Weather Service Report


619 
FXUS66 KSGX 250440
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
940 PM PDT Mon Apr 24 2017

.UPDATE...
At 9 pm PDT, water vapor satellite showed an upper-level low
pressure trough moving by to the north. Pressure gradients
remained onshore, with +8.8 mb from San Diego to Salt Lake City.
This was creating westerly wind gusts of 45-55 mph over portions 
of the mountains and deserts. A wind advisory for the mountains
and deserts remains in effect through 3 am tonight. A highest
observed wind gusts so far PNS was issued at 930 pm, with
Whitewater Raws at the top of the list with 67 mph. Conditions 
will improve overnight, with a deep marine layer remaining in 
place through early Tuesday. No major changes to the forecast this
evening. Previous forecast remains on track.

&&

.SYNOPSIS... 
A low pressure system will continue moving by to the north this 
afternoon and bring cool weather west of the mountains and partly to 
mostly cloudy conditions. Areas of strong winds will occur in the 
mountains and deserts through tonight. The low pressure trough will 
be focused more on the interior western United States from Tuesday 
through next weekend as high pressure aloft prevails over the East 
Pacific. This will bring warmer weather Tuesday and Wednesday and 
less extensive coastal low clouds. Slight cooling and increasing 
winds could occur late in the week as the inland trough deepens and 
expands.

&&

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

.PREV DISCUSSION...
Broad low pressure trough covers the west coast and in the 
interior west with a fast wave moving through northern California 
today. The trough will deepen, but shift east Tue/Wed and result 
in a warming trend. There should be one last night of a deep 
marine layer west of the mountains tonight, with a weakening 
inversion, though enough of an inversion could linger in San Diego
County for widespread stratus then and possible local drizzle. 
The marine layer should be more shallow by mid-week though, with 
only patchy night/morning stratus/fog near the coast. Wednesday 
and Thursday should be the warmest days as the effects of the 
upper high off the coast will be greatest on So-Cal. A low-
amplitude, fast-moving wave associated with a strong WNW-to-ESE 
jet stream moving through northern Oregon could broaden the trough
a bit farther west late in the week and bring slight cooling and 
increasing winds in the mountains/deserts. Weak offshore flow 
could occur next weekend as the flow aloft becomes more northerly 
due to amplification of the ridge and trough. Other than the small
chance of drizzle tonight, no precipitation is expected through 
early next week.

&&

.AVIATION... 
250400...Coast/Valleys/Coastal Mountains Slopes...Areas of SCT-BKN 
cloud layers with bases 1700-4500 ft MSL along and west of the 
mountains through about 16Z with the greatest coverage over San 
Diego County. Low clouds becoming FEW-SCT 16-18Z. Low confidence of 
CIGS redeveloping Tuesday night.

Mountains/Deserts...West winds will produce strong UDDFS and LLWS 
over and east of the mountains through 15Z. Sfc gusts 40-50 kt over 
the ridges, desert mountain slopes, and below the passes will 
continue through about 14Z, then gradually weaken through the 
afternoon. Local blowing dust may reduce VIS to 3-5 SM over portions 
of the Coachella Valley and San Diego County deserts.

&&

.MARINE...
Northwest winds with gusts 20-30 kt will continue through Tuesday 
evening. Combined seas will be around 10-12 near and south of San 
Clemente Island and 6-10 ft elsewhere. A small craft advisory is in 
effect through Tuesday evening. Winds and seas will lower Wednesday, 
before breezy northwest winds and choppy seas return Thursday and 
Friday.

&&

.BEACHES...
A mix of northwest and south swells will produce 3-6 ft surf at area 
beaches at times through late Friday. Strong rip currents are 
possible as well.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 3 AM PDT Tuesday for Apple and Lucerne 
     Valleys-Coachella Valley-Riverside County Mountains-San 
     Bernardino County Mountains-San Diego County Deserts-San 
     Diego County Mountains-San Gorgonio Pass Near Banning.

PZ...Small Craft Advisory until 10 PM PDT Tuesday 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...JJT/Maxwell
AVIATION/MARINE/BEACHES...SS

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