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527
FXUS66 KLOX 202322
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
422 PM PDT Fri Sep 20 2024

.SYNOPSIS...20/127 PM.

Shower and thunderstorm chances have shifted to LA County and
eastern Ventura County today into this evening as a cold upper
continues to move through the area. Some showers or thunderstorms
could have heavy downpours, and gusty winds. High pressure will
build in over the weekend and bring a warming and drying trend to
the region over the weekend into early next week.

&&

.SHORT TERM (TDY-MON)...20/149 PM.

An active upper low continues to generate showers and
thunderstorms across southern California, though the dry/wet axis
continues to shift towards the east following the low into
Arizona. But at least until around 6pm the eastern portion of LA
County will be susceptible to periods of heavy rain and
thunderstorms. At this time all the activity is in San Bernardino
and Riverside counties but there`s still just enough of a westerly
trajectory that could bring those storms into LA County. Of
particular concern is the area around the Bridge fire, which has
the added factor of the mountain terrain to enhance updrafts. No
flood watch is in effect at this time but chances aren`t zero that
very heavy rain could still develop there and across other areas
of eastern LA County. Based on the lack of cumulus clouds west of
there it`s unlikely, but not impossible, that an isolated shower
could drift off the Tehachapi mountains and move into northwest LA
or northeast Ventura County this afternoon.

After this evening the weather calms down considerably, returning
to typical night and morning low clouds and fog and warming
temperatures. However, models have definitely trended not as warm
early next week as a weak upper low is now favored to develop just
west of the Bay Area Sunday and drift slowly south Monday. Still
expecting a warming trend but perhaps 2-4 degrees cooler than
earlier forecasts.

.LONG TERM (TUE-FRI)...20/209 PM.

Very low impact weather next week with highs mostly within a few
degrees of normal. A little cooling Tue-Thu with that upper low
still lingering and onshore flow increasing. Likely a steady does
of night and morning low clouds and fog at least for coastal
areas.

While the deterministic model solutions show significant
differences for the latter part of next week and beyond and at
least one solution showing a deep trough along the West Coast late
next weekend, the ensemble means favor very little change or
slight warming and overall very low impact weather conditions.

&&

.AVIATION...
-- Changed Discussion --
20/2322Z.

At around 2330Z at KLAX, there was a deep moist layer up to
roughly 3300 feet. The top of the weak inversion was at 4800 feet
with a temp of 16 C.

Moderate confidence in TAFs for KPMD and KWJF. There is a 20%
chc of TSTMs thru 01Z.

Low confidence in remaining TAFs due to the uncertainty of cigs
arrival time and height. There is a 20% chance KPRB remains VFR
thru the period. There is a chance for VLIFR conds at KSMX (40%)
and KSBP (30%) between 04Z and 16Z.

For all coastal and valley sites, arrival of cigs may be off by
+/- 5 hours from current forecast. The flight cat may be off by at
least one cat during any point once cigs arrive.

Any thunderstorms that form may produce brief +RA and gusty,
erratic winds.

KLAX...Low confidence in TAF. There is a 30% chance BKN010-020
may arrive as early as 02Z. There is a 10% chance for cigs
BKN008-010 between 04Z-15Z, or once cigs arrive. VFR conds are
likely by 19Z-20Z Sat. No significant east wind component
expected.

KBUR...Low confidence in TAF. Low confidence in hgt and timing of
CIGs, which might be off +/- 3 hours from current forceast. There
is a 30% chance of IFR cigs.
-- End Changed Discussion --

&&

.MARINE...20/1251 PM.

Isolated thunderstorms will be possible across the eastern
portion of the Santa Barbara Channel through the southern inner
waters and out to Santa Cruz Island into this evening. Any
thunderstorm that forms has the potential for frequent cloud to
surface lightning, gusty and erratic winds with rough seas, and
small hail.

For the Outer Waters (Central coast south to San Nicolas
Islands), moderate to high confidence in the forecast. High
confidence in winds and seas remaining below Small Craft Advisory
(SCA) level thru early next week in the northern zone (off the
Central Coast). For the southern zones (Pt Sal to San Nicolas
Island), there is a 60-70% chance of SCA level winds continuing
through late tonight across the waters from Point Conception to
San Nicolas Island. From Saturday thru Wednesday, high confidence
in winds and seas remaining below SCA level, and then there is a
20-30% chance of winds picking up Wednesday night.

For the inner waters along the Central coast, high confidence in
conds remaining below advisory levels through Wednesday.

For the Santa Barbara Channel, moderate confidence in the
forecast. SCA level winds expected in the western portion of the
zone thru late tonight. Then, moderate to high confidence in
conditions remaining below SCA levels through Wednesday.

For the inner waters off the coast of LA and Orange Counties,
moderate to high confidence in conditions remaining below
advisory levels through Wednesday. However, there is a 20-30%
chance of SCA level wind gusts thru the San Pedro Channel Sun
afternoon.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 3 AM PDT Saturday for
      zones 650-673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...MW
AVIATION...Gomberg
MARINE...Lewis
SYNOPSIS...MW

weather.gov/losangeles

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