FXUS66 KSGX 071715
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
930 AM PST MON DEC 7 2009
.SYNOPSIS...
A STRONG PACIFIC STORM WILL BRING RAIN TODAY. HEAVY SNOW AND NEAR
BLIZZARD CONDITIONS ARE LIKELY IN THE SAN BERNARDINO MOUNTAINS ABOVE
6000 FEET...AND IN THE SAN JACINTO MOUNTAINS ABOVE 7000 FEET. STRONG
AND GUSTY WINDS ARE POSSIBLE WITH THE PASSAGE OF THE COLD FRONT THIS
AFTERNOON...ESPECIALLY IN SAN DIEGO COUNTY. THE STORM WILL EXIT
TUESDAY...BUT A MOIST FLOW OFF THE PACIFIC WILL BRING A CHANCE FOR
MORE RAIN THURSDAY AND FRIDAY.
&&
.DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO...
ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES.
WIDESPREAD STRATIFORM RAIN HAS BEGUN OVER THE FORECAST AHEAD OF AN
APPROACHING COLD FRONT. SNOW IS FALLING ABOVE 5000 FT. WINDS ARE
CURRENTLY LIGHT...BUT THIS WILL LIKELY CHANGE AS THE DAY PROGRESSES.
A BROAD...COLD TROUGH WILL DIG SOUTHWESTWARD TODAY AS A 140-150 KT
JET DEVELOPS OVER SOUTHERN CA. A DEEPENING SURFACE LOW IS FORECAST
TO APPROACH THE ORANGE COUNTY / SAN DIEGO COUNTY BORDER EARLY THIS
AFTERNOON...WITH A TRAILING COLD FRONT AND AN IMPRESSIVE 60 KT LOW
LEVEL JET. MODEL FORECAST SOUNDINGS SHOW 40 KT WINDS AT 800 MSL AND
50 KT WINDS AT 1200 FT MSL OVER LINDBERGH AROUND 1 PM. WITH SUCH
STRONG WINDS JUST ABOVE THE SURFACE...ANY HEAVY RAIN OR CONVECTION
ALONG THE FRONT WILL EASILY TRANSPORT THESE WINDS TO THE SURFACE.
THE STRONGEST WINDS WILL OCCUR DURING THE EARLY AFTERNOON HOURS.
ALSO...GIVEN THE VERY STRONG SHEAR IN THE 0-1KM LAYER IN SAN DIEGO
COUNTY...GREATER THAN 400 HELICITY...AN ISOLATED TORNADO CANNOT BE
RULED OUT. IN ADDITION TO THE WIND THREAT...HEAVY RAIN AND ISOLATED
THUNDERSTORMS ARE POSSIBLE WITH THE FRONTAL PASSAGE LATER TODAY.
IT NOW LOOKS AS THOUGH THE LOW LEVEL JET MAY NOT EXTEND INTO AREAS
NORTH OF SAN DIEGO COUNTY...HENCE THE HIGH WIND WARNING FOR ORANGE
COUNTY AND THE INLAND EMPIRE HAS BEEN DOWNGRADED TO A WIND ADVISORY.
HOWEVER GUSTY WINDS TO 35 MPH OR MORE ARE STILL POSSIBLE.
IN THE MOUNTAINS...HEAVY SNOW WITH BLIZZARD LIKE CONDITIONS ARE
EXPECTED AT THE HIGHER ELEVATIONS. STRONG WARM AIR ADVECTION AHEAD
OF THE SURFACE LOW AND COLD FRONT WILL CAUSE SNOW LEVELS TO RISE TO
ABOUT 6000 FT IN SBD COUNTY...TO GREATER THAN 7000 FT OVER SAN DIEGO
COUNTY EARLY THIS AFTERNOON. SNOW LEVELS WILL THEN PLUMMET BEHIND
THE FRONT TO 3000 FT OR LOWER LATE THIS EVENING. WHERE THE PRECIP
REMAINS MOSTLY SNOW...MAINLY SAN BERNARDINO MTNS ABOVE 6000-6500
FEET...TWO FEET LOOKS LIKE A GOOD BET. WHATEVER SNOW FALLS IN THE
SAN DIEGO COUNTY MTNS WILL QUICKLY BE COMPACTED BY THE CHANGEOVER TO
RAIN DURING THE MID-LATE MORNING HOURS...SO AMOUNTS SHOULD NOT BE
ALL THAT GREAT THERE. RIVERSIDE COUNTY LOOKS TO BE SOMEWHERE IN
BETWEEN.
STORM TOTAL RAINFALL ESTIMATES ARE FOR ABOUT 1 TO 2 INCHES IN THE
FLATS...2 TO 4 INCHES ON THE COASTAL MOUNTAIN SLOPES...UP TO 1/2 AN
INCH IN THE DESERTS. PRECIPITATION WILL QUICKLY DIMINISH AFTER THE
FRONT MOVES THROUGH IN THE EVENING...EXCEPT AT HIGHER ELEVATIONS
WHERE STRONG WEST WINDS WILL CONTINUE UPSLOPE PRECIPITATION. MON
NIGHT IS WHEN THE SAN DIEGO COUNTY MOUNTAINS COULD SEE SEVERAL
INCHES OF SNOW. SOME LIGHT PRECIPITATION COULD LINGER IN THE SAN
DIEGO MOUNTAINS THROUGH TUE MORNING BEFORE COMPLETELY DRYING OUT.
OTHERWISE PARTLY CLOUDY AND CONTINUED BREEZY AND COOL.
ANOTHER WARMER SYSTEM FROM THE CENTRAL PACIFIC IS EXPECTED BY THU
INTO FRI WITH LIGHT TO MODERATE RAIN POSSIBLE.
&&
.AVIATION...
071500Z...BROKEN TO OVERCAST LAYERS BETWEEN 2500 AND 4500 FEET MSL
WITH TOPS ABOVE FL250 AT TIMES WILL LOWER TO BETWEEN 1000 AND 2000
FEET AT TIMES IN HEAVIER PRECIPITATION TODAY. APPEARS COLD FRONT
SHOULD PASS THROUGH THE AREA BETWEEN 18Z AND 00Z THIS AFTERNOON.
EMBEDDED THUNDERSTORMS CAN BE EXPECTED WITH THE FRONT. VISIBILITIES
MOSTLY 3 TO 5 MILES IN PRECIPITATION AND FOG BUT LOCALLY BELOW 3
MILES IN HEAVIER PRECIPITATION. STRONG SOUTHWEST WINDS BETWEEN 30
AND 50 KNOTS CAN BE EXPECTED AHEAD AND VICINITY OF THE FRONT FROM
ABOUT FL010 ON UP. MOUNTAINS WILL REMAIN OBSCURED IN CLOUDS AND
PRECIPITATION. FREEZING LEVEL SHOULD BE AROUND 5000 FEET THIS
MORNING RISING TO ABOUT 6500 FEET THIS AFTERNOON THEN LOWERING TO
AROUND 4500 FEET OVERNIGHT. HORTON
&&
.MARINE...
A STRONG COLD FRONT WILL BRING HAZARDOUS SEAS AND WINDY CONDITIONS
TODAY THROUGH TUESDAY MORNING. THERE WILL BE A GALE WARNING FOR THE
INNER AND OUTER WATERS THROUGH TUESDAY MORNING. A RAPID RISE IN
WESTERLY SWELL WILL ACCOMPANY THE FRONT MONDAY EVENING...THEN
DECREASE EARLY TUESDAY. A HIGH RIP CURRENT RISK WILL DEVELOP THIS
AFTERNOON AS SWELL AND SURF RISE RAPIDLY.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING...SEE LAXWSWSGX.
HIGH WIND WARNING...SEE LAXNPWSGX.
GALE WARNING...SEE LAXMWWSGX.
FLASH FLOOD WATCH...SEE LAXFFASGX.
HIGH SURF ADVISORY...SEE LAXCFWSGX.
&&
$$
PUBLIC...SCV
AVIATION/MARINE...HORTON
