Severe Thunderstorm Warning 22, NWS Las Vegas, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
320 PM PDT WED AUG 18 2004

.SYNOPSIS...A WEAK RIDGE OF HIGH PRESSURE WILL SLOWLY BUILD OVER THE
SOUTHERN GREAT BASIN AND MOJAVE DESERT THROUGH THE END OF THE WEEK.
THIS WILL BRING DRIER CONDITIONS TO THE AREA...HOWEVER ENOUGH
MOISTURE TO REMAIN ACROSS THE DISTRICT TO ALLOW FOR ISOLATED
AFTERNOON THUNDERSTORMS THROUGH FRIDAY MAINLY OVER NORTHWEST ARIZONA
AND EXTREME SOUTHEAST NEVADA. TEMPERATURES TO REMAIN NEAR NORMAL.
&&

.SHORT TERM...WEAK SHORT WAVE MOVING ACROSS SOUTHERN NEVADA THIS
AFTERNOON BEST SEEN ON WATER VAPOR HAS HELPED DYNAMICS ACROSS THE
SOUTHEAST PORTION OF THE CWA. SCATTERED THUNDERSTORMS HAVE ONCE
AGAIN FORMED AND ANTICIPATE THAT ISOLATED ACTIVITY TO LINGER WELL
INTO THE TONIGHT PERIOD. AS THE SHORT WAVE MOVES ACROSS THE AREA
WEAK NORTHWEST FLOW TO REMAIN ACROSS THE CWA INTO THE FIRST PART OF
FRIDAY. OVERALL AIRMASS BEGINS TO DRY OUT UNDER NORTHWEST FLOW...BUT
FLOW REMAINS ON THE LIGHT SIDE THUS MOISTURE WILL BE SLOW TO EXIT
THE AREA. THUS DAYTIME HEATING TO CONTINUE TO COMBINE WITH NEG LI TO
PRODUCE ISOLATED AFTERNOON CONVECTION INTO THURSDAY AND FRIDAY. BEST
AREA FOR CONVECTION TO BE OVER LINCOLN/MOHAVE COUNTIES...BUT MAY
NEED TO TWEAK A LITTLE FURTHER WEST ESPECIALLY THURSDAY AND WILL LET
MID CREW LOOK AT THIS. BY SATURDAY MODELS DEPICT WEAK TROUGH FORMING
OFF CALIFORNIA COAST AND TURNING FLOW ALOFT TO MORE SOUTHWEST WHICH
SHOULD FURTHER DRYING OF CWA. HOWEVER...ENOUGH DYNAMICS REMAIN
OVER THE NORTHERN MOUNTAINS WITH ASSOCIATED NEG LI/RESIDUE MOISTURE
TO KEEP ISOLATED ACTIVITY THIS AREA FOR THE AFTERNOON. OVERALL
LITTLE CHANGE IN TEMPS WITH MOST READINGS BEING NEAR NORMAL THROUGH
THE SHORT TERM.
&&

.LONG TERM...TEMPERED FORECAST FROM PREVIOUS SHIFT LOOKING PRETTY
GOOD AS LATEST MODEL RUNS ARE BEGINNING TO BACK OFF ON THE STRENGTH
AND SOUTHERN TRACK OF THE LOW PRESSURE SYSTEM. LAST FEW GFS RUNS
HAVE KEPT THE BULK OF THE SYSTEM OVER THE PACNW...WITH TROUGHING
OVER THE REST OF THE WESTERN US BY MONDAY. IT DOES APPEAR THE GFS IS
DIGGING SOME ENERGY DOWN THE BACKSIDE OF THE TROUGH THROUGH CA AND
NV ON TUESDAY TO CARVE IT A LITTLE DEEPER OVER THE FORECAST
AREA...BUT EVEN SO...THIS IS MUCH WEAKER THAN THE CLOSED LOW
SCENARIO DEPICTED BY THE 00Z MODELS LAST NIGHT. NEW GFS RUNS ARE
SUPPORTED BY THE 12Z EURO...AND THE UKMET AND CANADIAN. INCREASED
WINDS A LITTLE BIT IN THE GRIDS...ESP OVER NORTHWEST ARIZONA WHERE
WE COULD SEE SOME BREEZY CONDITIONS DEVELOP BY MONDAY AS THE TROUGH
APPROACHES. TWEAKED A FEW TEMPS..BUT OVERALL THEY LOOKED PRETTY
GOOD. DID ADD SOME SLIGHT CHANCE POPS TO THE NORTHERN ZONES ON
TUESDAY JUST AHEAD OF THE TROUGH AXIS. THINK THERE WILL BE ENOUGH
MOISTURE/INSTABILITY AVAILABLE FOR THIS.
&&

.AVIATION...BIGGEST THREAT FROM SURROUNDING THUNDERSTORMS WILL BE
SUDDEN CHANGES IN WIND SPEED/DIRECTION DUE TO OUTFLOW WINDS. WILL
PROBABLY KEEP A TEMPO GROUP IN FOR THE FIRST FEW HOURS OF THE 00Z
TAF ISSUANCE TO COVER STORMS NORTH OF THE LAS VEGAS VALLEY THAT ARE
DRIFTING SOUTHWARD...BUT THESE COULD FALL APART BEFORE THEY GET
HERE. OTHERWISE...TAF ADEQUATELY COVERS ALL SIGNIFICANT WEATHER
EXPECTED AT KLAS.
&&

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

JENSEN/DAVIS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LAS VEGAS NV
910 AM PDT WED AUG 18 2004

AZZ001>003-036-CAZ026>029-NVZ014>022-191700-
DEATH VALLEY NATIONAL PARK-ESMERALDA AND CENTRAL NYE COUNTY-
LAKE HAVASU AND FORT MOJAVE-LAKE MEAD NATIONAL RECREATION AREA-
LAS VEGAS VALLEY-LINCOLN COUNTY-NORTHEAST CLARK COUNTY-
NORTHWEST DESERTS-NORTHWEST PLATEAU-
OWENS VALLEY AND ADJACENT EASTERN SIERRA SLOPES-
SAN BERNARDINO COUNTY DESERTS-SAN BERNARDINO COUNTY-
UPPER COLORADO RIVER VALLEY-SHEEP RANGE-SOUTHERN CLARK COUNTY-
SPRING MOUNTAINS-RED ROCK CANYON-
WESTERN CLARK AND SOUTHERN NYE COUNTY-
910 AM PDT (910 AM MST) WED AUG 18 2004

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

.DAY ONE...TODAY.

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE THIS AFTERNOON AND
EVENING...PARTICULARLY OVER MOHAVE AND LINCOLN COUNTIES. ALTHOUGH
THE THREAT OF WIDESPREAD HAZARDOUS WEATHER IS LOW...ISOLATED HEAVY
RAIN CANNOT BE RULED OUT.

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

THE PROBABILITY OF WIDESPREAD HAZARDOUS WEATHER IS LOW.

JENSEN