Heavy Snow Warning 1, NWS Las Vegas, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
820 PM PST THU JAN 11 2007

.SYNOPSIS...COLD UPPER LOW OVER THE NORTHERN GREAT BASIN WILL SLOWLY
MIGRATE ACROSS THE SOUTHERN GREAT BASIN FRIDAY AND SATURDAY. SNOW
SHOWERS WILL OCCUR OVER MUCH OF THE REGION WITH HEAVIER SNOW BANDS
OCCURRING OVER LINCOLN AND MOHAVE COUNTIES. TEMPERATURES WILL BE
WELL BELOW NORMAL THROUGH THE WEEKEND.
&&

.UDPATE...LATEST SATELLITE AND MODEL TRENDS POINT TO LESS CLOUD
COVER ACROSS THE SOUTHERN PORTION OF THE FORECAST AREA MOST OF THE
NIGHT. ALSO LOOKS LIKE VERY MINIMAL CHANCE FOR PRECIPITATION WORKING
DOWN INTO LAS VEGAS AND POINTS SOUTHWARD. UPDATED FORECAST TO REMOVE
PRECIPITATION CHANCES AND FOR LESS CLOUD COVER TONIGHT IN SEVERAL
ZONES. ALTHOUGH MODEL QPF AND GUIDANCE POPS ARE ON THE LIGHT
SIDE...QUICK LOOK AT TIME/HEIGHT SECTIONS INDICATE A DECENT AMOUNT
OF MOISTURE AND LIFT IN THE FAVORED DENDRITIC GROWTH REGION OVER LAS
VEGAS FRIDAY AFTERNOON AND EVENING AND WILL KEEP THE WINTER STORM
WATCH GOING.
&&

.PREV DISCUSSION...345 PM PST THU JAN 11...SHORT TERM...COLD UPPER
TROUGH CURRENTLY OVER THE NORTHERN GREAT BASIN/PACIFIC NORTHWEST
WITH WATER VAPOR IMAGERY INDICATING VORTICITY CENTER DIGGING SOUTH
INTO NORTHERN CALIFORNIA. NAM/GFS IN AGREEMENT PINCHING OFF A 532
LOW CENTER OVER THE SOUTHERN SIERRA BY 12Z FRIDAY. THE ASSOCIATED
COLD FRONT CURRENTLY LIES FROM BISHOP TO ELY AND WITHIN THE PAST TWO
HOURS SATELLITE SHOWS FRONT IS GETTING RE-ENERGIZED. FOR
TONIGHT...NORTHERN LINCOLN COUNTY IS UNDER THE GUN. MODELS HAVE
STAYED CONSISTENT PLACING EAST CENTRAL NEVADA UNDER JET ENTRANCE
REGION WITH STRONG FRONTOGENESIS TAKING PLACE. THE HEAVIEST SNOW
TONIGHT WILL OCCUR NORTH OF HIGHWAY 93. DEEP LOW SLATED TO SHIFT
EAST ACROSS SOUTHERN NEVADA FRIDAY. FRONTOGENESIS/JETSTREAM DYNAMICS
SHIFT SOUTHEAST OVER NORTHWEST ARIZONA FRIDAY WITH BOTH NAM/GFS
KICKING OUT THE HIGHEST QPF FROM NEAR KINGMAN NORTH INTO SOUTHWEST
UTAH. ISSUED A SNOW ADVISORY FOR ZONES 1 AND 3 FROM 11 AM UNTIL 11
PM. WHAT TO DO WITH THE WINTER STORM WATCH FOR THE SOUTHERN NEVADA
ZONES. BOTH THE 12Z AND 18Z MODELS NOT AS IMPRESSIVE WITH DYNAMICS
VERSUS WEDNESDAYS MODELS. STILL ENOUGH UNCERTAINTY EXISTS ESPECIALLY
IF LOW DIGS FURTHER SOUTH TONIGHT BEFORE IT SWINGS EAST ACROSS
SOUTHERN NEVADA FRIDAY. DUE TO TRACK UNCERTAINTY LEFT THE WATCH UP
BUT WILL TRIM ACCUMULATING AMOUNTS FOR CLARK COUNTY VALLEYS. COLD
TROUGH REMAINS OVER THE AREA SATURDAY WITH DRY NORTHERLY FLOW
AREAWIDE WITH LINGERING SNOW SHOWERS OVER SOUTHERN UTAH AND NORTHERN
ARIZONA. CLEAR SKIES...DYING WINDS WILL LEAD TO THE COLDEST READINGS
SUNDAY MORNING SINCE FEB. 2002.

.LONG TERM...COLD AIR WILL STILL BE ENTRENCHED OVER THE AREA SUNDAY
ONWARDS. GFS DOES BRING A SHORT WAVE THROUGH UTAH MONDAY. EXPECT
LITTLE OUT OF IT DUE TO ITS LONG OVERLAND TRAJECTORY AS IT MOVES
SOUTH ON BACKSIDE OF THE WEEKEND TROUGH. ALTHOUGH A QUICK LOOK AT
THE 18Z GFS LOOKS VERY INTERESTING IN ITS DEVELOPMENT OF A
RETROGRADING LOW TO THE SOUTH OF US FROM THIS TROUGH. WILL IGNORE
FOR NOW AS 18Z RUN HAS A HISTORY OF BEING ECCENTRIC. TEMPERATURE
FORECASTS A CONCERN AS GUIDANCE RAMPS UP THEM QUICKER THAN THEY
SHOULD. EXPECT COLD AIR IN VALLEYS TO REMAIN DIFFICULT TO WARM UP
FAST.
&&

.AVIATION...BREEZY SOUTHWEST WINDS WILL CONTINUE SOUTH OF THE
FRONT..WHICH AT 22Z WAS SOUTH OF KTPH AND IS PROGGED MOVE SOUTH
FASTER THAN PREVIOUSLY ANTICIPATED. A SHIFT OVER TO NORTHWEST TO
NORTH WINDS IS NOW LIKELY IN THE 08Z TO 11Z TIME FRAME FOR KLAS. THE
SNOW THREAT FOR FRIDAY AFTERNOON IS GOING TO BE SOMEWHAT DIMINISHED
DUE TO THE APPROACHING STORMS LACK OF MOISTURE. FOR THE 00Z TAFS
WILL GO WITH SNOW BUT NOT BRING DOWN CONDITIONS TOO FAR. AS
PREVIOUSLY MENTIONED DO NOT EXPECT ACCUMULATIONS TO BE A PROBLEM ON
PAVED SURFACES. TAFS WILL GIVE MORE DETAILS FOR EXPECTED CONDITIONS

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

.VEF WATCHES/WARNINGS/ADVISORIES...
.NV...SNOW ADVISORY ZONE 15 MIDNIGHT TONIGHT THROUGH 4 AM
      SATURDAY.
      WINTER STORM WATCH ZONES 16 20 AND 22 NOON AFTERNOON
      THROUGH LATE FRIDAY NIGHT.
.AZ...SNOW ADVISORY ZONES 1 AND 3 11 AM FRIDAY THROUGH 11 PM
      FRIDAY EVENING.
.CA...NONE.

PIERCE/JACQUES/HARRISON

HTTP://WEATHER.GOV/LASVEGAS