Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 311055
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
355 AM PDT FRI OCT 31 2014

.SYNOPSIS...
A TROUGH OF LOW PRESSURE DEEPENING ALONG THE WEST COAST TODAY WILL
BRING COOLER WEATHER AND A RAPIDLY DEEPENING MARINE LAYER. RAIN IS
LIKELY FRIDAY NIGHT INTO EARLY SATURDAY MORNING WITH LINGERING
RAIN AND HIGH ELEVATION SNOW SHOWERS THROUGH SUNDAY MORNING.
SEVERAL INCHES OF SNOW IS LIKELY ABOVE 7000 FEET. WARMER DAYS
EARLY NEXT WEEK WITH WEAK TO MODERATE OFFSHORE FLOW AS HIGH
PRESSURE BUILDS OVER THE GREAT BASIN.

&&

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

.SHORT TERM...
UPPER LOW IS SITUATED JUST OFF THE PACIFIC NORTHWEST COAST EARLY
THIS MORNING. DEEP UPPER LEVEL TROUGH STRETCHES ALONG THE U.S.
WEST COAST TO NORTHERN CALIFORNIA AND THEN OFFSHORE FROM SOUTHERN
CALIFORNIA. UPPER TROUGH WILL TAKE A BIG SWING AT CENTRAL AND
SOUTHERN CALIFORNIA TONIGHT AND SATURDAY MORNING WITH A SECONDARY
TROUGH LINGERING IN SOCAL SUNDAY.

NO SIGNIFICANT CHANGES TO THE ONGOING FORECAST THIS MORNING. THE
SHORT RANGE MODELS ARE IN GOOD AGREEMENT AND OVER THE LAST COUPLE
RUNS HAVE RAMPED UP THE MOISTURE ADVECTION INTO OUR REGION LATE
TONIGHT AND SATURDAY MORNING. FRONTAL BAND PRECIPITATION LOOKS TO
BE THE MOST SIGNIFICANT BATCH OF PRECIP...ALTHOUGH SOME WARM AIR
ADVECTION LIGHT PRECIP WILL BE POSSIBLE THIS EVENING AHEAD OF THE
FRONT...AND THEN SCATTERED SHOWERS MAY LINGER INTO SUNDAY DUE TO
THE COLD UPPER TROUGH LINGERING THROUGHOUT OUR AREA. SURFACE BASED
INSTABILITY COINCIDENT WITH FRONTAL BAND IS FORECAST BY THE VERY
HIGH RESOLUTION SHORT RANGE TO REACH 300-400 K/KG SO ALTHOUGH
WE`RE NOT FORECASTING THUNDERSTORMS THERE WILL LIKELY BE SOME
ENHANCED HEAVIER BURSTS OF CONVECTIVE SHOWERS LATE TONIGHT AND
EARLY SATURDAY MORNING.

A FLASH FLOOD WATCH REMAINS IN EFFECT FOR THE SILVERADO BURN SCAR
IN THE SANTA ANA MOUNTAINS AND FOOTHILLS WHERE RAINFALL AMOUNTS
GENERALLY AROUND ONE-HALF INCH WILL BE LIKELY. AS MENTIONED BRIEF
HEAVIER BURSTS OF CONVECTIVE RAIN COULD INITIATE A DEBRIS FLOW. IN
ADDITION...URBANIZED FLOODING COULD OCCUR ANYWHERE IN
ORANGE AND RIVERSIDE COUNTIES DUE TO POOR DRAINAGE CONDITIONS.

IN THE HIGHER MOUNTAINS PRECIPITATION AMOUNTS WILL BE AROUND ONE
INCH WITH RAIN TURNING TO SNOW ABOVE 6500 FEET LATE TONIGHT INTO
SATURDAY MORNING. A FEW HOURS OF HEAVIER SNOW COULD ACCUMULATE
SEVERAL INCHES OF SNOW. A WINTER WEATHER ADVISORY CONTINUES FOR
THE HIGHER MOUNTAINS ABOVE 6500 FEET WITH UP TO 6 INCHES IN THE
HIGHER MOUNTAINS POSSIBLE. ALTHOUGH GROUND CONDITIONS ARE
OBVIOUSLY QUITE WARM...THE TIMING OF THE SYSTEM SHOULD ALLOW
ADEQUATE TIME TO COOL OVERNIGHT BEFORE THE HEAVIER PRECIP MOVES IN
LATE TONIGHT...ALLOWING SOME ACCUMULATION TO TAKE PLACE DURING
THE HEAVIER BURSTS OF SNOW.

PRECIP WILL BECOME SCATTERED LATER SATURDAY MORNING BUT WILL
LINGER THROUGH SUNDAY ESPECIALLY IN THE MOUNTAINS GIVEN THE BROAD
FORCING OF THE UPPER TROUGH AND STEEP LAPSE RATES.

ANOTHER WEATHER CONCERN WILL BE THE STRONG SOUTHWEST TO WEST WINDS
LATE TONIGHT AND INTO SATURDAY. IN THE MOUNTAINS AND
DESERTS...GUSTS OF 50 TO 60 MPH WILL BE LIKELY WITH GUSTS UP TO
70 MPH IN THE MOST FAVORABLE MOUNTAIN PASSES AND CANYONS.

&&

.LONG TERM...
UPPER LEVEL TROUGH WILL FINALLY DEPART SOCAL SUNDAY NIGHT AND
REPLACED WITH EAST PAC RIDGING. A SURFACE HIGH WILL BECOME
ESTABLISHED OVER THE GREAT BASIN TUESDAY THROUGH THURSDAY BRINGING
THE POTENTIAL FOR A MODERATE OFFSHORE WIND EVENT ACROSS THE INLAND
VALLEYS. ALTHOUGH GRADIENTS WILL NOT BE STRONG ENOUGH TO CAUSE
STRONG WINDS...THE PROLONGED NATURE OF THE EVENT WILL ALLOW
RELATIVE HUMIDITY VALUES TO PLUMMET INTO THE TEENS ACROSS THE
INLAND VALLEYS. UPPER LEVEL HIGH PRES RIDGING WILL PERSIST INTO
NEXT WEEKEND...CONTINUING ABOVE NORMAL TEMPERATURES AND MINIMAL
MARINE LAYER INFLUENCE.

&&

.AVIATION...
311040Z...MULTIPLE BKN CLOUD LAYERS WITH BASES 1500-3000 FT MSL
FILLING IN WEST OF THE MOUNTAINS THROUGH THE MORNING. CLOUDS
BECOMING SCT-BKN WITH BASES 2500-3500 FT MSL AFTER 16-18Z. BASES
LOWERING BACK TO AROUND 2000 FT MSL AFTER 01/00Z. A COLD FRONT WILL
BRING SCATTERED LIGHT SHOWERS ALONG AND WEST OF THE MTNS BEGINNING
AROUND 01/01-03Z...BECOMING HEAVIER AND MORE WIDESPREAD AFTER
MIDNIGHT. LIGHT SHOWERS POSSIBLE OVER THE HIGH DESERTS AFTER
01/10Z...WITH LITTLE IF ANY PRECIP IN THE LOW DESERTS. LOCAL
MVFR/IFR CIGS AND VIS POSSIBLE IN HEAVIER SHOWERS. COASTAL SLOPES OF
THE MOUNTAINS WILL BE OBSCURED IN CLOUDS AND PRECIPITATION THROUGH
SAT MORNING.

SW TO W WINDS 20-30 KT GUSTING TO 40-50 KT OVER MOUNTAIN RIDGES AND
ALONG DESERT SLOPES/ADJACENT DESERT FOOTHILLS WILL CREATE MOD-STG
UDDFS...LLWS AND ROTORS E AND NE OF THE MOUNTAINS AFTER 21Z. VIS
LOCALLY REDUCED TO 5SM OR LESS IN BLDU/HZ.

&&

.MARINE...
350 AM...NO HAZARDOUS MARINE WEATHER IS EXPECTED TODAY. A COLD FRONT
MOVING OVER THE COASTAL WATERS WILL BRING WEST TO NORTHWEST WINDS
GUSTING TO 25-30 KT AND STEEP WAVES SATURDAY. A SMALL CRAFT ADVISORY
WILL BE IN EFFECT FROM EARLY SATURDAY MORNING THROUGH LATE SATURDAY
NIGHT...SEE LAXMWWSGX FOR DETAILS. CONDITIONS WILL IMPROVE DURING
THE DAY SUNDAY.

&&

.SKYWARN...
SKYWARN ACTIVATION IS NOT REQUESTED FOR TODAY. SKYWARN MAY BE
REQUESTED FOR LATE TONIGHT AND SATURDAY MORNING...PRIMARILY FOR
URBANIZED AND BURN SCAR FLOODING CONCERNS AND SNOW IN THE HIGHER
ELEVATIONS. WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT
WEATHER CONDITIONS.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY FROM 8 PM THIS EVENING TO 5 PM PDT SATURDAY FOR
     THE APPLE AND LUCERNE VALLEYS...COACHELLA VALLEY...
     RIVERSIDE COUNTY MOUNTAINS...SAN BERNARDINO COUNTY
     MOUNTAINS...SAN DIEGO COUNTY DESERTS...SAN DIEGO COUNTY
     MOUNTAINS.

     WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 2 PM PDT
     SATURDAY ABOVE 6500 FEET FOR THE RIVERSIDE COUNTY
     MOUNTAINS...SAN BERNARDINO COUNTY MOUNTAINS.

     FLASH FLOOD WATCH FROM THIS EVENING THROUGH SATURDAY MORNING FOR
     THE SANTA ANA MOUNTAINS AND FOOTHILLS.

PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 5 AM PDT SATURDAY TO 4 AM
     PST SUNDAY FOR THE COASTAL WATERS FROM SAN MATEO POINT TO
     THE MEXICAN BORDER AND OUT 30 NM...WATERS FROM SAN MATEO
     POINT TO THE MEXICAN BORDER EXTENDING 30 TO 60 NM OUT
     INCLUDING SAN CLEMENTE ISLAND.


&&

$$

PUBLIC...BROTHERTON
AVIATION/MARINE...SS







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