Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 301646
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
946 AM PDT THU JUL 30 2015

.SYNOPSIS...
WARM AND HUMID TODAY WITH ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS OVER THE AREA. FLASH FLOOD WATCH FOR
MOUNTAINS/DESERTS/INLAND EMPIRE THROUGH THIS EVENING. DRIER...WITH
NEAR NORMAL HIGH TEMPERATURES...THIS WEEKEND INTO EARLY NEXT WEEK
AS HIGH PRESSURE BUILDS ALOFT. NIGHT/MORNING LOW CLOUDS ALONG THE
COAST AND BREEZY WESTERLY WIND THROUGH MOUNTAIN PASSES AND ALONG
DESERT MOUNTAIN SLOPES THROUGH THE PERIOD.

&&

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

AT 9 AM PDT...WATER VAPOR SATELLITE IMAGERY DISPLAYED A BROAD
UPPER-LEVEL RIDGE STRETCHING FROM THE LOWER MISSISSIPPI VALLEY TO
CENTRAL NEVADA...AND A WEAK UPPER-LEVEL LOW AROUND 200 MILES SSW
OF SAN DIEGO. THE 30/1200 UTC KNKX SOUNDING DISPLAYED A VERY MOIST
AND UNSTABLE PROFILE...WITH A CALCULATED PRECIPITABLE WATER OF
2.02 INCHES AND MOST-UNSTABLE CAPE OF 2030 J/KG. A WEAK UPPER-
LEVEL WAVE MOVING ACROSS THE REGION WAS GENERATING LIGHT SHOWERS
OVER PORTIONS OF THE SAN BERNARDINO COUNTY MOUNTAINS AND DESERTS.

WITH DIURNAL HEATING...CONDITIONS SHOULD COME TOGETHER LATE THIS
MORNING THROUGH THIS EVENING TO GENERATE SHOWERS AND THUNDERSTORMS
OVER THE REGION...MAINLY OVER THE DESERTS...MOUNTAINS AND THE
INLAND EMPIRE. THE 30/1500 UTC HRRR SHOWS SHOWER AND THUNDERSTORM
ACTIVITY DEVELOPING OVER THE SAN DIEGO AND RIVERSIDE COUNTY
MOUNTAINS AROUND NOON...THEN DEVELOPING OVER PORTIONS OF SW SAN
BERNARDINO COUNTY LATER THIS AFTERNOON AS CLOUDS CLEAR THE AREA.
THIS WILL LIKELY BE THE CASE GIVEN MODERATE NEGATIVE VORTICITY
ADVECTION IN THE WAKE OF THE UPPER-LEVEL WAVE MOVING OUT OF THE
AREA THIS MORNING. IF ANY OF THESE STORMS BECOME STATIONARY...OR
TRAIN OVER A LOCATION...THERE IS A GOOD POTENTIAL FOR FLASH
FLOODING. HOWEVER...MOST STORMS ARE EXPECTED TO MOVE AROUND 15 MPH
GIVEN THE MID AND UPPER-LEVEL WINDS. THE FLASH FLOOD WATCH FOR THE
MOUNTAINS...DESERTS AND INLAND EMPIRE REMAINS IN EFFECT THROUGH 8
PM PDT THIS EVENING. A WEAK UPPER-LEVEL WAVE MOVING ACROSS THE
REGION TONIGHT WILL CREATE THE POSSIBILITY OF AN ISOLATED
SHOWER/THUNDERSTORM OVER THE MOUNTAINS AND DESERTS.

ON FRIDAY...FLOW WILL SHIFT FROM SE TO MORE SOUTHERLY...ADVECTING
DRIER AIR INTO THE REGION. THIS WILL CREATE LESS OF A FLASH FLOOD
THREAT AND LOWER THE COVERAGE OF AFTERNOON THUNDERSTORMS COMPARED
TO TODAY. MODELS ARE TRENDING DRIER FOR THE WEEKEND INTO EARLY
NEXT WEEK AS THE AFOREMENTIONED UPPER-LEVEL RIDGE BUILDS TO THE
SE. WILL WAIT FOR THE 12 UTC MODEL RUNS BEFORE CHANGING THE POP
FORECAST. HOWEVER...CONFIDENCE IS INCREASING FOR DRY WEATHER FOR
THE WEEKEND THROUGH NEXT TUESDAY. THE 30/0600 GFS BRINGS MOISTURE
BACK INTO THE AREA NEXT WEDNESDAY...AND GENERATES THUNDERSTORMS
OVER THE MOUNTAINS AND DESERTS NEXT WEDNESDAY AND THURSDAY.
BUILDING HEIGHTS OVER THE AREA WILL HELP RAISE HIGH TEMPERATURES
TO NEAR NORMAL...AND MAINTAIN A SHALLOW MARINE LAYER WITH PATCHY
NIGHT/MORNING LOW CLOUDS/FOG ALONG THE COAST AND COASTAL VALLEYS.
NORMAL ONSHORE PRESSURE GRADIENTS WILL CREATE BREEZY WESTERLY
WINDS THROUGH MOUNTAIN PASSES AND ALONG DESERT MOUNTAIN SLOPES IN
THE AFTERNOONS/EVENINGS THROUGH THE PERIOD.

&&

.AVIATION...
301530Z...COAST/VALLEYS...SCT-BKN LOW CLOUDS PERSIST
OVER THE COASTAL BASIN AND INLAND IN/NEAR KCRQ WITH BASES NEAR 1500
FT MSL AND TOPS 2000 FT MSL. THE LOW CLOUDS WILL ERODE THE COAST
BETWEEN 30/1500-1800Z. THERE IS A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS THROUGH THIS EVENING ACROSS THE ENTIRE REGION...THOUGH
THE MOUNTAINS WILL BE FAVORED. HOWEVER...CONFIDENCE ON TIMING IS LOW
SO WILL MONITOR FOR VCTS INCLUSION IN THE TAFS. STRATUS WITH SIMILAR
BASES AND HEIGHTS AS THIS MORNING WILL PUSH BACK INLAND AFTER
31/0300Z.

MTNS/DESERTS...A CHANCE OF SHOWERS AND THUNDERSTORMS EXISTS THROUGH
THIS EVENING ACROSS THE MTS AND DESERTS. GREATEST STORM COVERAGE
WILL BE AFT 30/2000Z. THUNDERSTORM BASES WILL GENERALLY BE AOA 8000
FT MSL WITH TOPS TO 40000 FT MSL. THE MAIN THREATS FROM THESE STORMS
WILL BE BRIEF HEAVY RAIN...LOWERED VIS...AND FREQUENT CLOUD-TO-CLOUD
AND CLOUD-TO-GROUND LIGHTNING.

&&

.MARINE...
830 AM...THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS OVER
THE INNER COASTAL WATERS THROUGH THIS EVENING AS AN UPPER LEVEL
DISTURBANCE MOVES OVER THE AREA. OTHERWISE...NO HAZARDOUS MARINE
WEATHER IS EXPECTED THROUGH SUNDAY.

&&

.BEACHES...
830 AM...THE ELEVATED SURF WILL SUBSIDE TODAY AS THE
SWELL DECLINES TO AROUND 2 FT AT 14-15 SEC...BUT THE RISK OF STRONG
RIP CURRENTS AND LIGHTNING CONTINUES THROUGH THE EVENING. THEREFORE
THE BEACH HAZARDS STATEMENT WILL CONTINUE THROUGH THIS EVENING. THE
SLOW DOWNWARD TREND IN THE SWELL WILL CONTINUE THROUGH THE
WEEKEND.

&&

.SKYWARN...
SKYWARN ACTIVATION MAY BE REQUESTED LATER TODAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...FLASH FLOOD WATCH UNTIL 8 PM PDT THIS EVENING FOR APPLE AND
     LUCERNE VALLEYS-COACHELLA VALLEY-RIVERSIDE COUNTY MOUNTAINS-
     SAN BERNARDINO COUNTY MOUNTAINS-SAN BERNARDINO AND
     RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-SAN DIEGO COUNTY
     DESERTS-SAN DIEGO COUNTY MOUNTAINS-SAN GORGONIO PASS NEAR
     BANNING.

     BEACH HAZARDS STATEMENT UNTIL 8 PM PDT THIS EVENING FOR ORANGE
     COUNTY COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS.

PZ...NONE.
&&

$$

PUBLIC...JJT
AVIATION/MARINE/BEACHES...TS



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