Hi Vista, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

594
FXUS66 KLOX 181243
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
443 AM PST Sat Jan 18 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)...18/443 AM.

The marine layer across the region was fairly deep, generally
around 3000 feet deep or so. N of Pt. Conception, low clouds were
widespread in coastal and valley areas, and have pushed into the
interior valleys and mtns of SLO County. South of Pt. Conception,
clouds were widespread in coastal and valley areas of L.A. County
and the valleys of VTU County, and have pushed into the coastal
slopes of the San Gabriel mountains.

The stratus field was more solid in nature this morning.
However W-E onshore pressure gradients between KLAX and KDAG have
begun to weaken, and N-S gradients between KSBA and KSMX, and
KSBA and KBFL have flipped offshore. Likely due to the gradients,
clouds have backed out of the Santa Clarita Valley during the
past hour or two, and it remained mostly clear in coastal
sections of VTU County and on the south coast of SBA County.
However, it is possible that some clouds may drift into these
areas by daybreak.

Skies should clear in most areas by late morning. Slight height
rises, a degree or two of warming at 950 mb and weakening
onshore gradients may allow for a couple of degrees of warming
in most areas, but max temps will still be several degrees below
normal.

The upper high in the eastern Pacific will amplify a bit tonight
and Sun, and the upper flow will veer to a more northwesterly
direction. N-S gradients will remain weakly offshore, while W-E
gradients between KLAX and KDAG will become 3 to 4 mb offshore.
There may be some gusty NW-N winds through the I-5 Corridor and
across southwestern SBA County this evening into tonight, then
some NE breezes are possible in the mtns and locally in the
valleys of L.A./VTU Counties late tonight/Sun morning. With
minimal upper level support, expect any winds to remain well below
advisory levels.

Low clouds tonight/Sun morning will likely be limited to south
coastal sections of L.A. County and perhaps the Central Coast.
Where skies remain clear and winds remain light, it will be quite
chilly tonight, with frost likely in clear portions of the
Central Coast, and in portions of the valleys of VTU County and
western L.A. County. Any low clouds should clear by mid morning
Sun. Max temps should be up a few degrees in most areas Sun,
possibly reaching 70 degrees in the warmest valley locations of
L.A./VTU Counties, about normal for the second half of January.

The upper ridge off the West Coast will amplify Sun night and
Mon, with ridging extending all the way into central and northern
British Columbia. This will send a rather strong short wave
southward through the western states, resulting in a positively-
tilted trough over Arizona and far eastern California. This will
produce an increasingly sharp height gradient over the region by
Mon, with increasing northerly flow aloft. At the surface, N-S
offshore gradients will sharpen Sun night and Mon morning. This
should bring some gusty NW to N winds to the Interstate 5 Corridor
and to southern SBA County Sun night, possibly close to advisory
levels, but most likely just below. W-E offshore gradients will
actually weaken Sun night, before becoming more strongly offshore
during the day Mon. Low clouds should be minimal Sun night/Mon
morning, and if there are any, will likely be confined to southern
L.A. County and southern portions of the Central Coast and Santa
Ynez Valley.

W-E offshore gradient will increase during the day Mon, bucking
the typical diurnal trend, and cold advection and subsidence spill
southward into the area. The beginning of the  cold advection on
Mon will likely lead to cooling in the mtns and the Antelope
Valley, while developing N to NE downslope winds will offset
cooling west and south of the mountains, leading to mostly minor
change in max temps, and perhaps some warming near the coast.

.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...18/1156Z.

At 08Z at KLAX, there was no marine layer nor inversion.

Overall, moderate confidence in 12Z TAF Package. Timing of flight
cat changes may be off +/- 2 hours with minimum flight cats off
by +/- 1. There is a 30% chance of LIFR or even VLIFR conds at
KSMX from 06Z to 12Z Sun. Similar chances for MVFR conds at KSMO
and IFR conds at KLGB from 06Z to 12Z Sun.

KLAX...Moderate confidence in 12Z TAF. Timing of flight cat
changes may be off by up to +/- 2 hours. There is a slight chance
for 380. (See LAXRFWLOX).
PZ...NONE.

&&

$$

PUBLIC...DB/MW
AVIATION...Black
MARINE...Black
SYNOPSIS...MW/Smith

weather.gov/losangeles

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