Arrowhead Highlands, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

782
FXUS66 KSGX 111722
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
922 AM PST Wed Dec 11 2024

.SYNOPSIS...
Santa Ana winds continue to dissipate and will end this afternoon
as offshore flow weakens. High clouds ahead of a Pacific weather
system will prevail. This weather system moves through on Thursday
and brings moisture, desert winds, cooler air, and scattered
light precipitation. Another fast moving Pacific system goes by
just to the north and brings another threat for light
precipitation late Saturday and then weak offshore flow for Sunday
night and Monday. Another fast moving weather system takes a
similar track for Monday and result in more offshore flow by
Tuesday.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

Santa Ana winds continue to weaken but wind prone passes, Cajon,
San Gorgonio and I-8 San Diego mountains, having gusts 30 to 40
mph due to 1032 mb surface high pressure over Utah (peaked at 1036
mb). Satellite depicts a large swath of overcast cirrus clouds
coming up from the tropics, ahead of the incoming Pacific trough.
Cold start to the day in valleys, especially low lying areas in
mountains due to dewpoints still 0 to -25F across the higher
terrain. Dewpoints in the single digits for inland valleys and
elevated coastal areas. Therefore with heating today the relative
humidity will very low again today, and thermal belt areas that
kept wind had very poor recovering overnight.

With the passage of the Pacific upper trough and frontal band
there will be rapid moistening and thickening clouds on Thursday
with scattered light rainfall with the trough axis passage in the
afternoon. This also brings moderate onshore wind flow so opposite
high winds over the deserts slopes than the recent Santa Ana.

Short wave upper ridge for dry mild weather on Friday and another
fast moving system in the developed zonal flow arrives on
Saturday. This is nearly a repeat track and threat for scattered
light precipitation. This exits and weak offshore sets up Sunday
night. A final system in the Pacific jet stream is expected to
dig across Socal on Monday. This system has potential for stronger
offshore flow for Tuesday and Wednesday, and moderate surface
high pressure settles over Utah for Santa Ana wind pattern.

&&

.AVIATION...
111600Z....Coasts/Valleys...SCT-BKN clouds at or above 25,000ft MSL
with unrestricted VIS through tonight. Low stratus redevelops again
tonight, generally remaining offshore, but may move inland around 15-
18z Thursday. There is a 30% chance of a CIG at KSAN by 18z
Thursday, with lower chances for other coastal TAF sites.

.Mountains/Deserts...Northeast to east winds gusting 20-30kts in
favored locations of the mtns and foothills this morning, weakening
through the afternoon. Areas of weak up/downdrafts over and west of
the mtns this morning. Otherwise, SCT-BKN clouds mostly above
20,000ft MSL through Thursday with unrestricted VIS.

&&

.MARINE...
No hazardous marine weather conditions are expected through
Tuesday.

&&

.FIRE WEATHER...
Santa Ana winds weakening but continue in main passes this
morning, becoming light this afternoon. Air mass is very dry with
widespread humidity 10 to 15 percent today.

&&

.CLIMATE...
Precipitation is 1 to 15 percent of average for this time of
year, so very slow start to the rain season and water year. Only
the San Bernardino mountains are around 20 percent of average. Key
climate locations such as Santa Ana and Riverside with only 0.01
inches since October 1.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC/FIRE WEATHER...Tardy
AVIATION/MARINE...Zuber