Wildfire in California, May 9, 2002

EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
900 AM PDT THU MAY 9 2002

.SYNOPSIS...A TROUGH OF LOW PRESSURE WILL MOVE INLAND ACROSS THE
GREAT BASIN FRIDAY BRINGING STRONG...GUSTY WINDS AND SOME COOLING TO
THE MOUNTAINS AND DESERTS. WEST OF THE MOUNTAINS...IT WILL BRING A
DEEPER MARINE LAYER WITH MORE EXTENSIVE NIGHT AND MORNING LOW CLOUDS
WITH PATCHY DRIZZLE FRIDAY MORNING...AND SOMEWHAT LIMITED AFTERNOON
CLEARING. WEAK HIGH PRESSURE ALOFT AND MUCH WEAKER ONSHORE FLOW WILL
OCCUR SUNDAY FOR WARMER WEATHER.

.DISCUSSION...LOW CLOUDS WERE ERODING OVER THE SAN DIEGO COUNTY
VALLEYS...THOUGH ORANGE COUNTY HAD NOT BEGUN TO CLEAR. PILOT REPORTS
INDICATE THAT CLOUD THICKNESSES WERE 1000 FEET OR LESS...SO EXCEPT
FOR THE IMMEDIATE COAST...ALL AREAS SHOULD CLEAR BY ABOUT 11
AM...WITH SAN DIEGO COUNTY CLEARING BEFORE ORANGE COUNTY. 5 OR MORE
DEG C OF WARMING OCCURRED IN THE PAST 24 HOURS IN ABOUT THE 830-890
MB LAYER...SO THAT WILL CERTAINLY TRANSLATE TO SIGNIFICANT WARMING
FOR THE MTNS/DESERTS/FOOTHILLS...AND THE EARLIER CLEARING WILL BRING
A FEW DEGREES OF WARMING CLOSER TO THE COAST TOO.

HOWEVER...OUR TREND WILL REVERSE SHARPLY FRIDAY AS BOTH THE LOCAL
WORKSTATION-ETA AND THE NEW 12Z MSO INDICATE AN EDDY
DEVELOPING...BUT MORE IMPORTANTLY...WE HAVE THE TROUGH TO OUR N/NE.
WE SEE 850 MB TEMP DROPS...ESPECIALLY ALONG THE W COASTAL SLOPES
WHICH INDICATES A RAPIDLY DEEPENING MARINE LAYER...SO INLAND TEMPS
WILL DROP SIGNIFICANTLY...MORE THAN WHAT AVN/NGM MOS IS INDICATING.
WE COULD EASILY SEE A REVERSE CLEARING SCENARIO...SO I WILL PROBABLY
HAVE AT LEAST PARTLY CLOUDY FOR FRI AFTERNOON IN THE INLAND EMPIRE.
DURING THE MOST RAPID PHASE OF THE MARINE LAYER DEEPENING IS USUALLY
WHEN WE HAVE THE DRIZZLE...SO IN THE AFTERNOON PACKAGE I WILL ALSO
THROW IN PATCHY DRIZZLE FOR FRI AM. THE ONSHORE FLOW GETS QUITE
STRONG FRI WITH THE SURFACE TROUGH MOVING OVER THE DESERTS TO OUR
NE...AND THE CAA WILL ALLOW SOME OF THE 35-KNOT WIND AT 700 MB TO
TRANSLATE DOWN TO THE SURFACE. SO THE APPLE/YUCCA VALLEYS MIGHT NEED
A WIND ADVISORY FRI. SAT WILL LIKELY BE A DAY SIMILAR TO WED WHERE
WE HAVE A DEEP MARINE LAYER BUT WITH MORE SCT-BKN VERSUS OVC WHICH
SHOULD CLEAR LATE IN THE DAY. SAT NIGHT SHOWS PRETTY GOOD OFFSHORE
TRENDS...SO THAT COULD MOSTLY WIPE OUT THE LOW CLOUDS EXCEPT FOR THE
IMMEDIATE COAST...SO FOR NOW...SUNDAY LOOKS FAIR AND WARMER BEFORE
MORE HEIGHT FALLS OCCUR AS A BROAD BUT FAIRLY WEAK LOW MOVES OVER
THE NE PAC TOWARDS THE PAC NW. THUS...EARLY NEXT WEEK LOOKS
FAVORABLE FOR BELOW NORMAL TEMPS.

A QUICK ZONE UPDATE WILL BE ISSUED SHORTLY...MOSTLY FOR LOW CLOUD
WORDING.

.SAN...NONE.

MAXWELL