Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 220444
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
844 PM PST SUN DEC 21 2014

.SYNOPSIS...
BUILDING HIGH PRESSURE OVER THE EASTERN PACIFIC...AND SURFACE HIGH
PRESSURE OVER THE GREAT BASIN WILL BRING FAIR...VERY DRY...AND
WARMER WEATHER THROUGH WEDNESDAY...WITH GUSTY SANTA ANA WINDS BELOW
FAVORED PASSES AND CANYONS ALONG THE COASTAL FOOTHILLS. A TROUGH OF
LOW PRESSURE WILL BRING COOLER CONDITIONS TO SOUTHERN CALIFORNIA AND
GUSTY WESTERLY WINDS TO THE MOUNTAINS AND DESERTS ON CHRISTMAS DAY.
FAIR...DRY...AND SEASONAL FOR THE BALANCE OF THE HOLIDAY WEEKEND.

&&

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

EXTENSIVE HIGH CLOUDS CONTINUE TO STREAM OVER THE AREA FROM THE
NORTH THIS EVENING...HOWEVER OBSERVATIONS SHOWED FEW IF ANY
LOWER...MARINE CLOUDS. SURFACE PRESSURE GRADIENTS WERE TURNING
OFFSHORE FROM NV AT 4-5 MBS...BUT REMAINED VERY WEAK ONSHORE TO THE
LOWER DESERTS. A FEW REMOTE SITES IN THE SANTA ANA/SAN BERNARDINO
MTS WERE SHOWING NE WIND GUSTS OF 30-35 MPH AT 8 PM PST. THE 00Z
MIRAMAR SOUNDING STILL HAD WINDS WEST BELOW 7K FT AND NW ABOVE...
BUT WARMING WAS INDICATED THROUGHOUT THE COLUMN WITH ALMOST 10
DEGREE C OF WARMING IN THE 900 MB LAYER.

THE HIGH CLOUDS ARE FORECAST TO THIN ON MON AS SURFACE PRESSURE
GRADIENTS TURN OFFSHORE. THIS COMBINATION SHOULD MEAN FAIR...DRY AND
WARMER DAYS THROUGH MIDWEEK. ON CHRISTMAS DAY...THE GRADIENT WILL
TURN BACK ONSHORE AND IT WILL BE COOLER AS THE MARINE LAYER REBUILDS
WEST OF THE MTS.

A STRONG 594 DM HIGH PRESSURE AREA WAS CENTERED AT 30N/130W THIS
EVENING. WINDS CIRCULATION AROUND THE HIGH ARE STEERING HIGH CLOUDS
ACROSS CA THIS EVENING. THESE CLOUDS SHOULD THIN AS THE HIGH BUILDS
A RIDGE NE ALONG THE WEST COAST THROUGH TUE MORNING. THE RIDGE WILL
BE FLATTENED BY A SHARP SHORTWAVE TROUGH ON WED. THIS FEATURE WILL
DIG INTO THE GREAT BASIN WED NIGHT/THU...WEAKENING THE OFFSHORE
GRADIENT AND TURNING WINDS BACK ONSHORE FOR CHRISTMAS DAY. EXPECT
SOME COOLING AND A FEW MORE CLOUDS...OTHERWISE DRY.

THE COOLER WEATHER SHOULD LINGER FOR THE BALANCE OF THE HOLIDAY
WEEKEND UNDER DRY...NW FLOW ALOFT.

WINDS...A HIGH WIND WATCH HAS BEEN POSTED FOR LATE MON THROUGH TUE
AFTERNOON. THE OFFSHORE SURFACE PRESSURE GRADIENT WILL BUILD
INLAND...WITH MODERATE SUPPORT ALOFT FROM THE NORTH. THE PATTERN
MAINLY FAVORS AREAS BELOW THE CAJON PASS AND SANTA ANA MTN CANYONS
FOR WIND GUSTS ABOVE 55 MPH. BUT BASED ON HIRES MODEL CROSS
SECTIONS...STRONG GUSTS MAY SURFACE ON TUE ALONG WIND PRONE FOOTHILL
AREAS OF THE SAN DIEGO COUNTY MTS AS WELL. BASED ON THIS PATTERN...
MOST WIND PRONE AREAS OF THE COASTAL FOOTHILLS WILL LIKELY
EXPERIENCE ADVISORY STRENGTH WINDS MON/TUE. GUSTY WINDS WILL
CONTINUE IN SOME AREAS THROUGH EARLY WED BEFORE DIMINISHING. THE
WIND WILL TURN BACK ONSHORE WED AFTERNOON...AND INDICATIONS ARE THEY
MAY BECOME RATHER STRONG ON THE DESERT SLOPES AND THROUGH THE PASSES
WED NIGHT/THU.

EXTENDED DISCUSSION...LOOKS LIKE OUR WET PATTERN HAS ENDED FOR THE
TIME BEING. THE LATEST GLOBAL MODEL RUNS WANT TO REESTABLISH MORE OF
A MERIDIONAL PATTERN ACROSS THE HEMISPHERE WITH A DEEP CONTINENTAL
TROUGH AND SHARP EASTPAC RIDGE. THERE HAVE BEEN OCCASIONAL MODEL
RUNS UNDERCUTTING THE RIDGE WITH A MOIST SUBTROPICAL TAP TOWARD THE
END OF THE MONTH...BUT SUCCESSIVE RUNS HAVE NOT SUPPORTED IT.
ASSUMING THIS HIGHLY AMPLIFIED PATTERN HOLDS...EXPECT DRY
CONDITIONS...LESS MARINE LAYER DAYS...AND FAIR SKIES WITH PERIODS OF
OFFSHORE FLOW INTO NEW YEARS DAY UNDER COOL...NORTHERLY FLOW ALOFT.
PERHAPS A WETTER PATTERN WILL RESUME NEXT YEAR...BUT FOR NOW...
CONSENSUS IS FOR NO SIGNIFICANT PRECIPITATION UNTIL AFTER THE FIRST
OF THE NEW YEAR.

&&

.AVIATION...
220400Z...FEW LOW CLOUDS ALONG THE COAST THIS EVENING WILL CLEAR BY
09Z. OTHERWISE...SCT-BKN CLOUDS AOA 15000 FT MSL AND UNRESTRICTED
VIS THROUGH MON AFTERNOON.

&&

.MARINE...
800 PM...COMBINED SEAS TO 8 FEET WILL CONTINUE OVER PORTIONS OF THE
OUTER COASTAL WATERS THROUGH TONIGHT. OTHERWISE NO HAZARDOUS
MARINE WEATHER IS EXPECTED THROUGH FRIDAY.

&&

.BEACHES...
800 PM...A LARGE...LONG PERIOD WEST-NORTHWEST SWELL WILL CONTINUE
ELEVATED SURF THROUGH MONDAY MORNING...MAINLY IN SOUTHERN SAN DIEGO
COUNTY...AND STRONGER RIP CURRENTS THROUGH TUESDAY. IN
ADDITION...MORNING HIGH TIDES AROUND 7 FEET COULD CONTRIBUTE TO
MINOR TIDAL OVERFLOW THROUGH TUESDAY. SEE THE BEACH HAZARD STATEMENT
FOR DETAILS...LAXCFWSGX.

&&

.FIRE WEATHER...
OFFSHORE FLOW WILL DEVELOP ACROSS SOUTHERN CALIFORNIA MON AND
CONTINUE THROUGH WED...WITH PERIODS OF GUSTY NORTH TO NORTHEAST
WINDS NEAR THE COASTAL FOOTHILLS.  WINDS WILL SLOWLY INCREASE
TONIGHT AND MON...REACHING MAXIMUM STRENGTH MON NIGHT/TUE.
STRONGEST WINDS WILL OCCUR THROUGH AND BELOW THE FAVORED PASSES AND
CANYONS BEFORE WEAKENING ON WED. MAXIMUM GUSTS WILL LIKELY EXCEED 55
MPH FOR SEVERAL HOURS IN THE WINDIEST SPOTS. THE OFFSHORE FLOW WILL
MEAN VERY DRY AND WARMER CONDITIONS WEST OF THE MTS...WITH
TEMPERATURES RUNNING AROUND 10 DEGREES ABOVE NORMAL...AND THE LOWEST
DAYTIME HUMIDITY FALLING TO 15 TO 20 PERCENT TUE/WED. INCREASED FUEL
MOISTURE DUE TO RECENT PRECIPITATION WILL LIMIT THE POTENTIAL FOR
WILDFIRES.

&&

.SKYWARN...
SKYWARN ACTIVATION WILL NOT BE NEEDED ON MONDAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HIGH WIND WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON
     FOR THE COACHELLA VALLEY...ORANGE COUNTY COASTAL AREAS...
     RIVERSIDE COUNTY MOUNTAINS...SAN BERNARDINO COUNTY
     MOUNTAINS...SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE
     INLAND EMPIRE...SAN DIEGO COUNTY MOUNTAINS...SAN DIEGO
     COUNTY VALLEYS...SANTA ANA MOUNTAINS AND FOOTHILLS.

     BEACH HAZARDS STATEMENT THROUGH TUESDAY MORNING FOR THE BEACHES
     IN THE ORANGE COUNTY COASTAL AREAS...SAN DIEGO COUNTY
     COASTAL AREAS.

PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...JAD
AVIATION/MARINE...PG








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