Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 251416 AAA
AFDSGX

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE SAN DIEGO CA
715 AM PDT FRI JUL 25 2014

.SYNOPSIS...
HIGH PRESSURE TO THE EAST WILL BRING NEAR SEASONAL TEMPERATURES
THROUGH EARLY NEXT WEEK WITH SLIGHTLY ABOVE SEASONAL TEMPERATURES
POSSIBLE AROUND THE MIDDLE OF NEXT WEEK. MID LEVEL MOISTURE WILL
BRING A SLIGHT CHANCE OF AFTERNOON AND EARLY EVENING THUNDERSTORMS
FOR THE MOUNTAINS. THE MARINE LAYER WILL KEEP COASTAL AREAS COOLER
WITH AREAS OF NIGHT AND MORNING LOW CLOUDS AND FOG. THE MARINE
LAYER WILL BE A LITTLE DEEPER THROUGH THE WEEKEND...THEN A LITTLE
SHALLOWER NEXT WEEK.

&&

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

THUNDERSTORMS HAVE BEEN ADDED TO THE FORECAST FOR THE COAST AND
VALLEYS OF SAN DIEGO COUNTY THIS MORNING. A NARROW BAND OF ELEVATED
INSTABILITY WILL DRIFT NORTH WITH SCATTERED THUNDERSTORMS AND
ISOLATED CLOUD-TO-GROUND LIGHTNING STRIKES.

.SHORT TERM (TODAY THROUGH SUNDAY)...
THE COMBINATION OF MID AND HIGH LEVEL MOISTURE AND CLOUDS FROM A
WEAK INVERTED TROUGH MOVING WESTWARD ACROSS FAR SOUTHERN
CALIFORNIA...A DEEPER MARINE LAYER FROM A COASTAL EDDY...AND A
SHALLOW INCREASE IN LOW LEVEL MOISTURE IN THE LOWER DESERTS WILL
BRING 5 TO LOCALLY 10 DEGREES OF COOLING TODAY. THIS WOULD RETURN
HIGH TEMPERATURES TO A FEW DEGREES ABOVE TO A FEW DEGREES BELOW
SEASONAL LEVELS FOR MOST LOCATIONS. THE DECREASE IN TEMPERATURES IN
THE LOWER DESERTS WILL BE OFFSET WITH AN INCREASE IN HUMIDITY WITH
THE PEAK HEAT INDEX VALUES NEAR TO SLIGHTLY HIGHER THAN THURSDAY.

THE RADAR ECHOES ACROSS SOUTHERN CALIFORNIA ARE LIKELY NOTHING MORE
THAN VIRGA GIVEN THE ATMOSPHERIC MOISTURE PROFILE WITH MOISTURE
CENTERED NEAR 600 MB WITH A DEEP DRY SUBCLOUD LAYER. AS THIS BAND
HAS MOVED ACROSS YUMA...IMPERIAL...AND THERMAL...IT HAS BEEN A
STRUGGLE TO GET ANY CLOUD LAYERS AS LOW AS 12000 FEET. AT MOST...
SOME MOUNTAIN AREAS MIGHT GET A FEW SPRINKLES WITH LIMITED CHANCES
FOR ANYTHING MEASURABLE.

THE 06Z NAM APPEARS TO BE BETTER INITIALIZED WITH THE MID LEVEL
MOISTURE BAND ACROSS THE AREA THAN THE 00Z RUN AND SIMILAR TO THE
GFS AND ECMWF. THE NAM MOVES THIS BAND ONLY VERY SLOWLY WESTWARD
ACROSS FAR SOUTHERN CALIFORNIA TODAY WITH THE AXIS OF GREATEST
MOISTURE FROM NEAR SAN DIEGO THROUGH THE SAN BERNARDINO MOUNTAINS TO
NEAR LAS VEGAS. THERE MAY BE SOME THINNING OF THIS MID AND HIGH
LEVEL MOISTURE OVER THE LOWER DESERTS AND ADJACENT MOUNTAIN SLOPES
DURING THE AFTERNOON.

AS WITH RECENT EVENTS...THE MOISTURE DISTRIBUTION REMAINS SUBOPTIMAL
FOR THUNDERSTORM DEVELOPMENT WITH THE BULK OF THE MOISTURE AROUND
600 MB AND ABOVE WITH A DRIER SUBCLOUD LAYER. AIRCRAFT SOUNDINGS
OVERNIGHT FROM NEAR SAN DIEGO AFTER MIDNIGHT AND FROM PHOENIX AROUND
3 AM SHOW LITTLE CHANGE IN THE GENERAL MOISTURE PROFILE WITH THE
GREATEST SATURATION JUST BELOW 600 MB IN A SHALLOW LAYER.

THE CURRENT FORECAST RETAINS A SLIGHT CHANCE OF THUNDERSTORMS NEAR
THE MOUNTAINS THE NEXT FEW AFTERNOONS...BUT ANY THUNDERSTORMS THAT
DO DEVELOP WOULD BE MORE LIKELY TO PRODUCE LOCALLY STRONG GUSTY
WINDS AND LESS LIKELY TO PRODUCE MUCH RAINFALL.

&&

.LONG TERM (MONDAY THROUGH THURSDAY)...
RESIDUAL MOISTURE ON MONDAY MIGHT BE SUFFICIENT FOR AFTERNOON
THUNDERSTORMS ON MONDAY WITH DRYING OF THE MOISTURE SHOWN FOR
TUESDAY THROUGH THURSDAY AS THE RIDGE AXIS SHIFTS SOUTHWARD
SOMEWHAT...ENOUGH TO KEEP GREATER MOISTURE FARTHER SOUTH. THE 00Z
GFS HAD SHOWN A MOISTURE DISTRIBUTION FOR MONDAY AFTERNOON THAT
MIGHT BE A LITTLE MORE FAVORABLE FOR THUNDERSTORM DEVELOPMENT WITH
SOME MID LEVEL MOISTURE EXTENDING LOWER BELOW 600 MB...DRYING ALOFT
AND SLIGHTLY LESS STABILITY. THE 06Z GFS BACKED OFF FROM THIS
MOISTURE DISTRIBUTION WITH MID LEVEL MOISTURE MORE ELEVATED WITH A
DEEPER DRY SUBCLOUD LAYER.

WITH THE SOUTHWARD SHIFT OF THE RIDGE AXIS AND THE END TO THE
COASTAL EDDY...THE MARINE LAYER WILL BE A LITTLE SHALLOWER NEXT
WEEK. HIGH TEMPERATURES WILL BE NEAR AVERAGE ON MONDAY...THEN WARM
TO SLIGHTLY ABOVE AVERAGE FOR THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...
250900Z...COAST/VALLEYS...AREAS OF LOW CLOUDS WITH BASES 700-1000 FT
MSL AND TOPS TO 1200 FT MSL EXTENDING 5 TO LOCALLY 10 MILES INLAND.
THE LOW CLOUDS ARE SPREADING NORTH INTO ORANGE COUNTY...AND ARE
EXPECTED TO REACH KSNA BY 12Z...ALTHOUGH EXACT TIMING COULD BE
EARLIER. LOCAL VIS BELOW 3 SM COULD OCCUR ON THE COASTAL
MESAS...WHERE CLOUDS AND TERRAIN INTERSECT. LOW CLOUDS AND FOG WILL
ERODE TO THE COAST BETWEEN 25/1300Z-1600Z. SCT HIGH CLOUDS AOA 15000
FT THROUGH THE DAY. LOW CLOUDS WITH SIMILAR BASES AND TOPS WILL
SPREAD INLAND AGAIN AFT 0700Z SAT.

MTNS/DESERTS...UNRESTRICTED VIS THROUGH FRI NIGHT. MOSTLY SCT CLOUDS
ABOVE 15000 FT MSL THROUGH FRI...WITH SOME CU/TCU WITH BASES 9000 FT
MSL FRI MIDDAY/AFTERNOON WITH A SLIGHT CHANCE OF THUNDERSTORMS OVER
THE MOUNTAINS.

&&

.MARINE...
200 AM PDT...NO HAZARDOUS MARINE WEATHER THROUGH WEDNESDAY.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HEAT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR THE COACHELLA
     VALLEY...SAN DIEGO COUNTY DESERTS.

PZ...NONE.

&&

$$

PUBLIC...JAD/17
AVIATION/MARINE...PG











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