Severe Thunderstorm Warning 18, NWS Las Vegas, NV

MOJAVE DESERT/SOUTHERN GREAT BASIN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
900 PM PDT FRI AUG 7 1998

SYNOPSIS...A FLOW OF MONSOONAL MOISTURE WILL INCREASE OVER THE
WEEKEND...ESPECIALLY ON SUNDAY...LEADING TO MORE LATE DAY
THUNDERSTORMS ACROSS THE MOJAVE DESERT AND SOUTHERN GREAT BASIN
INTO EARLY NEXT WEEK. THE EXCEPTION WILL BE FROM THE SIERRA NEVADA
MOUNTAINS AND INTO PARTS OF WESTERN NEVADA WHERE DRIER AIR WILL MAKE
THUNDERSTORM DEVELOPMENT MORE LIMITED.

DISCUSSION...FEW STRONG/SEVERE STORMS DEVELOPED THIS AFTERNOON FROM
CENTRAL SAN BERNARDINO COUNTY NEWD ACROSS THE LAS VEGAS VALLEY AND
INTO NORTHERN MOHAVE COUNTY IN AZ. STORMS WERE GENERALLY OVER THE
MOUNTAINS AND HIGHER TERRAIN WITH A FEW MAKING THEIR WAY ONTO THE
DESERT FLOOR. IN THE LAS VEGAS VALLEY...THE MCCULLOUGH RANGE ONCE
AGAIN SUPPLIED THE INITIAL LIFTING MECHANISM AS THE STORM FIRST
FORMED OVER THE N END OF THE RANGE AND THEN MOVED OVER GREEN VALLEY
AND MOVED N ACROSS THE CITY. HAIL TO NEAR 3/4 OF AN INCH WAS REPORTED
ALONG WITH WIND GUSTS OVER 50KTS IN A COUPLE SITES. THIS STORM
INTENSIFIED AND APPARENTLY PRODUCED GOLF BALL SIZE HAIL SW OF
LOGANDALE. STORMS WERE AIDED BY WEAK TWIST IN CLOUDS THAT ROTATED UP
FROM S DURING THE AFTERNOON ALONG WITH BATCH OF DEEPER SUBTROPICAL
MOISTURE SEEN ON WATER VAPOR SHOTS. UPPER FLOW RATHER COMPLEX WITH NO
LONG FETCH OF ORGANIZED SE FLOW YET. DEEP NLY FLOW IN FACT DOWN INTO
NRN MEXICO WITH WLY FLOW ABOVE 500MB JUST S OF THAT. MORE ORGANIZED
SLY FLOW MOVING UP GULF OF CALIFORNIA AHEAD OF TROPICAL STORM FRANK.
NEW ETA DEVELOPS MUCH STRONGER SE FLOW TOMORROW AFTERNOON IN AREA S
OF AZ BORDER AND THIS MAY BEGIN TO PICK UP BETTER MOISTURE FOR
SUNDAYS STORMS. ALSO LONGER DURATION SLY LOW LEVEL FLOW MAY
EVENTUALLY HELP TO INCREASE LOW LEVEL MOISTURE AND BREAK CAP THAT WAS
IN PLACE TODAY ACROSS FAR SERN CA AND SW AZ (AIDING IN SLY SURGE AS
EARLY AS TOMORROW NIGHT). NEW ETA DOES SHOW THIS. IT APPEARS TO ME
THAT THERE MAY BE A SLIGHT INCREASE IN LOW LEVEL MOISTURE SAT...PER
THE MODELS ALSO...WITH LITTLE INCREASE IN MID LEVEL MOISTURE. SO WILL
NOT CHANGE FORECAST FOR SAT. SUNDAY LOOKS BETTER AS MORE ORGANIZED SE
FLOW MAY HAVE TIME TO DEEPEN MOISTURE LAYER AND PRODUCE MORE
WIDESPREAD CONVECTION AND POSSIBLE FLASH FLOOD PROBLEMS INTO EARLY
NEXT WEEK.  WE WILL JUST HAVE TO WAIT AND SEE EFFECT OF TS FRANK
EARLY IN THE EXTENDED PERIOD. ONLY UPDATES THIS EVENING IS TO TOUCH
UP FIRST PERIROD AND REMOVE MOST CONVECTION. LAS 0334. SKRBAC