Flash Flood Warning 36, NWS Las Vegas, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
418 PM PDT WED AUG 20 2003

.SYNOPSIS...A MOIST AND UNSTABLE AIRMASS WILL REMAIN OVER THE
SOUTHERN GREAT BASIN AND MOJAVE DESERT TONIGHT AND THURSDAY
RESULTING IN ISOLATED TO SCATTERED THUNDERSTORMS. DEEP MOISTURE IN
THE ATMOSPHERE WILL PRODUCE FAVORABLE CONDITIONS FOR HEAVY RAIN
PRODUCING STORMS OVER MUCH OF THE REGION THROUGH TONIGHT. A
SOUTHWEST FLOW DEVELOPING FRIDAY WILL LEAD TO A DRYING TREND GOING
INTO THE WEEKEND.
&&

.SHORT TERM...THE MAJORITY OF CONVECTION WAS FOCUSED OVER TWO AREAS
THIS AFTERNOON...SOUTHERN CALIFORNIA AND CENTRAL NEVADA. THE
SOUTHERN CALIFORNIA CONVECTION WAS DEVELOPING ON THE NORTHERN EDGE
OF A CIRCULATION MOVING UP THE COAST OF NORTHERN BAJA. CONVECTION IN
CENTRAL NEVADA WAS IN A DECENT AREA OF UPPER LEVEL DIVERGENCE. THE
NORTHWARD MOVEMENT OF THE DISTURBANCE OVER SOUTHERN CALIFORNIA
PLACES MUCH OF THE AREA UNDER A CHANCE FOR THUNDERSTORMS THIS
EVENING AND TONIGHT. THE FLASH FLOOD WATCH IN PLACE HAS BEEN
EXTENDED UNTIL MIDNIGHT. MOISTURE GENERALLY REMAINS IN PLACE
THURSDAY BUT ANY WELL DEFINED DYNAMICS ARE A LITTLE DIFFICULT TO
PINPOINT AT THIS TIME. SURFACE HEATING SHOULD DRIVE MOST OF THE
CONVECTION THURSDAY. THE ETA KEEPS A MORE SOUTHEASTERLY FLOW THAN
THE GFS OVER THE SOUTHERN HALF OF THE AREA FRIDAY. IN EITHER
CASE...ENOUGH LOW LEVEL MOISTURE SHOULD BE IN PLACE FOR OROGRAPHICS
AND HEATING TO DRIVE CONVECTION. JET DYNAMICS SHOULD ENHANCE
DEVELOPMENT OVER CENTRAL NEVADA. WILL GO WITH THE GFS TREND SATURDAY
OF INCREASING SOUTHWEST FLOW PUSHING THE MOISTURE BOUNDARY EAST.
HOWEVER...WILL HAVE TO WATCH AND SEE IF LOW LEVEL MOISTURE ACTUALLY
GETS SCOURED OUT.
&&

.LONG TERM...MODELS CONTINUE TO SHOW A DRIER PATTERN FOR SUNDAY AND
MONDAY AS THE UPPER FLOW TURNS TO THE SOUTHWEST OVER EVERYWHERE BUT
THE SOUTHEAST CWA. AS PER PREVIOUS LONG TERM DISCUSSION...A
MONSOONAL FLOW IS ADVERTISED BY A COUPLE OF THE MODELS TO RETURN
TUESDAY AND WEDNESDAY. WILL HOLD OFF ON INCREASING POPS UNTIL THERE
IS SOME RUN TO RUN CONSISTENCY SHOWING THIS TREND.
&&

.LAS...FLOOD WATCH UNTIL MIDNIGHT FOR SOUTHERN NEVADA...NORTHWEST
ARIZONA...AND PORTIONS OF SOUTHEAST CALIFORNIA. PLEASE SEE THE
LATEST STATEMENT FOR DETAILS.
&&

JA/JS

AZZ001>003-036-CAZ026>029-NVZ013>022-211400-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LAS VEGAS NV
500 AM PDT WED AUG 20 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST CALIFORNIA/SOUTHERN
NEVADA/NORTHWEST ARIZONA

.DAY ONE...TODAY.

A FLASH FLOOD WATCH IS IN EFFECT TODAY FOR SOUTHERN NEVADA...
NORTHWEST ARIZONA...AND PORTIONS OF SOUTHEAST CALIFORNIA. SCATTERED
THUNDERSTORMS WILL CONTINUE ACROSS THE AREA THIS MORNING...WITH
MORE DEVELOPMENT EXPECTED THIS AFTERNOON. THE STORMS ARE EXPECTED TO
BE SLOW MOVERS...AND A VERY MOIST AIRMASS IS IN PLACE. THUS...FLASH
FLOODING WILL AGAIN BE A THREAT TODAY.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

SCATTERED THUNDERSTORMS ARE EXPECTED AGAIN ON THURSDAY...WITH FLASH
FLOODING A POSSIBILITY ONCE AGAIN. DRIER AIR IS EXPECTED TO BEGIN
MOVING IN FROM THE WEST ON FRIDAY...WITH THUNDERSTORM CHANCES
LIMITED TO AREAS EAST OF A LINE FROM TONOPAH TO NEEDLES. FOR
SATURDAY THROUGH TUESDAY...THE PROBABILITY FOR WIDESPREAD HAZARDOUS
WEATHER IS LOW.