119
FXUS66 KLOX 130506
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1006 PM PDT Thu Mar 12 2026

UPDATED AVIATION SECTION

.SYNOPSIS...12/758 PM.

A heat wave is expected to continue to affect the region through
Sunday, aside from minor cooling on Saturday. For next week,
significant additional warming is likely, with potential for
MODERATE to HIGH heat impacts as a very strong ridge of high
pressure builds over the area. Heat stress will be a threat each
day, especially in coastal areas.

&&

.SHORT TERM (TDY-SAT)...12/846 PM.

***UPDATE***

Highs climbed into the 80s and 90s for the valleys, coastal
plains, and much of the coasts under clear skies and easterly
winds. Southern Ventura County reached into the low to mid 90s in
spots, crushing a few daily records set back in 2015. Tomorrow,
expecting similar temperatures with a few degrees of cooling near
the coasts. Highs were warmed for Friday to closer reflect
today`s high temperatures.

Sub-advisory level northeast to east winds are expected over
higher terrain tonight, becoming more northerly into Friday
morning. Still, the offshore winds look weaker than this morning,
so expecting a bit cooler temperatures near the coasts. High
pressure weakens over the weekend, leading to a slight cool down.
Otherwise, the forecast looks on track.

***From Previous Discussion***

Overall, 12Z models in good synoptic agreement through the short
term period. At upper levels, the high, just offshore, peaks in
strength today then weakens gradually Friday/Saturday before
restrengthening on Sunday. Near the surface, weak offshore flow
prevails through Friday morning, switches weakly onshore Friday
afternoon through Saturday before shifting back weakly offshore
on Sunday.

Forecast-wise for the short term, main focus will remain on
temperatures. As expected, today has been a very warm day, topping
out in the mid 80s to mid 90s. For Friday, the return of the weak
onshore flow in the afternoon will allow for some slight coastal
cooling, but keep temperatures near persistence across inland
areas. So, high temperatures on Friday will still be warm enough
(15-25 degrees above normal) to warrant heat products. So, will
keep the HEAT ADVISORIES in effect for the coasts and coastal
valleys through Friday afternoon. On Saturday, all areas will
experience a cooling trend with coastal/valley areas cooling as
much as 5-10 degrees. However on Sunday, as the upper level high
begins to strengthen again and weak offshore surface gradients
develop, temperatures will increase yet again, generally into the
80s to lower 90s. HEAT ADVISORIES could be needed on Sunday for
some coastal valley areas.

Other than temperatures, no significant issues are expected
through the period. The weak offshore pressure gradients today
through Friday morning and again on Sunday will generate some
gusty northeasterly winds. However without any noticeable upper
level support, will expect winds to remain below advisory levels.
As for clouds, mostly clear will be likely for most areas through
the period. However, on Saturday and Sunday, there may be some
night and morning stratus/fog along the coastal plain (mainly LA
county coast and the Central Coast).

.LONG TERM (SUN-WED)...12/123 PM.

For the extended, 12Z models continue to remain in good synoptic
agreement through the period. At upper levels, an extraordinarily
strong high pressure will build right over the area. At the
surface, there is the potential for weak diurnal flow (best case
scenario based on the GFS) or weak offshore flow (worst case
scenario based on the ECMWF). Either way, nothing in the latest
guidance indicates anything but an extremely impressive heat wave
next week.

Details that make this heat event very impressive:

1. 500 MB heights are forecast to range between 590 and 595 DM
which would be the highest March H5 heights since 1948.

2. 1000-500 MB thickness are forecast to peak in the 580 to 584
DM range. Based on the 25+ year history of TEMP STUDY, the highest
thicknesses recorded in March are 571 DM.

3. The Extreme Forecast Index (EFI) indicates values between 0.8
and 1.0 for both Maximum and Minimum temperatures, signifying a
very usual or extreme event.

4. If the weak offshore flow, forecasted by the ECMWF, pans out
then temperatures west of the mountains could be higher than
currently forecast.

5. Based on current forecasts, both daily and monthly March
temperatures records could fall for most climate sites.

At this time, there is high confidence in the need for HEAT
ADVISORIES for most areas next Tuesday through Thursday, and
possibly as early as Monday for some areas. Additionally, there is
a 40-50% chance that EXCESSIVE HEAT WARNINGs may be needed for
some areas Tuesday through Thursday.

Given the unprecedented length and magnitude of this extreme heat
wave, heat stress will be a real threat each day, especially in
areas that aren`t used to the heat, like the coastal areas, where
people may not have methods to cool off their homes. Try to
complete outdoor activities early in the day or in the evening,
and don`t leave people or pets in cars.

As for any rain chances, deterministic and ensembles do not
indicate any chances for significant rain through the 28th.

&&

.AVIATION...13/0505Z.

At 0356Z at KLAX, there was no marine layer. There was a surfaced
based inversion with a top at 1100 ft and a temperature of 29 C.

High confidence in VFR TAFs and moderate confidence in winds.

Light LLWS is possible through 13/18Z. There is a 20% percent
chance northeast winds 15-20 kt briefly surface at KSBP thru
aforementioned time period.

KLAX...High confidence VFR TAF. No significant east wind component
expected.

KBUR...High confidence VFR TAF.

&&

.MARINE...12/749 PM.

Moderate to high confidence in Small Craft Advisory (SCA) level
northwest to north winds up to 25 kt through tonight, increasing
to 20-30 knots tomorrow and impacting the Outer Waters through at
least Sunday night. There is a 50% chance of low end Gale Force
winds (roughly 35 knots) across the waters beyond 30 NM from shore
Friday evening through late Saturday night, with a Gale Watch in
effect. Seas will increase during this period, with moderate
confidence in seas reaching at least 10 feet across the outer
waters. Conditions are likely to improve early next week, with
relatively small seas expected.

Small Craft Advisory (SCA) level winds will affect the Inner
Waters along the Central Coast during the afternoon to evening
hours Friday and Saturday, with a 30% chance of SCA winds Sunday
afternoon and evening.

Inside the Southern California Bight, conditions are expected to
remain below SCA levels for the foreseeable future, except for
very localized SCA level winds across the far northwestern
portion of the Santa Barbara Channel Saturday.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory remains in effect until 8 PM PDT Friday for
      zones 88-340>342-346>352-354>358-362-366>375-548. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 3 PM Friday to 3 AM PDT
      Saturday for zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 9 PM PDT Friday for
      zones 670-673. (See LAXMWWLOX).
     Gale Watch in effect from Friday evening through late
      Saturday night for zones 670-673. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Saturday for
      zone 676. (See LAXMWWLOX).
     Gale Watch in effect from late Friday night through late
      Saturday night for zone 676. (See LAXMWWLOX).

&&

$$

PUBLIC...Phillips/Thompson
AVIATION...Black
MARINE...BL/CC
SYNOPSIS...RAT/CC

weather.gov/losangeles

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

NWS Los Angeles (LOX) Office