Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/15/19

Area Forecast Discussion

National Weather Service Hastings NE

 648 PM CDT Sun Apr 14 2019

.SHORT TERM...(This evening through Monday)
Issued at 348 PM CDT Sun Apr 14 2019

Aloft: Aircraft winds/WV imagery/RAP dynamic tropopause analyses
indicated low-amplitude flow over the Plns/Wrn USA...behind a
fairly deep trof over the MS Vly. A wk shrtwv trof extended from
MT-CO. This trof will cross the CWA tonight. Nearly zonal flow
will remain over the Plns thru tomorrow. Heights will begin to
modestly rise though as a potent shrtwv trof reaches the Pac NW
coast by 00Z/Tue.

Surface: Weak high pres was over ON with an axis that extended
just E of the CWA to TX. Low pres was over SA with a wk cool front
extending SW acrs the NW USA. This system has resulted in
development of a warm front from Wrn NEB to W TX. As the SA low
conts E tonight...the warm front will lift NE acrs the CWA while
the cool front approaches from the NW. The wk cool front will
stall from SW-NE acrs the CWA tomorrow as a lee low organizes over
CO.

Tonight: Mostly cldy. Lift associated with the trof mvg thru will
generate a lot of clds and some brief passing light shwrs or
sprinkles N of Hwy 6. Not nearly as chilly as this AM. Lows will
be 9-15F higher.

Mon: Partly-mostly sunny as the mtns should generate some patchy
cirrostratus. Much warmer. About 15F warmer than today. There is
some temp uncertainty N of Hwy 92. The 06Z/12Z NAM...06Z/12Z CMC
rgnl and 12Z WRF-ARW still maintain highs in the 50s behind the
cool front that slips in. It seems like a stretch without some low
stratus to suppress temps that much. Discounted it for now...but
keep in mind this is a possibility.

.LONG TERM...(Monday night through Sunday)
Issued at 348 PM CDT Sun Apr 14 2019

Aloft: The flow will reamplify Tue as the Pac NW trof moves
onshore and deepens over the Wrn USA. Winds will back to SW here.
A low is fcst to form in the trof base over the Desert SW Tue
night...and this trof/low will emerge onto the Cntrl/Srn Plns Wed
into Wed night. This trof will move E of the rgn Thu with highly
amplified NNW flow. There still remains uncertainty on whether the
low opens up into a trof and remains a trof...or a low reforms
and crosses NEB/KS Wed night. The 00Z EC ens mean has enough
members in agreement that it does have a closed 546 dm low over IA
00Z/Fri. Heights will rise here Fri as the trof moves into the
Ern USA...but the flow will remain from the NNW. The flow will
deamplify next wknd. Mdls are tightly-clustered on a low-amplitude
shrtwv rdg arriving Sat...but sig uncertainty develops Sun as the
mdls struggle with falling heights over the W...and where one or
more shrtwv trofs might be.

Surface: The wk cool front that should bisect the CWA Mon night
is fcst to sink into Nrn KS as the lee low ejects into Nrn KS.
That low will dissipate Tue as another low forms over CO.
Meanwhile...the front will remain stalled near the NEB-KS border.
As the upr trof moves in...the CO low will become mobile Tue
night. By 12Z/Wed the mdls are clustered on the low being near PHG
while the front rotates cyclonically...with the warm front
lifting into Cntrl/Ern NEB...and the cool front surging S into Wrn
KS. The low is fcst to move into Wed with the CWA into the cold
sector. Svrl mdls and the EC ens mean suggest another low will be
over OK. It lifts NE and combines with the IA low Wed night
creating a deeper low near 990 mb. Thu the CWA will remain the
cold sector. Weak high pres will drift thru Fri followed by return
flow Sat as it departs. A wk cold frontal passage could occur Sat
night or Sun.

Temps: Tue temps uncertainty is abv normal. We are probably too
warm by svrl degs...espcly N of I-80 where low stratus will
probably move in and suppress temp curve N of the front. Best
chance for 70s will be S of Hwy 6. Uncertainty Wed as well as the
fronts bisect the CWA...warmest SE of the Tri-Cities...coolest to
the NW. Thu a little cooler than normal. Fri near normal. Sat-
Sun probably back to abv normal.

Precip: Isolated tstms psbl Tue night as a 50 kt low-lvl jet
results mstr advection/WAA and development of instability. MUCAPE
of 1500-2000 J/kg. A shrtwv trof will be mvg thru. An inhibiting
factor will be shear. As 1 km wind veer to SW the winds will
become unidirectional above the frontal inversion which will
decrease shear to less than 20 kts. There still could be some
tstms on the cool side of the front Wed as the Nrn portion of the
Wrn upr trof approaches...but SREF MUCAPE is fcst to dcrs to 1000
J/kg or less. The mdl consensus has the front just S and E of the
CWA Wed afternoon suggesting the risk for svr tstms late Wed
aftn/eve will miss the CWA. This is still 3 days away...and the
mdls hv been struggling with coming to a consensus with this sys.
If it slows down even a little...that will open the door for svr
wx potential over the SE 1/3 Wed aftn/eve.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday)
Issued at 643 PM CDT Sun Apr 14 2019

VFR ceilings and visibility will continue throughout the TAF valid
period. The primary thing to watch out for will be some strong low
level wind shear this evening between 9 PM and 4 AM. Can not rule
out a sprinkle this evening, but its too low of a probability to
include mention of it in the TAF.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&

$$

SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Wesely



Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 759 PM PDT Sun Apr 14 2019

.SYNOPSIS...14/615 PM.

Afternoon temperatures will be even cooler tomorrow and well
below normal on Tuesday. Coastal areas will have overnight and
morning low clouds and fog and there is a chance of light rain
across the region tomorrow night and Tuesday. Dry and much warmer
conditions return Wednesday and continue into next weekend.

&&

.SHORT TERM (SUN-WED)...14/758 PM.

Current satellite imagery showing a mixture of higher level
clouds and lower clouds near the coast. Weak upper level trough of
low pressure over region combined with strengthening onshore flow
has resulted in a cooling trend today across many areas,
especially near the coast. LAX-Daggett gradient has peaked at +6.7
mb onshore which is up considerably from yesterday. As a result,
there have been increasing onshore winds in the mountains and
deserts this afternoon and evening, with Lake Palmdale in the
foothills of the Antelope Valley reaching a peak gust of 47 mph.

The marine layer clouds are expected to reach some of the valleys
overnight with slower clearing time on Monday as upper trough
deepens and onshore flow strengthens. LAX ACARS data showing
marine layer fairly shallow this evening around 800 feet, but is
expected to deepen to at least 1500 feet by Monday morning due to
increasing onshore flow and a weak eddy circulation. The low
clouds will likely linger across some of the immediate coastal
areas on Monday afternoon. Cooling trend will continue as well on
Monday. Look for increasing onshore winds in the mountains and
Antelope Valley on Monday afternoon, with gusts in the 35 to 45
mph range, except isolated gusts over 50 mph in the foothills of
the Antelope Valley.

*** From previous discussion ***

A sharper upper level trof will push into central and nrn CA from
the E Pac Mon evening then quickly slide SE thru srn CA late Mon
night thru Tue. The upper level trof will move E of the area Tue
night while an upper level ridge builds along and just off the
coast thru Wed. By Wed afternoon, 500 mb heights should rebound to
around 580 dm over swrn CA.

A cold front associated with the aforementioned upper level trof
will move into the Central Coast Mon night then across VTU/L.A.
Counties while dissipating thru Tue morning. This system should have
enough over-water trajectory to pick up some moisture and bring a
chance of showers to SLO/SBA Counties Mon evening then spread into
L.A./VTU Counties later Mon night into Tue morning. A few showers
should then linger mainly on the N slopes Tue afternoon. Some
snow showers will also be possible above about 6500 ft on Tue as
colder air moves in with the upper trof.

Precip amounts will be highly variable due to the showery nature
of this system and rainfall should be light. Generally less than
0.10 inch is expected, except locally higher amounts are possible
across north facing mountain slopes.

Skies will become mostly cloudy Mon night as the front moves in.
Mostly cloudy conditions Tue morning should give way to some
clearing S of the mtns Tue afternoon as increasingly northerly flow
sets up behind the front. Much of the mtns and some of the vlys
of L.A. County should remain mostly cloudy with those lingering
chances of showers thru Tue afternoon.

Gusty NW to N winds will affect the SBA/VTU/L.A. County mtns Tue
afternoon and evening, with gusty NW winds expected along the
Central Coast, and gusty W winds into the Antelope Vly. Many of
these areas will likely need a Wind Advisory for Tue afternoon
into the evening.

Skies will become mostly clear in all areas Tue night as a drier
air mass moves in with a bit of offshore flow. Sunny skies will
prevail in all areas on Wed with offshore breezes weakening and
turning onshore in the afternoon.

Temps will turn much cooler on Tue and should be about 5-10 deg
below normal for many areas. Highs for the coast and vlys should
top out in the 60s. Temps will turn warmer again on Wed with highs
near to slightly above normal. The warmest vlys and inland coastal
areas are expected to reach the mid 70s to around 80 by Wed
afternoon.

.LONG TERM (THU-SUN)...14/206 PM.

The upper level ridge will persist over srn CA along with some
offshore flow night and morning hours thru Thu. It looks like an
upper level low well SW of the area will approach the region Thu
night and Fri before moving inland over srn CA Fri night. An upper
level trof should then approach the area from the NW Sat then
move slowly across the region Sat night and Sun along with a
dissipating cold front. Onshore flow is expected to increase next
weekend

These systems will have a limited amount of moisture associated
with them, and dry weather is forecast thru Sun. However, there is
a small chance (less than 15%) a few showers may affect swrn CA
at times Fri night thru Sun especially over northern parts of the
area. The extended models do indicate this possibility but the
timing is off between models and day to day consistency is
suspect. So for now will keep pcpn out of the fcst thru this time
period pending additional model runs. These systems will likely
bring some cloudiness to the area at times.

Temps are expected to be well above normal on Thu, as much as 5-10
deg warmer than seasonal norms. High Thu should reach well into
the 80s in the warmest vlys. Temps will remain above normal Fri
with the warmest vlys and inland coastal areas reaching the low
to mid 80s. A cooling trend should develop next weekend with the
warmest vlys and inland coastal areas reaching only into the
lower 70s by Sun.

&&

.AVIATION...14/2314Z.

At 2320Z, the marine later was around 800 ft deep at KLAX. The
top of the inversion was around 1700 ft with a temp of 17C.

The marine clouds continue to linger across portions of the
immediate coast late this afternoon. The marine clouds will then
move into the coastal TAFS this evening and into the valleys
after midnight. Expect MVFR to IFR conditions in coastal and
valley sections.

KLAX...High confidence in IFR/MVFR cigs tonight into Monday
morning, however there is a 30 percent chance of marine clouds
arriving plus or minus two or more hours from the forecasted time.
There is a 30 percent chance of east to southeast winds of 8
knots or more.

KBUR...Moderate confidence in IFR/MVFR cigs developing late
tonight or early Monday morning, however there is a 30 percent
chance of marine clouds arriving plus or minus two or more hours
from the forecasted time.

&&

.MARINE...14/759 PM.

For the Outer Waters, moderate confidence in the forecast. Winds
and seas are expected to reach Small Craft Advisory (SCA) levels
across the northern two outer waters zones (PZZ670 and PZZ673)
this evening thru late tonight, then SCA conds are likely again
Monday afternoon thru Wednesday, possibly continuing into Thursday.

There is a 30% chance that winds will reach SCA levels across the
southern outer waters zone (PZZ676) this evening, and again Monday
afternoon and evening. SCA conds are then likely Tuesday through
Wednesday, possibly continuing into Thursday.

For the Inner Waters north of Pt Sal, there is a 30% chance of
SCA level winds during the afternoon/evening hours on Monday,
then SCA level winds are likely Tuesday afternoon thru Wednesday
evening.

For the Inner Waters south of Pt Conception, winds and seas
should remain below SCA levels thru Monday. There is a 30% chance
of SCA level winds Monday afternoon and evening across the
western portions of the SBA Channel. SCA level winds are likely
Tuesday afternoon/evening across at least western portions of the
inner waters south of Pt Conception, then are not expected
Wednesday thru Thursday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Monday for
      zones 670-673. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (WED-SUN).

No significant hazards expected.

&&

$$

PUBLIC...Gomberg/Sirard
AVIATION...Gomberg/Sweet
MARINE...Sweet/RAT
SYNOPSIS...Kj

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