Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 051011
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
311 AM PDT SUN JUL 5 2015

.SYNOPSIS....MOIST AND UNSTABLE AIR WILL ONCE AGAIN ALLOW FOR
SHOWERS AND THUNDERSTORMS TO DEVELOP ACROSS THE AREA AGAIN TODAY AND
AGAIN ON MONDAY MAINLY IN THE AFTERNOON AND EVENING WITH THE
GREATEST ODDS OVER THE HIGHER ELEVATIONS. ANY ACTIVITY SHOULD MOVE
TO THE EAST. SLIGHTLY DRIER AIR WILL START TO WORK INTO THE AREA ON
TUESDAY WHICH SHOULD DECREASE THE COVERAGE OF SHOWERS AND
THUNDERSTORMS. TEMPERATURES WILL REMAIN SLIGHTLY BELOW NORMAL
THROUGH THE WEEK.
&&

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT.

A PESKY AREA OF SHOWERS IS STILL HEADING NORTHEAST THIS MORNING PER
RADAR ACROSS SOUTHERN NYE AND NORTHWEST CLARK COUNTIES. THIS SHOWER
ACTIVITY WAS TRIGGERED BY A WEAK MID-LEVEL DISTURBANCE THAT WAS
EVIDENT ON BOTH WATER VAPOR AND INFRARED SATELLITE OVER SOUTHERN NYE
COUNTY. THIS WEAK DISTURBANCE IS NOTED IN THE 500 MB PROGS AS A
RIPPLE IN THE HEIGHTS WITH A WEAK AREA OF POSITIVE VORTICITY NOTED
THAT MOVES TOWARD LINCOLN AND NORTHERN CLARK COUNTIES BY LATER
TODAY. IT IS THIS FEATURE THAT LOOKS TO SERVE AS AN INSTIGATOR FOR
CONVECTION TODAY ACROSS CLARK/LINCOLN COUNTIES ALONG WITH HEATING OF
THE TERRAIN. ONE CONCERN IS HOW EARLY STUFF MAY FIRE TODAY AS SOME
MODELS DO GENERATE QPF THIS MORNING ACROSS CLARK COUNTY OVER THE
HIGHER ELEVATIONS. AS A RESULT, I ADDED A SLIGHT CHANCE OF SHOWERS
AND THUNDERSTORMS IN FOR CLARK COUNTY FOR THIS MORNING, ALTHOUGH
ACTIVITY SHOULD LIKELY FAVOR DEVELOPING THIS AFTERNOON. THE STEERING
FLOW IS WEST-SOUTHWEST ACROSS ACROSS THE AREA, WHICH WILL DRIVE
WHATEVER FORMS OFF TO THE EAST. THUS, THERE IS SOME RISK FOR A FEW
AFTERNOON SHOWERS OR A THUNDERSTORM TO HEAD TOWARD THE LAS VEGAS
VALLEY, ESPECIALLY THE WEST SIDE.

OTHERWISE, THE MID/UPPER LEVEL LOW REMAINS OFF THE COAST OF
CALIFORNIA WHICH SHOULD ONCE AGAIN FAVOR ACTIVITY DEVELOPING ACROSS
INYO COUNTY. POPS WERE RAISED OVER THE HIGHER ELEVATIONS BASED ON
THE 4KM AND 9KM ARW AND NMM MODELS. SIMILAR TO YESTERDAY, ACTIVITY
OVER THE SIERRA SHOULD HEAD FOR THE OWENS VALLEY BY THE LATE
AFTERNOON AND EARLY EVENING AND ACTIVITY OVER THE WHITES, INYO AND
PANAMINT RANGES SHOULD HEAD TOWARD DEATH VALLEY, DEEP SPRINGS AND
THE FISH LAKE VALLEY.

WE MAY STILL SEE A FEW SHOWERS AND THUNDERSTORMS POP OVER MOHAVE
COUNTY BY THIS AFTERNOON AND EVENING WHICH LOOK DRIVEN BY HEATING OF
THE TERRAIN. THERE IS SOME RISK FOR A SHOWER OR THUNDERSTORM TO HEAD
IN FROM THE WEST TOWARD THE LAUGHLIN-BULLHEAD CITY AND NEEDLES AREAS
BASED ON THE ARW AND NMM MODELS QPF OUTPUT. ADDITIONALLY, DESPITE
SHOWING LOTS OF STABLE AIR ON THE GFS OVER THE SAN BERNARDINO COUNTY
DESERTS TODAY, MODELS BLOW UP ACTIVITY OVER THE SAN BERNARDINO RANGE
AND PUSH SOME OF IT NORTHEAST WHICH MAY IMPACT BARSTOW OR THE AREA
BETWEEN THERE AND LUDLOW AND LANDERS THIS AFTERNOON AND EVENING.
HOWEVER, THIS AREA LOOKS TO BE VERY SPOTTY IN COVERAGE.

HIGH TEMPS SHOULD BE CLOSE TO WHAT WE SAW ON SATURDAY BASED ON
MOISTURE CONTENT AND SIMILAR HEIGHTS.

WE REMAIN IN A SOUTHWEST FLOW ALOFT MONDAY INTO TUESDAY AS THE
MID/UPPER LEVEL LOW STAYS OFFSHORE OF CALIFORNIA. THE LOW WILL HEAD
SLOWLY TOWARD THE COAST BY LATE TUESDAY INTO TUESDAY NIGHT. ONCE
AGAIN ACTIVITY LOOKS TO BE PRIMARILY TERRAIN DRIVEN BY THE HEATING
OF THE DAY. PWATS ARE FORECAST TO REMAIN NEAR OR JUST OVER AN INCH
IN THE COLORADO RIVER VALLEY AND MOHAVE COUNTY WITH LOWER VALUES
ELSEWHERE. THUS, THE BEST RISK FOR WETTER STORMS WILL BE IN THE
SOUTHEAST CWFA. BY TUESDAY, HOWEVER, DRIER AIR STARTS TO WORK ON IN
WHICH WILL LOWER PWATS AREAWIDE AND TRIM BACK THE COVERAGE OF STORMS
EVEN FURTHER TO MAINLY THE SIERRA, MT CHARLESTON, THE HIGHER TERRAIN
OF LINCOLN AND CENTRAL NYE COUNTIES AND NORTHERN MOHAVE COUNTY.
TEMPS WILL REMAIN CLOSE TO WHAT WE SEE TODAY FOR HIGHS.

THE PRIMARY THREATS IN STORMS WILL REMAIN LIGHTNING AND GUSTY WINDS
WITH ANY WETTER STORMS POSSIBLY TRIGGERING FLASH FLOODING.

.LONG TERM...WEDNESDAY THROUGH SUNDAY.

AN UPPER LOW OFF OF THE CENTRAL CALIFORNIA COAST WILL KEEP A DRY AND
STABLE SOUTHWEST FLOW ALOFT ACROSS THE FORECAST AREA TO START THE
LONG TERM PERIOD. MODELS ARE NOW DIVERGING ON JUST WHEN THAT UPPER
LOW WILL MOVE INLAND. THE GFS AND SOME OF ITS ENSEMBLE MEMBERS ARE
MORE PROGRESSIVE, MOVING THE UPPER LOW INLAND STARTING LATE
WEDNESDAY AND TRACKING IT, IN A WEAKENING STATE, ACROSS NEVADA ON
THURSDAY. THE ECMWF KEEPS THE CENTER OF THE LOW ACROSS CALIFORNIA
AND SWEEPS THE TROUGH AXIS NORTHWARD OVER NORTHERN CALIFORNIA AND
BRUSHING WESTERN NEVADA.

EITHER SOLUTION MAY PROVIDE A BETTER CHANCE OF SHOWERS AND STORMS
ACROSS THE SIERRA NEVADA WEDNESDAY AND THURSDAY, BUT THE GFS
SOLUTION WOULD PUSH THAT CHANCE OF SHOWERS AND STORMS ACROSS THE
SOUTHERN GREAT BASIN THURSDAY. THE NAEFS MEAN IS A LITTLE SLOWER AND
ALIGNING MORE WITH THE ECMWF. THERE IS QUITE A BIT OF SPREAD IN
SOLUTIONS AND THIS 00Z GFS RUN IS A BIT DIFFERENT FROM YESTERDAYS
00Z AND 12Z RUNS. SO, WILL NOT MAKE MAJOR CHANGES TO THE RUNNING
FORECAST AT THIS TIME. ONE ITEM WE CAN COUNT ON WILL BE THE BREEZY
SOUTHERLY WINDS WEDNESDAY THROUGH AT LEAST FRIDAY.

HOWEVER THAT WAVE PANS OUT, MODELS SEEM TO AGREE IT SHOULD BE
EXITING THE AREA FRIDAY, WITH FLOW ALOFT BECOMING MORE SOUTHWEST TO
SOUTH. IF THE FLOW BECOMES MORE SOUTH SATURDAY, AS INDICATED BY THE
ECMWF, OR SUNDAY, AS INDICATED BY THE GFS, MONSOONAL MOISTURE MAY
START TO TRACK BACK INTO NORTHWEST ARIZONA OVER THE WEEKEND. AS FOR
TEMPERATURES, TEMPS ALOFT WILL SLIGHTLY DECREASE AS THE LOW MOVES
INLAND, WHICH WILL CAUSE SURFACE TEMPS TO TREND COOLER FROM MIDWEEK
INTO THE WEEKEND. AS THE WAVE DEPARTS, TEMPS SHOULD TREND A LITTLE
WARMER TO END THE WEEKEND.
&&

.AVIATION...FOR MCCARRAN...WINDS SHOULD FAVOR TYPICAL DIURNAL
DIRECTIONS AGAIN TODAY WITH GUSTS TO AROUND 20 KTS IN THE LATE
AFTERNOON AND EVENING EXPECTED. MAINLY SCT CLOUDS AOA 10K-12K FEET.
ISOLATED SHRA/TSRA ARE POSSIBLE MAINLY AFTER 20Z TODAY AND ENDING BY
03Z OR SO MONDAY IN THE MOUNTAINS AROUND THE LAS VEGAS VALLEY. THERE
IS SOME POTENTIAL FOR THIS ACTIVITY TO MOVE INTO THE LAS VEGAS
VALLEY AS IT WORKS EAST - WHICH COULD RESULT IN LOWER CIGS OR GUSTY
AND ERRATIC WINDS AT THE AIRPORT COMPLEX ITSELF. FOR NOW THE TAF
WILL REFLECT VCTY ACTIVITY DUE TO THE REDUCED CONFIDENCE WITH ANY
SHRA/TSRA.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...ONCE AGAIN TODAY WE SHOULD SEE SHRA/TSRA DEVELOP AFTER
18Z MAINLY ACROSS THE HIGHER TERRAIN OF INYO, ESMERALDA, LINCOLN,
CENTRAL NYE, AS WELL AS NORTHERN AND EASTERN MOHAVE COUNTIES AND IN
THE SPRING MTS AND SHEEP RANGE. GUSTY AND ERRATIC WINDS AND
VSBY/CIGS REDUCED TO MVFR OR LOWER ALONG WITH POSSIBLE MOUNTAIN
OBSCURATIONS. OTHERWISE LOOK FOR WINDS TO FAVOR TYPICAL DIURNAL WIND
DIRECTIONS GUSTING BETWEEN 15 AND 25 KTS FROM THE SOUTH TO SOUTHWEST
IN THE AFTERNOON AND EVENING.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTERS ARE ENCOURAGED TO REPORT
ANY SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING
PROCEDURES.
&&

$$

SHORT TERM/AVIATION...STACHELSKI
LONG TERM...PADDOCK

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