Small Craft Advisory 1, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
931 AM PST Mon Jan 6 2025

.SYNOPSIS...
Warmer for the mountains and little cooler for coast and valleys
today. Cooler conditions are expected for Tuesday and Wednesday with
strong and gusty north to northeasterly Santa Ana winds. Critical
fire weather conditions are expected for some areas Tuesday, with
more widespread critical fire weather conditions expected Wednesday.
Warmer conditions expected for Thursday and Friday with periods of
Santa Ana winds.

&&

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

Visible satellite this morning was showing mostly clear skies across
the area. Highs today are expected to be a few degrees cooler than
yesterday for the coast and valleys with a few degrees of warming
for the mountains and most desert locations. A colder low pressure
system from the north will move quickly southward into the area
tonight with strong north to northeast flow aloft for Tuesday into
Wednesday. High temperatures on Tuesday continue to cool, with a few
degrees of continued cooling for the coast and valleys and more
significant cooling for the mountains and High Desert. The southward
progression of the low will generate northerly flow at the surface
over Point Conception which should generate a coastal eddy over the
California Bight tonight. That should bring low clouds and fog back
to coastal areas, locally into the western valleys tonight.

Moisture from the low is expected to reach the deserts and eastern
mountain slopes Tuesday as it digs south towards the
California/Arizona border. The moisture influx may generate a few
light showers on the desert facing mountain slopes. There is a 15 to
20 percent chance of showers in the San Bernardino Mountains
Tuesday morning and afternoon. Shower chances decrease Tuesday
afternoon into Wednesday. Chances of showers are closer to 10
percent for Riverside and San Diego County mountains. Snow levels
will fall to 5500 feet early Tuesday morning falling to 4000 to
4500 feet for the late morning and afternoon.

There is higher confidence in winds picking up earlier in the day
Tuesay for Orange County, the Inland Empire, and San Bernardino
county mountains. The model guidance is also showing a more
significant drying trend, especially for lower elevations on
Tuesday. Given the recent trends, periods of critical fire weather
conditions are expected Tuesday. Northeast winds are expected to
arrive in San Diego county later in the day Tuesday. Winds are still
expected to peak Tuesday night into Wednesday morning. By Wednesday
more dry air will be in place with widespread critical fire weather
conditions expected. More details in wind speeds and humidity levels
can be found in the fire weather discussion below. Latest guidance
is showing the potential for a secondary peak in winds for Thursday
morning, mainly for mountain locations and the Inland Empire. Some
guidance continues to show the potential for moderate winds on
Friday, but confidence is low at this time.

Warming is expected on Thursday with slight cooling for the coast
and valleys on Friday as the mountains and deserts continue to warm.
The general pattern for the latter half of the week going into next
weekend will be high pressure aloft over the eastern Pacific into
British Columbia with northerly flow across the western states.
There are some model differences in the timing and strength of
mostly weak weather systems moving southward across the area. Ahead
of these systems it will generally be a little warmer with weaker
winds with it a little cooler and breezy behind them.

&&

.AVIATION...
061715Z...Mostly clear skies except for FEW-SCT clouds at/above
20000 ft MSL will continue today and tonight. Low clouds may develop
as early as 03z this evening for coastal airports. 60% chance for
low clouds in the vicinity of KSAN and 30-50% chance elsewhere along
the coast. Any coastal low clouds should dissipate by 12z as winds
become offshore. SCT-BKN clouds with bases near 8000-10000 ft MSL
will briefly develop for the eastern San Bernardino Mtns 12Z Tues-
00Z Wed. 20% chance of -SHRA in the vicinity of Big Bear City.

A Santa Ana winds event will begin to unfold Tuesday morning with
gusty N to NE winds beginning around 12z for the mountains and
Inland Empire between KONT and KRIV. Winds will continue to
strengthen and expand to include most of Orange County and the
Coachella Valley by 18z. Widespread wind gusts of 25-40 kts in these
areas with gusts of 40-50 kts or higher for parts of the mountains
and Inland Empire. LLWS and moderate to strong updrafts and
downdrafts are likely where Santa Ana winds are present, especially
near the coastal slopes of the mountains. Looking ahead, gusty N to
NE winds will fill in to include all of Southern California Tuesday
evening into Wednesday.

&&

.MARINE...
No hazardous marine conditions are expected through early Tuesday.
Offshore winds of 20-30 kt are expected late Tuesday morning through
Wednesday morning, with a 40% chance that they will exceed 30 kt in
the outer coastal waters. This will result in choppy and hazardous
conditions. No additional hazardous marine conditions are expected
Thursday through Friday.

&&

.FIRE WEATHER...

Moderate to strong northerly to northeasterly Santa Ana winds will
develop Tuesday morning, with widespread gusts of 50 to 60 mph along
the coastal slopes of the San Bernardino Mountains, below the Cajon
Pass, and into the Santa Ana Mountains and Foothills. Gusts 35 to 45
mph are possible into the Inland Empire below the Cajon Pass and
near the foothills of the Santa Ana mountains in Orange County.
Relative humidity on Tuesday is trending drier for locations north
of San Diego County. Orange County and the Inland Empire may see
relative humidity values 10 to 15 percent Tuesday afternoon, with
higher humidity closer to 20 percent in the Santa Ana mountains. The
San Bernardino mountains will be slow to dry out due to an influx of
mid-level moisture into the area. On the coastal slopes of the
mountains lowest afternoon relative humidity will be 20 to 30
percent with higher relative humidity on the desert facing slopes
and mountains peaks. Winds will be slower to develop and relative
humidity will be slower to fall in San Diego County and Riverside
County mountains. Winds will become northeasterly by Tuesday
afternoon in Riverside County mountains, with northeasterly winds
reaching San Diego county around sunset. Afternoon humidity values
will stay 20 to 35 percent.

Winds are still expected to peak Tuesday night into Wednesday
morning. Widespread gusts of 50 to 65 mph expected on the coastal
slopes of the mountains, below passes, and into portions of the San
Diego valleys and inland Orange County. Wind prone locations have
the potential to see gusts exceed 75 mph during the peak of the
winds. Winds look to very slowly weaken from their peak, with gusts
40 to 60 mph still possible into late Wednesday afternoon. The drier
air is expected to become more widespread Wednesday, reaching into
San Diego county and the area mountains. Relative humidity values on
Wednesday are expected to fall to the 10 to 15 percent for Orange
County and the Inland Empire, some locations in the Inland Empire
could see relative humidity values below 10 percent. For San Diego
County and the Riverside County mountains minimum relative humidity
will fall to the 15 to 25 percent range with those higher values
more likely in the San Diego County mountains. Winds are expected to
be stronger along the Orange County coast compared to much of the
San Diego County coast. For coastal Orange County max gusts of 45 to
55 mph possible Tuesday night into Wednesday morning. For coastal
San Diego County gusts will peak in the 20 to 35 mph range for the
most part. North of Oceanside some gusts to 45 or 50 mph may occur.
Relative humidity near the coast will be near 15 percent Wednesday
afternoon.

There is still some uncertainty surrounding the winds on Thursday.
Much higher confidence in dry air being in place so any elevated
winds will bring critical fire weather conditions. Latest high
resolution guidance indicates a secondary peak in winds Thursday
morning for the most mountain locations and portions of the Inland
Empire. The strongest winds are currently being depicted on the
coastal slopes of the San Bernardino mountains, below the Cajon
Pass, and locally into the Inland Empire. There is a 60 percent
chance of moderate to locally strong winds continuing into Thursday
morning, with higher chances of more moderate winds continuing. Poor
humidity recovery is expected for Wednesday night into Thursday,
especially for the locations where the winds stay elevated. Minimum
relative humidity for inland areas is expected to fall to the 9 to
15 percent range Thursday.

Dry conditions will continue into Friday, but there is much lower
confidence in wind speeds at this time. Latest ensemble guidance
indicates a 40 percent chance of moderate winds continuing into
Friday with a 20 percent chance of moderate to locally strong winds
continuing. With the dry air in place, critical fire weather
conditions may continue into Friday for some locations depending on
how the wind forecast develops.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Watch from Tuesday morning through late Wednesday
     night for Orange County Inland Areas-San Bernardino County
     Mountains-San Bernardino and Riverside County Valleys-The
     Inland Empire-Santa Ana Mountains and Foothills.

     Fire Weather Watch from late Tuesday night through Thursday
     afternoon for Orange County Inland Areas-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 Gorgonio Pass Near Banning-Santa Ana
     Mountains-Including The Trabuco Ranger District of the
     Cleveland National Forest.

     High Wind Watch from Tuesday evening through late Wednesday
     night for Riverside County Mountains-San Diego County
     Mountains-San Diego County Valleys-San Gorgonio Pass Near
     Banning.

     Fire Weather Watch from Wednesday morning through Thursday
     afternoon for Riverside County Mountains-Including The San
     Jacinto Ranger District 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.

PZ...None.

&&

PUBLIC/FIRE WEATHER...CO
AVIATION/MARINE...APR/KWW