Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 212230
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
330 PM PDT THU AUG 21 2014

.SYNOPSIS...A CIRCULATION MOVING FROM SOUTHERN CALIFORNIA INTO
SOUTHWEST ARIZONA WILL CONTINUE TOWARD THE FOUR CORNERS REGION
FRIDAY. SHOWERS AND THUNDERSTORMS WILL DIMINISH TONIGHT THEN A FEW
LINGERING STORMS MAY OCCUR OVER NORTHWEST ARIZONA FRIDAY. A BROAD
AREA OF LOW PRESSURE BRUSHING NORTHERN NEVADA WILL LEAD TO DRY
CONDITIONS WITH TEMPERATURES A LITTLE BELOW NORMAL ACROSS THE ENTIRE
REGION THROUGH THE MIDDLE OF NEXT WEEK.
&&

.SHORT TERM...THROUGH SATURDAY NIGHT

CONVECTION STARTED EARLY ACROSS SOUTHERN NEVADA AND NORTHWEST
ARIZONA BUT WAS WANING THIS AFTERNOON. AS THE CLOSED UPPER LOW MOVES
FROM FAR SOUTHERN CALIFORNIA INTO WESTERN ARIZONA THIS EVENING...MID
LEVEL FLOW WILL BECOME NORTHEAST TO NORTH ACROSS SOUTHERN NEVADA AND
EASTERN SAN BERNARDINO COUNTY. STORM DEVELOPMENT WILL CONTINUE TO
WANE THIS EVENING ON THE BACK SIDE OF THE SYSTEM BUT CANNOT
COMPLETELY RULE OUT ADDITIONAL THUNDERSTORMS FROM CLARK COUNTY
SOUTHWARD THROUGH LATE THIS EVENING. THE LOW IS FORECAST TO SLOWLY
OPEN UP AND LIFT TOWARD THE FOUR CORNERS REGION FRIDAY AS A LONG
WAVE TROUGH DIGS INTO NORTHERN NEVADA THEN MOVES INTO THE NORTHERN
INTERMOUNTAIN REGION SATURDAY. THE RESULTING DRY SOUTHWEST FLOW WILL
SCOUR OUT MOST OF THE MOISTURE ACROSS OUR CWA FRIDAY THOUGH A FEW
THUNDERSTORMS MAY STILL OCCUR OVER MOHAVE COUNTY. SHOWERS AHEAD OF
THE FRONT ASSOCIATED WITH THE NORTHERN GREAT BASIN TROUGH MAY BRUSH
NORTHERN LINCOLN COUNTY FRIDAY NIGHT THROUGH SATURDAY BUT THE
MAJORITY OF MOISTURE AND FORCING WILL BE TO THE NORTH AND EAST OF
LINCOLN COUNTY. TEMPERATURES WILL REMAIN BELOW NORMAL UNDER THE
INFLUENCE OF THESE LOW PRESSURE SYSTEMS.


.LONG TERM...SUNDAY THROUGH THURSDAY NIGHT.

AN INTERESTING PATTERN IS SHOWN FOR THE FIRST HALF OF NEXT WEEK,
ESPECIALLY IF YOU GO FULL BLAST WITH THE 00Z OPERATIONAL RUN OF THE
ECMWF. AT THIS POINT, SINCE THAT MODEL IS SO OUT THERE IN LEFT
FIELD, I HAVE GIVEN IT ONLY LIMITED WEIGHT WITH THIS MORNING`S
FORECAST. THAT SAID, THE ECMWF HAS A GOOD TRACK RECORD OF DEVIATING
FROM THE NORM AND BEING THE FIRST TO PICK UP THINGS, SO THE BEST
COURSE OF ACTION IS TO SEE WHAT TREND ARE SHOWN IN THE NEXT FEW
MODEL RUNS AND ADJUST BASED ON THAT.

FOR SUNDAY, BROAD TROUGHING IN THE MID AND UPPER LEVELS IS SHOWN TO
OUR NORTH, WITH A SECOND TROUGH AXIS WAITING IN THE WINGS TO SWOOP
ON DOWN. OUR AREA LOOKS TO BE A IN MORE A QUASI-WESTERLY FLOW.
OVERALL, THE PATTERN SUPPORTS A DRY FORECAST WITH HIGH TEMPS NEAR
NORMAL.

THINGS GET MORE COMPLICATED IN THE MONDAY THROUGH WEDNESDAY TIME
FRAME. THE 00Z OPERATIONAL ECMWF DROPS THE NEXT TROUGH INTO NORCAL
AND FORMS A CLOSED MID/UPPER LEVEL LOW THAT FLOATS EAST EVENTUALLY
ACROSS THE NORTHERN HALF OF NEVADA ON TUESDAY AND WEDNESDAY. THIS
LOW WOULD KEEP US MUCH COOLER AND POTENTIALLY EVEN DRAW NORTHWARD
MOISTURE THAT COULD TRIGGER SHOWERS AND THUNDERSTORMS ESPECIALLY IN
THE EASTERN HALF OF THE AREA. THIS SOLUTION HAS SOME SUPPORT FROM A
FEW OF THE 00Z GFS ENSEMBLES. THE SECOND SOLUTION IS WHAT WE SAW ON
PREVIOUS RUNS OF THE ECMWF AND THE LATEST AND PREVIOUS RUNS OF THE
GFS, GEM AND DGEX WHICH BRINGS THE TROUGH THROUGH MONDAY INTO
TUESDAY ACROSS UTAH. THERE IS SOME CHANCE THIS TROUGH COULD BE DEEP
ENOUGH TO CLIP NORTHERN LINCOLN COUNTY WITH A FEW SHOWERS OR AT
LEAST INCREASED CLOUDS AND THIS WAS PLACED IN THERE FOR TUESDAY
AFTERNOON/EVENING. OTHERWISE I LEFT THE FORECAST DRY BUT DID GO
AHEAD AND TRIM TEMPS BY A FEW DEGREES GIVEN THE UNCERTAINTY. THIS
PLACES THEM NEAR TO A HAIR BELOW NORMAL. EITHER WAY THE PATTERN
LOOKS MORE LIKE THAT OF LATE SEPTEMBER TO EARLY OCTOBER VERSUS LATE
AUGUST.
&&

.AVIATION...FOR MCCARRAN...ISOLATED TO SCATTERED THUNDERSTORMS WILL
CONTINUE THROUGH EARLY THIS EVENING IN THE CORRIDORS SURROUNDING LAS
VEGAS WITH COVERAGE DIMINISHING QUICKLY AFTER SUNSET. OUTFLOW
BOUNDARIES FROM THUNDERSTORMS MAY STILL PRODUCE ERRATIC WINDS
THROUGH EARLY EVENING...BUT THE PREVAILING WIND DIRECTION WILL BE
FROM THE SOUTH. DRIER AIR ARRIVES ON FRIDAY ALTHOUGH SOUTHWEST WINDS
WILL INCREASE WITH GUSTS UP TO 25 KTS POSSIBLE.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...ISOLATED/SCATTERED SHOWERS AND THUNDERSTORMS WILL
AFFECT AREAS ROUGHLY EAST OF A LINE FROM BARSTOW TO HIKO THROUGH THE
EARLY EVENING. WINDS WILL FAVOR A SOUTH-SOUTHWEST DIRECTION BUT WILL
BE GUSTY AND ERRATIC IN DIRECTION DUE TO NEARBY SHOWERS OR
THUNDERSTORMS. A DRY SOUTHWEST FLOW WILL SPREAD ACROSS THE REGION
FRIDAY LEADING TO MOSTLY CLEAR CONDITIONS WITH SOUTHWEST WINDS
GUSTING 15-25 KNOTS IN THE AFTERNOON.
&&

.SPOTTER INFORMATION STATEMENT...SPOTTERS SHOULD REPORT INSTANCES OF
FLASH FLOODING...STRONG GUSTY WINDS...HAIL...AND BLOWING DUST
THROUGH WEDNESDAY.
&&

$$

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

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