Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 061525
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
824 AM PDT MON JUL 6 2015

.SYNOPSIS... A DEEP MARINE LAYER AND STRONG INVERSION MAY HOLD JULY
GLOOM OVER SOME COASTAL AREAS AGAIN TODAY...WHILE AREAS FARTHER
INLAND SLOWLY CLEAR. THIS WILL MAKE FOR A COOL JULY DAY. FARTHER
INLAND OVER THE MOUNTAINS AND DESERTS...MOISTURE AND INCREASING
INSTABILITY WILL ONCE AGAIN RESULT IN SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS BY AFTERNOON. THE SHOWER THREAT WILL DIMINISH AFTER
TODAY AS DRIER AIR ASSOCIATED WITH LOW PRESSURE OFF THE COAST
SPREADS INLAND. THE UPPER LOW WILL KEEP AN UNSEASONABLY DEEP MARINE
LAYER IN PLACE WEST OF THE MOUNTAINS FOR THE REMAINDER OF THE
WEEK...RESULTING IN FURTHER INLAND COOLING AND PERIODS OF GUSTY
WESTERLY WINDS THROUGH THE MOUNTAIN PASSES AND INTO THE DESERTS.

&&

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

UPDATED FORECAST TO INCREASE THUNDERSTORM CHANCE OVER THE
MTS/DESERTS THIS AFTERNOON/EVENING.

SOUNDING DATA FROM THE 12Z MIRAMAR RELEASE...THE 12Z NAM...AND EVEN
THE LIMITED EXPERIMENTAL SATELLITE PASSES AT 09Z SHOW INCREASED
INSTABILITY TODAY OVER YESTERDAY WITH SIMILAR LAYER PW...WHILE LOWER
LEVEL OBSERVATIONS SHOW SLIGHTLY HIGHER DEWPOINTS ALONG AND EAST OF
THE MTS. WINDS BELOW 500 MBS CONTINUE TO BE RATHER LIGHT AND HAVE
BACKED TO THE SE. THIS WILL MAINTAIN THE MOISTURE BELOW 9000 FT
THROUGH THIS AFTERNOON...WHILE HIGHER LEVEL WINDS AT AND ABOVE 500
MBS GRADUALLY VEER AND INCREASE FROM THE SW. COUPLE THIS WITH FULL
HEATING...AND CONVECTIVE POTENTIAL LOOKS BETTER THAN YESTERDAY
OVER THE MTS...AND MOVING OFF INTO THE DESERTS.

THE 12Z NAM12 SHOWS THE ADVECTION OF DRIER AIR A BIT SLOWER THAN
PREVIOUSLY FORECAST...AND HAS WEAK VORTICITY MOVING ACROSS THE
REGION THIS AFTERNOON FOR ADDED LIFT. THE 14Z HRRR RUN ALSO HAS
CONSIDERABLE ACTIVITY DEVELOPING ALL ALONG THE MTN CRESTS BY 20Z.

EXPECT A FEW STRONG CELLS WITH GUSTY DOWNDRAFT OUTFLOWS...CLOUD-TO-
GROUND LIGHTNING STRIKES AND LOCALLY HEAVY DOWNPOURS THROUGH EARLY
EVENING.

SATELLITE IMAGERY THROUGH 15Z THIS MORNING SHOWED EXTENSIVE MARINE
STRATUS EXTENDING ALL THE WAY TO THE LOWER COASTAL SLOPES...WHILE
SKIES WERE CLEAR OVER THE MTS AND DESERTS. THE 12Z MIRAMAR SOUNDING
HAD A STRONG 11 DEGREE C INVERSION BASED NEAR 2950 FT MSL.

LOW PRESSURE OFF THE CA COAST WILL SLOWLY MOVE INLAND OVER CENTRAL
PORTIONS OF THE STATE BY THU. FALLING/HEIGHTS AND THICKNESS WILL
MAINTAIN MODERATE TO STRONG ONSHORE FLOW FOR THIS TIME OF YEAR AND
FURTHER COOLING THROUGH THU...ESPECIALLY INLAND WHERE MAX TEMPS WILL
BE AROUND TEN DEGREES F BELOW AVERAGE. THE DRYING ALOFT WILL SNUFF
OUT ANY CHANCE FOR SHWRS/TSTMS AFTER TODAY.

GRADUALLY WARMER THIS COMING WEEKEND INTO EARLY NEXT WEEK AS HIGH
PRESSURE BUILDS NW FROM THE GULF COAST REGION TO THE CENTRAL
ROCKIES AND THE MARINE LAYER DECREASES.

&&

.AVIATION... 061450Z...COAST/VALLEYS...OVC-BKN STRATUS FILLING THE
COAST AND VALLEYS...WITH BASES 1600-1900 FT MSL AND TOPS 2900-3200
FT MSL...WILL SLOWLY CLEAR OUT OF THE VALLEYS THROUGH 1900
UTC...WITH BKN-OVC STRATUS 2000-3000 FT MSL LINGERING WITHIN 10 SM
OF THE SAN DIEGO COUNTY COAST THROUGH 07/0200 UTC...INCLUDING KCRQ
AND KSAN. BETTER CHANCE OF THE ORANGE COUNTY COAST CLEARING. 11 DEG
C MARINE LAYER INVERSION THIS MORNING. 07/0200-1500 UTC...OVC
STRATUS FILLING IN OVER THE COAST AND VALLEYS AGAIN...WITH BASES
1800-2200 FT MSL AND TOPS 3000-3500 FT MSL. FORECAST CONFIDENCE
MODERATE-TO-HIGH.

MTNS/DESERTS...SCT-BKN CLOUDS DEVELOPING WITH ISOLATED SHOWERS AND
THUNDERSTORMS POSSIBLE DURING THE 1900-07/0200 UTC TIME-PERIOD OVER
THE MTNS AND DESERTS...WITH BASES 8000-10000 FT MSL AND CB TOPS TO
40000 FT MSL. OTHERWISE...UNRESTRICTED VIS THROUGH TUESDAY MORNING.

&&

.MARINE... 750 AM...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH
FRIDAY.

&&

.SKYWARN... SKYWARN ACTIVATION MAY BE NEEDED LATER TODAY. ISOLATED
THUNDERSTORMS ARE EXPECTED AND MY BECOME LOCALLY STRONG.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&

$$

PUBLIC...JAD
AVIATION/MARINE...HARRISON



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