FXUS65 KVEF 081739 AAA
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
940 AM PST TUE DEC 8 2009

SYNOPSIS...DRY NORTHWEST FLOW WILL BE OVER THE REGION THROUGH
WEDNESDAY BEHIND THE RECENT STORM WHICH IS QUICKLY MOVING ACROSS THE 
ROCKIES TODAY. THE WEATHER PATTERN WILL REMAIN UNSETTLED THE REST 
OF THE WEEK AS A WEAK PACIFIC SYSTEM MOVES INLAND THURSDAY AND 
FRIDAY FOLLOWED BY A STRONGER ONE FOR THE WEEKEND.
&&

.UPDATE...ONLY A FEW CLOUDS REMAIN OVER NORTHERN MOHAVE AND LINCOLN 
COUNTIES. ALTHOUGH THERE MAY BE A FEW SNOW FLURRIES THROUGH THIS 
AFTERNOON...ACCUMULATIONS ARE NOT EXPECTED AND COVERAGE WILL BE 
MINIMAL. DID MAKE A FEW CHANGES TO THESE AREAS. ELSEWHERE EVERYTHING 
ELSE ON TRACK. MAIN CONCERN FOR THE SHORT TERM WILL BE OVERNIGHT LOW 
TEMPERATURES. CURRENT MODEL GUIDANCE FOR LAS VEGAS SHOWS BETWEEN 27 
AND 31 DEGREES WHILE NELLIS GUIDANCE SHOWS 23 DEGREES. THERE IS THE 
POTENTIAL FOR A HARD FREEZE IN THE LAS VEGAS VALLEY TONIGHT. 
&&

.AVIATION...FOR MCCARRAN...VARIABLE WINDS BECOMING SOUTH TO 
SOUTHWEST THIS EVENING AROUND 5 KTS.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...A FEW CLOUDS AROUND 7K FEET THIS MORNING IN NORTHERN 
MOHAVE COUNTY OTHERWISE CLEAR CONDITIONS EXPECTED. WEST TO SOUTHWEST 
WINDS IN NORTHWEST ARIZONA THIS MORNING GUSTING TO AROUND 25 KTS... 
OTHERWISE WINDS GENERALLY UNDER 10 KTS. WINDS WILL FOLLOW NORMAL 
DIURNAL DIRECTIONAL TRENDS TONIGHT. 
&&

.PREV DISCUSSION.../415 AM PST TUE DEC 8/

.SHORT TERM...THE CENTER OF THE UPPER LOW WAS OVER NORTHERN ARIZONA 
NEAR PAGE AT 11Z AND OUR FORECAST AREA WAS QUICKLY DRYING OUT ON THE 
BACK SIDE OF THE SYSTEM. LINGERING LOW CLOUDS COULD BE SEEN OVER 
MOHAVE COUNTY AND ALSO EASTERN SAN BERNARDINO COUNTY. THE 06Z NAM 
PICKED UP THE LOW LEVEL MOISTURE OVER EASTERN SB COUNTY AND QUICKLY 
CLEAR IT OUT BETWEEN 12Z AND 15Z. FLURRIES OR SCATTERED LIGHT SNOW 
SHOWERS MAY STILL OCCUR OVER NORTHERN MOHAVE COUNTY EARLY THIS 
MORNING BUT LITTLE IF ANY ADDITIONAL ACCUMULATION IS EXPECTED. ALL 
WINTER WEATHER PRODUCTS WITHIN THE AREA HAVE BEEN CANCELLED. GUSTY 
WINDS OVER 40 MPH STILL REMAIN OVER SAN BERNARDINO COUNTY BUT A 
DECREASING TREND IS EVIDENT FROM RECENT OBSERVATIONS. A GENERALLY 
DRY NORTHWEST FLOW WILL REMAIN OVER THE FORECAST AREA TODAY AND 
WEDNESDAY. A WEAK IMPULSE COMING OUT OF THE PACIFIC NORTHWEST IS 
FORECAST TO QUICKLY BRUSH NORTHEAST NEVADA TONIGHT. THIS SHOULD NOT 
HAVE MUCH EFFECT ON LINCOLN COUNTY. PACIFIC MOISTURE CURRENTLY 
BETWEEN 130W AND 140W IS FORECAST TO BE PULLED INLAND THURSDAY AND 
FRIDAY. HOWEVER...THE GFS SHOWS A VERY WEAK UPPER LOW ASSOCIATED 
WITH IT WHICH PROVIDES LITTLE HELP TO PRODUCE PRECIPITATION. THE 
ECMWF IS A LITTLE STRONGER AND INDICATE THE CHANCES FOR PRECIP
INCREASING THURSDAY NIGHT THOUGH AMOUNTS APPEAR QUITE LIGHT. THE 
FORECAST IS A BLEND OF THE TWO SOLUTIONS AND POPS WERE SUBSEQUENTLY 
TRIMMED BACK THURSDAY.
&&

.LONG TERM...A RIPPLE OF ENERGY CROSSING THE SOUTHWESTERN U.S. ON 
FRIDAY AFTERNOON WILL CONTINUE TO BRING THE POSSIBILITY OF 
PRECIPITATION TO MUCH OF THE AREA. THIS LOOKS TO BE AN EVENT THAT 
SHOULD BRING SOMETHING TO THE HIGHER ELEVATIONS...WHILE IN THE LOWER 
ELEVATIONS THIS SHOULD BE AN EVENT WITH PLENTY OF CLOUDS AND SOME 
PRECIPITATION BUT PROBABLY NOT ALL THAT MUCH OF IT. WET BULB ZERO 
HEIGHTS ACROSS THE NORTHERN VALLEYS ARE AROUND 4000-4500 FEET ON 
FRIDAY SO PRECIPITATION HERE WILL BE MAINLY SNOW WITH SOME RAIN 
MIXING IN AT TIMES BY THE AFTERNOON. THIS WAVE SHOULD BE EAST OF THE 
AREA BY FRIDAY NIGHT AND A SHORTWAVE RIDGE BUILDS IN WHICH SHOULD 
DRY US OUT AND BRING A BRIEF BREAK BEFORE THE NEXT SYSTEM ARRIVES. 

OUR FINAL SYSTEM OF THE WEEK HEADS EAST FROM THE PACIFIC TOWARDS THE 
OREGON COAST BY SATURDAY NIGHT. GIVEN THE TRAJECTORY WILL BE FURTHER 
NORTH THIS WILL PUT OUR AREA IN MORE OF A SOUTHWEST TO WEST FLOW. 
WHILE WARMER AIR APPEARS TO COME IN ALOFT...MODELS KEEP WET BULB 
ZERO HEIGHTS AROUND 4500 FEET IN THE NORTHERN VALLEYS YET AGAIN 
DURING THIS EVENT. SO ANOTHER ROUND OF SNOW LOOKS TO OCCUR THERE 
THOUGH GIVEN THE WARMER AIR WORKING IN PRECIPITATION SHOULD LIKELY 
MIX WITH RAIN OR EVEN CHANGE TO RAIN UP THERE AT TIMES. THE 
TRAJECTORY OF THIS SYSTEM ALSO FAVORS THE EASTERN SIERRA AND 
SOUTHERN GREAT BASIN SEEING THE MOST MOISTURE FROM THIS SYSTEM WITH 
AMOUNTS DROPPING OFF SHARPLY SOUTH OF I-40. ONE CONCERN NOT AS 
EVIDENT A FEW DAYS AGO MAY BE SOME INCREASED WINDS ON SATURDAY AHEAD 
OF THIS SYSTEM. MODELS ARE SHOWING A STRONG WESTERLY JET DIVING 
ACROSS THE AREA WHICH COULD ENHANCE WIND SPEEDS AT TIMES SATURDAY 
AFTERNOON. THE MOST LIKELY WINDOW FOR PRECIPITATION IN LAS VEGAS 
LOOKS TO BE SATURDAY AFTERNOON INTO SATURDAY EVENING. THIS SYSTEM 
HEADS EAST BY SUNDAY MORNING AND WITH THE OPERATIONAL MODELS IN 
DECENT AGREEMENT ALLOWED FOR A DRYING TREND BY SUNDAY EVENING 
AREAWIDE.

AN UPPER-LEVEL RIDGE IS SLATED TO BUILD IN FOR NEXT MONDAY AND 
TUESDAY. THIS SHOULD KEEP PRECIPITATION MAINLY NORTH OF THE AREA 
THOUGH THE SOUTHERN GREAT BASIN MAY GET SKIMMED BY THICKER CLOUDS 
AND SOME SHOWERS AT TIMES AS SYSTEMS PASS BY TO THE NORTH. OTHERWISE 
EXPECT DRIER AND MILDER WEATHER WITH HIGH TEMPS POSSIBLY A FEW 
DEGREES ABOVE NORMAL FOR A CHANGE.
&&

.AVIATION...FOR MCCARRAN...ANY CLOUDS SHOULD BE GONE BY LATER THIS 
MORNING. VARIABLE WINDS THIS MORNING...THEN EXPECT WINDS TO BECOME 
SOUTHERLY TO SOUTHWESTERLY THIS EVENING AROUND 5 KTS.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...THE LAST OF ANY SHOWERS SHOULD BE DONE BY 18Z TODAY 
ACROSS THE EASTERN PARTS OF THE AREA. THE REMAINDER OF THE AREA WILL 
SEE A FEW CLOUDS AROUND 7K FEET THIS MORNING CLEAR OUT BY THIS 
AFTERNOON. GUSTY WEST TO SOUTHWEST WINDS IN NORTHWEST ARIZONA THIS 
MORNING AROUND 25 KTS...OTHERWISE EXPECT WINDS UNDER 10 KTS. WINDS 
WILL FOLLOW NORMAL DIURNAL DIRECTIONAL TRENDS TONIGHT. 
&&

.VEF WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
AZ...NONE.
CA...NONE.
&&

$$

GORELOW/ADAIR/STACHELSKI

HTTP://WEATHER.GOV/LASVEGAS