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000
FXUS66 KSGX 111655
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
855 AM PST WED DEC 11 2013

.SYNOPSIS...
UPPER LEVEL LOW OFF THE SOUTHERN CALIFORNIA COAST WILL BRING SOME
MID AND HIGH LEVEL CLOUDS TO THE REGION AS WELL AS A FEW ISOLATED
SPRINKLES THROUGH THURSDAY.  OTHERWISE...EXPECT TEMPERATURES TO
REMAIN NEAR OR SLIGHTLY BELOW SEASONAL NORMALS...WITH COLD OVERNIGHT
TEMPERATURES.  ANOTHER WEAK DISTURBANCE WILL PASS BY TO OUR
NORTHEAST ON FRIDAY...WITH SLIGHTLY COOLER CONDITIONS PREVAILING.
HOWEVER...HIGH PRESSURE WILL REBUILD OVER THE SOUTHWEST THIS WEEKEND
AND EARLY NEXT WEEK...WITH DRY AND WARMER CONDITIONS PREVAILING.
WEAK TO MODERATE OFFSHORE WINDS WILL BE POSSIBLE THESE DAYS AS WELL.

&&

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

WATER VAPOR IMAGERY SHOWS A REX BLOCK ALONG THE WEST COAST THIS
MORNING...WITH HIGH PRESSURE OFF THE NORTHERN CALIFORNIA COAST AND
AN UPPER LEVEL LOW OFF THE SOUTHERN CALIFORNIA AND NORTHERN BAJA
COAST.  THIS LOW IS CENTERED 29.25 NORTH AND 119 WEST...SPREADING
SOME MID AND HIGH LEVEL CLOUDS ACROSS THE REGION.  THE 12Z KNKX
SOUNDING SHOWS THIS MOISTENING TREND QUITE WELL...WITH THE MOISTURE
INCREASING BETWEEN 700 AND 500 MBS...AND PRECIPITABLE WATER VALUES
UP TO 0.43 INCHES.  THE SOUNDING ALSO SHOWS QUITE OF BIT OF ELEVATED
INSTABILITY.  AT THIS TIME...VISIBLE IMAGERY SHOWS TWO SEPARATE
CLOUD BANDS.  THE FIRST ONE IS EXTENDING ACROSS THE SOUTHEASTERN
HALF OF THE INLAND EMPIRE AND NORTHERN SAN DIEGO COUNTY...PRODUCING
SOME VIRGA...GIVEN THE VERY SIGNIFICANT DRY LAYER BELOW 750 MBS.
THE SECOND BAND IS LIFTING NORTHWESTWARD ACROSS NORTHERN BAJA AND
IMPERIAL COUNTIES...AND IS COMPRISED OF ALTOCUMULUS CASTELLANUS.
RADAR IMAGERY ALSO SHOWS A FEW LIGHT RETURNS WITH THIS SECONDARY
CLOUD BAND...SO CANNOT RULE OUT MORE VIRGA AND ISOLATED SPRINKLES
THIS AFTERNOON.  THE LATEST 12Z MODELS SHOW THE GREATEST ELEVATED
INSTABILITY THOUGH LIFTING ACROSS SAN DIEGO AND RIVERSIDE COUNTY
THIS EVENING AND OVERNIGHT TONIGHT...AS THIS A WEAK DISTURBANCE
MOVING AROUND THIS UPPER LEVEL LOW MOVES ACROSS THE REGION AND THIS
LOW STARTS TO MOVE INLAND.  THEREFORE...EXPECT THE THREAT OF
ISOLATED SHOWERS TO CONTINUE THROUGH TONIGHT IN THESE AREAS.  AT
THIS TIME...CANNOT RULE OUT THE POTENTIAL FOR A STRAY ELEVATED
NOCTURNAL THUNDERSTORM EITHER...BUT DO NOT HAVE ENOUGH CONFIDENCE IN
THIS OCCURRING JUST YET.  WILL AWAIT THE REST OF THE 12Z MODELS
BEFORE DECIDING WHETHER OR NOT TO ADD THEM TO THE FORECAST FOR
TONIGHT.

OTHERWISE...EXPECT A RELATIVELY MILD DAY ACROSS THE REGION...AS
TEMPERATURES WARM A FEW DEGREES OVER YESTERDAY...AFTER ANOTHER
SOMEWHAT CHILLY START TO THE MORNING.  IN FACT...IT LOOKS LIKE THE
HARD FREEZE WARNING FOR THE HIGH DESERT WORKED OUT WELL AS WELL AS
THE FROST ADVISORY FOR THE INLAND EMPIRE AND SOUTHERN DESERT AREAS.
WILL ALLOW THESE PRODUCTS TO EXPIRE AT 9 AM...AND UPDATE THE
FORECAST AT THAT TIME.

THIS UPPER LEVEL LOW WILL MOVE EAST DURING THE DAY ON
THURSDAY...WITH DRIER CONDITIONS DEVELOPING ONCE AGAIN.  ANOTHER
DISTURBANCE WILL THEN DIVE ACROSS NORTHERN CALIFORNIA AND INTO THE
DESERT SOUTHWEST ON THURSDAY NIGHT AND FRIDAY.  AT THIS
TIME...SOUTHERN CALIFORNIA WILL REMAIN DRY...AS THIS INSIDE SLIDER
PASSES BY TO OUR NORTH AND EAST.  HOWEVER...THE ONSHORE WINDS WILL
INCREASE ACROSS THE REGION...WITH SOME LOCALLY GUSTY WINDS
DEVELOPING IN THE MOUNTAINS AND DESERTS.  SOME MINOR COOLING WILL
ALSO DEVELOP ACROSS THE SOUTHLAND.  HOWEVER...HIGH PRESSURE WILL
REBUILD OVER THE EASTERN PACIFIC...WITH DRY AND WARMER CONDITIONS
DEVELOPING FOR THE WEEKEND AND EARLY NEXT WEEK.  SOME LIGHT TO
LOCALLY MODERATE OFFSHORE WINDS WILL ALSO BE POSSIBLE AT TIMES THESE
DAYS.

&&

.AVIATION...
111615Z...VFR CONDITIONS WILL PREVAIL THROUGH THURSDAY MORNING WITH
VARIABLE CLOUDS BETWEEN 10000-20000 FT MSL. ISOLATED DOWNDRAFTS AND
LIGHT RAIN SHOWERS MAY BE ASSOCIATED WITH THESE CLOUDS JUST UNDER
BASE LEVEL.

&&

.FIRE WEATHER (PREVIOUS DISCUSSION)...
OFFSHORE WINDS CONTINUING IN THE MOUNTAINS THROUGH THURSDAY MORNING
WITH ISOLATED GUSTS OF 20-30 MPH. LIGHTER WINDS THURSDAY AFTERNOON.
VERY LOW HUMIDITIES AGAIN THIS AFTERNOON RANGING FROM THE UPPER
SINGLE DIGITS TO MID TEENS. HUMIDITIES GRADUALLY IMPROVING THURSDAY
AFTERNOON THROUGH FRIDAY WITH THE RETURN OF WEAK ONSHORE FLOW.
BUILDING HIGH PRESSURE OVER THE WEEKEND WILL BRING WARMER
WEATHER...LOW HUMIDITIES AND OFFSHORE FLOW SATURDAY THROUGH TUESDAY.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...FROST ADVISORY UNTIL 9 AM PST THIS MORNING FOR THE COACHELLA
     VALLEY...SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE
     INLAND EMPIRE...SAN DIEGO COUNTY DESERTS.

     HARD FREEZE WARNING UNTIL 9 AM PST THIS MORNING FOR THE APPLE
     AND LUCERNE VALLEYS.

PZ...NONE.

&&

$$

PUBLIC...PALMER
AVIATION/MARINE...JT
FIRE...MOEDE