Arroyo Grande, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

853
FXUS66 KLOX 180554
AFDLOX

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
954 PM PST Fri Jan 17 2025

.SYNOPSIS...17/746 PM.

Cooler weather is expected through Saturday with areas of morning
low clouds. Weak offshore flow returns Sunday, with local
northeast breezes, less morning low clouds, and a few degrees of
warming. Additional Santa Ana winds are likely beginning later
Monday into Tuesday, and again on Thursday. Temperatures will
likely be below normal for much of next week, with frost possible
in wind sheltered areas away from the coast.

&&

.SHORT TERM (TDY-MON)...17/815 PM.

Onshore flow increased today, with LAX-Daggett gradient peaking
over +5 mb this afternoon. As a result, there was a cooling
trend today across coastal and valley areas, along with increasing
humidities. Current satellite imagery showing areas of low clouds
forming in areas north of Point Conception this evening, with
patchier coverage south of Point Conception where there is
a weaker inversion. Forecast soundings indicate a stronger
inversion overnight, but low confidence in that as the pattern is
not really conducive to warming aloft. Aside from the impacts on
aviation, if clouds end up being more solid then overnight
temperatures will be warmer and some or all of the freeze warnings
(in effect for the Central Coast and the Ojai Valley) may not pan
out. Either way, it will be another cool day across the area
Saturday with highs from the upper 50s to mid 60s at lower
elevations.

*** From previous discussion ***

Saturday night into Sunday the models have been consistent showing
a significant weakening in the onshore flow, and actually turning
at least lightly offshore Sunday morning. The NAM has bumped the
LAX-DAG gradient up to -5 but upper support is almost nil and
most of the high res models are keeping winds under 20 mph.
Probably a good bet that any marine layer south of Pt Conception
will be gone and daytime temperatures should rise at least a few
degrees. The GFS remains onshore until Monday so still some
uncertainty with the Sunday forecast.

On Monday a trough will dig through the Great Basin and down
through AZ providing the necessary ingredients for at least a
moderate Santa Ana event Monday afternoon into Tuesday. ECMWF
ensembles still clustering around the 30-50 mph range at lower
elevations through the traditional Santa Ana wind-favored areas,
with likely some gusts to around 60 mph in the mountains. PW`s
crash to under a tenth of an inch Monday, meaning humidities will
likely be well under 10 percent.

.LONG TERM (TUE-FRI)...17/223 PM.

Part 1 of next week`s Santa Ana wind will peak early Tuesday,
then likely decrease a fair amount late Tuesday afternoon and
evening as upper support drops off. Temperatures expected to be
right around normal, which is mid to upper 60s for coast and
valleys. Potentially some frost/freeze hazards overnight in wind
protected areas.

On Wednesday, models have been pretty consistent showing a
relative break in the Santa Ana winds. Not zero, but mostly below
35 mph. Still quite dry with humidities under 20%.

For Wednesday night and Thursday, a second upper level trough
will follow almost the exact same path and create another Santa
Ana wind event. While some of the models are showing a stronger
gradient with this event, the ensembles are slightly weaker
overall. Still likely in the 30-50 mph range with some stronger
mountain gusts.

Winds expected to drop off later Thursday afternoon with at least
light onshore flow returning by Friday afternoon.

There are increasing signals for some rain next weekend but so far
it`s not looking like an atmospheric river. Both the EC and GFS
deterministic solutions are definitely not an AR pattern with
little to no tap of moisture to the southwest. And all but a few
of the 100+ ensemble solutions indicate rain totals under a half
inch.

&&

.AVIATION...18/0553Z.

At 0515Z at KLAX, there was no marine layer nor inversion.

Overall, moderate confidence in 06Z TAF Package. Timing of flight
cat changes may be off +/- 2 hours with minimum flight cats off by
+/- 1. There is a 30% chance KPRB never falls below LIFR or even
IFR conds from 06Z to 18Z Sat. Similar chances at KSMX for LIFR or
even VLIFR conds from 08Z to 16Z Sat. There is a 20% chance of IFR
conds at KSBA from 12Z to 18Z Sat.

KLAX...Moderate confidence in 06Z TAF. Timing of flight cat
changes may be off by up to +/- 2 hours. Good confidence that any
east wind component remains below 8 kt thru the fcst pd.

KBUR...Moderate confidence in 06Z TAF. There is a solid chance
of periodic MVFR cigs (~BKN020) from 08z to 16z Sat.

&&

.MARINE...17/858 PM.

In the Outer Waters, Small Craft Advisory (SCA) level winds from
Pt. Conception to San Nicolas Island are expected at least through
midnight, with 30% chance through 0300 AM. There is also a
40%-50% chance of SCA conds again Sun night/Mon, and a 30% chance
of SCA wind gusts out of the NE for Mon night and Tue morning for
the southern outer waters (PZZ676). Otherwise, sub- advisory
conditions are expected through Wed night.

For the Inner Waters North of Pt Sal, there is a 30% chance of
SCA level wind gusts at times Sun night. Otherwise, sub-advisory
conditions are expected through Wed night.

In the Santa Barbara Channel, there is a a 30%-40% chance of SCA
easterly wind gusts over the eastern portions Mon night and
Tuesday. Otherwise, sub-advisory conds are expected thru Wed
night.

In the Southern Inner Waters, there is a 40%-60% chance of SCA
level NE winds Mon night and Tue mainly nearshore from Malibu to
Santa Monica. Otherwise, SCA conds are not expected thru Wed
night.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Freeze Warning in effect until 9 AM PST Saturday for zones
      340-341-346>348-357. (See LAXNPWLOX).
     Fire Weather Watch in effect from Monday morning through
      Tuesday evening for zones 288-354-355-358-362-369>380. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect until 3 AM PST Saturday for
      zones 673-676. (See LAXMWWLOX).

&&

$$

PUBLIC...Gomberg/MW
AVIATION...Black
MARINE...Sirard/Smith
SYNOPSIS...MW/Smith

weather.gov/losangeles

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