Severe Thunderstorm Warning 5, NWS Las Vegas, NV

MOJAVE DESERT/SOUTHERN GREAT BASIN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
412 PM PDT WED JUL 4 2001

SYNOPSIS...A MOIST AND UNSTABLE AIR MASS WILL REMAIN IN PLACE ACROSS
THE MOJAVE DESERT AND SOUTHERN GREAT BASIN THROUGH FRIDAY. THIS WILL
CONTINUE TO PROVIDE THE FUEL FOR SCATTERED AFTERNOON AND EVENING
THUNDERSTORMS. IT WILL REMAIN QUITE WARM BUT TEMPERATURES ARE
EXPECTED TO GRADUALLY LOWER 2 TO 3 DEGREES EACH OF THE NEXT COUPLE
DAYS.

DISCUSSION...THUNDERSTORMS FIRING AS EXPECTED WITH STORM MOTION
GENERALLY NW. BETTER STORM ENVIRONMENT TODAY WITH HIGHER CAPE TO
FEED STORM INFLOW AND DECENT SPEED SHEAR ALOFT. GETTING HIGHER VILS
ON 88D WHICH SUGGESTS BETTER UPDRAFT DEVELOPMENT. WELL MIXED
BOUNDARY LAYER THIS AFTERNOON WITH INVERTED-V THERMODYNAMIC PROFILES
SO PRIMARY THREAT THIS EVENING WILL REMAIN STRONG DOWNBURST WINDS.
EXTREME SOUTHERN NV AND NORTHWEST AZ UNDER THE GUN FOR OUTFLOW GUSTS
AS STORMS PROPAGATE OFF HIGHER TERRAIN. EXCELLENT SUPPORT AND
COORDINATION FROM SPC AND DECISION WAS TO ISSUE SEVERE THUNDERSTORM
WATCH AS A COURSE OF LEAST REGRET.

STRONG MID AND UPPER-LEVEL HIGH OVER UT WILL CONTINUE TO SLOWLY
SHIFT EAST THROUGH FRIDAY...ALLOWING STEERING FLOW ALOFT TO VEER TO
SOUTH. THIS WILL CONTINUE TO CIRCULATE MID-LEVEL MOISTURE INTO THE
FORECAST AREA WITH GRADUAL INCREASE IN LOW-LEVEL MOISTURE..RESULTING
IN DAILY THUNDERSTORM DEVELOPMENT. STORM THREAT WILL GRADUALLY SHIFT
TO MORE OF A FLASH FLOOD POTENTIAL AS LOW-LEVEL MOISTURE SLOWLY
INCREASES (OR AT LEAST A COMBINATION OF FLASH FLOOD AND STRONG
WINDS). UNKNOWNS REMAIN THE POSSIBILITY OF A LOW-LEVEL GULF SURGE OR
A DISTURBANCE ROTATING AROUND THE PERIPHERY OF THE HIGH WHICH WOULD
PROVIDE FORCING AND FOCUS STORMS. IF MCS DEVELOPS OVER SONORA
THURSDAY NIGHT...LOW-LEVEL OUTFLOW COULD EASILY PUSH MOISTURE SURGE
INTO SOUTHERN NV AS ALL MODELS INDICATE DECENT SOUTHERLY FLOW AT
850 MB. FRIDAY COULD THEN BE THE MOST ACTIVE DAY AS BOTH ETA/AVN
SHOW A DISTURBANCE ROTATING UP FROM MEXICO. HOWEVER...OPERATIONAL
MODELS NOT THE BEST AT PICKING UP ON THESE DETAILS (IF AT ALL) SO
WILL USE BROAD BRUSH APPROACH FOR NOW AND CONTINUE TO WATCH.

IN THE EXTENDED...HIGH CONTINUES TO SHIFT EAST AND REACHES THE
CENTRAL PLAINS BY MONDAY. FLOW ALOFT BECOMES INCREASINGLY SW WITH
TIME WITH DRYING INDICATED FOR WESTERN AND NORTHERN ZONES SUNDAY AND
MONDAY. INDICATED THIS IN EXTENDED BUT HIGH THEN QUICKLY REBUILDS
WESTWARD TUESDAY AND WEDNESDAY FOR A RETURN OF MOIST S-SE FLOW
ALOFT. KEPT DAILY MENTION OF THUNDERSTORMS ELSEWHERE (SOUTHERN NV
AND NORTHWEST AZ) AS DRYING MORE SUSPECT. LIKELY TO BE A DECREASE IN
THUNDERSTORM CHANCES SUNDAY AND MONDAY BUT NOT CONFIDENT ENOUGH
RIGHT NOW TO PULL FROM FORECAST.

NEMETH

.LAS....A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED. SEE THE LATEST
STATEMENTS FOR DETAILS.