Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 271535
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
835 AM PDT WED MAY 27 2015

.SYNOPSIS...AN AREA OF LOW PRESSURE PASSING ACROSS NORTHERN MEXICO
WILL PULL EAST BY THIS AFTERNOON RESULTING IN MOST OF THE CLOUDS
CLEARING OUT BY THIS AFTERNOON OVER THE MOJAVE DESERT. ACROSS THE
SOUTHERN GREAT BASIN SHOWERS AND A FEW THUNDERSTORMS WILL BE AROUND
AGAIN TODAY AND TO A LESSER EXTENT ON THURSDAY AND FRIDAY IN THE
AFTERNOON AND EVENING. OTHERWISE LOOK FOR A WARMING TREND WITH THE
WARMEST WEATHER OF THE YEAR SO FAR BY THIS WEEKEND.
&&

.UPDATE...QUIET WEATHER THIS MORNING. INCOMING MODEL DATA SUPPORTS
PREVIOUS SHIFT THINKING THAT THUNDERSTORM CHANCES WILL BE CONFINED
TO AREAS WELL NORTH OF LAS VEGAS AND FAVOR THE HIGHER TERRAIN. NO
UPDATE PLANNED THIS MORNING.
&&

.PREV DISCUSSION...
253 AM PDT WED MAY 27 2015

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT.

THE MAIN FEATURE OF NOTE THIS MORNING ON WATER VAPOR NEAR OUR AREA
IS A BIG SWIRL SOUTHWEST OF SAN DIEGO OVER THE PACIFIC. THIS SWIRL
IS A MID/UPPER LEVEL LOW THAT WILL PROGRESS EAST TODAY ACROSS
NORTHERN MEXICO. QUITE A BIT OF HIGH LEVEL MOISTURE WAS FED BY THIS
LOW INTO THE SOUTHERN HALF OF OUR AREA STARTING YESTERDAY AND HAS
RESULTED IN HIGH CLOUDS BEING AROUND. THE HIGH CLOUD COVER HAS
BECOME MORE PATCHY OVERNIGHT PER SATELLITE. BASED ON THE GFS AND
ECMWF 500-300 MB MEAN LAYER RELATIVE HUMIDITY PROGS, WE SHOULD SEE
THIS LAYER DRY OUT BY THIS AFTERNOON, THUS THE MOJAVE DESERT WILL
TRANSITION TO MOSTLY SUNNY CONDITIONS AS WE MOVE THROUGH THE DAY IN
ANY AREAS THAT START OFF PARTLY TO MOSTLY CLOUDY. TEMPS SHOULD BE
NEAR OR PERHAPS A DEGREE OR TWO ABOVE WHAT WE SAW ON TUESDAY AS A
BROAD MID/UPPER LEVEL TROUGH REMAINS OVER THE AREA.

WITH THIS TROUGH STILL IN PLACE, ENOUGH MID-LEVEL MOISTURE AND
ENERGY REMAINS OVER THE SOUTHERN GREAT BASIN THAT WITH THE HEATING
OF THE DAY SHOWERS AND A FEW THUNDERSTORMS SHOULD POP UP ONCE AGAIN.
THE COVERAGE OF ACTIVITY WAS LOWER YESTERDAY THAN MONDAY AND APPEARS
TO BE A LITTLE LESS TODAY. BASED ON THE WRF, GFS AND THE LOCAL 4 KM
ARW AND NMM HIGH RESOLUTION MODELS, ACTIVITY AGAIN LOOKS TO BE MOST
LIKELY IN NORTHERN LINCOLN COUNTY, NORTHERN INYO COUNTY AND
ESMERALDA COUNTY WITH A GENERAL WEST TO EAST MOVEMENT. MODELS HINT
THAT ACTIVITY MAY PUSH OFF THE WHITE MOUNTAINS INTO ESMERALDA COUNTY
LATER THIS AFTERNOON AND EARLY THIS EVENING SO THE HIGHEST POPS WERE
PLACED HERE.

THE BROAD TROUGH THAT HAS PERSISTED FOR MUCH OF MAY WILL FINALLY GO
AWAY TOMORROW AS A RIDGE ALOFT STARTS TO BUILD INTO CALIFORNIA. THIS
RIDGE IS SLATED TO MOVE OVER CALIFORNIA ON FRIDAY. THE RESULT WILL
BE A WARMING TREND WITH ABOVE NORMAL HIGHS FOR A CHANGE. WE HAVE
LEANED TOWARD THE WARMER MAV (GFS) NUMBERS. MIXING LOOKS WEAK SO FOR
NOW WE HAVE KEPT LAS VEGAS IN THE UPPER 90S ON FRIDAY AT MCCARRAN
FOR A HIGH BUT LOW TEMPS WERE BUMPED UP A FEW DEGREES ESPECIALLY AS
THE HEAT BUILDS IN AND THE TARMAC AT MCCARRAN AND HEAVILY CONCRETED
AREAS NEAR THE STRIP AND DOWNTOWN FAIL TO COOL OFF AT NIGHT. THIS
WILL PUSH LOWS TO WHAT HIGHS WERE NOT ALL THAT LONG AGO INTO THE MID
TO UPPER 70S IN THE WARMER PARTS OF LAS VEGAS. CHECK YOUR AIR
CONDITIONER AND GET THEM READY FOR THE WEEKEND AS THEY WILL
CERTAINLY GET A GOOD USE FINALLY.

THERE WILL STILL BE ENOUGH MID-LEVEL MOISTURE AND INSTABILITY AND A
BIT OF WEAK ENERGY ON THURSDAY PRESENT TO POP OFF A FEW SHOWERS AND
THUNDERSTORMS IN THE HIGHER TERRAIN OF THE SOUTHERN GREAT BASIN IN
THE AFTERNOON AND EVENING. HOWEVER, THE COVERAGE OF STORMS LOOKS
LESS THAN TODAY. ISOLATED ACTIVITY IS AGAIN POSSIBLE FRIDAY BUT
WITHOUT ANY REAL TRIGGER OTHER THAN HEATING OF THE DAY AND TERRAIN,
ACTIVITY LOOKS LIMITED ON COVERAGE. STILL A SHOWER OR THUNDERSTORM
MAY POP OVER THE SOUTHERN SIERRA AND IN FAR NORTHERN LINCOLN COUNTY.

ONE THING WORTH NOTING WITH THE WARMER TEMPS IS THAT ANY AREAS THAT
SAW SNOW THIS MONTH WILL SEE SNOWMELT TAKE PLACE THIS WEEKEND. THIS
WILL RESULT IN RAPID FLOWS IN THE SIERRA IN STREAMS AND CREEKS AND
ALSO RESULT IN THAWING AND REFREEZING OF SNOW ON TRAILS THAT WILL
CREATE ICY PATCHES IN THE SHADE. USE CAUTION IF YOU HAVE OUTDOOR
PLANS.

.LONG TERM...SATURDAY THROUGH WEDNESDAY MORNING.

A SHORTWAVE RIDGE WILL BE IN THE PROCESS OF BUILDING OVER THE
SOUTHERN GREAT BASIN/DESERT SOUTHWEST BY SATURDAY
MORNING...CONTINUING THE RECENT WARMING TREND ACROSS THE AREA.
OPERATIONAL GUIDANCE SEEMS TO HAVE CONVERGED ON A SLIGHTLY FLATTER
SOLUTION INITIALLY...WITH THE RIDGE AMPLIFYING SOME AHEAD OF THE
NEXT UPPER LEVEL TROUGH THE IMPACT THE AREA BY EARLY NEXT WEEK. THIS
SOLUTION MAY ALLOW FOR A FEW HIGH CLOUDS TO TRAVERSE THE AREA ON
SATURDAY...WHICH COULD SLIGHTLY INHIBIT DAYTIME HEATING.
HOWEVER...CONFIDENCE REMAINS HIGH THAT MANY AREAS WILL SEE THE
WARMEST TEMPERATURES SINCE LATE SEPTEMBER 2014...WITH MOST DESERT
LOCALES EXCEEDING 100 DEGREES AND LOWER DESERT LOCALES APPROACHING
OR EXCEEDING 110 THROUGH MONDAY. SUNDAY CONTINUES TO LOOK LIKE THE
WARMEST DAY OF 2015 THUS FAR...WITH STRONGER SOUTHWESTERLY FLOW
BUILDING INTO THE AREA IN RESPONSE TO AN APPROACHING UPPER LEVEL
TROUGH. EARLY INDICATIONS OF FAVORABLE UNIDIRECTIONAL WIND PROFILES
WILL ALLOW FOR MAXIMUM MIXING...BUMPING TEMPERATURES UP A FEW
DEGREES FROM SATURDAY.

AS QUICKLY AS WE HAVE WARMED UP...THE IMPENDING TROUGH WILL
INTRODUCE A COOL DOWN FOR THE FIRST HALF OF NEXT WEEK...WITH
TEMPERATURES GRADUALLY FALLING BACK TOWARD SEASONAL NORMALS BY MID-
WEEK AS THE AFOREMENTIONED TROUGH IMPINGES ON THE AREA. CURRENT
OPERATIONAL GUIDANCE HAS NOTABLE DIFFERENCES IN STRENGTH/AMPLITUDE
WITH THIS SYSTEM TONIGHT THAT WILL DETERMINE THE RATE OF COOLDOWN
WITH RESPECT TO TEMPERATURES. HOWEVER...THERE IS REASONABLE
AGREEMENT ALREADY IN SEVERAL WAVES OF ENERGY TRAVERSING THE AREA
AROUND THE BASE OF THE TROUGH MONDAY-WEDNESDAY...MAKING THIS FEATURE
ONE TO WATCH AFTER THIS WEEKEND.

.AVIATION...FOR MCCARRAN...EAST TO SOUTHEAST WINDS AT 4-8 KTS SHOULD
BECOME MORE SOUTHERLY BETWEEN 22Z TODAY AND 00Z THURSDAY AND
INCREASE TO 10-14 KTS WITH GUSTS TO 22 KTS BEFORE DECREASING TO 7-10
KTS BETWEEN 03Z AND 05Z THURSDAY. SCT-BKN CLOUDS MAINLY AOA 25K FEET
THIS MORNING WITH A FEW BASES AS LOW AS 12K FEET THIS AFTERNOON AND
EVENING.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...WINDS SHOULD MAINLY FOLLOW DIURNAL DIRECTIONAL TRENDS
AT 12 KTS OR LESS THROUGH TONIGHT. SOUTH OF KIYK-KDRA-KSGU LINE
EXPECT SCT-BKN CLOUDS AOA 25K FEET THIS MORNING THEN A FEW CLOUDS
AOA 12K FEET THIS AFTERNOON. NORTH OF THIS LINE SHRA/TSRA WILL BE
AROUND MAINLY AFTER 20Z TODAY AND BEFORE 05Z OR SO THURSDAY. GUSTY
AND ERRATIC WINDS ARE POSSIBLE IN AND NEAR ANY SHRA/TSRA WITH CIGS
LOWERING TO 5K-8K FEET AND MOUNTAIN OBSCURATIONS POSSIBLE.

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

$$

UPDATE...MORGAN
SHORT TERM/AVIATION...STACHELSKI
LONG TERM...PULLIN

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