecast. Winds and seas
are expected to remain below Small Craft Advisory (SCA) criteria
through Tuesday morning across all the waters. There is a 30%
chance of SCA level winds on Tuesday night across the waters from
Point Conception to San Nicolas Island. The chance will increase
slightly on Wednesday and Thursday and will also include the
waters along the Central Coast.
Areas of fog will likely remain over the coastal waters through
Sunday, especially north of Point Mugu.
An elevated long-period south swell of 3 to 4 feet will likely
impact the waters through late next week.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect through Monday afternoon
for zones 40-41-87. (See LAXCFWLOX).
PZ...NONE.
&&
.HAZARD POTENTIAL OUTLOOK (TUE-SAT).
Gusty southwest winds are expected in the Antelope Valley and
surrounding foothills Tuesday through Wednesday. Gusty northwest
winds are possible along the Central Coast Wednesday. Gusty north
winds can be expected for many areas Friday into Saturday.
&&
$$
PUBLIC...Gomberg/Sirard
AVIATION...Gomberg
MARINE...Gomberg/Stewart
SYNOPSIS...Kittell
weather.gov/losangeles
Area Forecast Discussion
National Weather Service Blacksburg VA
940 PM EDT Sat May 9 2020
.SYNOPSIS...
High pressure will build over our region tonight. Our active
weather pattern looks to keep conditions unsettled across the
area, especially in the mountains, through the middle of next
week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 930 PM EDT Saturday...
Again, no big changes to our current forecast. Skies have
cleared across the region, and winds are continuing to trend
lighter. Some high level cloud cover will stream into the
region from west to east after midnight, but these are not
expected to prevent temperatures from falling into the 25 to 30
degree range for lows across the mountains and lower 30s across
the Piedmont. Our Freeze Warning is still in effect starting at
midnight, and continuing through 1000 AM Sunday.
As of 645 PM EDT Saturday...
Current forecast is on track and very little in the way of
changes is needed currently. The diurnal cumulus clouds across
the mountains are quickly eroding on cue as the sun lowers in
the sky. We are not even needing sunset today for cloud erosion.
Clear skies, and winds becoming light and variable are expected
this evening, with temperatures starting a nose dive as dew
point depressions are around 30 degrees for most locations. Have
made minor adjustments to hourly temperature, dew point, and sky
cover to better reflect the latest observations and expected
trends through the early evening.
As of 205 PM EDT Saturday...
High pressure will build overhead tonight. This will result in
a good radiational cooling with light winds and clear skies. Low
temperatures tonight will vary from the mid to upper 20s in the
mountains to the lower 30s in the foothills and piedmont. Since
temperatures will again fall below freezing tonight, another
Freeze Warning will be in effect into Sunday morning.
Cold high pressure will move off the Carolina coast Sunday.
Meanwhile, a low pressure system over the Great Lakes will drift
southeast over the upper Mississippi Valley. By late afternoon,
this low will push a cold front across the Ohio and Tennesse
Valleys. A few isolated showers/sprinkles are possible along
western slopes of southeastern West Virginia by the evening.
Given that we are in between systems, south to southwest flow
will help the area warm into the 60s Sunday, mid 50s across
higher elevations. These temperatures are still cooler than
normal by 10F.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 200 PM EDT Saturday...
There is good agreement in the deterministic medium-range
models that the leading edge of a reinforcing surge of below
normal temperatures in the form of a cold front arrive Sunday
night. With limited moisture, precip amounts will be the light
with this event, but lingering upslope flow will bring rain and
even some snow showers to western Greenbrier county well into
Monday. Any snow accumulations will be light.
In the wake of this front on Monday, a deep west/northwest flow
and good mixing will result in wind gusts approaching 40 MPH in
the higher elevations on Monday, and pushed up wind gusts for
this portion of the forecast. Good downsloping will allow
temperatures to recover east of the Blue Ridge, but below normal
values persist in the mountains.
In this progressive pattern, the upper level trof responsible
for this system quickly shifts east and low level ridging noses
into the western portion of our forecast area by Tuesday
morning. Went a few degrees below guidance for lows and added
some patchy frost for the mountain valleys.
As our upper level flow becomes zonal on Tuesday, temperatures
should climb from Monday`s forecast highs, despite an increase
in mid and high level clouds. Low level moisture remains limited
per forecast soundings, so kept dry conditions in place on
Tuesday.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 200 PM EDT Saturday...
Confidence continues to increase that the upper level flow
transitions from zonal to ridging in the southeast U.S. which
likely will bring much warmer temperatures more typical for May.
There is a considerable spread in the ensemble members about
the magnitude of warmth late next week. For now, just a blend of
models for temperatures during this period which conveys the
message of warming temperatures.
The 12Z GFS is more bullish on precip chances Wednesday and
Thursday and will need to monitor the potential influence of an
upper level low undercutting the upper level ridge an
approaching the southeast U.S. for late in the week and into
next week as advertised by the 12Z GFS and 12Z Canadian models.
With individual ensemble members showing a huge spread in
solutions, continued to keep scattered POPS for late in the week
due to increased moisture and instability. Best focus for
organized convection appears to be north of our area during this
time.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
As of 715 PM EDT Saturday...
VFR conditions are expected through the duration of the valid
TAF forecast period, 00Z Monday/8PM Sunday.
Gusty northwest winds will quickly subside to light and
variable after sunset. Winds will remain calm or light and
variable through mid-day Sunday. After this time, a southwest
wind of 5 to 10 kts is expected at most locations.
Near- or sub-freezing temperatures will allow for a layer of
frost to form on most aircraft parked outside late tonight into
Sunday morning.
Confidence in the above aviation scenario is high.
Extended Aviation Discussion...
Scattered MVFR showers with more gusty winds may be possible
late Sunday into Monday, especially the mountains. After a brief
return to VFR conditions for Tuesday, expect a good probability
of sub-VFR conditions as our weather pattern remains unsettled
through the middle of next week.
&&
.CLIMATE...
As of 1010 AM EDT Saturday...
May 9 - Record cool Highs:
Bluefield WV...46 in 1992
Danville VA....57 in 1978
Lynchburg VA...47 in 1923
Roanoke VA.....53 in 1989
Blacksburg VA..51 in 1960
May 10 - Record Lows:
Bluefield WV...24 in 1966
Danville VA....35 in 2010
Lynchburg VA...33 in 1983
Roanoke VA.....33 in 1983
Blacksburg VA..26 in 1966
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Freeze Warning until 10 AM EDT Sunday for VAZ007-009>020-
022>024-032>035-043>047-058-059.
NC...Freeze Warning until 10 AM EDT Sunday for NCZ001>006-018>020.
WV...Freeze Warning until 10 AM EDT Sunday for WVZ042>044-507-508.
&&
$$
SYNOPSIS...RCS
NEAR TERM...DS/RCS
SHORT TERM...PH
LONG TERM...PH
AVIATION...DS/RCS
CLIMATE...AMS