Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 290555
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
930 PM PST SUN DEC 28 2014

.SYNOPSIS...
FAIR BUT COOL WEATHER WILL CONTINUE THROUGH MONDAY. A STORM SYSTEM
MOVING ALL THE WAY FROM CANADA TO SOUTHERN CALIFORNIA WILL BRING
RAIN AND SNOW TUESDAY AFTERNOON THROUGH WEDNESDAY...WITH SNOW LEVELS
POSSIBLY DOWN TO 2000 FEET ABOVE SEA LEVEL. IT WILL ALSO BE
COLD...WITH HIGHS ONLY IN THE UPPER 40S AND 50S WEDNESDAY AND
THURSDAY AT LOWER ELEVATIONS...WITH BELOW FREEZING WEATHER IN THE
MOUNTAINS. AN ISOLATED THUNDERSTORM IS POSSIBLE NEAR THE COAST
TUESDAY NIGHT INTO WEDNESDAY. FAIR WEATHER WILL RETURN BY THURSDAY
NIGHT...WITH A GRADUAL WARMING TREND BACK TO NEAR NORMAL
TEMPERATURES BY NEXT SUNDAY.

&&

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

IT IS QUITE CHILLY AGAIN THIS EVENING...WITH TEMPERATURES NEAR OR
SLIGHTLY ABOVE THOSE FROM 24 HOURS AGO. THERE WILL BE PATCHY FROST
OVERNIGHT IN THE VALLEYS AND LOWER DESERTS...THOUGH NOT QUITE AS
WIDESPREAD AS LAST NIGHT.

THE MAIN EVENT WILL BE THE STORM FOR LATE TUESDAY THROUGH WEDNESDAY.
MODELS ARE PRETTY CONSISTENT WITH THIS...WITH THE COLD AIR ARRIVING
LATE TUESDAY DUE TO THE CANADIAN ORIGIN OF THIS TROUGH. THE CLOSED
UPPER LOW WILL TAKE A TRACK FROM THE SIERRA THROUGH THE MOHAVE
DESERT TUESDAY NIGHT AND THEN INTO FAR WESTERN ARIZONA BY WED
AFTERNOON. THERE WILL INITIALLY BE LOW-LEVEL WEST FLOW TO BRING IN
PACIFIC MOISTURE...ESPECIALLY OVER SAN DIEGO COUNTY...WITH BEST
PRECIPITATION AMOUNTS GENERALLY IN SAN DIEGO AND WESTERN RIVERSIDE
COUNTIES. OVERALL...ABOUT 1/4 TO 1/2 INCH WILL FALL...WITH HIGHER
AMOUNTS IN LOCAL CONVECTIVE SHOWERS AND IN THE SAN DIEGO/RIVERSIDE
COUNTY MOUNTAINS. OFFSHORE FLOW WILL DEVELOP LATE TUESDAY
NIGHT...ESPECIALLY NORTH OF SAN DIEGO COUNTY AND GRADUALLY BRING
DRYING WEDNESDAY FOR A DECLINE OF THE PRECIP. WITH 850 MB TEMPS
BETWEEN -3 AND -5 DEG C...AND EVEN LOWER IN SAN BERNARDINO
COUNTY...AND THE CONVECTIVE NATURE OF THE SHOWERS...SNOW LEVELS WILL
BE QUITE LOW...ESPECIALLY INLAND...WITH SNOW LEVELS POSSIBLY 2000
FEET IN THE INLAND EMPIRE AND 2500 FEET IN SAN DIEGO COUNTY.
HENCE...NOT ONLY INTERSTATES 8 AND 15 WILL HAVE SNOW IN THE
MOUNTAINS BUT POSSIBLY INTERSTATE 10 THROUGH BANNING PASS. SNOWFALL
AMOUNTS OF 4 TO 8 INCHES WILL PREVAIL IN THE MOUNTAINS...WITH
LOCALLY HIGHER AMOUNTS IN RIVERSIDE/SAN DIEGO COUNTIES. LATEST
GUIDANCE IS SUGGESTING THE SAN BERNARDINO COUNTY MOUNTAINS MAY GET A
LITTLE LESS WITH THE EARLIER DRYING UP THERE LATE TUESDAY NIGHT/WED.
WITH LOW-LEVEL NORTH FLOW OVER THE HIGH DESERTS OF SAN BERNARDINO
COUNTY...THERE COULD BE SOME SNOW THERE...PROBABLY AROUND 1-2
INCHES. WINTER STORM WATCHES ARE IN EFFECT FOR THE MOUNTAINS AND
HIGH DESERTS. TEMPS WILL BE QUITE LOW WED...WITH HIGHS BARELY ABOVE
50 IN MANY VALLEY/LOWER DESERT LOCATIONS.

WE MOSTLY DRY OUT BY WEDNESDAY NIGHT...THOUGH WE CONTINUE A SLIGHT
CHANCE OF PRECIP THEN DUE TO THE PROXIMITY OF THE UPPER LOW. WED
NIGHT WILL BE A COLD NIGHT...THOUGH SOME NORTHEAST WINDS AND
LINGERING CLOUD COVER WILL KEEP FROST FROM BEING TOO WIDESPREAD IN
THE VALLEYS. WITH SNOW COVER IN THE MOUNTAINS...IT COULD BE IN THE
SINGLE DIGITS IN COLDEST AREAS...POSSIBLY EVEN AROUND ZERO NEAR BIG
BEAR. THU NIGHT LOOKS LIKE A BETTER CHANCE OF FROST IN THE
VALLEYS/LOWER DESERTS WITH LESS WIND AND CLOUDS. A WARMING TREND
WILL BEGIN FRIDAY AND CONTINUE THROUGH THE WEEKEND AS A RIDGE
DEVELOPS OFF THE COAST.

&&

.AVIATION...
290430Z...SCT020 LOCALLY BKN020 AFTER 10Z AS MARINE LAYER CLOUDS
RETURN TO THE COASTAL AIRPORTS. VIS IS FORECAST TO REMAIN ABOVE 6SM
THROUGH MONDAY MORNING.

VALLEY...MOUNTAINS AND DESERTS...MOSTLY CLEAR WITH UNRESTRICTED VIS
THROUGH MONDAY.

&&

.MARINE...
830 PM...NO MARINE CONCERNS THROUGH MONDAY. WINDS WILL INCREASE
TUESDAY AHEAD OF A STRONG WINTER STORM THAT WILL BRING SCATTERED
SHOWERS AND A CHANCE FOR THUNDERSTORMS TUESDAY AND WEDNESDAY.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
     AFTERNOON FOR THE APPLE AND LUCERNE VALLEYS...RIVERSIDE
     COUNTY MOUNTAINS...SAN BERNARDINO COUNTY MOUNTAINS...SAN
     DIEGO COUNTY MOUNTAINS.
PZ...NONE.

&&

$$

PUBLIC...MAXWELL
AVIATION/MARINE...MOEDE





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