Area Forecast Discussion
Issued by NWS Las Vegas, NV

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000
FXUS65 KVEF 211104
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
304 AM PST SUN DEC 21 2014

.SYNOPSIS...A STRONG JET STREAM PASSING ACROSS NEVADA WILL KEEP A
GOOD AMOUNT OF CLOUDS AROUND THROUGH THIS AFTERNOON AND ALSO ALLOW
FOR A STRAY SHOWER IN NORTHERN LINCOLN COUNTY. A SYSTEM WILL PUSH
ACROSS UTAH ON MONDAY INCREASING NORTHERLY WINDS ACROSS THE AREA.
OTHERWISE EXPECT DRY CONDITIONS WITH HIGH TEMPERATURES CLOSE TO
RECORD LEVELS ON MONDAY. MILD WEATHER WILL CONTINUE THROUGH
CHRISTMAS EVE. ANOTHER SYSTEM WILL PASS ACROSS THE AREA LATE
CHRISTMAS EVE INTO CHRISTMAS DAY FOLLOWED BY COLDER CONDITIONS ALONG
WITH GUSTY WINDS FOR FRIDAY AND SATURDAY.
&&

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT.

THE CIRRUS INVASION CONTINUES AND WILL CONTINUE THROUGH THIS
AFTERNOON AS A POWERHOUSE 140 KT+ JET AT 250 MB PLOWS INTO THE PAC
NW. THIS IS SHUNTING A CONSIDERABLE AMOUNT OF HIGH LEVEL MOISTURE
AND TO A LESSER EXTENT MID-LEVEL MOISTURE SOUTH INTO OUR AREA.
MEANWHILE THE LOW-LEVELS REMAIN MOIST AS FROM THE RECENT STORMS AND
NOTHING HAS REALLY FLUSHED THIS OUT OF THE AREA. THE RESULT WAS A
RATHER DECENT PWAT OF 0.63 INCH ON YESTERDAY EVENING`S KVEF SOUNDING
BUT VERY LITTLE IN THE WAY OF PRECIPITATION ACROSS THE AREA SITS IN
THE FORECAST. WHY? WELL THERE REALLY IS NO FEATURE TO KICK OFF
ANYTHING OTHER THAN THE JET STREAM. SO AS A RESULT THE ONLY SHOT FOR
SHOWERS TODAY WILL BE ACROSS NORTHERN LINCOLN COUNTY WHERE A FEW
LIGHT SHOWERS MAY MATERIALIZE IN THE HIGHER ELEVATIONS. OTHERWISE
EXPECT A DRY AND MILDER DAY AS THE CIRRUS SHIELD AND MID-LEVEL CLOUD
DECK SHOULD THIN SOME BY THIS AFTERNOON AND WARMER AIR ALOFT COMES
IN COURTESY OF A BUILDING AREA OF HIGH PRESSURE ALOFT OFF THE
CALIFORNIA COAST. AN INVERSION WILL HOLD DOWN TEMPS SOME ESPECIALLY
IN THE LOWER VALLEYS.

THE HIGH OFFSHORE WILL STICK AROUND TONIGHT THROUGH TUESDAY.
LINGERING LOW-LEVEL MOISTURE, LESS CLOUDS AND LIGHT WINDS AT THE
SURFACE MAY ALLOW FOR PATCHY FOG ACROSS NW SAN BERNARDINO AND FAR SW
INYO COUNTIES TONIGHT AS THE TEMP-DEWPOINT SPREAD THERE REMAINS
RATHER CLOSE.

THE STRONG JET OVER THE PAC NW WILL SHIFT INTO THE INTERMOUNTAIN
WEST ON MONDAY WITH A 150 KT+ JET STREAK PROGGED OVER NORTHERN UTAH
AT 250 MB PER THE 00Z OPERATIONAL GFS. THIS WILL SEND A PUSH OF
NORTHERLY WINDS INTO OUR AREA WHICH WILL HELP TO BREAK THE INVERSION
BY THE AFTERNOON AND GIVE TEMPS A SHOT AT RECORD HIGHS IN PARTS OF
THE AREA INCLUDING LAS VEGAS. SEE THE CLIMATE SECTION BELOW. WINDS
AT THE SURFACE WILL PICK UP IN RESPONSE TO THE STRONGER WINDS ALOFT
AND TIGHTENING NORTH-SOUTH SURFACE PRESSURE GRADIENTS. HOWEVER, NO
HEADLINES LOOK NEEDED AT THIS TIME, BUT FAVORED NORTH-SOUTH VALLEYS
SUCH AS THE COLORADO RIVER COULD SEE GUSTS OVER 30 MPH BY THE
AFTERNOON.

BEHIND THIS PUSH OF NORTHERLY WINDS SOME COOLER AIR WILL GET
FILTERED DOWN FOR TUESDAY, HOWEVER, THE RIDGE OFFSHORE HOLDS AND
TEMPS SHOULD STILL BE 4-6 DEGREES ABOVE NORMAL. LITTLE IN THE WAY OF
CLOUD COVER IS EXPECTED UNTIL TUESDAY NIGHT WHEN SOME CIRRUS MAY
DRIFT IN FROM THE WEST.

.LONG TERM...WEDNESDAY THROUGH SATURDAY.

HIGH PRESSURE OVER THE EASTERN PACIFIC WILL BE THE MAIN FEATURE
WEDNESDAY MORNING...WITH A SHORTWAVE TROUGH APPROACHING THE PACIFIC
NORTHWEST BEING THE NEXT ITEM OF INTEREST. PREVIOUS MODEL RUNS HAD
DISAGREED ON WHETHER/HOW MUCH TO AMPLIFY THIS WAVE. 00Z/21 RUNS HAVE
COME CLOSER TO A COMPROMISE SOLUTION...WEAKER THAN PREVIOUS RUNS OF
THE ECMWF AND A BIT STRONGER THAN PREVIOUS RUNS OF THE GFS. ENSEMBLE
MEMBERS ARE ALSO CLUSTERED MORE TIGHTLY THAN IN PREVIOUS DAYS...SO
CONFIDENCE IS INCREASING. THE TROUGH SHOULD REACH THE PACIFIC
NORTHWEST COAST WEDNESDAY AFTERNOON...SWING THROUGH THE GREAT BASIN
CHRISTMAS MORNING AND REACH THE ROCKIES CHRISTMAS AFTERNOON. PRECIP
CHANCES FOR OUR AREA WILL BE MINIMAL AND LIMITED TO THE FAR NORTHERN
FRINGE OF THE CWA. TEMPERATURES WILL COME DOWN SEVERAL DEGREES. THE
NEW GFS MOS GIVES 54F FOR KLAS FRIDAY AND THE ECMWF MOS GIVES
51F...MUCH BETTER AGREEMENT THAN THE 60F AND 47F RESPECTIVELY IN
YESTERDAYS RUNS. MODELS ARE HINTING AT A NORTH WIND EVENT FRIDAY AND
SATURDAY AS THE DEPARTING TROUGH AMPLIFIES OVER THE ROCKIES AND HIGH
PRESSURE AMPLIFIES NEAR THE WEST COAST.
&&

.AVIATION...FOR MCCARRAN...VARIABLE WINDS AT 5 KTS OR LESS
ARE EXPECTED AROUND 17Z SUNDAY THROUGH 03Z MONDAY BEFORE SOUTHWEST
WINDS AT 5-10 KTS RETURN. MAINLY BKN CLOUDS AOA 20K FEET WITH
FEW-SCT CLOUDS AS LOW AS 10K FEET THIS MORNING WITH CLOUDS TRENDING
TOWARD THE FEW-SCT RANGE AT AOA 10K FEET BY SUNDAY AFTERNOON.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST
CALIFORNIA...WINDS WILL GENERALLY BE 8 KTS OR LESS AND TREND TOWARD
TYPICAL DIURNAL DIRECTIONS THROUGH TONIGHT. A FEW SHOWERS WILL BE
POSSIBLE ACROSS THE HIGHER ELEVATIONS OF NORTHERN LINCOLN COUNTY
TODAY. CIGS AS LOW AS 6K-8K FEET IN AND NEAR ANY SHOWER ACTIVITY
OTHERWISE MAINLY SCT-BKN CLOUDS AOA 15K FEET WITH FEW-SCT CLOUDS AS
LOW AS 10K-12K FEET TRENDING TOWARD FEW-SCT TONIGHT.
&&

.CLIMATE...HIGH TEMPERATURES WILL BE CLOSE TO RECORD LEVELS ON
MONDAY AT SOME LOCATIONS ESPECIALLY LAS VEGAS. RECORD HIGHS ARE
LISTED BELOW.

LAS VEGAS          68/1950
DESERT ROCK        69/1985
MT CHARLESTON      56/2005
BISHOP             71/2000
BARSTOW-DAGGETT    78/1955
DEATH VALLEY       82/1914
NEEDLES            74/1955
KINGMAN            72/1906
&&

.SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION IS NOT EXPECTED.
&&

$$

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

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