Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 210957
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
256 AM PDT THU AUG 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM NEAR SAN DIEGO WILL MOVE TOWARD
ARIZONA LEADING TO INCREASING THUNDERSTORM COVERAGE OVER SOUTHEAST
CALIFORNIA...SOUTHERN NEVADA AND NORTHWEST ARIZONA TODAY. LINGERING
STORMS MAY CONTINUE OVER NORTHWEST ARIZONA EARLY IN THE WEEKEND THEN
DRY CONDITIONS CAN BE EXPECTED ACROSS THE ENTIRE REGION THROUGH THE
MIDDLE OF NEXT WEEK.
&&

.SHORT TERM...THROUGH SATURDAY NIGHT
ISOLATED RAIN SHOWERS ALONG WITH A FEW THUNDERSTORMS RUNNING FROM
LAS VEGAS EAST ACROSS THE WESTERN GRAND CANYON. THE AREA IS SHIFTING
NORTH AND WILL AFFECT EASTERN CLARK AND NORTHERN MOHAVE COUNTY
THROUGH THE REMAINDER OF THE EARLY MORNING HOURS.

WATER VAPOR SHOWS AN UPPER LOW JUST WEST OF SAN DIEGO THAT HAS
PULLED MAINLY MID/HIGH CLOUDS OFF OF TROPICAL STORM LOWELL NORTHWARD
OVER THE COLORADO RIVER VALLEY/MOHAVE COUNTY. AS OF 2 AM
PDT...LOWELL WAS LOCATED NEAR 19.7N/121.9 OR 805 MILES WSW OF CABO
SAN LUCAS. UPPER LOW WILL SLOWLY SHIFT EAST ALONG THE INTERNATIONAL
BORDER TODAY. FAVORED NORTHEAST QUADRANT WITH DIFFLUENCE REGION
ALOFT PROGGED TO BE OVER MOHAVE COUNTY TODAY SO KEPT HIGHEST POPS IN
THE SOUTHERN HALF OF MOHAVE COUNTY THIS AFTERNOON. MOISTURE VALUES
WEST OF THE RIVER WILL NOT BE AS GREAT AS WESTERN ARIZONA BUT KEPT
IN A MENTION OF THUNDERSTORMS FOR MAINLY LINCOLN, CLARK AND EASTERN
SAN BERNARDINO COUNTIES. COULD SEE A FEW STORMS LINGER THROUGH THE
NIGHT OVER WESTERN ARIZONA AS UPPER LOW CONTINUES ITS SLOW TREK EAST
ACROSS THE GRAND CANYON STATE. ON FRIDAY, UPPER LOW WILL WEAKEN AND
ACCELERATE EAST THROUGH THE FOUR CORNERS AS A LONGWAVE TROUGH
DEVELOPS ACROSS THE PAC NW. MAINTAINED OUR SLIGHT CHANCE OF POPS FOR
MOHAVE COUNTY BEFORE MOISTURE GETS SCOURED OUT ON SATURDAY. DID
INCREASE POPS A BIT ACROSS FAR NORTHERN LINCOLN COUNTY FRIDAY AND
SATURDAY IN PROXIMITY OF A COLD FRONT DRAPED ACROSS CENTRAL NEVADA.
WITH TROUGH OFF TO OUR NORTH FRIDAY AND SATURDAY GRADIENT WINDS WILL
INCREASE LEADING TO BREEZY TO LOCALLY WINDY CONDITIONS. OUR BELOW
NORMAL STRETCH OF TEMPERATURES WILL CONTINUE INTO THE WEEKEND.

.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 SHOWERS/THUNDERSTORMS AROUND THE
AREA TODAY. THUNDERSTORM COVERAGE WILL BE MORE EXTENSIVE THIS
AFTERNOON IN THE MORMON MESA AND PEACH SPRINGS CORRIDORS AS A LOW
PRESSURE SYSTEM MOVES INLAND ACROSS FAR SOUTHERN CALIFORNIA. THIS
WILL PRODUCE GUSTY AND ERRATIC WINDS THROUGH THIS EVENING. 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 THUNDERSTORM WILL AFFECT
AREAS ROUGHLY EAST OF A LINE FROM BARSTOW TO HIKO THROUGH THE DAY
AND INTO THE EVENING. WINDS WILL FAVOR A SOUTH-SOUTHWEST DIRECTION
BUT WOULD BECOME GUSTY AND ERRATIC IN DIRECTION DUE TO NEARBY
SHOWERS OR THUNDERSTORMS.
&&

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

$$

SHORT TERM/AVIATION...PIERCE
LONG TERM...STACHELSKI

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