Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 040416
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
916 PM PDT SUN MAY 3 2015

.SYNOPSIS...

A WEAK LOW PRESSURE SYSTEM OFF THE COAST OF SOUTHERN CALIFORNIA WILL
MOVE INLAND THROUGH MONDAY BRINGING ADDITIONAL CLOUDS...COOLING...
AND A CHANCE FOR LATE DAY SHOWERS AND THUNDERSTORMS OVER THE
HIGHER MOUNTAINS. ONSHORE FLOW WILL INCREASE THROUGH FRIDAY AS A
COLDER LOW PRESSURE SYSTEM DIVES SOUTH OVER THE STATE. GUSTY
WESTERLY WINDS WILL DEVELOP OVER THE MOUNTAINS AND DESERTS...AND
THE MARINE LAYER WILL DEEPEN FURTHER...RESULTING IN MUCH BELOW
NORMAL DAYTIME TEMPERATURES...AND A CHANCE OF SHOWERS MAINLY
THURSDAY AND FRIDAY. DRY AND A LITTLE WARMER BY NEXT WEEKEND AS
THE SYSTEM EXITS THE REGION.

&&

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

PERSISTENT SHOWERS AND STORMS OVER SOUTHEAST SAN BERNARDINO
COUNTY NEAR AMBOY AND LUDLOW THIS EVENING. CELLS AND PULSY AND
SLOW MOVING AND LIKELY COINCIDENT WITH A LITTLE SPIKE IN
INSTABILITY AND NEAR A VERY SLOW MOVING MESO LOW AND LOW LEVEL
TROUGH. COULD BE OCCASIONAL PULSES OF CONVECTION IN THE VCNTY
OVERNIGHT. ON MONDAY...ADDITIONAL BROAD FORCING FROM A WEAK UPPER
LEVEL TROUGH PASSING JUST SOUTH OF THE BORDER...ALONG WITH
RESIDUAL MID LEVEL MOISTURE IS STILL EXPECTED TO SUPPORT THE
DEVELOPMENT OF A FEW SHOWERS AND STORMS OVER THE MOUNTAINS AND
DESERTS DURING THE AFTERNOON AND EVENING. ACTIVITY SHOULD DIMINISH
SHORTLY AFTER DARK.

MARINE LAYER AND MODERATE ONSHORE PUSH WILL CONTINUE OVERNIGHT
WITH WIDESPREAD CLOUDINESS THROUGH THE VALLEYS. GUSTY ONSHORE
WINDS THROUGH THE SLOPES AND PASSES PRODUCING GUSTS OF 30 TO 35
MPH ATTM AND SHOULD PERSIST OVERNIGHT. GUSTY ONSHORE WINDS AGAIN
MONDAY AFTERNOON AND EVENING.

NO CHANGES TO THE ONGOING FORECAST DATABASE WERE MADE THIS
EVENING.

...PREVIOUS LONGER TERM DISCUSSION...
IT WILL BE A COOLER WEEK AHEAD...EVEN AS THE WEAK LOW PRESSURE AREA
OFFSHORE MOVES AWAY FROM THE AREA MON NIGHT. BECAUSE MODELS SHOW A
MUCH COLDER...LONGWAVE TROUGH TAKING SHAPE ACROSS THE STATE THROUGH
FRI. THE TROUGH IS CURRENTLY OVER THE GULF OF ALASKA...BUT WILL
TRACK INTO THE PACNW ON TUE...AND THEN DIVE ALMOST DUE SOUTH INTO
CENTRAL CA BY FRI. THERE IS STILL SOME SPREAD IN THE MODEL SOLUTIONS
REGARDING THE EXACT TRACK AND TIMING...BUT THERE IS CONSENSUS ON THE
PATTERN TO BRING BLUSTERY AND COOLER WEATHER ACROSS SOCAL TO END THE
WORK WEEK.

THE 00Z ECMWF MODEL CONTINUES TO BE THE MOST AGGRESSIVE WITH THE
DEEPENING OF THE SYSTEM...WHICH RESULTS IN SLIGHTLY SLOWER MOVEMENT
AS IT CUTS OFF OVER CENTRAL CA. THE 12Z GFS SEEMS TO BE TRENDING
CLOSER TO THE ECMWF MODEL SO CONFIDENCE IS BUILDING IN THE OUTCOME
FOR SOCAL.

FOR WINDS...LOOK FOR A GRADUAL INCREASE IN WESTERLY WINDS MON
THROUGH TUE. BY TUE AFTERNOON A SFC PRESSURE GRADIENTS TO THE
DESERTS LOOK SUFFICIENT FOR SOME WIND GUSTS OF 40 MPH OR MORE IN
WIND PRONE AREAS LATE IN THE DAY. STRONGER WINDS ARE POSSIBLE ON
THU...BUT THIS IS BEYOND THE HIRES MODELS AT THIS POINT SO ONCE WE
GET CLOSER...A BETTER ESTIMATION IS LIKELY. BUT FOR NOW...IT LOOKS
LIKE AT LEAST ADVISORY STRENGTH WINDS WILL DEVELOP OVER THE
MTS/DESERTS. CONTINUED BREEZY/WINDY ALL AREAS ON FRI WHEN SOME
MOUNTAIN WAVES COULD DEVELOP OVER THE DESERT SLOPES BENEATH A STRONG
JET.

PRECIPITATION...AT THIS TIME...AMOUNTS LOOK TO BE LIGHT BASED ON THE
TRACK OF THIS SYSTEM...BUT THE MARINE LAYER IS FORECAST TO DEEPEN
ABOVE 5000 FT...SO THERE WILL BE A CHANCE FOR SOME LIGHT SHOWERS
BREAKING OUT ALONG AND WEST OF THE MTS WED NIGHT THROUGH FRI NIGHT.
THE MODEL PW FIELD IS QUITE LOW OVER THE REGION...CONSEQUENTLY NOT
MUCH OF ANY PRECIP IS BEING GENERATED. WITH THIS IN MIND...POPS ARE
CURRENTLY QUITE LOW. BUT BOTH OF THE LATEST OPERATIONAL RUNS OF THE
GFS/ECMWF SUGGEST A CYCLONICALLY CURVED...90 KT JET WILL WILL SWING
OVER THE REGION ON FRI...PLACING NORTHERN PORTIONS OF THE CWA INTO
A FAVORED AREA OF LIFT AND INSTABILITY. IF THAT HAPPENS...IT IS HARD
TO BELIEVE WE WOULD NOT HAVE SUFFICIENT DYNAMICS TO DRIVE SOME
PRECIP DEVELOPMENT FOR A FEW HOURS. BASED ON THE CURRENT TIMING...
THE BEST CHANCE FOR THAT MEASURABLE PRECIP WOULD BE ON FRI MORNING.

THE SYSTEM IS FORECAST TO REMAIN PROGRESSIVE THROUGH NEXT WEEKEND SO
LOOK FOR FAIR SKIES AND A WARMER WEATHER THEN.

&&

.AVIATION...
040300Z...COAST/VALLEYS...STRATUS...WITH BASES FROM
1700-2300 FT MSL AND TOPS NEAR 2500 FT MSL...WILL CONTINUE TO
DEVELOP ALONG THE COAST THIS EVENING...AND PUSH INLAND TO THE
COASTAL MTN SLOPES BY EARLY MONDAY MORNING. APPROACHING LOW PRESSURE
WILL HELP LOW CLOUD BASES AND TOPS RISE AROUND 500 FT BY MID MON
MORNING...AND COULD OBSCURE HIGHER TERRAIN AT TIMES. LOW CLOUDS WILL
SLOWLY CLEAR TOWARDS THE COAST BY LATE MONDAY MORNING...THEN
REDEVELOP AGAIN MONDAY EVENING WITH SLIGHTLY HIGHER TOPS AND BASES.
FORECASTER CONFIDENCE IN STRATUS TIMING AND HEIGHTS IS MEDIUM TO
HIGH.

MTNS/DESERTS...WESTERLY WIND GUSTS TO 45KT WILL BE POSSIBLE MONDAY
AFTERNOON/EVENING THROUGH MTN PASSES AND ALONG DESERT MTN SLOPES.
ISOLATED TSRA WILL BE POSSIBLE OVER THE MTNS AND DESERTS MONDAY AFTN
AND EVENING. STRONG UP/DOWN DRAFTS...SMALL HAIL...LIGHTNING AND
GUSTY SURFACE WINDS WILL BE POSSIBLE NEAR T-STORMS.

&&

.MARINE... 800 PM...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH
TUESDAY. BREEZY NORTHWEST WINDS...WITH GUSTS OF 20 TO LOCALLY 25
KT...ARE POSSIBLE IN THE AFTERNOONS WEDNESDAY THROUGH
FRIDAY...MAINLY IN THE OUTER WATERS. A TROUGH MOVING ACROSS THE
REGION WILL CREATE A SLIGHT CHANCE OF SHOWERS THURSDAY AND FRIDAY.

&&

.BEACHES...
800 PM...ELEVATED SOUTHERLY SWELLS...WITH LONG PERIODS...WILL
CONTINUE HIGH SURF ALONG SAN DIEGO AND ORANGE COUNTY BEACHES THROUGH
EARLY THIS WEEK. WIDESPREAD SURF OF 3 TO 7 FT IS EXPECTED...WITH
SETS OF 8 TO 12 FT POSSIBLE ALONG SOUTHERLY-FACING BEACHES. STRONG
RIP AND LONGSHORE CURRENTS...BEACH EROSION AND MINOR TIDAL FLOODING
OF LOW-LYING VULNERABLE COASTAL AREAS DURING THE EVENING HIGH TIDES
IS EXPECTED. SURF WILL SLOWLY LOWER THROUGHOUT THE WEEK. SEE
LAXCFWSGX FOR DETAILS ON THE HIGH SURF ADVISORY CURRENTLY IN EFFECT
THROUGH TUESDAY EVENING.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HIGH SURF ADVISORY UNTIL 11 PM PDT TUESDAY FOR ORANGE COUNTY
     COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS.

PZ...NONE.
&&

$$

PUBLIC...BROTHERTON
AVIATION/MARINE...JJT
PREVIOUS...JAD


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