Flash Flood and Lightning Strike in Nevada, July 30 to 31, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
318 PM PDT WED JUL 30 2014

.SYNOPSIS...SHOWERS AND THUNDERSTORMS OVER THE SOUTHERN SIERRA AND
WEST CENTRAL NEVADA WILL DIMINISH LATE THIS EVENING. THUNDERSTORM
DEVELOPMENT WILL BE MORE ISOLATED OVER THE SOUTHERN SIERRA AND
SOUTHERN GREAT BASIN UNDER A DRIER AND MORE STABLE WESTERLY FLOW
THURSDAY AND FRIDAY. ANOTHER PUSH OF MOISTURE IS EXPECTED TO
SPREAD UP ACROSS THE REGION OVER THE WEEKEND FOR AN UPSWING IN
SHOWERS AND THUNDERSTORMS.
&&

.SHORT TERM...THROUGH FRIDAY NIGHT...SHOWERS AND EMBEDDED
THUNDERSTORMS HAVE BEEN EXPANDING ACROSS MUCH OF THE SOUTHERN SIERRA
AND NORTHERN INYO COUNTY THIS AFTERNOON AND WILL PERSIST INTO THE
EVENING AS REMNANT MOISTURE FROM FORMER TROPICAL SYSTEM HERNAN IS
PULLED ACROSS THE SOUTHERN SIERRA. PRECIPITATION WILL THEN TAPER OFF
LATE THIS EVENING AND OVERNIGHT. ELSEWHERE...ISOLATED THUNDERSTORMS
WERE DEVELOPING OVER THE MOUNTAINS OF SOUTHERN NEVADA AND NORTHWEST
ARIZONA. PRECIPITATION HAS BEEN GENERALLY LIGHT WITH THESE CELLS.
DRIER AIR WILL SPREAD OVER INYO COUNTY LATE TONIGHT AND THURSDAY AND
THE REST OF THE REGION WILL SEE A SLIGHT DECREASE IN MOISTURE WITH
MODERATELY UNSTABLE CONDITIONS PERSISTING OVER THE SAME AREA AS
TODAY. THIS WILL KEEP A SLIGHT CHANCE OF THUNDERSTORMS OVER ZONES
FROM THE MOUNTAINS OF SOUTHERN NEVADA AND NORTHWEST ARIZONA
NORTHWARD. A LITTLE DRIER AND MORE STABLE AIR WILL SPREAD OVER THE
REGION FRIDAY LEAVING ONLY A SLIGHT CHANCE OF THUNDERSTORMS OVER THE
SOUTHERN SIERRA...SOUTH CENTRAL NEVADA AND NORTHWEST ARIZONA. THIS
RELATIVELY DRY PATTERN WILL BREAK AFTER FRIDAY AND THE 12Z MODELS
SUPPORT THE TRENDS DETAILED IN THE LONG TERM DISCUSSION. NO
SIGNIFICANT CHANGES WERE MADE TO THE FORECAST BEYOND FRIDAY.
&&

.LONG TERM...SATURDAY THROUGH WEDNESDAY.

WELL GET READY FOR ANOTHER PUSH OF JUICIER MOISTURE THIS WEEKEND,
ESPECIALLY OVER THE EASTERN HALF OF THE AREA, AS THE FLOW ALOFT
TRANSITIONS TO THE SOUTHEAST BY SATURDAY MORNING ACROSS OUR AREA AS
THE CLASSIC SUMMERTIME FOUR CORNERS HIGH SETS BACK UP. AT LEAST
INITIALLY, IT APPEARS THAT WHATEVER SHOWER AND THUNDERSTORM ACTIVITY
THAT DEVELOPS ON SATURDAY AFTERNOON AND EVENING SHOULD DEVELOP
COURTESY OF ANY DIFFERENTIAL HEATING BOUNDARIES OR BE TERRAIN
INDUCED. THE LATEST ECMWF AND GFS ARE MORE STABLE OVER THE WESTERN
CWFA AND THUS IF THIS TREND CONTINUES WE MAY NEED TO TRIM POPS THERE
DOWN. PWAT VALUES PUSHING 1.50 INCHES WILL MEAN THE ATMOSPHERE WILL
HAVE A LOT OF JUICE AND THUS FLASH FLOODING WILL BE THE PRIMARY
THREAT IN STRONGER OR SLOWER MOVING STORMS.

THINGS GET MORE INTERESTING SATURDAY NIGHT THROUGH MONDAY AS AN
INVERTED TROUGH OR SOME SORT OF VORTICITY MAXIMUM OR LOBE HEADS
NORTHWEST FROM CENTRAL ARIZONA AND CROSSES THE AREA. THIS FEATURE
SHOULD LIFT SLOWLY NORTHEAST ON MONDAY BUT CONTINUES TO TREND TOWARD
A SLOWER EXIT ON THE MODELS. THE PRESENCE OF THIS FEATURE IS SHOWN
ON THE BIG 4 MEDIUM RANGE OPERATIONAL MODELS (GFS, ECMWF, GEM AND
DGEX) AND THIS TRIGGER FEATURE COMBINED WITH THE HIGH MOISTURE
CONTENT AVAILABLE SHOULD RESULT IN AN EVEN BETTER CHANCE FOR SHOWERS
AND THUNDERSTORMS EVEN AT NIGHT. POPS WERE RAISED AGAIN TO SHOW A
BETTER UPTICK IN ACTIVITY FOR SUNDAY THROUGH MONDAY. THE MAIN
CONCERN CONTINUES TO BE HOW MUCH CLOUD COVER EXISTS AS THIS WOULD
LIMIT HEATING AND RESULT IN MORE SHOWERS AND LOW-GRADE
THUNDERSTORMS. HOWEVER, IF WE GET ENOUGH HEATING SUNDAY, ACTIVITY
WOULD SUPPORT THE POTENTIAL FOR STRONGER THUNDERSTORMS WITH 0-6 KM
BULK SHEAR VALUES SHOWN BY THE GFS TO EXCEED 20 KTS ACROSS THE
EASTERN CWFA. HEAVY RAIN PRODUCING THUNDERSTORMS WILL BE THE MAIN
THREAT ALONG WITH THE RISK FOR FLASH FLOODING. HIGH TEMPS WILL BE
VERY TRICKY ESPECIALLY ON SUNDAY AS CLOUDS COULD EASILY HOLD TEMPS
DOWN ANOTHER 6-8 DEGREES FROM WHAT IS FORECAST.

THE LATEST MODELS NOW SHOW A SLOWER EXIT TO THIS FEATURE KEEPING IT
OVER THE NORTHEAST CWFA THROUGH TUESDAY BEFORE FINALLY GIVING IT THE
BOOT. THUS POPS WERE RAISED MONDAY THROUGH TUESDAY ESPECIALLY IN
LINCOLN COUNTY. DRIER AIR SHOULD FINALLY WORK IN FROM THE SOUTHWEST
AS THE FLOW ALOFT TURNS IN THAT DIRECTION AND THIS SHOULD CUT BACK
ON THE COVERAGE OF STORMS OUT THAT WAY. WITH LESS CLOUDS, TEMPS
SHOULD TREND BACK CLOSER TO NORMAL.
&&

.AVIATION...FOR MCCARRAN...SHOWERS NEAR THE SPRING MOUNTAINS WILL
DIMINISH DURING THE LATE AFTERNOON AND EVENING. WINDS WILL DECREASE
TO AROUND 10 KTS FROM THE WEST-SOUTHWEST THROUGH LATE EVENING THEN
BECOME LIGHT DIURNAL PATTERNS EARLY THURSDAY MORNING. SCATTERED
SHOWERS AND THUNDERSTORMS WILL PERSIST IN THE BEATTY CORRIDOR
THROUGH LATE EVENING. ISOLATED THUNDERSTORMS WILL BE POSSIBLE
THURSDAY AFTERNOON AND EVENING OVER THE SPRING MOUNTAINS AND THE
BEATTY/MORMON MESA CORRIDORS.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...SCATTERED SHOWERS AND THUNDERSTORMS OVER NORTHERN
INYO...ESMERALDA AND CENTRAL NYE COUNTIES WILL PERSIST THROUGH THIS
EVENING THEN DIMINISH OVERNIGHT. WIND GUSTS OF 25-35 KTS WILL OCCUR
NEAR STORMS. SCT-BKN BASES AROUND 10 KFT MSL CAN BE EXPECTED WITH
MOUNTAIN TOP OBSCUREMENT. ISOLATED THUNDERSTORMS ELSEWHERE ACROSS
THE SOUTHERN GREAT BASIN AND NORTHWEST ARIZONA WILL DISSIPATE EARLY
THIS EVENING. CONSIDERABLY LESS THUNDERSTORM COVERAGE IS EXPECTED
THURSDAY WITH ISOLATED STORMS CONFINED TO THE HIGHER MOUNTAINS AND
ONLY SCT BASES AROUND 12-15KFT MSL.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS NOT EXPECTED
AT THIS TIME. HOWEVER...SPOTTERS ARE ENCOURAGED TO REPORT ANY
SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING
PROCEDURES.
&&

SHORT TERM/AVIATION...ADAIR
LONG TERM...STACHELSKI

FOR MORE FORECAST INFORMATION...SEE US ON OUR WEBPAGE:

HTTP://WEATHER.GOV/LASVEGAS OR FOLLOW US ON FACEBOOK AND TWITTER