206
FXUS66 KSGX 170442
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
930 PM PDT Mon Sep 16 2024

.SYNOPSIS...
Gusty southwest to west winds will continue through this evening. A
few light showers will occur through early Tuesday morning, with
areas of drizzle west of the mountains Wednesday morning. From
Wednesday evening through Thursday or Friday, unsettled weather is
expected again with additional chances of precipitation. Drier and
warmer conditions will return by the weekend.

&&

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

Update...

Island band showers due to convergence downwind of Catalina Island
were occurring from Oceanside to Escondido to San Pasqual Valley,
while mostly cloudy skies prevailed from the mountains west to the
coast. Most of the precipitation will be localized tonight with
greatest concentration in San Diego County due to the island
banding. The precip should end early Tuesday morning as the trough
axis shifts east of the area and height gradients weaken. However,
Tuesday will continue to be cool with only a slight warmup (mainly
mountains and high deserts) as 850 MB temperatures only recover a
few degrees C in the afternoon and a deep marine layer will
continue, possibly remaining over 5000 feet deep through Tue night.
Areas of moderately strong gusty winds continued in desert/desert
slope areas, especially in Riverside and San Diego counties. The
Whitewater observations had gusts to 54-55 MPH at mid-evening. The
winds should slowly weaken overnight.

From Previous Discussion...

Weaker winds and mostly dry conditions are expected after Tuesday
morning. A few degrees of warming are expected Tuesday west of the
mountains and in the low desert with 5 to 10 degrees of warming in
the mountains and High Desert. It looks like the marine layer will
be deep enough on Wednesday morning to allow for areas of drizzle to
develop west of the mountains and along the coastal mountain slopes.

On Wednesday an upper level low will begin to dig south along the
coast of the Pacific Northwest. Latest guidance has the low moving
slower, now moving inland across Central and Southern California
on Thursday. This system is expected to bring additional chances
of precipitation to Southern California. Some showers or drizzle
may develop late Wednesday night but the highest chances of
precipitation are on Thursday. With the slowing of the trough,
slight chances of showers have been added to the forecast for
Friday morning. This system looks like a warmer one, so only minor
fluctuations in temperatures are expected for Tuesday through
Thursday. Current ensemble guidance does not have a very
significant uptick in winds with ensembles indicating winds may be
weaker than today. NBM chances of wind gusts greater than 45 mph
are 35 to 45 percent for Wednesday and Thursday afternoon and
evenings and confined to wind prone passes, like the San Gorgonio
Pass.

Due to the slow down of the trough, there is more uncertainty in the
high temperature forecast for Friday. Some warming may occur
compared to Thursday, but more substantial warming may not occur
until the weekend. High temperatures will be several degrees
warmer for Saturday with high temperatures for next Sunday warming
to a few degrees above average for the deserts to around 5
degrees above average for the coast and valleys, mostly in the 90s
for the inland valleys and 100 to 105 for the lower deserts.

&&

.AVIATION...
170410Z...Coast and Valleys...Low clouds with bases varying 2500-
3500 feet MSL and tops to 5200 feet will continue through tonight.
Brief periods of CIG impacts are possible...mainly at KSAN and KCRQ
but timing is uncertain. Much of the terrain above 3000 ft MSL will
be obscured with VIS reduces to 1 mile or less locally where clouds
and terrain intersect. Clearing is expected to begin around 15Z
Tuesday, starting at the coast and working inland scattering out
last along the coastal mtn slopes.

Smoke from the Line, Bridge and Airport fires will continue to
reduce VIS in mountains, with hazy conditions over the Inland Empire
and parts of the deserts.

West-northwest winds will gust 40-50 knots through mountain passes,
through tonight. Local moderate up/downdrafts east of mountain
ridges.

&&


.MARINE...
Northwest gusts around 20 knots are expected in the outer waters
this evening and again Wednesday afternoon and evening. Otherwise,
no hazardous marine conditions are expected through Friday.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until midnight PDT tonight for San Diego County
     Deserts-San Gorgonio Pass Near Banning.

PZ...None.

&&

$$

PUBLIC...Maxwell (Update)/CO (Previous Discussion)
AVIATION/MARINE...PG