Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 270359
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
859 PM PDT Wed Apr 26 2017

.SYNOPSIS...
A deepening trough over the Great Basin and a strong ridge over the
eastern Pacific will bring gusty onshore winds over the mountains
and deserts through Thursday morning. The winds will abate on
Thursday, but remain onshore. For Friday, winds will turn northerly
and then offshore by Saturday morning, resulting in much drier and
warmer conditions to the coast. The winds could become strong and
gusty for a time Saturday morning west of the mountains before
weakening. Continued dry with above average temperatures through the
weekend into next week.

&&

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

Satellite imagery this evening showed patches of high clouds
drifting from NW to SE over SoCal while lower, marine clouds were
indicated well offshore. The 00Z Miramar sounding had a weak
inversion near 2200 FT. Over the past 24 hours, warming of from 2 to
7 degrees C was indicated below 8K FT. At 8 PM PDT...Surface
pressure gradients were accelerating onshore at 6 to 8 MBS and so
were the winds over the mts/deserts where peak gusts of 45 to 55 MPH
were reported near the gaps and over onshore wind prone areas. A
Wind Advisory remains in effect until 3 AM Thursday for the
mountains and deserts for sustained winds of 20-35 mph with gusts 50-
60 mph.

Expect lower clouds and patchy fog to reform late tonight into Thu
morning over mainly San Diego County. Fair and a bit warmer on Thu.

A forecast update was issued earlier this evening to reduce winds
over Orange County. No other changes were made.

From previous discussion...

Friday and Saturday: The 12Z WRF and GFS runs are trending much
stronger with the offshore wind event. Initially, the northerly
winds will surface mainly from Cajon Pass into Orange County Friday
morning. Then on Friday night and Saturday the models are projecting
stronger and more widespread offshore winds in the mountains and
foothill, surfacing across all of Orange County and out over the
coastal waters of Orange County. Trends will continue to be
evaluated, but this is shaping up to be a moderately strong Santa
Ana Saturday in the mountains, foothills, inland valleys and Orange
County.

Temperatures with remain a little above average through the weekend.
The offshore flow will bring minor cooling to the mountains and
deserts, while downslope warming west of the mountains will bring
warming, especially to the Orange County coast on Saturday due to
the Santa Ana. The wind event weakens Saturday night with lighter
offshore winds Sunday.

Outlook for early next week: Quiet weather with seasonal
temperatures as the large upper ridge remains firmly anchored over
the eastern Pacific. Onshore flow will bring minor cooling to the
coastal areas, and warming to the mountains and deserts.

&&

.AVIATION...
270325Z...Coast/Valleys...Patchy stratus with bases 1000-1500 ft MSL
possible along the San Diego Coast and up to 20 miles inland 08-16Z.
Otherwise SCT cloud layers AOA 20000 ft MSL through Thursday evening.

Mountains/Deserts...W-NW winds with surface gusts 35-45 kt along
mountain ridges, desert slopes and through the passes will result in
strong uddfs/llws over and east of the mountains. Vis locally
reduced in BLDU. Otherwise SCT cloud layers AOA 20000 ft MSL and
unrestricted vis through Thursday evening.

&&

.MARINE...
Northwest winds gusting 20-25 kt will develop tonight. Winds will
increase to 25-30 kt over the outer coastal waters Thursday
afternoon. Gusts near 25 kt may briefly reach the inner coastal
waters Thursday afternoon and evening, becoming more widespread
Friday afternoon and evening. Combined seas will increase to 9-12
ft. A Small Craft Advisory for the outer waters remains in effect
through late Friday night. A Small Craft Advisory for the inner
waters is in effect from 3 pm Thursday through late Friday night.

&&

.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 Thursday 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 5 AM PDT Saturday for Waters from
     San Mateo point to the Mexican Border Extending 30 to 60 nm
     out including San Clemente Island.

     Small Craft Advisory from 3 PM Thursday to 5 AM PDT Saturday for
     Coastal Waters from San Mateo Point to the Mexican Border
     and out to 30 nm.
&&

$$

PUBLIC...JAD/Moede
AVIATION/MARINE...SS


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