Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/22/19

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 805 PM PDT Sun Apr 21 2019

.SYNOPSIS...21/619 PM.

Continued cool tonight then significant warming beginning Monday
and through mid week. Afternoon temperatures will cool a bit by
the weekend but will remain above normal. Overnight and morning
coastal low clouds will be patchy through midweek then more
widespread into the weekend.

&&

.SHORT TERM (SUN-WED)...21/805 PM.

***UPDATE***

Overall, a quiet evening across the forecast area. Latest
satellite and surface observations indicate generally clear skies
across the area except for some patchy stratus along the Central
Coast. As for winds, northerly gradients are generating some gusty
northerly winds across the Santa Ynez range and through the I-5
Corridor. Wind speeds have slowly diminished and become more
localized, so will let the WIND ADVISORY end at 900 PM.
Additionally, there are some gusty westerly winds across the
Antelope Valley, generating some blowing dust and sand. However
these winds will diminish noticeably this evening and are not
expected to be much of an issue.

For tonight, main issue will be the potential for some stratus
along the coastal plain. Currently, sounding data across the
Central Coast indicates two inversion, one around 1500 feet and
another around 5200 feet while AMDAR data indicates a weak
inversion around 4200 feet south of Point Conception. The
inversion across the Central Coast is stronger and should allow
for some continued stratus and fog overnight. For areas south of
Point Conception, the weak inversion will hamper stratus
development. However, there is a chance of some stratus overnight
across the LAX coastal plain and lower coastal valleys although
confidence in development is low. Otherwise, no issues are
anticipated in the immediate short term.

Will issue a minor forecast update to remove advisory headline and
tweak sky condition a little bit. However, changes will be minor
as current forecast has a good overall handle on the situation.

***From Previous Discussion***

Afternoon visible imagery shows stratocumulus clouds lingering
over some of the valleys and foothills south of Point Conception
with clear skies further north. An upper low currently near Las
Vegas will continue to dig due southward this afternoon and
tonight, with northerly gradients increasing across the area.
Gusty northerly winds are expected in the usual locations, with
gusts to around 40 mph along the SBA South Coast - where a Wind
Advisory will be in effect from 2 PM to 9 PM - and through the
Interstate 5 Corridor. The north flow should limit the marine
layer cloud coverage somewhat even as heights aloft lower and a
weak eddy sets up over the San Pedro Channel. Expect we will see
some low clouds over the LA Coast, extending into the San Gabriel
Valley, and along the Central Coast.

As the low aloft pushes south of the area, SW Ca will be between
a ridge building over the northern half of the state and the low
to the southeast. Heights will rise some by Monday afternoon, with
daytime highs expected to bump up a few degrees compared to
today`s highs. This will be the start of a warming trend that will
persist through Wednesday, as the ridge expands over the southern
half of the state. In addition, gradients will begin to trend
offshore Monday night into Tuesday, setting up a weak Santa Ana
wind event. At this time winds over the mountains and valleys of
LA/VTA Counties look to remain near/ just below Advisory levels.

There will be enough offshore flow Monday night into Tuesday to
preclude any stratus formation, except for the southern portion
of the LA coast where a weak eddy will have enough of an effect to
bring clouds to the area. The eddy is forecast to strengthen some
Tuesday night into Wednesday, pushing low clouds further north
along the coastline. However, the Ventura County is unlikely to
see low clouds and fog, except possibly along the immediate
coastline.

As the ridge moves overhead on Wednesday, heights should rise
to 582 mb, with highs in the 70`s near the coast and 80`s inland.

.LONG TERM (THU-SUN)...21/132 PM.

The upper ridge over California will weaken on Thursday as it
begins to shift east of the area. This supports a cooling trend
that will likely persist through Sunday. An upper low over the
East Pacific is forecast to form a closed circulation and slowly
move toward the coast along 30 N Latitude, finally approaching the
coast either Saturday or Sunday depending on the model. The EC
and GFS agree reasonably well with this solution through Friday
afternoon, but after that time the GFS moves the low more quickly.
The GFS solution shows the low along the coast by Saturday
evening, with the EC trailing behind by at least 12 hours. Both
solutions bring some rain chances to the area, with the EC later
and slightly wetter. As with most closed low solutions in the
extended, this is a low confidence forecast so have kept pops
below slight chance, and maintained cooler temperatures.

&&

.AVIATION...21/2315Z.

At 2300Z, the marine inversion was based around 4300 feet. The
top of the inversion was 5500 feet with a temperature of
12 degrees Celsius.

Overall, low to moderate confidence in coastal/valley TAFs and
high confidence in desert TAFs. There is an equal chance of
coastal and valley sites being either clear or developing CIG
restriction late tonight and Monday morning.

KLAX...Low confidence in 00Z TAF. There is a 50% chance that CAVU
conditions will persist through TAF period. If CIG restrictions do
develop, confidence in flight category is low.

KBUR...Low confidence in 00Z TAF. There is a 50% chance that CAVU
conditions will persist through TAF period. If CIG restrictions do
develop, confidence in flight category is low.

&&

.MARINE...21/805 PM.

For the Outer Waters, good confidence in current forecast.
Northwest winds are expected to remain at Small Craft Advisory
(SCA) levels through Monday evening. For Tuesday through Friday,
winds and seas are expected to remain below SCA levels.

For the Inner Waters north of Point Sal, good confidence in
current forecast. Winds and seas are expected to remain below SCA
levels tonight through Friday.

For the Inner Waters south of Point Conception, good confidence in
the current forecast. Tonight through Friday, winds and seas are
expected to remain below SCA levels. However, there is a 20-30%
chance of SCA level winds across the western half of the Santa
Barbara Channel Monday afternoon and evening.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 9 PM PDT this evening for zone
      39. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
      for zones 645-650. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 PM PDT Monday for
      zones 670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (WED-SUN).

No significant hazards expected.

&&

$$

PUBLIC...Smith/RAT
AVIATION...RAT
MARINE...RAT
SYNOPSIS...Kj

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