Flash Flood Warning 23, NWS Las Vegas, NV

MOJAVE DESERT/SOUTHERN GREAT BASIN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
930 AM PDT SUN JUL 11 1999

SYNOPSIS...A VERY MOIST AND UNSTABLE AIR MASS WILL REMAIN OVER THE
REGION THROUGH MONDAY. THIS WILL RESULT IN A CONTINUED THREAT FOR
MAINLY AFTERNOON SHOWERS AND THUNDERSTORMS. SOME OF THE STORMS WILL
CONTAIN HEAVY RAINFALL. DAYTIME TEMPERATURES WILL REMAIN BELOW
NORMAL.

DISCUSSION...AIRMASS STILL VERY MOIST WITH PRECIPITABLE WATER AROUND
1.5 INCHES MANY AREAS. A LITTLE MORE UNSTABLE WITH MORE CAPE ON DRA
SOUNDING AS WARMING TOOK PLACE BELOW ROUGHLY 700 MB VERSUS SATURDAY.
WEAK CONVERGENCE ZONE SEEN THIS MORNING WITH SOME DIFFLUENCE ALOFT.
BASED ON THIS INFO...FLASH FLOOD WATCH AND FORECAST IN GENERAL LOOK
GOOD. HOWEVER...EARLY LOOKS AT MODEL DATA INDICATE LOW LEVEL
CONVERGENCE AND UPPER LEVEL DIVERGENCE BOTH DIMINISHING BY 00Z. ALSO
CONVECTIVELY INDUCED VORT MAX SEEN OVER SOUTHERN AZ PROGGED TO MOVE
NORTH INTO SOUTHERN MOHAVE COUNTY. THIS AREA WILL LIKELY BE AN
INHIBITING FACTOR IN REALITY...SIMILAR TO THE VORT MAX OVER INYO
COUNTY YESTERDAY WHERE AIRMASS WAS ACTUALLY COOL AND RELATIVELY
STABLE. THIS LEADS ME TO BELIEVE THAT FLASH FLOOD THREAT MAY NOT BE
QUITE AS STRONG AS WAS THOUGHT EARLIER. ANOTHER HOWEVER...ETA PROGS
700 MB WINDS TO INCREASE TO 20 KNOTS OVER CLARK COUNTY WHICH WOULD
HELP MOVE STORMS OFF MOUNTAINS AND KEEP WIDESPREAD THREAT OF FLASH
FLOODING A DEFINITE CONCERN. THE NGM ONLY INCREASES THIS FLOW TO 10
TO 15 KNOTS. BOTTOM LINE IS ENOUGH OF A THREAT TO LEAVE WATCH IN
PLACE. TEMPS WILL BE A TOUGH CALL AS TEMPS COULD WARM NICELY WITH
ENOUGH BREAKS IN THE CLOUDS. LOOKS LIKE MORE BREAKS SHOWING UP NOW SO
WILL LEAVE FORECAST TEMPS ALONE FOR NOW.  NO UPDATES PLANNED AT THIS
TIME.   JMH

.LAS...A FLASH FLOOD WATCH CONTINUES FOR NW AZ AND PORTIONS OF SRN NV
       AND ERN CA DESERTS FROM 10 AM PDT (17Z) UNTIL 9 PM PDT (04Z).
       REFER TO THE FLASH FLOOD WATCH STATEMENT FOR DETAILS.