Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 280511
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
915 PM PST TUE JAN 27 2015

.SYNOPSIS...
PARTLY CLOUDY TONIGHT AS HIGH PRESSURE ALOFT MOVES IN...THEN DRY AND
A LITTLE WARMER FOR WEDNESDAY. FOR THURSDAY THROUGH SATURDAY...A
WEAK LOW PRESSURE SYSTEM FROM THE SOUTHWEST WILL BRING INCREASING
CLOUDS AND A CHANCE OF SHOWERS TO THE REGION. DRIER AND WARMER WITH
OFFSHORE FLOW AND LOCALLY GUSTY NORTHEAST WINDS FOR SUNDAY AND
MONDAY...FOLLOWED BY MINOR COOLING TOWARDS THE MIDDLE OF THE WEEK AS
ONSHORE FLOW RETURNS.

&&

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

CURRENT SATELLITE IMAGERY SHOWS PATCHY LOW CLOUDS LINGERING OVER THE
HIGH DESERT AND A LARGE SWATH OF HIGH CLOUDS HEADING EAST TOWARDS
SOUTHERN CALIFORNIA. WITH RESIDUAL MOISTURE STILL IN PLACE OVER THE
HIGH DESERT...THINK THERE COULD BE SOME PATCHY FOG THERE TONIGHT.

A BRIEF LITTLE WARM UP WILL OCCUR WEDNESDAY AS A WEAK SHORT WAVE
RIDGE MOVES OVER BEHIND THE DEPARTING LOW. BY THURSDAY...MID-LEVEL
MOISTURE FROM AN UPPER LOW TO THE SOUTHWEST BEGINS TO ADVECT TOWARDS
SOUTHERN CALIFORNIA. THIS COULD BRING SOME LIGHT SHOWERS AS EARLY AS
THURSDAY MORNING...MAINLY TO THE MOUNTAINS AS LOW-LEVEL DRY AIR
REMAINS IN PLACE ELSEWHERE. AS LOW-LEVELS BEGIN TO MOISTEN THU
AFTERNOON AND FRIDAY...PRECIP CHANCES WILL INCREASE ACROSS THE AREA.
A CLOSED LOW FORMS IN THE BASE OF THE TROUGH OVER SOUTHERN CA ON
FRIDAY BEFORE IT SLOWLY PROGRESSES EASTWARD LATE FRI AND SATURDAY.
MOISTURE WRAPPING AROUND THE LOW WILL CONTINUE PRECIP CHANCES OVER
THE MOUNTAINS AND DESERTS INTO SATURDAY MORNING...WITH SHOWERS
TAPERING OFF WEST OF THE MOUNTAINS BY FRIDAY EVENING. STORM TOTAL
RAINFALL ACCUMULATIONS WILL GENERALLY BE LESS THAN ONE-QUARTER INCH
IN THE COASTAL AREAS...VALLEYS...AND DESERTS...AND ONE-QUARTER TO
ONE-HALF INCH IN THE MOUNTAINS. LOCAL AMOUNTS OF ONE-HALF TO
TWO-THIRDS INCH ARE POSSIBLE IN THE MOUNTAINS...MAINLY ON THE DESERT
SLOPES OF THE SAN BERNARDINO AND SAN JACINTO MOUNTAINS WHERE
WRAP-AROUND MOISTURE AND UPSLOPE FLOW EXIST. SNOW LEVELS WILL BE
AROUND 7000-7500 THURSDAY...LOWERING TO 6500-7000 FT BY SATURDAY
MORNING. SNOWFALL ACCUMULATIONS WILL RANGE FROM A TRACE TO 2 INCHES
ABOVE 6500 FT...2 TO 4 INCHES ABOVE 7000 FT. LOCAL AMOUNTS TO 6
INCHES POSSIBLE ABOVE 8000 FT IN THE SAN BERNARDINO MOUNTAINS. AS
THE LOW MOVES OUT EXPECT COOL AND FAIR WEATHER FOR THE REMAINDER
OF SATURDAY.

BY SUNDAY...THE AFOREMENTIONED LOW PRESSURE SYSTEM WILL CONTINUE TO
PUSH FURTHER SOUTHEAST OF THE REGION AND INTO NORTHERN MEXICO.
RAPIDLY RISING 500 MB HEIGHTS AND LIGHT TO MODERATE OFFSHORE FLOW
WILL DEVELOP OVER SOUTHERN CALIFORNIA IN ITS WAKE. HIGH TEMPERATURES
WILL GENERALLY BE 5 TO 10 DEGREES ABOVE NORMAL WEST OF THE MOUNTAINS
WITH FAIR SKIES. ON MONDAY...SURFACE GRADIENTS BEGIN TO TREND WEAKLY
ONSHORE WITH HIGH TEMPERATURES SIMILAR TO SUNDAY. BOTH THE 27/1200Z
ECMWF AND 27/1800Z GFS INDICATE A RETURN OF THE MARINE LAYER TO THE
COASTAL AREAS MONDAY NIGHT INTO TUESDAY MORNING. A WEAK TROUGH
PASSAGE ON TUESDAY WILL LEAD TO SLIGHTLY COOLER WEATHER AND A
CONTINUATION OF ONSHORE FLOW AND NIGHT AND MORNING LOW CLOUDS WEST
OF THE MOUNTAINS.

&&

.AVIATION...
280400Z...MOUNTAINS AND DESERTS...LIGHT E TO NE FLOW WILL KEEP SCT
CLOUDS IN THE 3500 TO 5500 FT MSL LAYER ALONG THE E AND NE SLOPES OF
THE MOUNTAINS THROUGH 19Z WEDNESDAY...WITH A HIGHER CLOUD DECK AOA
20000 FT MSL DEVELOPING AFTER 12Z. HOWEVER...NO CIGS ARE EXPECTED AT
PSP OR TRM. PATCHY FOG WILL BE POSSIBLE OVER UPPER DESERTS THROUGH
16Z WEDNESDAY...OTHERWISE NO VIS RESTRICTIONS ARE EXPECTED THROUGH
06Z THURSDAY. SURFACE WINDS WILL REMAIN LIGHT THROUGH THE PERIOD.

COASTS AND VALLEYS...LIGHT WINDS WITH SKC TRANSITIONING TO BKN AOA
20000 FT MSL THROUGH 18Z WEDNESDAY. NO VIS RESTRICTIONS WILL OCCUR
THROUGH 06Z THURSDAY.

&&

.MARINE...
800 PM....NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH SUNDAY
EVENING.

&&

.SKYWARN...
SKYWARN ACTIVATION WILL NOT BE NEEDED TODAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...SS/JT
AVIATION/MARINE...BA





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