Flash Flood in California, July 4, 2006

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
850 PM PDT TUE JUL 4 2006

.SYNOPSIS...A MOIST AND UNSTABLE AIR MASS WILL REMAIN OVER MUCH OF
THE AREA THROUGH WEDNESDAY RESULTING IN A CHANCE OF SHOWERS AND
THUNDERSTORMS. DRIER AIR WILL ATTEMPT TO PUSH IN FROM THE WEST LATER
IN THE WEEK WITH THUNDERSTORM CHANCES CONFINED MAINLY TO NORTHWEST
ARIZONA.
&&

.UPDATED...OVERALL CONVECTIVE ACTIVITY ON THE DECREASE THIS EVENING.
ISOLATED ACTIVITY STILL OVER SOUTHERN INYO COUNTY AND NORTHWEST
LINCOLN COUNTY ATTM AND EXPECT ISOLATED ACTIVITY POSSIBLE ACROSS
MUCH OF THE AREA THROUGH THE NIGHT. HOWEVER THE THREAT OF WIDESPREAD
FLASH FLOOD PROBLEMS APPEARS TO BE OVER AND HAVE CANCELLED THE WATCH
FOR THE REST OF THE EVENING. WILL HANDLE ANY LOCALIZED PROBLEMS AS
OR IF THEY COME UP. QUICK LOOK AT 00Z NAM SHOWS THAT OVERALL TREND
OF THE FORECAST STILL ON TRACK AS SLOW DRYING TREND TO TAKE PLACE
INTO THE WEEKEND. HOWEVER STRONG DRY SOUTHWEST FLOW NEVER REALLY
MAKES IT OVER THE ENTIRE CWA...THUS THE EASTERN PORTION WILL STILL
SEE AFTERNOON/EVENING ACTIVITY THROUGH THE WEEKEND. WILL UPDATE
ZONES TO REMOVE FLASH FLOOD WATCH AND EVENING WORDING... OTHERWISE
NO CHANGE TO REMAINDER OF FORECAST.
&&

.PREV DISCUSSION...325 PM PDT SHORT TERM...VERY MOIST AND UNSTABLE
AIR MASS COMBINED WITH A JET STREAK MOVING OVER THE AREA WILL LEAD
TO SCATTERED THUNDERSTORMS AND A THREAT OF FLASH FLOODING THROUGH
THIS EVENING OVER ROUGHLY THE EASTERN TWO THIRDS OF THE FORECAST
AREA WITH MORE ISOLATED THUNDERSTORMS WEST. WHILE MOISTURE LOOKS TO
DECREASE SOMEWHAT WEDNESDAY I STILL EXPECT ISOLATED TO SCATTERED
THUNDERSTORMS OVER MOST OF THE FORECAST AREA. THE ONLY AREA WHERE
MODELS DEPICT DRY AND STABLE AIR IS OVER SOUTHERN INYO COUNTY.
THUNDERSTORM CHANCES SHOULD MAINLY BE CONFINED TO MOHAVE COUNTY AND
FAR EASTERN PORTIONS OF SOUTHERN NEVADA BY THURSDAY AS THE UPPER
HIGH GETS PUSHED TO SOUTHEAST NEW MEXICO AND SOUTHWEST FLOW DEVELOPS
OVER NEVADA AND CENTRAL CALIFORNIA. A WEAK INVERTED UPPER TROUGH
MOVING NORTH TO NORTHWEST MEXICO WILL KEEP THE FAR EASTERN PORTIONS
OF THE FORECAST AREA FROM DRYING OUT.

.LONG TERM...MEDIUM RANGE MODELS BRING A WEAK DISTURBANCE INTO THE
SOUTHWEST CONUS THROUGH THE EXTENDED PERIOD. THE GFS IS SOMEWHAT
STRONGER WITH THIS FEATURE AND KEEPS SOME LOW AND MID LEVEL MOISTURE
IN THE CENTRAL AND EASTERN CWA INTO SATURDAY. A DRIER AIRMASS IS
THEN FORECAST TO MOVE INTO THE CENTRAL AREAS MONDAY AND OVER THE
ENTIRE CWA TUESDAY. WITH THIS TREND IN MIND...KEPT SLIGHT CHANCE
POPS CENTRAL AND EAST SUNDAY WHERE A STRONG MOISTURE GRADIENT MAY
PROVIDE A FOCUS FOR TSTORMS THAT DAY. ON MONDAY...LEFT IN 10 TO 20
POPS IN MOHAVE COUNTY AS MOISTURE HANGS ON IN THIS REGION. WENT DRY
TUESDAY DUE TO INCREASINGLY DRY AIRMASS DISPLACING MOISTURE TO THE
EAST. TEMPS PRETTY MUCH UNCHANGED FROM PREVIOUS PACKAGE BUT IF
MODELS CONTINUE TO SHOW A DRYING TREND...WILL HAVE TO CONSIDER
BUMPING THEM UP EARLY NEXT WEEK.
&&

.AVIATION...TAFS AND TWEBS ADEQUATELY DESCRIBE EXPECTED WEATHER
CONDITIONS FOR AREA TERMINALS. SEE TAFS FOR KLAS... KVGT... KDRA...
KBIH... KDAG... KEED.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&

.VEF WATCHES/WARNINGS/ADVISORIES...
.NV...NONE.
.AZ...NONE.
.CA...NONE.

JENSEN/HARRISON

HTTP://WEATHER.GOV/LASVEGAS