Severe Thunderstorm Warning 12, NWS San Diego, CA

SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
920 AM PDT WED AUG 6 1997

                          ...SYNOPSIS...
EXCESSIVE HEAT WARNING IS IN EFFECT FOR THE VALLEYS OF SAN DIEGO...
RIVERSIDE AND SAN BERNARDINO COUNTIES...FOR THE MOUNTAINS OF
SOUTHWESTERN CALIFORNIA AND THE DESERTS OF SAN DIEGO AND RIVERSIDE
COUNTIES THIS AFTERNOON. HEAVY SURF ADVISORY THROUGH THURSDAY.

HIGH PRESSURE ALOFT CENTERED NEAR CENTRAL CALIFORNIA WILL KEEP HOT
WEATHER THROUGH FRIDAY WITH SOME EARLY MORNING LOW CLOUDS AND LOCALLY
DENSE FOG NEAR THE COAST. THERE IS A SLIGHT CHANCE FOR THUNDERSTORMS
TODAY...ESPECIALLY IN THE MOUNTAINS. OTHERWISE SKIES WILL BE CLEAR TO
PARTLY CLOUDY. MORE RECORD HIGH TEMPERATURE ARE LIKELY TODAY.

                          ...DISCUSSION...
NO NTRANS DATA AVAILABLE. A RIBBON OF STRATUS AND FOG DEVELOPED AGAIN
OVERNIGHT ALONG COASTAL AREAS BUT HAS DIMINISHED QUICKLY. WEAK EDDY
CIRCULATION AT THE COAST APPEARS TO BE SUPPORTED BY MODERATE OFFSHORE
NORTHWESTERLY FLOW. PGRADS NEUTRAL TO OFFSHORE THIS MORNING. 12Z NKX
RAOB LOOKS RATHER OMINOUS WITH K OF 34 AND LI -3. EASTERLY FLOW
BETWEEN 9K AND 18K FEET HAS BROUGHT IN SOME MID-LEVEL MOISTURE. DEEP
MOISTURE EVIDENT ON WATER VAPOR LOOP AND VIS IMAGERY COVERS EXTREME
SOUTHEASERN CALIFORNIA. THIS AREA HAD BEEN ADVANCING NORTHWEST THIS
MORNING BUT IS BEGINNING TO STALL AND TURN TO THE NORHTEAST DUE TO
NORTHEAST TO EAST FLOW ROUNDING CENTRAL CALIFORNIA HIGH. FEW MID
CLOUDS EVIDENT OVR MTNS AND SMALL PATCH OF TOWERING CU OVER COASTAL
WTRS OFF ORANGE CNTY REFLECT MOISTURE AND INSTABILITY.

12Z NGM AND ETA ARE IN AND SEE NO MAJOR CHANGES THROUGH FORECAST
PERIOD ON EITHER MODEL ALTHOUGH ETA WANTS TO HANG ONTO STRONGER UPPER
HIGH. NEITHER MODEL BRINGS RH UP THROUGH 48 HOURS. WAS CONSIDERING
UPDATING FCST TO INCLUDE MORE CLOUDS FOR THE SAN VALLEYS BUT WILL
WAIT TO SEE IF CONVECTION DOES INDEED DEVELOPE OVER THE MTNS. IF IT
DOES...WE WILL LIKELY HAVE TO UPDATE BOTH COASTAL AND VALLEY AREAS
FOR MORE MID-LEVEL CLOUDS. TEMPS MAY EVEN BE HOTTER INLAND TODAY DUE
TO EASTERLY FLOW AND MORE OFFSHORE TRENDS WHILE COASTAL AREAS MAY BE
A COUPLE OF DEGREES COOLER DUE TO EDDY. HEAVY SURF ADVISORY APPEARS
TO BE VERIFYING SO LOX WILL CONTINUE THROUGH THURSDAY. NO UPDATES TO
FORECAST PLANNED AT THIS TIME.

SAN UU 085/069 083/068 081 10000

JAD