Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 252152
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
152 PM PST TUE NOV 25 2014

.SYNOPSIS...
SURFACE HIGH PRESSURE OVER THE GREAT BASIN WILL BRING PERIODS OF
GUSTY SANTA ANA WINDS THROUGH WEDNESDAY...WITH THE STRONGEST WINDS
OCCURRING DURING THE LATE NIGHT THROUGH MID-MORNING HOURS. HIGH
TEMPERATURES WILL CONTINUE TO RISE OVER THE NEXT COUPLE DAYS...WITH
DAY-TIME HIGHS 10 TO 20 DEGREES ABOVE NORMAL ON THANKSGIVING.
ONSHORE FLOW WILL RETURN FOR FRIDAY INTO THE WEEKEND WITH SLOW
COOLING ON FRIDAY AND GREATER COOLING FOR THE WEEKEND. A PACIFIC LOW
PRESSURE SYSTEM IS LIKELY TO BRING MODERATE TO HEAVY PRECIPITATION
AND HIGH ELEVATION SNOW SOME TIME EARLY NEXT WEEK.

&&

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

SANTA ANA WIND CONDITIONS HAVE WEAKENED SIGNIFICANTLY THIS
AFTERNOON...WITH EAST TO NORTHEAST WIND GUSTS OF 15 TO 25 MPH OVER
THE MOUNTAINS...COASTAL SLOPES AND FOOTHILLS OF SAN DIEGO
COUNTY...AND A SEA-BREEZE KICKING IN AT THE COAST. THE OFFSHORE
PRESSURE GRADIENT IS NOW ONLY 4.8 MB FROM SAN DIEGO TO TONOPAH...AND
1.7 MB FROM SAN DIEGO TO SALT LAKE CITY. HOWEVER...CANSAC WRF AND
LOCAL WRF SHOW THAT WINDS WILL PICK UP AGAIN TONIGHT INTO WEDNESDAY
MORNING...GUSTS LOOK TO BE ONLY IN THE 35-50 MPH RANGE...MAINLY IN
THE SAN DIEGO COUNTY MOUNTAINS/VALLEYS AND THROUGH AND BELOW THE SAN
GORGONIO PASS. THE OFFSHORE WINDS AND UPPER LEVEL RIDGE CURRENTLY
OVER THE REGION IS ALSO BRINGING CONTINUED WARMING TODAY WITH
TEMPERATURES SEVERAL DEGREES HIGHER THAN 24 HOURS AGO. FOR
TOMORROW...HIGH TEMPERATURES WILL LIKELY REACH 10-20 DEGREES ABOVE
NORMAL. THURSDAY WILL LIKELY BE THE HOTTEST DAY FOR MOST INLAND
AREAS...EXCEPT AT THE COAST WHERE A LATE MORNING AND AFTERNOON SEA
BREEZE SHOULD MODERATE TEMPERATURES SOMEWHAT.

THE RIDGE WILL BREAK DOWN ON FRIDAY...WITH ZONAL FLOW ALOFT AND
ONSHORE FLOW RETURNING AT THE SURFACE...RESULTING IN THE START OF A
COOLING TREND. IT WOULD NOT BE SURPRISING IF THE COAST STARTS TO SEE
SOME DENSE FOG AS EARLY AS EARLY FRIDAY MORNING. AT THE LATEST...THE
NIGHT AND MORNING MARINE LAYER STRATUS/FOG SHOULD RETURN BY FRIDAY
NIGHT INTO SATURDAY MORNING...AS CLOUDS MOVE INTO THE COAST AND
WESTERN VALLEYS. COOLING AND CONTINUED DEEPENING OF THE MARINE LAYER
WILL CONTINUE SATURDAY INTO SUNDAY UNDER CONTINUED ZONAL FLOW ALOFT
AS A LARGE LOW PRESSURE SYSTEM OVER THE NORTHEAST PACIFIC OCEAN
APPROACHES THE WEST COAST.

THERE ARE DIFFERENCES IN THE TIMING OF THE SYSTEM AS IT DEEPENS
ALONG THE WEST COAST AND MOVES INLAND OVER CENTRAL AND SOUTHERN
CALIFORNIA EARLY NEXT WEEK. THE 12Z GFS STARTS BRINGING PRECIP INTO
THE AREA MONDAY MORNING...WITH THE TROUGH AXIS MOVING INLAND OVER
CENTRAL CALIFORNIA TUESDAY MORNING...AND MOVING QUICKLY TO THE
SOUTHEAST OF THE AREA BY WEDNESDAY MORNING. MEANWHILE...THE 12Z
ECMWF IS STILL SLOWER...BUT NOT QUITE AS SLOW AS THE 00Z RUN...AS IT
STARTS BRINGING PRECIP INTO THE AREA FROM THE SOUTHWEST LATE MONDAY
AS IT TAPS INTO SOME SUBTROPICAL MOISTURE...WITH THE TROUGH AXIS
EVENTUALLY MOVING INLAND OVER CENTRAL/SOUTHERN CALIFORNIA TUESDAY
AFTERNOON. SIMILAR TO THE 12Z GFS...THE 12Z ECMWF ALSO MOVES THE
TROUGH TO THE EAST BY WEDNESDAY MORNING...WHICH IS A FASTER
PROGRESSION THAN THE 00Z RUN DEPICTED. THE 12Z GEM IS SIMILAR TO THE
12Z ECMWF IN THAT IT ALSO DEPICTS THE TROUGH BEING ABLE TO TAP INTO
SOME SUBTROPICAL MOISTURE AS IT STARTS TO BRING PRECIPITATION INTO
THE AREA MONDAY MORNING. REGARDLESS OF THE TIMING...PRECIPITATION
AMOUNTS LOOK TO BE SIGNIFICANT...WITH 1 INCH OR GREATER POSSIBLE IN
THE COAST AND VALLEYS...2-3 INCHES OR MORE IN THE MOUNTAINS...AND
LESS THAN 1 INCH IN THE DESERTS. SNOW LEVELS ARE LIKELY TO START OUT
SOMEWHAT HIGH AT AROUND 8000-9000 FEET AS WE GET WARM AIR ADVECTION
IN FROM THE SOUTHWEST MONDAY. DOES NOT LOOK LIKE THE COLD AIR STARTS
TO MOVE OVER SOUTHERN CALIFORNIA UNTIL TUESDAY MORNING WHEN SNOW
LEVELS LOOK TO DROP TO AROUND 6000-6500 FEET...WITH THE ECMWF AND
GEM INDICATING HEAVY SNOWFALL POSSIBLE ABOVE THAT LEVEL.
HOWEVER...THE 12Z GFS IS DRIER AFTER TUESDAY MORNING AFTER THE COLD
FRONT MOVES THROUGH...WHICH WOULD MEAN LESS IN THE WAY OF SNOWFALL.
ALSO...DAY-TIME HIGHS WILL FALL TO 10 TO 20 DEGREES BELOW NORMAL.
FINALLY...WINDS WILL GET QUITE GUSTY AS WELL OVER THE MOUNTAINS AND
DESERTS AS THE TROUGH MOVES THROUGH...WITH POTENTIAL 40-60 MPH
GUSTS.

&&

.AVIATION...
252100Z...CLEAR SKIES WITH UNRESTRICTED VIS THROUGH WEDNESDAY. AREAS
OF EAST-NORTHEAST WINDS WILL REDEVELOP LATE TONIGHT...BUT WEAKER
THAN LAST NIGHT WITH SURFACE WIND GUSTS 35 TO 45 MPH. THE WINDS WILL
OCCUR MAINLY IN AND BELOW THE COASTAL FOOTHILLS OF SAN DIEGO COUNTY
TONIGHT THROUGH EARLY WEDNESDAY MORNING WITH POCKETS OF LLWS AND
STRONG UDDFS OVER AND WEST OF THE MOUNTAINS. THE WINDS WILL DIMINISH
AGAIN BY LATE MORNING.

&&

.MARINE...
100 PM...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH SATURDAY.

&&

.FIRE WEATHER...
VERY LOW HUMIDITIES CONTINUE THIS AFTERNOON ALTHOUGH WINDS HAVE
SLACKENED OFF. HOWEVER...WINDS WILL PICK UP AGAIN LATE TONIGHT INTO
WEDNESDAY MORNING...WITH GUSTS OF 35-45 MPH ALONG THE COASTAL
SLOPES...THROUGH AND BELOW THE PASSES AND CANYONS...AND INTO THE
COASTAL FOOTHILLS OF SAN DIEGO AND RIVERSIDE COUNTIES. THUS...THE
RED FLAG WARNING CONTINUES THROUGH 6 PM WEDNESDAY FOR THOSE AREAS.
THE WINDS WILL WEAKEN ON THURSDAY...WITH ONLY LOCAL GUSTS OF 25-35
MPH...AND SO THE RED FLAG WARNING WILL LIKELY NOT BE EXTENDED INTO
THURSDAY. HOWEVER...HUMIDITY WILL STILL BE IN THE LOW TEENS TO
SINGLE DIGITS...RESULTING IN ELEVATED FIRE WEATHER CONDITIONS.
LITTLE TO NO OVERNIGHT HUMIDITY RECOVERIES WILL CONTINUE. THE RED
FLAG WARNING FOR INLAND ORANGE COUNTY...SANTA ANA
MOUNTAINS/FOOTHILLS AND THE SAN BERNARDINO NATIONAL FOREST HAS BEEN
CANCELLED...AS FORECAST MODELS CONTINUE TO TREND WEAKER WITH THE
WINDS FOR THOSE AREAS FOR TODAY INTO TOMORROW...AND SO RED FLAG
CRITERIA IS VERY UNLIKELY TO BE MET.

ONSHORE FLOW WILL RETURN THURSDAY NIGHT INTO FRIDAY MORNING...WITH
THE MARINE LAYER RETURNING BY FRIDAY NIGHT AND DEEPENING INTO
SATURDAY NIGHT. THE RETURN OF ONSHORE FLOW...THE MARINE LAYER...AND
COOLER CONDITIONS WILL RESULT IN MUCH HIGHER HUMIDITIES AND A
DIMINISHED FIRE WEATHER THREAT. SIGNIFICANT WETTING PRECIPITATION IS
POSSIBLE FOR EARLY NEXT WEEK AS A STORM SYSTEM MOVES THROUGH THE
AREA.

&&

.SKYWARN...
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...RED FLAG WARNING UNTIL 6 PM PST WEDNESDAY FOR THE RIVERSIDE
     COUNTY MOUNTAINS-INCLUDING THE SAN JACINTO RANGER DISTRICT
     OF THE SAN BERNARDINO NATIONAL FOREST...SAN BERNARDINO AND
     RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE...SAN DIEGO
     COUNTY INLAND VALLEYS...SAN DIEGO COUNTY
     MOUNTAINS-INCLUDING THE PALOMAR AND DESCANSO RANGER
     DISTRICTS OF THE CLEVELAND NATIONAL FOREST.

     WIND ADVISORY UNTIL 4 PM PST WEDNESDAY FOR THE SAN DIEGO COUNTY
     MOUNTAINS...SAN DIEGO COUNTY VALLEYS.

     WIND ADVISORY UNTIL 4 PM PST WEDNESDAY FOR THE SAN BERNARDINO
     AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE.

PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...HARRISON
AVIATION/MARINE...TS




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