Area Forecast Discussion
Issued by NWS San Diego, CA

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642
FXUS66 KSGX 052050
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
200 PM PDT THU MAY 5 2016

.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL BRING SHOWERS AT TIMES THROUGH THE
WEEKEND...WITH THE GREATEST CHANCES LATE TONIGHT AND FRIDAY WHEN A
FEW THUNDERSTORMS ARE POSSIBLE. LOCALLY STRONG GUSTY WINDS WILL
OCCUR IN THE MOUNTAINS AND DESERTS LATE THIS AFTERNOON AND TONIGHT.
DAYTIME TEMPERATURES WILL BE WELL BELOW NORMAL THROUGH SUNDAY...THEN
HIGH PRESSURE ALOFT WILL MOVE IN FROM THE WEST AND BRING WARMER
WEATHER IN THE EARLY TO MIDDLE PARTS OF NEXT WEEK.

&&

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

SKIES WERE CLOUDY WEST OF THE MOUNTAINS AS MINIMAL AFTERNOON
CLEARING OCCURRED. PATCHY DRIZZLE AND VERY LIGHT SHOWERS OCCURREDAT
TIMES...WITH A FEW LOCATIONS RECEIVING A FEW HUNDREDTHS OF AN INCH
OF ACCUMULATION...EXCEPT THE HIGHLY OROGRAPHIC CRESTLINE RIDGE HAD
0.15 INCHES IN THE SAN BERNARDINO MOUNTAINS. LOCAL WIND GUSTS WERE
OVER 40 MPH ON THE DESERT MOUNTAIN SLOPES AT MID-MORNING...WITH SOME
INCREASE EXPECTED LATE THIS AFTERNOON AND TONIGHT.

THE STORM SYSTEM IS CURRENTLY AROUND 32N/124W AND IS SLOWLY MOVING
EAST. A VIGOROUS WAVE IS EVIDENT ON THE WATER VAPOR LOOP AROUND 120
DEGREES WEST...AND LIGHTNING HAS BEEN DETECTED PERIODICALLY WITH
CONVECTION ALONG THIS WAVE. MORE SIGNIFICANT PRECIP SHOULD START
THIS EVENING ALONG THE COAST...MOST LIKELY MID-EVENING...WITH A
GRADUAL INCREASE IN PRECIP ELSEWHERE OVERNIGHT. MODELS ARE TRENDING
A LITTLE FURTHER NORTH WITH THE PASSAGE OVER SO-CAL FRIDAY...WHICH
WOULD BE FAVORABLE FOR HIGHER PRECIPITATION TOTALS IN THE AREA WITH
THE SYSTEM. ALSO...A MODERATE SURFACE LOW...AROUND 1010-1013
MB...DEPENDING ON THE MODEL...WILL MOVE THROUGH THE COASTAL WATERS
FRIDAY MORNING. THERE SHOULD BE ENOUGH INSTABILITY...WITH 500 MB
TEMPS AS LOW AS AROUND -22 DEG C...AND UPWARD VERTICAL MOTION ALOFT
DUE TO DYNAMICS TO BRING A FEW THUNDERSTORMS. WITH SOME SURFACE
HEATING FRIDAY...THERE COULD BE ENOUGH UPWARD MOTION IN THE STORMS
FOR HAIL...AND HAIL DOES OCCASIONALLY OCCUR WITH CLOSED LOWS THIS
LATE IN THE SEASON. MOST LIKELY THE HAIL DIAMETERS WILL BE 1/2 INCH
OR LESS. RIGHT NOW...TOTAL RAINFALL AMOUNTS SHOULD BE AROUND ONE-
HALF INCH AT LOWER ELEVATIONS...BUT LOCALLY MORE WHERE CONVECTION
MOVES OVER. MOUNTAINS SHOULD HAVE AROUND ONE INCH...BUT AGAIN
LOCALLY MORE IN CONVECTION. SNOW LEVELS WILL MOSTLY BE AROUND OR
ABOVE 7000 FEET...SO THE AREAL EXTENT OF SNOW WILL BE SMALL...BUT A
FEW PLACES COULD GET SEVERAL INCHES. THE MAIN PART OF THE UPPER LOW
WILL MOVE NORTHEAST INTO SOUTHERN UTAH BY SATURDAY...BUT ANOTHER
LOBE OF THE LOW COULD SWING THROUGH SO-CAL AND THE COASTAL WATERS
FROM THE NORTH...THOUGH THE MAIN VORT MAX WITH THAT WILL MOSTLY TAKE
A PATH SOUTHWARD OFF THE COAST AND THEN EAST INTO NORTHERN BAJA.
STILL...SOME MOISTURE AND INSTABILITY SHOULD CONTINUE SHOWERS
SATURDAY...WITH SOME THUNDERSTORMS MAINLY OVER HIGHER TERRAIN. THE
LOW WILL MOSTLY BE EAST OF THE AREA SUNDAY...WITH ONLY A FEW SHOWERS
POSSIBLE THEN.

HIGH PRESSURE ALOFT WILL MOVE IN FROM THE WEST MOST OF NEXT WEEK AND
BRING WARMER WEATHER...WITH TEMPS A LITTLE ABOVE NORMAL INLAND BY
TUE OR WED. THERE WILL LIKELY BE A MARINE LAYER NEAR THE COAST
THOUGH...SO THE WARMUP WILL BE LESS PRONOUNCED THERE...AND THERE
WILL BE NIGHT/MORNING LOW CLOUDS.

&&

.AVIATION...
052030Z...COASTS/VALLEYS...BKN/OVC LOW CLOUDS WITH BASES 3500-4500
FT MSL AND TOPS TO 5500 FT MSL CONTINUE TO FILL THE COASTAL BASIN.
VIS ACROSS THE REGION MAINLY P6SM...LOWER WHERE THESE CLOUDS
INTERSECT TERRAIN ON THE UPPER COASTAL SLOPES. BKN CLOUDS WITH
SIMILAR BASES AND TOPS WILL CONTINUE TO AFFECT THE AREA THROUGH LATE
AFTERNOON. STARTING AROUND 06/0200Z...SKIES WILL BECOME OVC WITH
SHOWERS AND ISOLATED THUNDERSTORMS DEVELOPING. EXPECT VIS TO DROP
TO 3-5SM IN SOME OF THE HEAVIER SHOWERS. BKN/OVC CONDS WITH SHRA
AND ISOLATED T-STORMS WILL CONTINUE THROUGH A MAJORITY OF FRIDAY.

MOUNTAINS/DESERTS...ABOVE THE MARINE LAYER...SCT CLOUDS AOA 15000
FEET WITH UNRESTRICTED VISIBILITY TODAY. THROUGH TONIGHT...GUSTY
SW TO WEST WINDS WILL CONTINUE TO BRING WEAK TO MODERATE
UP/DOWNDRAFTS OVER THE MOUNTAIN SLOPES AND DESERTS THROUGH TONIGHT.

&&

.MARINE...
130 PM...A PACIFIC STORM WILL BRING A SLIGHT CHANCE OF THUNDERSTORMS
LATE THIS EVENING THROUGH LATE FRIDAY AFTERNOON. THESE STORMS COULD
PRODUCE CLOUD TO WATER LIGHTNING AND BRIEF GUSTY WINDS.
OTHERWISE...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH SATURDAY.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY FROM 3 PM THIS AFTERNOON TO 5 AM PDT FRIDAY FOR
     RIVERSIDE COUNTY MOUNTAINS-SAN DIEGO COUNTY DESERTS-SAN
     DIEGO COUNTY MOUNTAINS-SAN GORGONIO PASS NEAR BANNING.

PZ...NONE.

&&

$$

PUBLIC...MAXWELL
AVIATION/MARINE...JT



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