Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 312131
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
131 PM PST SAT JAN 31 2015

.SYNOPSIS...
ISOLATED LIGHT SHOWERS FROM A WEAK LOW PRESSURE SYSTEM OVER THE
SOUTHWEST STATES WILL MOSTLY END BY LATE THIS AFTERNOON...WITH
PERHAPS A SHOWER OR TWO OCCURRING THIS EVENING FOR SAN DIEGO COUNTY.
SURFACE HIGH PRESSURE OVER THE GREAT BASIN WILL CONTINUE TO BRING
GUSTY NORTH TO NORTHEAST WINDS NEAR THROUGH AND BELOW THE CAJON PASS
AND INTO THE COASTAL FOOTHILLS THROUGH EARLY SUNDAY MORNING.
CLEARING SKIES AND WARMER WEATHER FOR SUNDAY AS HIGH PRESSURE ALOFT
MOVES IN AND OFFSHORE FLOW WEAKENS. THE MARINE LAYER AND MOSTLY WEAK
ONSHORE OR NEUTRAL FLOW WILL BRING NIGHT AND MORNING LOW CLOUDS AND
PATCHY FOG FOR THE COAST AND PORTIONS OF THE VALLEYS SUNDAY NIGHT
THROUGH THE END OF THE WORK WEEK. HIGH TEMPERATURES WILL BE AROUND
SEASONAL NORMALS NEAR THE COAST TO AROUND 5 TO 10 DEGREES ABOVE
NORMAL FOR INLAND AREAS.

&&

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

CURRENT RADAR IMAGERY SHOWS SOME LIGHT RETURNS OVER THE SAN
BERNARDINO COUNTY MOUNTAINS...AND SAN DIEGO COUNTY...WITH SOME
MODERATE SHOWERS OVER THE CENTRAL TO SOUTHERN SAN DIEGO COUNTY
MOUNTAINS. THE 12Z MIRAMAR SOUNDING STILL SHOWED A MOIST ATMOSPHERE
UP THROUGH 300 MB...WITH 0.95 INCHES OF PRECIPITABLE WATER. THIS
MOISTURE...IN ADDITION TO A VORT MAX ASSOCIATED WITH A CLOSED LOW
MOVING THROUGH THE AREA...IS WHAT CONTINUES TO BRING THESE ISOLATED
SHOWERS TO THE REGION. THE LOCAL WRF AND HRRR ACTUALLY SHOW A COUPLE
LIGHT SHOWERS CONTINUING INTO EARLY EVENING FOR CENTRAL AND SOUTHERN
SAN DIEGO COUNTY...SO ADDED A 15 PERCENT CHANCE OF SHOWERS FOR THOSE
AREAS FOR THE EARLY TO MID EVENING HOURS. ANY ADDITIONAL RAINFALL
TODAY SHOULD BE VERY LIGHT...MOSTLY 0.01 OR LESS...WITH LOCAL 0.05
INCH AMOUNTS POSSIBLE. THE SNOW LEVEL WILL CONTINUE AT AROUND 7000
FEET THIS AFTERNOON...WITH ONLY LIGHT SNOWFALL ABOVE THAT ELEVATION
POSSIBLE TODAY INTO THIS EVENING.

SURFACE WIND-FLOW WILL START TO TURN OFFSHORE IN THE NORTH TO
NORTHEAST DIRECTION LATE TODAY...AS SURFACE HIGH PRESSURE BUILDS
OVER THE GREAT BASIN. HOWEVER...THE OFFSHORE WINDS DO NOT LOOK TO BE
VERY STRONG...AS OFFSHORE PRESSURE GRADIENTS FROM SAN DIEGO TO
TONOPAH ONLY INCREASE TO AROUND 6-8 MB...AND ONLY 2-3 MB FROM SAN
DIEGO TO LAS VEGAS. SOME STATIONS ARE ALREADY REPORTING SOME 30-40
MPH GUSTS...BUT SPOTS THAT ARE RECEIVING THE WIND ARE MOSTLY GUSTING
15-25 MPH AT THE MOMENT. SINCE THE OFFSHORE FLOW WILL BE
WEAK...LOCAL WRF INDICATES THAT SOME PATCHY MARINE LAYER STRATUS MAY
DEVELOP IN THE COASTAL AREAS TONIGHT INTO SUNDAY MORNING.

OFFSHORE FLOW WILL WEAKEN ON SUNDAY...AND AN UPPER LEVEL RIDGE WILL
NUDGE INTO THE REGION AS THE TROUGH CONTINUES TO MOVE FAR SOUTH OF
SOUTHERN CALIFORNIA. THIS WILL RESULT IN CLEARING SKIES AND WARMING
WEATHER...WITH DAY-TIME HIGHS RISING SEVERAL DEGREES ABOVE NORMAL.
MOSTLY WEAK ONSHORE TO NEUTRAL FLOW WILL THEN DEVELOP MONDAY THROUGH
FRIDAY...UNDER CONTINUED RIDGING ALOFT...RESULTING IN FAIR WEATHER
WITH BETTER NIGHT AND MORNING STRATUS/FOG COVERAGE FOR THE COAST AND
PORTIONS OF THE VALLEYS. THERE WILL ALSO BE CONTINUED WARMING WITH
DAY-TIME HIGHS RISING TO 5-10 DEGREES ABOVE NORMAL BY TUESDAY.
TEMPERATURES WILL BE NEAR NORMAL AT THE COAST DUE TO THE MARINE
LAYER. OCCASIONAL HIGH CLOUDS PASSING OVER THE AREA WILL MAKE FOR
PARTLY CLOUDY SKIES AT TIMES.

&&

.AVIATION...
312130Z...COAST/VALLEYS...MULTIPLE SCT-BKN CLOUD LAYERS AOA 3500 FT
MSL THROUGH THIS EVENING. PATCHY LOW CLOUDS AND FOG REDEVELOPING
AFTER 01/03Z ALONG THE COAST WITH CIGS 800-1500 FT MSL LIKELY AT
KSAN AND KCRQ...LESS LIKELY AT KSNA. AREAS OF 3-5 SM IN BR POSSIBLE
WITHIN 10 SM OF THE COAST. FORECAST CONFIDENCE IN COVERAGE AND CIG
HEIGHTS IS MODERATE. CIGS AND VIS EXPECTED TO CLEAR BY MID-MORNING
SUNDAY.

MTS/DESERTS...NORTHERLY WINDS 15-20 KT WITH SFC GUSTS UP TO 40 KT
WILL OCCUR ALONG THE RIDGES OF THE SAN BERNARDINO MTNS...BELOW THE
CAJON PASS...NORTHERN COACHELLA VALLEY...AND THROUGH THE CANYONS OF
THE SANTA ANA MTNS. WINDS GRADUALLY DECREASING THROUGH EARLY SUNDAY
MORNING...THOUGH REMAINING WEAKLY OFFSHORE TO THE NORTH.
OTHERWISE...SCT CLOUDS AOA 10000 FT MSL THROUGH SUNDAY MORNING.

&&

.MARINE...
130 PM....SLIGHT CHANCE OF MAINLY LIGHT SHOWERS OVER THE INNER
COASTAL WATERS THROUGH THIS EVENING. OTHERWISE...NO HAZARDOUS
MARINE WEATHER IS EXPECTED THROUGH WEDNESDAY.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...HARRISON
AVIATION/MARINE...23





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