FXUS65 KVEF 272253
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
253 PM PST FRI NOV 27 2009

.SYNOPSIS...AN AREA OF LOW PRESSURE OVER NORTHERN CALIFORNIA WILL 
IMPACT THE AREA WEATHER OVER THE WEEKEND WITH INCREASING CLOUD COVER 
AND WIND...A CHANCE OF SHOWERS AND COOLER TEMPERATURES. CONDITIONS 
ARE EXPECTED TO IMPROVE LATE SUNDAY INTO MONDAY AS THE LOW MOVES 
WELL SOUTH OF THE AREA AS IS REPLACED BY HIGH PRESSURE. 
&&

.SHORT TERM...SATELLITE IMAGERY SHOWS THAT A CLOSED CIRCULATION HAS 
FORMED OVER NORTHERN CALIFORNIA THIS AFTERNOON. AHEAD OF THE 
SYSTEM...ABUNDANT HIGH LEVEL CLOUD COVER WAS NOTED OVER THE CWA AND 
SOUTHERLY BREEZES WERE BEGINNING TO INCREASE WITH LOCAL GUSTS TO 
AROUND 35 MPH. TEMPERATURES ARE COOLER THAN EXPECTED TODAY IN AREAS 
THAT REMAIN UNDER THE THICKEST CLOUD COVER AND WHERE LACK OF WIND 
HAS LEAD TO LIMITED MIXING. 

THE STORM IS FORECAST TO MOVE SOUTH THROUGH CALIFORNIA OVER THE NEXT 
36 HRS AND THEN INTO NORTHERN MEXICO BY EARLY SUNDAY. PLENTY OF MID 
AND LOW LEVEL MOISTURE AVAILABLE TO THE SYSTEM ALONG THE WESTERN 
PORTIONS OF THE CWA. AS THE LOW SLIDES SOUTH...UPSLOPE FLOW WILL BE 
ENHANCED INTO THE EASTERN SLOPES OF THE SIERRA BUT CURRENT THINKING 
IS THAT THE LOW WILL MOVE QUICK ENOUGH THAT THERE WOULD NOT BE 
SUFFICIENT TIME FOR ADVISORY LEVEL SNOW TOTALS IN THE SIERRA. Q 
VECTOR ANALYSIS INDICATES LARGE SCALE LIFT FOR THE SIERRA BEGINNING 
LATE THIS AFTERNOON THROUGH ABOUT 18Z SATURDAY BEFORE SYNOPTIC SCALE 
DOWNWARD MOTION BRINGS AN END TO PRECIP ACTIVITY. THE CURRENT TRACK 
GIVES ABOUT A 12 HR WINDOW OR SO FOR UPSLOPE FLOW COUPLED WITH LARGE 
SCALE ASCENT INTO THE SPRING MOUNTAINS SATURDAY AFTERNOON THROUGH 
THE EVENING HOURS. WILL NEED TO EVALUATE THIS OVERNIGHT TO SEE IF 
ANY ADVISORIES ARE NEEDED THERE. WITH THE LOW IN THE VICINITY 
SATURDAY...FELT THAT THE MOS GUIDANCE TEMPERATURES WERE TOO WARM SO 
LOWERED THEM A COUPLE OF DEGREES FROM THE PREVIOUS FORECAST. SAME 
THING FOR SUNDAY AS COOL...MAINLY DRY AIR IS ADVECTED INTO THE AREA 
FROM THE NORTH AND NORTHEAST. HIGH PRESSURE SETTLES INTO THE REGION 
MONDAY AS THE LOW CONTINUES TO MOVE AWAY FROM THE AREA. 
               
.LONG TERM...A CONSIDERABLE AMOUNT OF MODEL UNCERTAINTY EXISTS IN 
THE EXTENDED AND AS A RESULT WE MADE VERY FEW CHANGES TO THE 
GRIDS/ZONES ONCE AGAIN WITH THIS FORECAST PACKAGE. AN UPPER RIDGE IS 
FORECAST TO BE OVER THE AREA ON TUESDAY AFTERNOON WHICH SHOULD 
RESULT IN A MILD DAY...HOWEVER GFS BUFR SOUNDINGS SHOW AN INVERSION 
OVER THE VALLEYS WITH NO LOW-LEVEL MIXING...SO ONCE AGAIN LEANED ON 
THE COOL SIDE OF THINGS. FOR THE MIDDLE OF THE WEEK BOTH THE 00Z AND 
12Z MODEL RUNS OF EACH MODEL TODAY WHERE ALL OVER THE PLACE WITH 
FEATURES ESPECIALLY THE OPERATIONAL GFS SO I LEANED TOWARDS THE MORE 
CONSISTENT GEM AND ECMWF MODELS WHICH PASS A SYSTEM BY TO OUR 
NORTHEAST ON WEDNESDAY AFTERNOON. THIS WOULD BRING OUR AREA HIGH 
LEVEL CLOUDS AND ENHANCE NORTHERLY WINDS FOLLOWED BY A PERIOD OF 
SLIGHTLY COOLER TEMPS UNDER NORTHWEST FLOW ALOFT BUT THINGS STAY 
DRY. BY NEXT WEEKEND ANOTHER STORM SYSTEM LOOKS TO HEAD TOWARDS THE 
PAC NW THOUGH MOST OF THE MODEL CONSENSUS FOR NOW TAKES THIS SYSTEM 
AS WELL TOWARDS IDAHO AND UTAH AND THUS A DRY FORECAST WAS 
MAINTAINED WITH HIGH TEMPS MODERATING A FEW DEGREES. BEYOND THAT THE 
MODELS HINT THINGS MAY GET MORE ACTIVE BUT FAR TOO OUT TO SPECULATE 
WITH WHAT WILL GO ON.
&&

.AVIATION...FOR MCCARRAN...MAINLY LIGHT SOUTHWEST WINDS TONIGHT WITH 
SCT-BKN CLOUDS AOA 15K FEET. ON SATURDAY A SYSTEM WILL APPROACH THE 
AREA LOWERING CLOUD LAYERS TO AT LEAST 8K-12K FEET BY THE AFTERNOON. 
THERE IS A CHANCE FOR SHOWERS FROM LATE SATURDAY AFTERNOON INTO 
SUNDAY MORNING FROM THIS SYSTEM HOWEVER THERE REMAINS UNCERTAINTY 
AS TO JUST WHERE ANY SHOWER BANDS SET UP. AS A RESULT WILL JUST GO 
WITH A VCTY SHOWER STARTING AT 21Z SATURDAY AND LET FUTURE SHIFTS 
ADJUST. WINDS ARE EXPECTED TO TURN THE NW TO N AROUND 17Z 
SATURDAY...AND SHOULD INCREASE IN SPEED BY SUNDAY MORNING AND REMAIN 
GUSTY INTO MONDAY MORNING.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...IN ADVANCE OF AN APPROACHING STORM SYSTEM EXPECT MAINLY 
LIGHT WINDS TONIGHT OVER THE MOHAVE DESERT. AS THE SYSTEM SINKS 
SOUTHWARD TONIGHT WINDS NORTHERLY WINDS WILL INCREASE OVER THE 
SOUTHERN GREAT BASIN. CLOUD LAYERS WILL LOWER TONIGHT AS A STORM 
SYSTEM APPROACHES THE AREA AND BRING A CHANCE OF SHOWERS MAINLY TO 
INYO AND WESTERN SAN BERNARDINO COUNTIES WITH MOUNTAIN OBSCURATIONS 
LIKELY. BY SATURDAY AFTERNOON THE CHANCE OF SHOWERS WILL SPREAD 
SOUTH AND EAST INTO CLARK...MOHAVE...SOUTHERN PARTS OF NYE AND 
LINCOLN COUNTIES AND EASTERN SAN BERNARDINO COUNTY AND CONTINUE OVER 
THESE LATER AREAS INTO SATURDAY NIGHT AND SUNDAY MORNING. MOUNTAIN 
OBSCURATIONS WILL ALSO BE POSSIBLE IN THESE LATER AREAS SATURDAY 
AFTERNOON INTO SUNDAY MORNING. CLOUD LAYERS SHOULD DROP TO LEAST 5K 
FEET IN THE HEAVIER SHOWERS WHILE IN LIGHTER SHOWERS SHOULD BE 
AROUND 8K FEET. WILL GO WITH VCTY SHRA IN ALL OF THE TAFS FOR NOW 
EXCEPT FOR KBIH WHERE SHOWERS LOOKS MORE LIKELY AND HAVE A FROM 
GROUP IN THERE FOR -SHRA.
&&

.CLIMATE...SO FAR THROUGH 2 PM FRIDAY THE AVERAGE TEMPERATURE FOR 
THE NOVEMBER AT MCCARRAN INTERNATIONAL AIRPORT HAS BEEN 59.6 
DEGREES. GIVEN THE CURRENT FORECASTED NUMBERS THERE IS SOME 
POTENTIAL FOR LAS VEGAS TO SEE THIS NOVEMBER RANK AMONG THE 10 
WARMEST ON RECORD. THE WARMEST NOVEMBERS ON RECORD AT LAS VEGAS 
ARE...

1. 60.9 DEGREES IN 2007
2. 60.8 DEGREES IN 2008
3. 59.8 DEGREES IN 1995
4. 59.3 DEGREES IN 2005
5. 58.9 DEGREES IN 1949
6. 58.8 DEGREES IN 1999
7. 58.6 DEGREES IN 2001
8. 58.4 DEGREES IN 2006
9. 58.0 DEGREES IN 1976 AND 1981
&&

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

$$

SALMEN/STACHELSKI

HTTP://WEATHER.GOV/LASVEGAS