Flash Flood Warning 47, NWS Las Vegas, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
935 AM PDT SUN AUG 7 2005

.SYNOPSIS...MONSOONAL MOISTURE WILL CONTINUE OVER THE AREA THROUGH
THE MIDDLE OF NEXT WEEK. THIS WILL CONTINUE TO RESULT IN MAINLY
AFTERNOON AND EVENING THUNDERSTORMS AND SHOWERS.
&&

.UPDATE...AIRMASS FAIRLY MOIST AND UNSTABLE TODAY. MID LEVEL
DEFORMATION ZONE EVIDENT IN 12Z ANALYSIS AND IN MODELS OVER
NORTHWEST ARIZONA. MODELS ACTUALLY SAG THIS FEATURE BACK TO THE
SOUTHEAST LATER TODAY AS HIGH PRESSURE REMAINS OVER NORTHEAST
NEVADA. EXPECTING MOST AREAS TO SEE SOME THUNDERSTORM DEVELOPMENT
TODAY WITH LINCOLN COUNTY PROBABLY THE LEAST ACTIVE BEING CLOSEST TO
THE HIGH AND THE SOUTHEAST PORTION OF THE FORECAST AREA MOST ACTIVE
NEAR THE DEFORMATION ZONE. FORECAST DOES NOT APPEAR TO BE IN NEED OF
UPDATING AT THIS TIME.
&&

.PREV DISCUSSION...255 AM PDT SUN AUT 7 2005...SHORT TERM...NOT MUCH
TO HANG THE HAT ON AS FAR AS CONVECTIVE FOCUSING MECHANISM. ON WATER
VAPOR THERE MAY BE A WEAK WAVE EVIDENT IN WESTERN AZ...BUT ITS NOT
CLEAR CUT AND MAY BE NOTHING. EITHER WAY...MONSOON MOISTURE IS IN
PLACE AND AS WEVE SEEN FOR THE LAST FEW WEEKS IN THE ABSENCE OF
UPPER SUPPORT...CONVECTION WILL FORM ON TERRAIN. OUTFLOWS FROM THE
INITIAL CONVECTION WILL THEN TRIGGER CONVECTION IN THE VALLEYS.
REALLY HAVENT CHANGED ANYTHING IN THE SHORT TERM FROM THE PREVIOUS
PACKAGE AS IT SEEMED TO HAVE A GOOD HANDLE ON THINGS.
&&

.LONG TERM...THE 00Z GFS AND ECMWF BEGIN TO DIVERGE THURSDAY AND
BECOME ABOUT 180 DEGREES OUT OF PHASE BY SATURDAY AFTERNOON WITH THE
GFS INDICATING A FOUR CORNERS RIDGE AND THE ECMWF A FAIRLY
SIGNIFICANT TROUGH. EVEN TAKING THE DRIER PATTERN OF THE ECMWF...
IT STILL INDICATES LITTLE IN THE WAY OF DRYING BELOW 700MB OVER THE
FORECAST AREA THROUGH THURSDAY. THE SOUTHERN SIERRA WILL PROBABLY
DRY OUT ENOUGH THURSDAY TO REMOVE THE MENTION OF THUNDERSTORMS BUT
NOT A LOT OF CHANGE EXPECTED ELSEWHERE. BOTH MODELS INDICATE A
DRYING TREND FRIDAY BUT THE GFS KEEPS THE HIGH OVER THE SOUTHWEST
AND BEGINS TO RETURN MOISTURE OVER THE WEEKEND. ONLY THE 00Z ECMWF
INDICATES DEEP ENOUGH DRY SOUTHWEST FLOW TO NORTHWEST FLOW
ASSOCIATED WITH THE TROUGH TO DRY OUT THE REGION BY SATURDAY. WILL
KEEP LOW CHANCE POPS GOING THROUGH THE PERIOD OVER EASTERN SAN
BERNARDINO COUNTY AND SRN NV/NW AZ.
&&

.AVIATION...TAF ADEQUATELY COVERS EXPECTED CONDITIONS AT KLAS.
SCATTERED THUNDERSTORMS WILL AFFECT ALL APPROACH CORRIDORS MAINLY
BETWEEN 20Z AND 03Z. THESE STORMS WILL HAVE LITTLE MOVEMENT AND ONCE
AGAIN WILL NEED TO WATCH OUTFLOW BOUNDARIES LATE THIS
AFTERNOON/EVENING FOR POSSIBLE IMPACTS ON KLAS.
&&

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

HARRISON/BAILEY/ADAIR

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LAS VEGAS NV
1000 AM PDT SUN AUG 7 2005

AZZ001>003-036-CAZ026>029-NVZ014>022-081700-
DEATH VALLEY NATIONAL PARK CA-ESMERALDA AND CENTRAL NYE COUNTY NV-
LAKE HAVASU AND FORT MOHAVE AZ-LAKE MEAD NATIONAL RECREATION AREA AZ-
LAKE MEAD NATIONAL RECREATION AREA NV-LAS VEGAS VALLEY NV-
LINCOLN COUNTY NV-NORTHEAST CLARK COUNTY NV-NORTHWEST DESERTS AZ-
NORTHWEST PLATEAU AZ-
OWENS VALLEY AND ADJACENT EASTERN SIERRA SLOPES CA-
SAN BERNARDINO COUNTY DESERTS CA-SAN BERNARDINO COUNTY-
UPPER COLORADO RIVER VALLEY CA-SHEEP RANGE NV-
SOUTHERN CLARK COUNTY NV-SPRING MOUNTAINS-RED ROCK CANYON NV-
WESTERN CLARK AND SOUTHERN NYE COUNTY NV-
1000 AM PDT SUN AUG 7 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST
CALIFORNIA...SOUTHERN NEVADA AND NORTHWEST ARIZONA.

.DAY ONE...TODAY.

A MOIST AND UNSTABLE AIRMASS REMAINS IN PLACE OVER THE AREA WITH
SCATTERED THUNDERSTORMS EXPECTED. STORMS THAT FORM WILL BE SLOW
MOVING RESULTING IN A THREAT FOR LOCALIZED HEAVY RAIN AND FLASH
FLOODING.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THE MONSOON PATTERN IS EXPECTED TO REMAIN IN PLACE THROUGH THE
MIDDLE OF THE WEEK. THIS WILL RESULT IN SCATTERED SHOWERS AND
THUNDERSTORMS MAINLY DURING THE AFTERNOON AND EVENING HOURS.
EXTENDED RANGE MODELS SHOW THAT SOME DRYING MAY TAKE PLACE BY FRIDAY
FOR A DECREASE IN ACTIVITY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED.