Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 301702
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
1000 AM PDT WED JUL 30 2014

.SYNOPSIS...LIMITED SHOWER AND THUNDERSTORM DEVELOPMENT WILL BE
CONFINED PRIMARILY TO NORTHERN INYO COUNTY AND SOUTHERN GREAT BASIN
UNDER A DRIER AND MORE STABLE WEST TO SOUTHWEST FLOW ALOFT THROUGH
FRIDAY. ANOTHER PUSH OF MOISTURE IS EXPECTED TO SPREAD UP ACROSS THE
REGION OVER THE WEEKEND FOR AN UPSWING IN SHOWERS AND THUNDERSTORMS.
&&

.UPDATE...THE 12Z LAS VEGAS SOUNDING SHOWED SUFFICIENT MOISTURE AND
INSTABILITY FOR A THUNDERSTORM TO DEVELOP OVER THE MOUNTAINS WITH
ONLY A WEAK CAP TO OVERCOME ABOVE 700 MB. RECENT SATELLITE/RADAR
LOOPS AND WEB CAMS SHOW CONSIDERABLE CLOUD COVER AND SHOWERS
SPREADING INTO THE CENTRAL AND SOUTHERN SIERRA BUT NOT MUCH PRECIP
SPILLING OVER TO THE OWENS VALLEY YET. WE SHOULD SEE A COMBINATION
OF STRATIFORM PRECIP WITH ISOLATED EMBEDDED THUNDERSTORMS OVER
NORTHERN INYO COUNTY. RECENT ANALYSES SHOW FAIRLY DRY AND STABLE
CONDITIONS FROM NORTHERN SAN BERNARDINO AND CENTRAL CLARK COUNTY
SOUTHWARD. THE GOING FORECAST LOOKS GOOD AND NO IMMEDIATE CHANGES
PLANNED.
&&

.PREV DISCUSSION...
258 AM PDT WED JUL 30 2014

.SHORT TERM...THROUGH FRIDAY NIGHT...MOSTLY CLOUDY OVER THE SOUTHERN
SIERRA/WRN INYO COUNTY THIS MORNING WITH ISOLATED
SHOWERS/THUNDERSTORMS ALONG THE WESTERN FOOTHILLS. ELSEWHERE,
SATELLITE SHOWS MOSTLY CLEAR TO PARTLY CLOUDY SKIES.

THE SUBTROPICAL RIDGE AXIS WILL EXTEND FROM SOUTHERN CALIFORNIA
SOUTHEAST INTO SOUTH TEXAS TODAY AND THURSDAY. AREA OF INTEREST THE
COMING DAYS WILL BE AREA OF MOISTURE AND EMBEDDED WEAK DISTURBANCES
PROGGED TO STREAM THROUGH CENTRAL CALIFORNIA TODAY, THEN SPREAD
NORTHEAST ACROSS THE SOUTHERN SIERRA AND INTO CENTRAL NEVADA TONIGHT
AND THURSDAY. REMNANTS FROM HERNAN WILL ALSO INJECT SOME ADDITIONAL
MOISTURE INTO THE MIX. DID INCREASE POPS A BIT MORE OVER NORTHERN
INYO, ESMERALDA AND CENTRAL NYE COUNTIES TODAY BASED ON THE LATEST
HRRR. STILL LOOKS LIKE A FEW SHOWERS OR THUNDERSTORMS WILL CONTINUE
ACROSS CENTRAL NEVADA TONIGHT AND FRIDAY WITH UPPER LEVEL
DISTURBANCE. BY FRIDAY, RIDGE EXPANDS NORTH INTO THE NORTHERN
ROCKIES. RESIDUAL MOISTURE AND LIMITED INSTABILITY OVER THE AREA
SHOULD BE ENOUGH TO GENERATE A FEW THUNDERSTORMS OVER THE HIGHER
TERRAIN OF THE SOUTHERN GREAT BASIN AND NORTHWEST ARIZONA. DAYTIME
HIGHS WILL BE NEAR NORMAL THROUGH FRIDAY WHILE NO SIGNIFICANT WINDS
ARE EXPECTED.

.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...A LIGHT EASTERLY WIND COMPONENT SHOULD
PERSIST INTO LATE AFTERNOON BEFORE WINDS SHIFT BACK MORE
SOUTHWESTERLY. SCT-BKN CLOUD BASES ABOVE 15 KFT CAN BE EXPECTED.
ISOLATED THUNDERSTORMS WILL BE POSSIBLE IN THE BEATTY AND MORMON
MESA CORRIDORS THIS AFTERNOON/EARLY EVENING.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...ISOLATED/SCATTERED SHOWERS AND THUNDERSTORMS WILL OCCUR
MAINLY IN NORTHERN INYO...ESMERALDA AND CENTRAL NYE COUNTIES TODAY
AND TONIGHT. ISOLATED THUNDERSTORM DEVELOPMENT CAN BE EXPECTED
ELSEWHERE ACROSS THE SOUTHERN GREAT BASIN AND NORTHWEST ARIZONA. THE
REST OF THE REGION WILL SEE WINDS GENERALLY LESS THAN 15 KTS AND
SCT-BKN MID TO HIGH LEVEL CLOUDS.
&&

.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.
&&

UPDATE...ADAIR
PREV DISCUSSION...PIERCE/STACHELSKI

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