Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/30/23

Area Forecast Discussion...UPDATED

National Weather Service Los Angeles/Oxnard CA

 521 PM PST Sun Jan 29 2023

updated aviation discussion

.SYNOPSIS...29/119 PM.

A cold winter storm will bring showers through Monday with very
low snow levels and accumulating snow on many highways through the
mountains and into the Antelope Valley. Temperatures will remain
in the 40s and 50s during the daytime and be cold with areas of
frost by Tuesday morning. Gusty northeast winds may affect
portions of Los Angeles and Ventura Counties Monday night into
Tuesday. High pressure will build later in the week, however,
there will be risk of light rain on the Central Coast on Friday.

&&

.SHORT TERM (TDY-WED)...29/104 PM.

Morning soundings and aircraft profiles showed a moist layer
rapidly increasing above 6500 feet across the region, with light
rain and drizzle falling in many areas today. Rainfall amounts so
far range from trace amounts to about 0.25 inch in the Santa
Lucia Range. Cyclonic flow was approaching the Central Coast this
afternoon with rain expected to increase through this evening.
Skies have remained mostly sunny on the northern mountain slopes
and Antelope Valley due to downsloping winds gusting at 35-45 mph.
Wind advisory for the AV will remain in place through 7pm this
evening. Other areas have remained cool and cloudy with light
precipitation at times.

12Z HREF data shows an uptick in precipitation along the Central
Coast early this evening as an upper low drops southward from
Monterey Bay. The trajectory of the low remains very similar to
previous model runs, moving just west of Pt Conception by sunrise
Monday. The main weather concern is how low will snow levels drop
when precipitation increases toward sunrise on Monday. Right now
is appears that Palmdale is likely to see precipitation increase
after 10Z (2 am PST) when the downslope winds drop off and switch
to colder northeast flow. Cold advection will continue to
increase as the upper low drops farther southward off the
southwest CA coast Monday. Latest NAM guidance indicates 850mb
temperatures below zero with surface temps around 34 degrees early
in the day and then only reaching about 40 degrees for the
afternoon high in Palmdale. The NAM and RDPS soundings reflect
snow and the potential for at least 1-2 inches between 2500-3000
feet Monday morning really playing havoc on morning driving
conditions along Highway 14 and the 138 from Pearblossom to
Palmdale. Precipitation may mix with or turn back to rain in the
AV late Monday morning, but precip is likely to persist into
Monday evening. The eastern San Gabriel Mountains remain favorable
to receive the highest amounts of snow, nearly 14 inches in a
24-hour period due to 15:1 snow ratios. This still warrants a
winter weather advisory as the highest totals will be isolated to
the higher elevations above 7000 feet. Precipitation will rapidly
decrease Monday night as the low weakens over northern Baja.
Offshore pressure gradients will increase to nearly
-6 mb from LAX-DAG by Tuesday morning, so expect locally breezy
E-NE winds in the typical areas. This does make for a tricky low
temperature forecast as most areas will radiate quickly and many
wind-sheltered locations will drop into the 30s with potential for
frost or freeze conditions. Readings in the AV could drop to the
upper teens and lower 20s depending on winds and cloud cover.

Wednesday is looking like a better day after another frosty start with
high pressure building along the West Coast and slight warming
across the entire region. Weak offshore flow will assist in the
warming as that will continue through much of the day.

.LONG TERM (THU-SUN)...29/1252 PM.

Confidence in the forecast goes downward for later in the week.
High pressure looks like it will be short-lived with the ridge
axis shifting to the east on Thursday. Model data, including the
NBM are already bringing in a shield of high clouds beginning on
Thursday. Then deterministic and ensemble mean ECM solutions do
have a trough approaching the West Coast on Friday, the GFS is
weakest. The ECM seems the most energetic with increasing chances
of rain on the Central Coast and eventually just about anywhere
in our region Friday afternoon/night. This is followed by a
stronger low pressure system late Sunday through Monday. All
medium guidance seems on-track for the second system late next
weekend, but diverge on the details with the first system on
Friday. That one does appear much weaker and precipitation may be
limited to the Central Coast, while the second system could be
generate more widespread precipitation. At this point, neither
system looks very strong with any Atmospheric River connection
remaining to our north. We have increased cloud cover and a
chance of rain on Friday so it appears the warming trend this week
will be cut-off and we`ll be back to a cool pattern late next week
and into the weekend.

&&

.AVIATION...30/0120Z.

At 0049Z at KLAX, there was a deep moist layer nearing 8000 ft
deep.

Low confidence in TAF. package. An area of low pressure will bring
scattered low clouds and showers through much of the period. There
will likely be frequent changes in cigs and vis with low
confidence in timing of changes. Conditions will likely be MVFR
with IFR conditions possible, especially with showers.

KLAX...Low confidence in TAF. There is a 50% chance of MVFR CIGs
or VSBYs developing and a 30 percent chance of IFR CIGs or VSBYs.
There is a 30 percent chance of east winds of 10 knots or more.

KBUR...Low confidence in TAF. There is a 50% chance of MVFR CIGs
or VSBYs developing and a 30 percent chance of IFR CIGs or VSBYs.

&&

.MARINE...29/100 PM.

No changes to the marine forecast in the afternoon issuance.

For the Outer Waters, moderate confidence in current forecast.
Through this evening, moderate confidence in Small Craft Advisory
(SCA) level winds. For tonight and Monday, high confidence in
winds and seas remaining below SCA levels. For Monday night and
Tuesday, there is a 40% chance of SCA level northeast winds
across PZZ676. For Wednesday and Thursday, high confidence in
winds and seas remaining below SCA levels for all the Outer
Waters.

For the Inner Waters north of Point Sal, high confidence in
current forecast. There is a 20% chance of SCA level winds late
this afternoon and evening. Otherwise, high confidence in winds
and seas remaining below SCA levels through Thursday.

For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Today through Monday, high
confidence in winds and seas remaining below SCA levels. For
Monday night and Tuesday, there is a 50% chance of SCA level
northeast winds from Ventura south to Santa Monica. For Wednesday
and Thursday, high confidence in winds and seas remaining below
SCA levels.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Weather Advisory in effect until 3 PM PST Monday for
      zones 53-353. (See LAXWSWLOX).
     Winter Weather Advisory in effect until 10 PM PST Monday for
      zone 54. (See LAXWSWLOX).
     Wind Advisory in effect until 7 PM PST this evening for zone
      59. (See LAXNPWLOX).
     Winter Weather Advisory in effect from 10 PM this evening to
      10 PM PST Monday for zone 59. (See LAXWSWLOX).
PZ...Small Craft Advisory in effect until 9 PM PST this evening
      for zones 670-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...EB
AVIATION...Stewart
MARINE...Sweet/RAT
SYNOPSIS...EB

weather.gov/losangeles

Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox



Area Forecast Discussion

National Weather Service Lubbock TX

 547 PM CST Sun Jan 29 2023

...New AVIATION...

.SHORT TERM...
(This evening through Monday)
Issued at 222 PM CST Sun Jan 29 2023

Stratus has been slow to dissipate early this afternoon but thinning
is becoming evident as of 1 pm. Expect this thinning/dissipating
trend to pick up this afternoon with at least partly sunny skies
area wide late this afternoon. A reinforcing cold front will drop
into the forecast area tonight bringing another round of cold air
advection to the forecast area. This will allow temperatures to drop
into the teens and lower 20s area wide by Monday morning. As this
happens isentropic ascent will increase over the forecast area
leading to the redevelopment of widespread low stratus. However,
lift within the saturated lower atmosphere should be sufficient for
some light precipitation development across the southern South
Plains into the Rolling Plains and southeastern Texas Panhandle
mainly in the form of freezing drizzle. The depth of cold air keeps
precipitation type in question as some of the colder spots may be
able to switch over to sleet rather than freezing drizzle. However,
where freezing drizzle occurs surface temperatures will be conducive
to accumulation and therefore a light glaze may develop on
sidewalks, roadways, and elevated surfaces Monday morning. Due to
this potential, have issued a Winter Weather Advisory from 5 am
until noon to account for potentially hazardous road conditions.
This advisory may need to be expanded farther west if newer guidance
shows better lift within this region tonight. The other big question
will be surface dewpoint depressions but with the prolonged nature
of lift would expect this dry air to be overcome eventually. Any
precipitation will come to an end late Monday morning but sky cover
will hang around through the day. The combination of this cloud
cover and cold air advection means temperatures will once again be
chilly with most locations struggling to warm above the freezing
mark. /WI

&&

.LONG TERM...
(Monday night through next Saturday)
Issued at 222 PM CST Sun Jan 29 2023

While wintry precip continues to look decent for tomorrow night
through Thursday, there is still great uncertainty in precip mode,
timing of precip, and accumulation amounts. Initially precip will be
fairly light starting around sunrise Tuesday morning as lift will be
from isentropic upglide while a surface to 1200 ft AGL dry layer is
present. Precip mode will likely be in the form of light freezing
rain and/or sleet as a warm nose will be present. The depth of the
warm nose will ultimately determine the final mode. A lull in precip
is expected late Tuesday afternoon through late Tuesday
evening/early Wednesday morning as weak shortwave ridging moves
overhead and the best lift remains just to the south of the FA. The
upper low will begin pushing eastward from the Baja Peninsula
Tuesday evening and make its way to northern Sonora by late
Wednesday afternoon. Models continue to struggle with the evolution
of the upper low as it approaches Chihuahua/southern New Mexico. The
ECMWF keeps the low closed until around midnight Wednesday night
before evolving to an open wave trough. The GFS opens the low by 00Z
Thursday and has the system further south than the ECMWF. The
position of the low/trough will be one of the deciding factors in
precip intensity/accumulation. The further south solution would keep
upper level diffluence mostly to the south of the FA until the axis
of the upper trough approaches eastern New Mexico. The ECMWF, which
has a further north solution, would bring lift into the region much
sooner. The next issue is precip mode. Currently a full bag of mixed
treats is possible with the current setup with the more dominate
modes being freezing rain followed by sleet. As temps are expected
to remain below freezing from tomorrow night through mid/late
Wednesday morning, forecasted ice accumulations are currently
between one hundredth of an inch to one quarter inch with the highs
amounts being across the southern Rolling Plains where a Winter
Storm Watch is in effect for this area starting 12Z Tuesday. Highs
for Wednesday are currently forecasted to be in the mid/upper 30s to
near 50 and would result in a transition to liquid rain area wide.
A mix of rain/snow will be possible Wednesday night into early
Thursday afternoon as the axis of the upper trough moves overhead.

Quieter weather will ensue by late week after the upcoming storm
system pushes to our east and upper ridging takes hold over the
central CONUS. This will allow highs to warm into the 50s and
possible 60s by the weekend.

&&

.AVIATION...
(00Z TAFS)
Issued at 537 PM CST Sun Jan 29 2023

VFR conditions at PVW and LBB will lower to IFR or lower at all
terminals early this morning as freezing drizzle begins to
develop at all terminals. The terminal that will have the best
chance of accumulation of freezing drizzle will be LBB. In
addition, aircraft icing will be possible at all three sites as
well. Ceilings will begin to briefly lift by the end of the TAF
period.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 AM to noon CST Monday for
TXZ024>026-030>032-035>038-041>044.

Winter Storm Watch from Tuesday morning through Wednesday
morning for TXZ037-038-042>044.

&&

$$

SHORT TERM...58
LONG TERM....51
AVIATION...10