Flash Flood Warning 10, NWS Hanford, CA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
1150 AM PDT MON JUL 14 2008

.UPDATE...CONVECTION DEVELOPING RAPIDLY OVER THE KERN AND TULARE
COUNTY MOUNTAINS. WITH THE RAPID DEVELOPMENT...THERE IS THE
POTENTIAL FOR LOCALLY HEAVY RAINFALL...ESPECIALLY IN AREAS THAT
EXPERIENCED FLOODING OVER THE WEEKEND. HAVE ISSUED A FLASH FLOOD
WATCH FOR THE KERN AND TULARE MOUNTAINS AND THE KERN DESERTS UNTIL
06Z TUESDAY.

&&

.PREVIOUS UPDATE...RELATIVELY HIGH /MID 50S TO LOWER 60S/
DEWPOINTS KEPT LOW TEMPERATURES ACROSS THE CENTRAL AND SOUTHERN
SAN JOAQUIN VALLEY THIS MORNING IN THE LOWER TO MID 70S.

THE FORECAST PROBLEM FOR TODAY IS THE POTENTIAL FOR LOCALLY HEAVY
RAIN ASSOCIATED WITH ANY MOUNTAIN OR DESERT CONVECTION THIS AFTERNOON
AND EVENING. THIS MORNING/S 12Z VANDENBERG AFB SOUNDING HAD 1.58 INCH
PRECIPITABLE WATER AND A NORTHEAST STEERING FLOW. TO THE EAST...
DESERT ROCK HAD 1.10 INCH PRECIPITABLE WATER AND A SOUTHEAST STEERING
FLOW...WHILE OVER THE KERN COUNTY DESERT...AT 13Z EDWARDS AFB HAD
1.31 INCH PRECIPITABLE WATER AND LIGHT WINDS ALOFT THROUGH 15000
FEET. THE WINDS ALOFT ARE CONSISTENT WITH THE EMBEDDED UPPER-LEVEL
LOW THAT TRACKED ACROSS SOUTHERN CALIFORNIA OVERNIGHT.

THE NAM-12 CONVECTIVE PARAMETERS FOR 21Z THIS AFTERNOON ARE A
SURFACE COMPUTED CAPES FROM 800 JOULES/KG OVER THE PIUTES AND THE
GRAPEVINE TO 1200+ JOULES/KG FROM KINGS CANYON NORTH TO YOSEMITE.
SURFACE COMPUTED LIFTED INDEXES RANGE FROM -3 OVER THE PIUTES TO -5
NORTH OF KINGS CANYON. 850-MB THETA-E VALUES ARE 344 K OVER THE
PIUTES RISING TO 356 K NORTH OF KINGS CANYON. AT 500 MB...A +26
VORTICITY MAXIMUM IS FORECAST TO TRACK OVER TEHACHAPI...WHILE A +23
MAXIMUM CROSSES NORTHEASTERN FRESNO COUNTY. DESPITE THESE WIDESPREAD
FAVORABLE DYNAMICS...THE NAM-12 CONFINES THE HIGHEST MID-LEVEL
MOISTURE /75+ PERCENT 850-700-MB RELATIVE HUMIDITY/ TO A NARROW BAND
ALONG THE CREST IN FRESNO AND TULARE COUNTIES AND OVER YOSEMITE.
THIS LIKELY WILL BE THE FOCUS WHERE CONVECTION INITIATES...AND THE
QUESTION BECOMES WHETHER STORMS THAT FORM OVER TULARE COUNTY WILL
HOLD TOGETHER AS THEY DRIFT INTO THE SLIGHTLY MORE STABLE AIRMASS
OVER THE LAKE ISABELLA/PIUTES AREA.

THIS MORNING/S LOW-LEVEL SOUNDING FOR FRESNO SHOWS LITTLE CHANGE IN
THE AIRMASS ABOVE 3000 FEET...SO EXPECT TEMPERATURES IN THE CENTRAL
AN SOUTHERN SAN JOAQUIN VALLEY TO BE SIMILAR TO SUNDAY.

NO CHANGE TO THE FORECAST AT THIS TIME...PENDING DEVELOPMENT OF
CONVECTION.

&&

.PREVIOUS DISCUSSION...INVERTED TROUGH REMAINS NEARLY STATIONARY
OVER THE DESERT SW. CONVECTION WAS ACTIVE AGAIN YESTERDAY...
HOWEVER THE MODELS ARE INDICATING LESS INSTABILITY AND NOT AS AS
ACTIVE ACROSS THE KERN CO DESERT AND MOUNTAIN AREA TODAY. WOULD
NOT RULE OUT AN ISOLATED HEAVY THUNDERSTORM...BUT DON/T THINK WE
WILL SEE AS MUCH CONVECTION TODAY AS YESTERDAY. THE MODELS ARE
MOVING THE CONVERGENCE BOUNDARY FURTHER TO THE NORTH TODAY AND
HAVE INCREASED POPS ACROSS THE FRESNO AND TULARE COUNTY PORTION OF
THE SIERRA RANGE. WOULD NOT RULE OUT AN ISOLATED STORM ACROSS THE
CREST AFTER WEDNESDAY AND CONTINUE THROUGH FRIDAY.

TEMPERATURES WILL REMAIN JUST ABOVE CLIMO AND REMAIN NEAR
OR JUST BELOW 100 IN THE VALLEY. THE EXTENDED GUIDANCE FROM THE
GFS MODEL IS DOING SOME VERY STRANGE THINGS WITH THE PATTERN FOR
THE WEEKEND. THE GFS REMAINS TO BE THE OUTLIER AND WILL GO WITH
PERSISTENCE FOR NOW. NO MAJOR CHANGES EXPECTED IN THE CURRENT
FORECAST.

&&

.AVIATION...VFR CONDITIONS EXPECTED THROUGH 18Z TUESDAY ACROSS THE
CENTRAL CA INTERIOR. OVER THE MOUNTAINS AND DESERTS...ISOLATED TO
SCATTERED THUNDERSTORMS WITH LOCAL IFR CONDITIONS FROM 19Z THRU 04Z
THIS EVENING.

&&

.AIR QUALITY ISSUES...
NONE.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH UNTIL 11 PM PDT THIS EVENING FOR THE TULARE
COUNTY MOUNTAINS AND THE KERN COUNTY MOUNTAINS AND DESERTS /CAZ095-
097>099/.

&&

PUBLIC...SANGER
AVN/FW...MOLINA
PREVIOUS DISCUSSION...JDB

WEATHER.GOV/HANFORD