000 
FXUS65 KVEF 222227
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
227 PM PST SAT DEC 22 2007

.SYNOPSIS...A DRY NORTHWEST FLOW WILL BE ACROSS THE SOUTHERN GREAT 
BASIN AND MOJAVE DESERT TONIGHT AND SUNDAY. THE NEXT STORM THAT WILL 
IMPACT THE AREA WILL MOVE INTO THE GREAT BASIN MONDAY. A COLD 
FRONT WILL LIE ACROSS CENTRAL NEVADA LATE MONDAY AFTERNOON THEN RACE 
THROUGH SOUTHERN NEVADA AND THE MOJAVE DESERT MONDAY NIGHT. A CHANCE 
OF SHOWERS WILL ACCOMPANY THE FRONT MAINLY ACROSS LINCOLN COUNTY 
WHILE IT WILL BECOME BREEZY TO WINDY BEHIND THE FRONT. THE GUSTY 
NORTH WINDS WILL LINGER THROUGH CHRISTMAS DAY.
&&

.SHORT TERM...GREAT BASIN/MOJAVE DESERT WILL LIE UNDER A NORTHWEST 
FLOW THROUGH SUNDAY NIGHT. AN AREA OF MAINLY MID/HIGH CLOUDS 
CURRENTLY OVER NORTHERN CALIFORNIA/NORTHWEST NEVADA WILL MOVE ACROSS 
THE REGION TONIGHT BEFORE EXITING EARLY SUNDAY. CLOUDS WILL PROVIDE 
SOME INSULATION SO WOULD NOT EXPECT TEMPERATURE TO BE MUCH DIFFERENT 
FROM THIS MORNING. BETTER MODEL AGREEMENT TODAY BETWEEN THE 
GFS/ECMWF WITH THE NEXT TROUGH DUE ACROSS THE GREAT BASIN LATE 
MONDAY/MONDAY NIGHT. THE ASSOCIATED COLD FRONT WILL LIE ACROSS 
CENTRAL NEVADA MONDAY AFTERNOON THEN SWEEP SOUTHEAST ACROSS SOUTHERN 
NEVADA AND THE MOJAVE DESERT MONDAY NIGHT. THERMODYNAMIC PROFILE 
WITH THIS COLD FRONT NOT NEARLY AS IMPRESSIVE AS WHAT WE WITNESSED 
THURSDAY EVENING. MOISTURE SOMEWHAT LACKING BUT BRIEF PERIOD OF LIFT 
WITH THE FRONT SHOULD BE SUFFICIENT TO PRODUCE ISOLATED-SCATTERED 
SHOWERS ACROSS SOUTHEAST NEVADA AND NORTHWEST ARIZONA. MAIN CONCERN 
WILL BE THE INCREASE IN NORTH WINDS FOLLOWING THE FRONT MONDAY NIGHT 
WITH BREEZY-WINDY CONDITIONS LINGERING THROUGH CHRISTMAS DAY. AS 
UPPER LEVEL TROUGH AXIS CLEARS THE SOUTHERN SIERRA CREST LATE MONDAY 
AFTERNOON AND EARLY EVENING WILL ALSO NEED TO WATCH FOR POTENTIAL 
DOWNSLOPE EVENT. THIS MORNINGS LOCALLY RUN WRF OUT THROUGH MONDAY 
AFTERNOON DOES SHOWS WINDS IN EXCESS OF 50 KNOTS AT RIDGETOP MONDAY 
AFTERNOON BUT AT THIS TIME THERE IS NOT MUCH INDICATION OF STRONGER 
WINDS MIGRATING DOWN THE LEESIDE SLOPES INTO THE OWENS VALLEY. 
TEMPERATURES WILL BE AT OR SLIGHTLY BELOW NORMAL TOMORROW AND MONDAY 
WITH THE COOLEST DAY BEING CHRISTMAS FOLLOWING THE COLD FRONT.
&&

.LONG TERM...PACIFIC JETSTREAM REMAINS VERY ACTIVE WITH THREE 
SUCCESSIVE SHORT WAVES FORECAST TO IMPACT THE INTERMOUNTAIN WEST 
BETWEEN WEDNESDAY AND SUNDAY OF NEXT WEEK. MOST OF THE FORECAST 
DETAILS ARE BASED ON A BLEND OF THE ECMWF AND THE GFS ENSEMBLE MEAN. 
THE OPERATIONAL GFS LACKS THE TYPE OF AMPLIFICATION EXPECTED GIVEN 
THE STRENGTH OF THE PACIFIC JET DIGGING INTO THE LONG WAVE NEXT 
WEEK. RECENT HISTORY OF SYSTEMS MOVING THROUGH THIS PATTERN ALSO 
SUGGESTS A PROGRESSION THAT IS DEEPER AND SLIGHTLY SLOWER THAN THE 
OPERATIONAL GFS INDICATES. ECMWF AND GFS ENSEMBLE MEAN BOTH PREDICT 
A CLOSED LOW FORMING WITHIN THE SOUTHERN STREAM OVER THE GREAT BASIN 
NEXT WEDNESDAY BUT THE ECMWF CLOSES THE LOW OFF FASTER AND FARTHER 
EAST THAN THE GFSEM. IF THE ECMWF POSITION VERIFIES SOUTHERN NEVADA 
WILL PROBABLY SEE LITTLE MORE THAN A FEW HOURS OF MIDDLE AND HIGH 
CLOUD AND SOME BLUSTERY NORTH WINDS...SIMILAR TO WHAT OCCURRED HERE 
YESTERDAY. ENSEMBLE MEAN SUGGESTS POTENTIAL FOR MEASURABLE PRECIP 
WEDNESDAY AFTERNOON AND EVENING. TOO MUCH UNCERTAINTY THIS FAR OUT 
TO BET ON ONE OVER THE OTHER SO WILL INCLUDE MENTION OF POPS IN MOST 
OF THE CENTRAL AND SOUTHERN ZONES. LOTS OF SPREAD AMONG ENSEMBLE 
MEMBERS FOR LATTER HALF OF NEXT WEEK BUT THE PATTERN REMAINS 
PROGRESSIVE AND SEVERAL MEMBERS INDICATE ANOTHER WAVE MOVING INTO 
THE INTERIOR WEST THURSDAY NIGHT INTO FRIDAY FOLLOWED BY A THIRD ON 
SUNDAY. BOTTOM LINE: CONFIDENCE IS LOW ON INTENSITY AND TIMING OF 
THESE FAST MOVING SHORT WAVES BUT THE CONTINUATION OF REINFORCING 
SHOTS OF COLD AIR EVERY DAY AND A HALF TO TWO DAYS LOOKS LIKELY FOR 
AT LEAST ANOTHER WEEK. SOME WILL HAVE A SUFFICIENT TAP OF MOISTURE 
ACCOMPANIED BY STRONG ENOUGH FORCING TO GENERATE PRECIPITATION AS 
THEY SWEEP ACROSS THE GREAT BASIN.       
&&

.AVIATION...FOR MCCARRAN...SURFACE WIND WILL REMAIN LIGHT AND 
VARIABLE THIS EVENING. HOWEVER SOME LGT-MOD CHOP MAY OCCUR DURING 
CLIMB AND DESCENT AS WINDS WILL INCREASE FAIRLY RAPIDLY FROM LESS 
THAN 10 KTS TO NORTHWEST AT 20-30 KTS IN THE 080-100 LAYER.  
  
FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...GUSTY NORTH WINDS WILL CONTINUE DOWN THE LOWER COLORADO 
RIVER VALLEY UNTIL AN HOUR OR TWO AFTER SUNSET. OTHERWISE LIGHT 
WINDS ARE EXPECTED AREA WIDE. MIDDLE AND HIGH CLOUDS WILL INCREASE 
FROM THE NORTH OVERNIGHT BUT CEILINGS WILL NOT BE LOW ENOUGH TO 
IMPACT AIR TRAFFIC FLOW.
&&  

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

$$

PIERCE/RUNK

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