Severe Thunderstorm Warning 28, NWS Las Vegas, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
315 AM PDT FRI SEP 10 2004

.SYNOPSIS...MONSOONAL MOISTURE WILL REMAIN IN PLACE OVER THE REGION
TODAY AS A LARGE RIDGE OF HIGH PRESSURE REMAINS OVER ARIZONA AND NEW
MEXICO. A TROUGH OF LOW PRESSURE WILL MOVE THROUGH ON
SUNDAY...BRINGING DRIER AIR IN BEHIND IT. TEMPERATURES WILL REMAIN
NEAR NORMAL UNDER THE RIDGE WITH THE CLOUD COVER AND INCREASED
MOISTURE.
&&

.SHORT TERM...MOISTURE AMOUNTS TO CHANGE LITTLE OVER THE FORECAST
AREA TODAY COMPARED TO YESTERDAY. ONLY CHANGE IS THAT MODELS ARE
INDICATING A SLIGHT DECREASE IN 850 DEWPOINTS AND PW TODAY AS THE
RIDGE EXPANDS TO OUR WEST. DO NOT THINK FLASH FLOOD WATCH IS
NECESSARY AS 500MB WINDS ARE FORECAST BY ETA/GFS TO BE BETWEEN 20
AND 30 KTS. MAY STILL SEE SOME ISOLATED AREAS OF FLASH FLOODING.
BEST CHANCE FOR THIS WILL BE OVER SOUTHERN MOHAVE...CLARK...AND SAN
BERNARDINO COUNTIES WHERE PW REMAINS ABOVE ONE INCH. OTHER CONCERN
FOR TODAY WILL BE ISOLATED SEVERE WEATHER WITH WINDS BACKING FROM
850-500MB AND SOME SPEED SHEAR AND NEG LIS EXPECTED AS WELL. JET
STREAK IS FORECAST TO REMAIN OVER SOUTHERN NEVADA TODAY WITH ETA/GFS
INDICATING SOME UPPER LEVEL DIVERGENCE OVER THE SOUTHERN 1/3 OF THE
CWA ASSOCIATED WITH THIS FEATURE. THIS DISTURBANCE IS MOST LIKELY
RESPONSIBLE FOR THE INCREASE IN CLOUD COVER CURRENTLY OCCURRING OVER
SOUTHERN SAN BERNARDINO AND MOHAVE COUNTIES ATTM. INCREASED POPS
TODAY AND TOMORROW TO MATCH MODEL TRENDS AND MOISTURE LEFT OVER FROM
YESTERDAY. THINK BEST AREAL COVERAGE WILL BE FROM SAN BERNARDINO
COUNTY UP THROUGH CLARK AND INTO LINCOLN COUNTY. MOISTURE SHOULD
REMAIN IN PLACE AGAIN TOMORROW AS A SHORTWAVE TROUGH CURRENTLY OFF
TO OUR WEST IS PICKED UP BY AND MERGES WITH THE MAIN TROUGH MOVING
INTO THE PACNW. THIS FEATURE SHOULD AID IN KICKING OFF ANOTHER ROUND
OF THUNDERSTORMS ON SATURDAY AFTERNOON AS IT MOVES THROUGH. MAY ALSO
SEE CONVECTION CONTINUING TO FIRE OVERNIGHT AHEAD OF THIS FEATURE.
TROUGH AXIS IS CURRENTLY EXPECTED TO MOVE THROUGH ON
SUNDAY...BRINGING DRIER AIR AND ENDING THUNDERSTORM CHANCES BEHIND
IT. WINDS WILL ALSO INCREASE AHEAD TROUGH AND BEHIND A WEAK COLD
FRONT THAT WILL MOVE NORTHWEST TO SOUTHEAST SUNDAY NIGHT.
&&

.LONG TERM...MODELS IN FAIR AGREEMENT FOR MONDAY THROUGH THURSDAY
WITH NO MAJOR CHANGES FROM PREVIOUS RUNS. SHORTWAVE TROUGH EXITING
JUST TO THE EAST MONDAY WITH MODERATE TO WEAK WESTERLY FLOW TUESDAY.
BROAD TROUGH OVER THE PACIFIC NORTHWEST STILL PROGGED TO DEEPEN OVER
THE FAR WESTERN U.S. WEDNESDAY AND THURSDAY. GFS AND DGEX KEEP THE
AIRMASS OVER THE SOUTHERN GREAT BASIN AND MOJAVE DESERT QUITE DRY
THROUGH THE PERIOD WHICH LOOKS REASONABLE. SO EXPECTING MOSTLY CLEAR
SKIES AND A COOLING TREND FOR MONDAY THROUGH THURSDAY WITH BREEZY
CONDITIONS WEDNESDAY INTO THURSDAY.
&&

.AVIATION....TAF ADEQUATELY COVERS ALL SIGNIFICANT WEATHER EXPECTED
AT KLAS.
&&

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

DAVIS/HARRISON