Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 201121
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
421 AM PDT Sat Jul 20 2019

.SYNOPSIS...19/645 PM.

Night through morning low clouds are expected over the coast and
adjacent valleys this weekend, gradually staying limited to over
the coastal areas next week. A strong area of high pressure will
dominate over the West Coast from Sunday through next week
yielding much warmer temperatures over inland areas.

&&

.SHORT TERM (TDY-MON)...20/238 AM.

The marine layer is 1900 feet deep. The marine layer stratus is
being pushed ashore by moderate onshore flow both to the north and
the east. The eddy was late to start tonight but is now spinning
and by dawn almost all of the coasts and vlys along with the Paso
Robles area will be covered with low clouds. Gradients are similar
to ydy and clearing should follow a similar pattern as Friday.
Later this morning the western edge of a conus spanning upper high
will begin to push into Srn CA. Hgts will rise from Friday`s 588
DM to 591DM. These hgt rises will bring a few degrees of warming
to the vlys and interior, but little or no warming for the coasts
where the marine layer will hold sway.

Higher hgts will squash the marine layer tonight. In addition
there will be 1 to 2 mb of offshore trends. Both of these will
combine to slow the marine layer stratus formation and limit its
extent. While most of the coastal areas (probably not the SBA
south coast) will have stratus most of the vly areas will remain
clear.

On Sunday the upper high migrates to the four corners area. Hgts
rise a few more DM. Higher hgts will smoosh any cooler marine
layer out of the vlys...this and offshore trends will kick off a
5 to 8 degree warm up in temps across the vlys and the interior.
Max temps over the coasts and vlys will reach normal seasonal
values. The coasts will not see much warming as there will still
be enough marine layer and onshore flow to keep temps from rising
much.

Not much change Monday. The high hgts may compress the marine
layer enough to create some dense fog at the beaches in the
morning. All mdls continue to show no monsoon push this far east.
Still the SSE flow may bring partly cloudy skies with some mid
and high level clouds. Max temps will rise everywhere even the
coasts where weaker onshore flow will reduce and delay the cooling
sea breeze. Max temps will be above normal across the vlys and the
interior but the coasts, while warmer, will still be a few degrees
below normal.

.LONG TERM (TUE-FRI)...20/302 AM.

Both the GFS and the EC show the four corners upper high spinning
in place through Thursday. Hgts really do not change much from day
to day. Gradients drop both Tue and Wed and in fact turn briefly
offshore on Wednesday. The marine layer clouds will diminish
further Tuesday and will likely not form at all on Wednesday. Tue
and Wed will be the two warmest days of the week with plenty of
triple digit heat in the deserts and mid and upper 90s with
isolated 100-101 degree readings in the vlys. Onshore trends will
bring some cooling to the coasts and vlys along with limited
stratus on Thursday.

Mdls continue to show no monsoon push through the period so have
removed the small amount of pops that were in the forecast. Still
anytime there is a four corners high cannot say with total
confidence that there will be no convection.

Models now showing the 4 corners high shifting to the west and over
California Friday through next weekend this would further warm the
interior and to a lesser extent the vlys. The low level onshore
flow is forecast to increase and there should be more night
through morning low clouds and fog. Both of these will combine to
bring cooling to the coasts and temper the warm up from the higher
hgts in the vlys.

&&

.AVIATION...20/1120Z.

At 0816Z at KLAX, the marine layer was 2000 feet deep. The top of
the inversion was near 4300 feet with a temperature near 20 C.

N of Point Conception... Moderate confidence in 12z TAFs. Expect
mainly MVFR Cigs with a 30% chance for brief IFR CIGs between
12-14z. Moderate confidence for IFR CIG for KPRB through 15z
before coming MVFR for a couple hours. CIGs should scour out +/-
1 hour from 12z TAF time. Higher confidence for VFR Conds at KPRB
tonight into Sunday morning, otherwise expect similar timing for
CIGs for coastal TAF sites.

S of Point Conception... Moderate confidence in 12z TAFs. Expect
MVFR CIGS for coastal TAF sites, except a 30% chance for IFR CIGs
between 12z-15z for Ventura Coastal TAF sites. There is a 50%
chance for IFR CIGs for KSBA thru 15z before rising to MVFR Conds.
CIGs should scour out +/- 2 hour from 12z TAF times.

Confidence is higher that Valley TAF sites will remain in VFR
category this evening through Sun morning. There is a 20% for IFR
Conds at KBUR/KVNY after 10z early Sun morning. Otherwise expect
IFR/MVFR Conds for coastal TAF sites. Timing could be a tad
slower filling across coastal areas this evening.

KLAX...Moderate confidence in 12z TAF. VFR transition could be as
late as 18Z. Good confidence in no east wind component over next
30-hours.

KBUR...Moderate confidence in 12z TAF.There is a 20% chance for
CIGs to lower to IFR conds through 15z. Higher confidence for VFR
Conds tonight into Sunday morning. 20% chance for IFR Conds
between 10z-12z

&&

.MARINE...20/110 AM.

For the Outer Coast Waters, winds and seas are expected to remain
below Small Craft Advisory (SCA) levels through Monday. There
will be a 40 percent chance of SCA level winds at times late
this afternoon through late in the evening for areas S of Point
Conception.

For the inner and nearshore waters, winds and seas will likely
remain below SCA levels through Tuesday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (MON-FRI).

No significant hazards expected.

&&

$$

PUBLIC...Rorke
AVIATION...Kaplan
MARINE...Kaplan
SYNOPSIS...Stewart

weather.gov/losangeles


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