Severe Thunderstorm Warning 12, NWS San Diego, CA

EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
200 PM PDT SUN AUG 27 2000

                              ...SYNOPSIS...

MOISTURE IN SOUTHERLY FLOW ALOFT WILL CONTINUE A CHANCE OF
AFTERNOON AND EVENING THUNDERSTORMS IN THE MOUNTAINS AND DESERTS
THROUGH TUESDAY. ONSHORE FLOW AND THE MARINE LAYER WILL BRING NIGHT
AND MORNING COASTAL LOW CLOUDS AND FOG. A LITTLE COOLER WITH DRIER
SOUTHWEST FLOW ALOFT BY THE MIDDLE OF THE WEEK AS UPPER LEVEL LOW
PRESSURE DEVELOPS OFF THE COAST.

                             ...DISCUSSION...

A WEAK EDDY APPEARS TO HAVE DEVELOPED ALONG THE COAST BASED ON THE
COASTAL WIND REPORTS. THE COMBINATION OF THE EDDY AND FAIRLY THICK
HIGH LEVEL CLOUDS KEPT THE LOWER CLOUDS IN PLACE ALONG THE COAST
MUCH LONGER THAN THE PAST SEVERAL DAYS.

ELSEWHERE...THE HIGHER CLOUDS HAVE BEEN THINNING OUT OVER THE
DESERTS ALLOWING MORE SUNSHINE AND MORE HEATING. THIS ALONG WITH
SOME OUTFLOW BOUNDARIES FROM THUNDERSTORMS OVER WESTERN ARIZONA
REACHING THE MOUNTAINS SHOULD KEEP SOME SHOWERS OR THUNDERSTORMS
OVER THE MOUNTAINS LATER THIS AFTERNOON AND TONIGHT. A THUNDERSTORM
WAS ALREADY DEVELOPING OVER THE MOUNTAINS OF NORTHERN BAJA BUT...SO
FAR ONLY MODERATE CU WERE SHOWING UP OVER THE LOCAL AREA MOUNTAINS
AS OF 20Z. WILL UP THE POPS FOR THE LOCAL MOUNTAINS AND DESERTS INTO
THE CHANCE CATEGORY FOR TONIGHT AND MONDAY...40 PERCENT FOR THE
MOUNTAINS AND 30 PERCENT FOR THE DESERTS. EXPECT THE ACTIVITY TO
DECREASE MONDAY NIGHT AND TUESDAY AND WILL PUT THE POPS DOWN INTO
THE 20 PERCENT CATEGORY FOR THE MOUNTAINS AND DESERTS FOR THOSE TWO
PERIODS. THE ETA MODEL APPEARS TO HAVE THE BETTER HANDLE ON THE
MOISTURE AND FEATURE THAN THE AVN MODEL...AVN MODEL WAS TOO DRY THE
PAST COUPLE OF RUNS. WILL LEAN TOWARDS THE ETA SOLUTION FOR THE
AFTERNOON FORECAST PACKAGE.

MEDIUM RANGE MODELS STILL INSIST THE DEVELOPING CUTOFF LOW OFF THE
COAST WILL MOVE INLAND AS A S/WV TROUGH DURING THE LATTER HALF OF
THE WEEK AND WILL GO ALONG WITH THAT. MODELS INDICATE THE FLOW ALOFT
WILL BEGIN TO SWING TO THE SOUTHWEST ON WEDNESDAY FOR DRYING WITH
CONTINUED SOUTHWEST FLOW ALOFT THROUGH THE END OF THE WEEK.
HOWEVER...HAVE TO KEEP IN MIND THAT CUTOFF LOWS CAN HAVE A TENDENCY
TO REMAIN OFF THE COAST LONGER THAN THE MODELS SUGGEST SO THERE IS
POSSIBILITY THE MOIST SOUTHERLY FLOW ALOFT COULD CONTINUE A FEW DAYS
LONGER THAN THE MODELS INDICATE.

SAN 0000

.SAN...MINOR TIDAL OVERFLOW THROUGH TUE...SEE LAXMWSSAN.

HORTON