Excessive Heat Warning 8, NWS San Diego, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
945 PM PDT FRI AUG 31 2007

.SYNOPSIS...
STRONG HIGH PRESSURE ALOFT WILL BRING HOT WEATHER THROUGH THE LABOR
DAY WEEKEND. HEAT WARNINGS ARE IN EFFECT FOR SOME AREAS. MOISTURE
AND INSTABILITY WILL BRING MORE AFTERNOON SHOWERS AND THUNDERSTORMS
THROUGH THE WEEKEND...SOME WITH HEAVY RAINFALL AND LOCAL FLOODING.
COOLER AND LESS HUMID WEATHER IS EXPECTED THE MIDDLE OF NEXT WEEK.

&&

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

THUNDERSTORMS PUMMELED THE REGION TODAY. A STRONG STORM HIT LAKE
ELSINORE WITH DOWNED POWER LINES REPORTED. TORRENTIAL RAINS ON I-10
THROUGH THE SAN GORGONIO PASS IN RIVERSIDE COUNTY RESULTED IN
TRAFFIC ACCIDENTS. FLOODING AND MINOR ROCK AND MUDSLIDES OCCURRED IN
THE SAN BERNARDINO COUNTY MTNS NEAR WRIGHTWOOD...AND ALSO IN THE
HIGH DESERTS NEAR PHELAN.

THE OTHER BIG STORY WAS THE OPPRESSIVE HEAT. TEMPS SOARED ABOVE 100
AGAIN IN THE VALLEYS AND FOOTHILLS...AND ABOVE 110 IN THE LOWER
DESERTS. EXPECT A REPEAT PERFORMANCE SATURDAY AND SUNDAY AS THE
STAGNANT UPPER HIGH OVER THE SOUTHWESTERN STATES CONTINUES TO
DOMINATE. AN EXCESSIVE HEAT WARNING IS ALREADY IN PLACE FOR
SATURDAY...AND WILL LIKELY BE ISSUED AGAIN FOR SUNDAY. OVERNIGHT
LOWS WILL BE NONE TOO LOW EITHER WITH MINIMUMS IN THE LOW 70S IN A
LOT OF VALLEY LOCATIONS.

DAYTIME HEATING WILL TRIGGER MORE SCATTERED THUNDERSTORMS OVER THE
MOUNTAINS...SOME OF WHICH WILL DRIFT OVER THE VALLEYS IN THE
AFTERNOON...PUSHED WESTWARD BY THE EASTERLY WINDS AROUND THE UPPER
HIGH.

THE FIRST SIGNS OF COOLING AND LOWER HUMIDITIES ARRIVES NEXT TUESDAY
AS WE COME MORE UNDER THE INFLUENCE OF A TROUGH OVER THE PACIFIC
NORTHWEST. DRIER NW FLOW AND LOWER HEIGHTS WILL CONTINUE INTO
WEDNESDAY...LEAVING ONLY SLIGHT CHANCES FOR PRECIPITATION IN THE
MTNS.

THE MODELS STILL WAVER ON THE TRACK AND INTENSITY OF TROPICAL STORM
HENRIETTE WHICH HAS AN OUTSIDE CHANCE OF IMPACTING SOCAL LATER NEXT
WEEK. BUT THE INCREDIBLE INCONSISTENCY OF THE LONG RANGE MODELS
PRECLUDE ANY DEGREE OF FORECAST PRECISION WITH THIS FEATURE. WILL
CONTINUE TO MONITOR.

FORECAST WAS UPDATED TO RAISE MIN TEMPS IN MANY AREAS THE NEXT TWO
NIGHTS...AND RAISE HIGH TEMPS A FEW DEGREES IN THE VALLEYS AND
DESERTS.

&&

.AVIATION...
010400Z...SHOWERS AND THUNDERSTORMS ENDED BY 02-03Z OVER THE AREA
WITH SOME DEBRIS CLOUDS LINGERING EARLY THIS EVE. A MOIST UNSTABLE
AIRMASS WILL KEEP FAVORABLE CONDITIONS FOR SHOWERS AND THUNDERSTORMS
THRU SATURDAY. ANY WEAK DISTURBANCE LATE TONIGHT OR SAT MORN COULD
TRIGGER ISOLATED CELLS...OTHERWISE THE MOST FAVORABLE CONDITIONS
WILL OCCUR DURING MAX DAYTIME HEATING FROM 19Z-02Z SAT. EXPECT
SCATTERED SHOWERS/TSTMS WITH LOCALLY HEAVY RAIN...POSSIBLE HAIL AND
GUSTY WINDS. BASES AROUND 6000 FT WITH TOPS TO FL400 OR HIGHER AT
TIMES. SOME STORMS COULD ONCE AGAIN MOVE INTO THE INLAND VALLEYS.

NEAR THE COAST THE MARINE LAYER WILL REMAIN SHALLOW WITH LITTLE OR
NO STRATUS. LOW CLOUDS IF ANY WILL BE PATCHY AND LIMITED TO NEAR THE
IMMEDIATE COAST...WITH LOCAL 3-5SM VISIBILITY POSSIBLE FROM 11-16Z
SAT. BASES APPROX 700 FT MSL.

ABOVE NORMAL TEMPERATURES WILL HAVE SOME EFFECTS ON DENSITY ALTITUDE
WITH SAT AFTERNOON READINGS AS HIGH AS 42 C AT KONT...46 C AT KPSP.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...EXCESSIVE HEAT WARNING SATURDAY FOR THE INLAND VALLEYS AND
ORANGE COUNTY.

PZ...NONE.

&&

PUBLIC...MOEDE
AVIATION/MARINE...LAVIS

NWS ON THE WEB AT WEATHER.GOV/SANDIEGO

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN DIEGO CA
805 PM PDT FRI AUG 31 2007

CAZ042-043-048-050-055-056-057-058-060-061-062-011200-
ORANGE COUNTY COASTAL AREAS-
SAN DIEGO COUNTY COASTAL AREAS-
SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-
SAN DIEGO COUNTY VALLEYS-
SAN BERNARDINO COUNTY MOUNTAINS-
RIVERSIDE COUNTY MOUNTAINS-
SANTA ANA MOUNTAINS AND FOOTHILLS-
SAN DIEGO COUNTY MOUNTAINS-
APPLE AND LUCERNE VALLEYS-
COACHELLA VALLEY-
SAN DIEGO COUNTY DESERTS-
805 PM PDT FRI AUG 31 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWESTERN CALIFORNIA.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

VERY HOT...HUMID WEATHER WILL CONTINUE THROUGH MONDAY. AN EXCESSIVE
HEAT WARNING FOR THE INLAND VALLEYS AND FOR FAR INLAND PORTIONS OF
ORANGE COUNTY SATURDAY. SEE LAXNPWSGX FOR DETAILS.

AFTERNOON AND EVENING THUNDERSTORMS WILL CONTINUE IN THE MOUNTAINS
AND DESERTS. A FEW STORMS MAY REACH THE INLAND VALLEYS.

THE FLASH FLOOD POTENTIAL IS MODERATE SATURDAY THROUGH MONDAY.

.SPOTTER INFORMATION STATEMENT...

SKYWARN WEATHER SPOTTER ACTIVATION MAY BE NEEDED EACH DAY THROUGH
MONDAY.

MOEDE