Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 191643
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
943 AM PDT SUN APR 19 2015

.SYNOPSIS...A WEAK LOW PRESSURE SYSTEM WILL MOVE SOUTHWARD OVER THE
CALIFORNIA COASTAL WATERS THROUGH MIDWEEK. IN RESPONSE...EXPECT
ONSHORE FLOW TO STRENGTHEN...A COOLING TREND TO PERSIST...AND A
DEEPENING OF THE MARINE LAYER WEST OF THE MOUNTAINS. A SECONDARY LOW
PRESSURE SYSTEM WILL BRING A CHANCE OF SHOWERS TO THE AREA MAINLY
LATE WEDNESDAY THROUGH FRIDAY OF THIS WEEK. A WEAK RIDGE OF HIGH
PRESSURE WILL BUILD OVER SOUTHERN CALIFORNIA THIS WEEKEND...BRINGING
A DRYING AND A SLIGHT WARMING TREND.

&&

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

THE 12Z KNKX RAOB SOUNDING SHOWS A MARINE TEMPERATURE INVERSION AT
AROUND 900 FT MSL WITH DRY AIR ALOFT. ONSHORE SURFACE PRESSURE
GRADIENTS ARE SIMILAR TO 24 HOURS AGO...THOUGH AROUND 1 MB STRONGER
BETWEEN A HANDFUL OF THE COASTAL AND DESERT SITES. VISIBLE SATELLITE
CONTINUES TO SHOW LOW CLOUDS ERODING ALONG THE COASTAL ZONES AND
BEING REPLACED BY MOSTLY SUNNY SKIES. ANOTHER SPECTACULAR SPRING DAY
IS ON TAP WITH DRY WEATHER TEMPERATURES AT OR SLIGHTLY ABOVE NORMAL
FOR THIS TIME OF YEAR.

THROUGH MIDWEEK...A WEAK LOW PRESSURE SYSTEM...WHICH CURRENTLY
RESIDES 200 MILES WEST OF SAN FRANCISCO...WILL CONTINUE TO SAG
SLOWLY SOUTHWARD OFF THE CALIFORNIA COAST. THIS FEATURE WILL HELP TO
DEEPEN THE MARINE STRATUS LAYER...LOWER TEMPERATURES TO NEAR OR
SLIGHTLY BELOW AVERAGE FOR THIS TIME OF YEAR...AND INCREASE ONSHORE
FLOW THROUGH WEDNESDAY. THAT BEING SAID...LOW MARINE STRATUS CLOUDS
WILL FILL THE COASTAL BASINS DURING THE NIGHTS AND MORNINGS...WITH
MOSTLY SUNNY SKIES DURING THE AFTERNOONS.

A SECONDARY...SLIGHTLY STRONGER...LOW PRESSURE SYSTEM WILL DROP
SOUTH AND INFLUENCE THE WEATHER PATTERN ACROSS SOUTHERN CALIFORNIA
WITH COOLER WEATHER AND A CHANCE OF SHOWERS WEDNESDAY THROUGH FRIDAY
OF THIS WEEK. LIGHT RAIN SHOWERS COULD BEGIN IN THE SAN BERNADINO
MOUNTAINS AS EARLY AS TUESDAY EVENING THEN OVER AREAS WEST OF THE
MOUNTAINS AND PORTIONS OF THE HIGH DESERTS BY WEDNESDAY AFTERNOON.
BOTH THE 12Z GFS AND 00Z ECMWF INDICATE CYCLONIC FLOW ALOFT OVER OUR
REGION THROUGH FRIDAY WITH THE MAIN ENERGY FROM THE STORM AND
HIGHEST VORTICITY MAXIMA PASSING OVER NORTHERN BAJA. THE BEST
CHANCES FOR PRECIPITATION APPEARS TO BE ON THURSDAY AS THE NORTHWEST
QUADRANT OF THE LOW PASSES OVERHEAD. THE SNOW LEVEL IS EXPECTED TO
RANGE BETWEEN 6000-6500 FEET WITH A FEW INCHES OF ACCUMULATION
POSSIBLE OVER THE HIGH MOUNTAIN PEAKS. AS THE SYSTEM MOVES EAST OF
THE AREA ON FRIDAY INTO SATURDAY...A TRANSIENT RIDGE OF HIGH
PRESSURE WILL TAKE ITS PLACE. THIS WILL BRING DRIER WEATHER WITH
ALONG WITH A SLIGHT WARMING TREND THROUGH THE WEEKEND.

&&

.AVIATION... 191530Z...COAST AND VALLEYS...PATCHY LOW CLOUDS WITH BASES
700-1000 FT MSL WILL CLEAR THE COAST BY 17Z. A FEW LOW CLOUDS WILL
LINGER OVER THE COASTAL WATERS THIS AFTERNOON...OTHERWISE FAIR
SKIES AND LIGHT WESTERLY WINDS WILL PREVAIL FROM 17Z SUNDAY TO 01Z
MONDAY. LOW CLOUDS WILL RETURN TO THE COAST AFTER 03Z MONDAY WITH
BASES IN THE 1000-1500 FT MSL RANGE EXTENDING UP TO 30 MILES
INLAND BY 12Z MONDAY. VIS RESTRICTIONS OF 3 SM OR LESS ARE LIKELY
WHERE LOW CLOUDS INTERSECT THE COASTAL MESAS AND INLAND VALLEYS
FROM 07Z-16Z MONDAY. LOW CLOUDS SHOULD CLEAR THE COAST BY 18Z
MONDAY MORNING.

MOUNTAINS AND DESERTS....FEW CLOUDS AOA 20000 FT MSL AND UNRESTRICTED
VIS THROUGH MONDAY AFTERNOON.

&&

.MARINE...
830 AM...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH TUESDAY.
A STORM SYSTEM MOVING INTO SOUTHERN CALIFORNIA WILL BRING A SLIGHT
CHANCE OF LIGHT SHOWERS TO THE COASTAL WATERS WEDNESDAY AND THURSDAY.

&&

.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...JT
AVIATION/MARINE...BA


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