San Diego Weather at Mission Trails, CA

566
FXUS66 KSGX 211726 CCA
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
916 AM PST Tue Jan 21 2025

.SYNOPSIS...
Strong Santa Ana winds and very dry conditions will continue
today but become weak and localized to foothills overnight.
Another surge of offshore wind is expected to arrive Wednesday
afternoon and night, through Thursday morning. The Santa Ana winds
weaken by Friday. A cold upper level storm system is expected to
arrive for the weekend and would bring showers and low snow levels
late Saturday through Sunday night.

&&

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

Santa Ana winds have peaked (max gust 102 mph) across the region
during Monday evening but a second surge is occurring now (max
gust 80 mph). This will weaken and spread out down valleys late
morning and afternoon. Pressure gradient reached about 16 mb
gradient from Salt Lake to San Diego behind the short wave trough
passage on Monday. Strongest wind was Sill Hill off of Cuyamaca
Peak in San Diego Laguna mountains where a gust to 102 mph was
measured during Monday evening. The inversion aloft was near 7000
feet MSL so this appears to be trapped mountain wave. Other
locations reached 70 to 80 mph gusts in wind prone areas. There
were 3 wildfires along I-15 and SR76, which ignited Monday evening
and just after midnight. Moisture is not around as dewpoint
temperatures are observed 0F to -40F in the higher terrain and
even single digits to the coast, so humidity recovery was very
poor overnight. The offshore wind decreases further this evening
and tonight but wind prone corridors will still gust 30 to 40 mph
overnight into Wednesday morning.

The next event blends in to the current but a separate cold short
wave in the northwest flow will dive further east across the
Rockies on Wednesday. This returns a 1045 mph surface high over
Salt Lake so we end up to 15 mph gradient from SLC to SAN again.

Break in the weather on Friday and guidance still as an very cold
upper low digging west as it drives south from Canada for the
weekend. This forms a closed upper low over the California Bight.
The dynamics and instability given this track could bring
widespread showers and even locally heavy showers favoring San Diego
and San Bernardino mountains and foothills. There is some concern
the upper low could be elongated or not directly over Socal which
would reduce precipitation amounts but right now looks to be wetting
rainfall and low elevation snows down to 3500 to 4000 feet MSL with
main system overhead on Sunday. Cold air showers could linger into
Monday.

&&

.AVIATION...
211630Z....Mostly clear skies this morning with SCT high clouds with
bases above 20 kft MSL entering the area this afternoon. NE to E
wind gusts of 30-50 kts this morning for inland valleys, foothills,
and mountains, weakening below 30 kts for everywhere but the
mountains by 22-23z. Strong updrafts/downdrafts remain possible in
vicinity of mountains through this evening. E winds will generally
remain light overnight, aside from wind prone mountain passes, where
winds may exceed 30kts through at least Wednesday morning. E to NE
winds look to increase again for inland areas and mountains by
Wednesday afternoon.

NWS San Diego is aware of limited communications of observations
from KTRM since January 8th. We are working with the FAA to address
this issue.

&&

.MARINE...
Offshore winds peaked this morning around 25 kts, but will continue
to weaken over the next few hours over the waters. A Small Craft
Advisory remains in effect until 10 AM and contains more
information. Otherwise, no hazardous marine conditions expected
through Saturday.

&&

.FIRE WEATHER...
Fuel moisture is critically dry and record low values due to the
driest start to any winter or rainy season. Santa Ana wind round 2
will return areas of gusty winds Wednesday afternoon and Thursday.
Only a small break with much lighter wind but still very dry for
Tuesday night. Red flag warning will be extended or combined with
additional fire weather watch, but much lighter wind tonight.

&&

.CLIMATE...
Driest start to the water year at San Diego and other climate
locations in Socal. Rainfall is 0.14 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...Red Flag Warning until 10 PM PST this evening for Orange County
     Inland Areas-Riverside County Mountains-Including The San
     Jacinto Ranger District Of The San Bernardino National
     Forest-San Bernardino County Mountains-Including The
     Mountain Top And Front Country Ranger Districts Of The San
     Bernardino National Forest-San Bernardino and Riverside
     County Valleys  -The Inland Empire-San Diego County Inland
     Valleys-San Diego County Mountains-Including The Palomar
     And Descanso Ranger Districts of the Cleveland National
     Forest-San Gorgonio Pass Near Banning-Santa Ana Mountains-
     Including The Trabuco Ranger District of the Cleveland
     National Forest.

     High Wind Warning until 4 PM PST this afternoon for Riverside
     County Mountains-San Bernardino County Mountains-San
     Bernardino and Riverside County Valleys-The Inland Empire-
     San Diego County Mountains-San Diego County Valleys-San
     Gorgonio Pass Near Banning-Santa Ana Mountains and
     Foothills.

     Fire Weather Watch from Wednesday evening through Thursday
     afternoon for Riverside County Mountains-Including The San
     Jacinto Ranger District Of The San Bernardino National
     Forest-San Bernardino County Mountains-Including The
     Mountain Top And Front Country Ranger Districts Of The San
     Bernardino National Forest-San Diego County Inland Valleys-
     San Diego County Mountains-Including The Palomar And
     Descanso Ranger Districts of the Cleveland National Forest-
     San Gorgonio Pass Near Banning-Santa Ana Mountains-
     Including The Trabuco Ranger District of the Cleveland
     National Forest.

PZ...Small Craft Advisory until 10 AM PST this morning for Coastal
     Waters from San Mateo Point to the Mexican Border and out
     to 30 nm-Waters from San Mateo Point to the Mexican Border
     Extending 30 to 60 nm out including San Clemente Island.


&&

$$

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