Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 211141
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
440 AM PDT TUE APR 21 2015

.SYNOPSIS...

A WEAK LOW PRESSURE SYSTEM OFF THE CALIFORNIA COAST WILL MOVE INLAND
TODAY BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON
AND EVENING...MAINLY TO THE SAN BERNARDINO COUNTY MOUNTAINS.
RESIDUAL MOISTURE AND WEAK INSTABILITY WILL BRING A SLIGHT CHANCE OF
AFTERNOON AND EARLY EVENING SHOWERS AND THUNDERSTORMS WEDNESDAY...
MAINLY TO THE SAN BERNARDINO COUNTY MOUNTAINS AND DESERTS. A SECOND
WEAK LOW PRESSURE SYSTEM MOVING INLAND THROUGH SOUTHERN CALIFORNIA
AND NORTHERN BAJA LATE WEDNESDAY NIGHT AND THURSDAY WILL BRING A
CHANCE OF SHOWERS...ALSO WITH A SLIGHT CHANCE OF THUNDERSTORMS NEAR
THE MOUNTAINS IN THE AFTERNOON AND EARLY EVENING. A THIRD WEAK LOW
PRESSURE SYSTEM MOVING INLAND THROUGH SOUTHERN CALIFORNIA WILL BRING
A CHANCE OF SHOWERS FRIDAY. SLIGHT WARMING ON SATURDAY...THEN DRY
WITH GREATER WARMING FOR SUNDAY AND MONDAY UNDER HIGH PRESSURE.

$$

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

.SHORT TERM (TODAY THROUGH THURSDAY)...

A WEAK CLOSED LOW PRESSURE SYSTEM OVER THE SOUTHERN CALIFORNIA BIGHT
EARLY THIS MORNING WILL MOVE INLAND THROUGH SOUTHERN CALIFORNIA
TODAY. THIS HAS BROUGHT DEEPENING OF THE MARINE LAYER TO ABOVE 4000
FEET WITH SATELLITE IMAGERY SHOWING COASTAL STRATUS EXTENDING INLAND
ONTO THE LOWER COASTAL MOUNTAIN SLOPES. AS THE MID LEVEL COLD POOL
WITH 500 MB TEMPERATURES AROUND -20C MOVES ACROSS SOUTHERN
CALIFORNIA THIS AFTERNOON AND EARLY EVENING...THERE MAY BE
SUFFICIENT INSTABILITY FOR SHOWERS AND A FEW THUNDERSTORMS...MAINLY
OVER THE MOUNTAINS OF RIVERSIDE AND SAN BERNARDINO COUNTIES INTO THE
SAN BERNARDINO COUNTY DESERTS. RESIDUAL MOISTURE AND WEAK
INSTABILITY WILL BRING A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS
TO SIMILAR AREAS FOR WEDNESDAY AFTERNOON AND EARLY EVENING.

A SECOND WEAK LOW PRESSURE SYSTEM WILL MOVE INLAND THROUGH SOUTHERN
CALIFORNIA AND NORTHERN BAJA LATE WEDNESDAY NIGHT AND THURSDAY
BRINGING GREATER CHANCES FOR SHOWERS ALONG WITH A SLIGHT CHANCE OF
AFTERNOON AND EARLY EVENING THUNDERSTORMS MAINLY NEAR THE MOUNTAINS.

&&

.LONG TERM (FRIDAY THROUGH SUNDAY)...

A WEAK TROUGH OF LOW PRESSURE WILL PUSH A WEAK FRONT THROUGH
SOUTHERN CALIFORNIA ON FRIDAY BRINGING A CHANCE OF SHOWERS. SLIGHT
WARMING FOR SATURDAY...THEN DRY AND WARMER FOR SUNDAY AND MONDAY
UNDER HIGH PRESSURE.

&&

.AVIATION...

210900Z...COAST/VALLEYS...LOW CLOUDS WILL FILL THE ENTIRE COASTAL
BASIN AND BANK UP AGAINST THE FOOTHILLS THROUGH SUNRISE. BASES WILL
BE AROUND 2500-3000 FEET MSL WITH TOPS UP TO 5000 FEET WITH LOCAL
TERRAIN OBSCURED AROUND THAT LEVEL. FULL CLEARING IS NOT EXPECTED
TODAY...BUT MOST PLACES WILL SCATTER OUT FOR AT LEAST SOME TIME
AFTER 17Z. BROKEN CLOUDS THAT PERSIST WILL BE AOA 3000 FEET MSL.
AFTER 03Z THIS EVENING THE LOW CLOUDS WILL FILL THE COASTAL BASIN
AGAIN WITH SIMILAR BASE LEVELS.

MOUNTAINS AND DESERTS...MOSTLY CLEAR AND THEN AFTER 18Z CLOUDS WILL
BUILD OVER MOUNTAIN CRESTS. ISOLATED SHOWERS OR THUNDERSTORMS ARE
POSSIBLE MAINLY IN SAN BERNARDINO AND RIVERSIDE COUNTIES. ANY STORMS
THAT DEVELOP WILL HAVE BASES NEAR 8000 FEET WITH TOPS TO 20000 FEET.
AND WILL BE CAPABLE OF PRODUCING GUSTY WINDS AND SMALL HAIL. SHOWERS
WILL END BY 02Z AND WITH RESIDUAL HIGHER DEBRIS CLOUDS OVERNIGHT.

&&

.MARINE...

200 AM...NO HAZARDOUS MARINE WEATHER IS FORECAST THROUGH SATURDAY.

&&

.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...17
AVIATION/MARINE...MM



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