Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 212221 CCA
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
250 PM PDT SUN SEP 21 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM WILL LIFT FROM NORTHERN NEVADA TO
THE NORTHERN INTERMOUNTAIN REGION TONIGHT. DRIER AIR WILL CONTINUE
TO SPREAD FROM SOUTHWEST TO NORTHEAST THROUGH THIS EVENING CAUSING
SHOWERS AND THUNDERSTORMS TO DISSIPATE ACROSS THE REGION. HIGH
PRESSURE WILL BUILD ACROSS THE AREA PROVIDING DRY CONDITIONS AND
ABOVE NORMAL TEMPERATURES THROUGH THE FIRST HALF OF THE COMING WEEK.
A SIGNIFICANT COOLING TREND IS THEN EXPECTED GOING INTO THE WEEKEND.
&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
THE CENTER OF THE UPPER LOW IS NOW SHIFTING OVER NEVADA...WITH THE
CIRCULATION CLEARLY VISIBLE IN SATELLITE IMAGERY. THIS SYSTEM WILL
CONTINUE TO PROGRESSIVELY LIFT NORTHEAST THIS EVENING AND OVERNIGHT.
THE ATMOSPHERE HAS DESTABILIZED IN A FAVORABLE REGION FOR
LARGE-SCALE LIFT THIS AFTERNOON...WHERE CONVECTION HAS DEVELOPED
THIS AFTERNOON. THUNDERSTORMS WILL CONTINUE ACROSS PORTIONS OF THE
SIERRA...ESMERALDA...NYE...LINCOLN...NORTHERN  MOHAVE...AND NORTHERN
CLARK BEFORE DRYING FROM SOUTHWEST TO NORTHEAST EARLY IN THE
EVENING. AVERAGE STORM MOTION WILL BE AROUND 20 MPH OR SO TO THE
NORTHEAST. THIS MOTION WILL GENERALLY LIMIT THE AMOUNT OF TIME
STORMS ARE OVER ONE PARTICULAR AREA. HOWEVER...THERE CAN BE SOME
ISOLATED AREAS WHERE REDEVELOPMENT OR TRAINING CONVECTION
OCCURS...CREATING A LOCALIZED FLOOD HAZARD. ALSO...THE STRONGEST
STORMS MAY PRODUCE GUSTY WINDS IN EXCESS OF 45 MPH AND SOME HAIL.

THE LOW WILL EXIT TO OUR NORTHEAST TONIGHT...WITH DRY SOUTHWEST TO
WESTERLY FLOW SWEEPING ACROSS THE AREA. DRY CONDITIONS ARE EXPECTED
OVERNIGHT AND THROUGH THE REMAINDER OF THE SHORT TERM PERIOD AS
UPPER LEVEL HIGH PRESSURE BUILDS ACROSS THE REGION. THIS WILL ALSO
PROVIDE A WARMING TREND THROUGH TUESDAY...WITH TEMPERATURES SEVERAL
DEGREES ABOVE NORMAL ANTICIPATED.

.LONG TERM...WEDNESDAY THROUGH SUNDAY...WARM CONDITIONS WILL
CONTINUE WEDNESDAY WITH THE AREA LYING ON THE BACK SIDE OF STRONG
RIDGING OVER THE ROCKIES. HIGH TEMPERATURES ARE EXPECTED TO BE
AROUND 4-8 DEGREES ABOVE NORMAL WITH LIGHT WINDS AND MOSTLY CLEAR
SKIES. HIGH PRESSURE IS PUSHED FURTHER EAST THURSDAY AS STRONG
PACIFIC TROUGHING MOVES TO THE WEST COAST. ALTHOUGH HEIGHTS ARE
FORECAST TO LOWER, TEMPERATURES SHOULD STILL BE WELL ABOVE NORMAL
UNDER AN INCREASING SOUTHWEST FLOW ON THURSDAY. MODELS ARE NOT AS
STRONG WITH THE WINDS THURSDAY AFTERNOON AND ONLY LOCALLY BREEZY
CONDITIONS ARE EXPECTED.

MODELS ARE STILL STRUGGLING OVERALL WITH THE THE EVOLUTION OF THE
TROUGH FOR FRIDAY AND THE WEEKEND. ESPECIALLY WITH DETAILS SUCH AS
WHERE A LOW CLOSES OFF AND HOW LONG THE LOW THEN LINGERS OVER THE
GREAT BASIN BEFORE MOVING EAST OF THE AREA. THE ECMWF CLOSES A LOW
OFF QUICKER BUT IS SLOWER IN MOVING IT OUT OF THE AREA. IT HAS IT
CLOSING OFF OVER CENTRAL CALIFORNIA EARLY SATURDAY AND SLOWLY MOVES
IT ACROSS THE GREAT BASIN THROUGH MONDAY. THE GFS MAINTAINS THE
TROUGH AS AN OPEN WAVE UNTIL THE TROUGH AXIS IS OVER UTAH LATE
SATURDAY BEFORE CLOSING IT OFF. THE GFS THEN TAKES THE LOW EAST WITH
HIGH PRESSURE NUDGING BACK OVER THE WESTERN CWA SUNDAY. BOTH
SOLUTIONS AGREE WITH THE RETURN OF BELOW NORMAL TEMPERATURES OVER
THE WEEKEND BUT DIFFER ON MOISTURE IMPACTS. THE ECMWF CONTINUES TO
BE THE WETTER MODEL AND WOULD BRING GREATER IMPACTS TO THE AREA DUE
TO ITS MORE WESTERLY CLOSED LOW SOLUTION AND SLOW LOW MOVEMENT. THE
GFS IS BEGINNING TO SHOW A LITTLE BETTER TAP OF MOISTURE BUT
GENERATES PRECIP FOR ONLY A RELATIVELY SHORT PERIOD OF TIME DUE TO
ITS QUICKER SOLUTION.

BACKING AWAY FROM THE DETAILS FOR A MOMENT AND TAKING A LOOK AT THE
BIG PICTURE...THERE IS GOOD MODEL AGREEMENT IN A CHANGING WEATHER
PATTERN LATE IN THE WEEK. THIS WILL USHER IN SOME INCREASING WINDS,
COOLER TEMPERATURES AND BRING THE NEXT CHANCE FOR SHOWERS AND
PROBABLY EVEN HIGH ELEVATION SNOW. A FITTING WAY TO INTRODUCE FALL
TO THE AREA.
&&

.AVIATION...FOR MCCARRAN...SCATTERED CLOUDS WITH BASES AROUND 10-12
KFT WILL DISSIPATE THIS EVENING LEAVING MOSTLY CLEAR SKIES
OVERNIGHT. PORTIONS OF THE MORMON MESA AND BEATTY CORRIDORS WILL SEE
CONVECTION THROUGH THE EVENING. LIGHT SOUTHEAST WINDS THIS AFTERNOON
WILL BECOME SOUTHWEST EARLY THIS EVENING.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...ISOLATED TO SCATTERED THUNDERSTORMS CAN BE EXPECTED
FROM THE SOUTHERN SIERRA ACROSS CENTRAL NEVADA AND INTO NORTHWEST
ARIZONA THROUGH THE EARLY EVENING HOURS. DRIER AND MORE STABLE AIR
SPREADING IN FROM THE SOUTHWEST WILL PROVIDE DRY CONDITIONS TONIGHT
AND THROUGH THE REMAINDER OF THE TAF PERIOD. WINDS WILL FAVOR
DIURNAL PATTERNS OVERNIGHT THROUGH MONDAY.
&&

.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.
&&

$$

SHORT TERM/AVIATION...PADDOCK
LONG TERM...SALMEN

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