FXUS65 KVEF 270449
AFDVEF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
850 PM PST THU NOV 26 2009

.SYNOPSIS...A PACIFIC LOW PRESSURE SYSTEM WILL MOVE INTO NORTHERN 
AND CENTRAL CALIFORNIA FRIDAY...BRINGING INCREASING HIGH CLOUDINESS 
AND SOME SOUTHERLY BREEZES. THIS LOW WILL THEN MOVE TO SOUTHERN 
CALIFORNIA FRIDAY NIGHT AND SATURDAY...BRINGING CHANCES FOR VALLEY 
RAIN AND MOUNTAIN SNOW. THE LOW WILL MOVE AWAY ON SUNDAY...WITH HIGH 
PRESSURE RETURNING EARLY NEXT WEEK.
&&

.UPDATE...GENERALLY CLEAR SKIES ACROSS THE CWA TONIGHT AHEAD OF A 
PACIFIC STORM MOVING INTO NORTHERN CALIFORNIA. EXPECT INCREASING 
HIGH CLOUDS ACROSS THE NORTHWEST PORTION OF THE DISTRICT BY MORNING 
AND THEN SPREADING ACROSS THE CWA ON FRIDAY AS THE LOW SHIFTS SOUTH 
OVER THE CENTRAL VALLEY OF CALIFORNIA. 00Z RUNS FAIRLY CLOSE TO 
PREVIOUS RUNS WITH CURRENT SHORT TERM ON TRACK. NO UPDATES EXPECTED 
TONIGHT.
&&

.PREV DISCUSSION...242 PM PST THU SHORT TERM...SATELLITE SHOWS CLEAR 
SKIES AREAWIDE. SURFACE OBS SHOW ABOVE NORMAL TEMPERATURES AND 
GENERALLY LIGHT WINDS...EXCEPT FOR LOCALLY GUSTY NORTH WINDS IN THE 
BULLHEAD CITY AREA. THE PRESSURE GRADIENT BETWEEN KELY AND KEED HAD 
COLLAPSED FROM 16.4 MB AT 8 PM LAST NIGHT TO 6.2 MB AT 2 PM THIS 
AFTERNOON...EXPLAINING THE REDUCED WIND SPEEDS AND AREAL COVERAGE 
DOWN THE RIVER VALLEY. MODELS REMAIN IN PRETTY GOOD AGREEMENT WITH 
THE INCOMING LOW...SEEN NEAR 42N 130W THIS AFTERNOON. AS THE TROUGH 
REACHES THE WEST COAST OVERNIGHT...THE FLOW SPLITS AND THE SOUTHERN 
END OF THE TROUGH FORMS A CLOSED LOW WHICH DIGS DOWN THE CALIFORNIA 
COAST TO SAN FRANCISCO TOMORROW AFTERNOON AND THEN TO THE MOJAVE 
DESERT SATURDAY AFTERNOON. THIS WILL BRING MOISTURE AND EASTERLY 
UPSLOPE FLOW TO THE EAST SIDE OF THE SIERRA FRIDAY NIGHT...AND HAVE 
RAISED POPS THERE. AS THE LOW SHIFTS SOUTH...THE MOISTURE AND 
FORCING WILL COME WITH IT...BUT THE LACK OF A WELL DEFINED NORTH 
SOUTH MOUNTAIN BARRIER FARTHER SOUTH WILL MAKE PRECIP PLACEMENT MORE 
PROBLEMATIC. BY SATURDAY AFTERNOON IT BECOMES VERY DIFFICULT TO 
PINPOINT THE HIGHEST PRECIP CHANCES...BUT THE LOWEST CHANCES APPEAR 
TO BE IN THE NORTHEAST CWFA WHICH WILL BE FARTHEST FROM THE LOW 
CENTER...SO TWEAKED POPS TO REFLECT THIS. SATURDAY NIGHT AND 
SUNDAY...THE LOW WILL SAG SOUTH TO SAN DIEGO AND THEN OFFSHORE OF 
THE BAJA IN RESPONSE TO RIDGING BUILDING INTO THE PACIFIC 
NORTHWEST...THUS ALLOWING DRY AIR TO SPREAD INTO OUR CWFA FROM THE 
NORTH. POPS REFLECT THIS...WITH ONLY SLIGHT CHANCES REMAINING IN 
CENTRAL AND SOUTHERN MOHAVE COUNTY BY THE END OF THE SHORT TERM 
SUNDAY AFTERNOON. AS THE LOW PASSES BY...TEMPERATURES WILL FALL IN 
RESPONSE TO FALLING HEIGHTS AND INCREASING CLOUDS AND PRECIP 
CHANCES. POINT TEMPERATURES WILL BE HIGHLY DEPENDENT ON CLOUD 
AMOUNTS AND PRESENCE/TIMING OF SHOWERS AND/OR VIRGA...THUS 
CONFIDENCE IN POINT TEMPS IS LOW. NORTH WINDS WILL LIKELY OVERSPREAD 
THE CWFA AS THE LOW MOVES AWAY TO THE SOUTH...WITH SPEEDS DEPENDENT 
ON THE EXACT TRACK OF THE LOW. WIND ADVISORIES MAY BE NEEDED AT SOME 
TIME FOR AREAS PRONE TO NORTH WINDS.

.LONG TERM...BY MONDAY THE AFOREMENTIONED SYSTEM IS FORECAST TO BE 
OVER SONORA ALLOWING DRIER AIR TO SPREAD ACROSS THE ENTIRE CWFA 
BRINGING ABUNDANT SUNSHINE. THE ONLY CONCERN WILL BE WINDS AS A 
PROGGED 16 MB ELY-NEEDLES SFC PRESSURE GRADIENT WILL BE SITTING OVER 
THE AREA EARLY MONDAY MORNING BEFORE GRADUALLY RELAXING BY THE LATE 
AFTERNOON. EXPECT GUSTY NORTHERLY WINDS IN AREAS THAT FAVOR THIS 
DIRECTION...ESPECIALLY DOWN THE COLORADO RIVER VALLEY...WHERE GUSTS 
TO AROUND 30 MPH CERTAINLY LOOK POSSIBLE. OTHERWISE WITH THE GFS 
BUFR SOUNDINGS SHOWING A SHALLOW INVERSION IN THE VALLEYS IN THE 
AFTERNOON AND NORTHEAST FLOW PRESENT I UNDERCUT MOS NUMBERS AS 
COLDER AIR SHOULD HAVE TROUBLE GETTING MIXED OUT. AN UPPER RIDGE 
MOVES IN OVERHEAD MONDAY NIGHT INTO TUESDAY AND THIS SHOULD RESULT 
IN A WARMER AFTERNOON ON TUESDAY THOUGH MIXING STILL LOOKS MINIMAL 
AND AGAIN UNDERCUT MOST OF THE FORECAST GUIDANCE VALUES FOR MAX 
TEMPS. 

BY WEDNESDAY THE NEXT SYSTEM LOOKS TO APPROACH FROM THE NORTH AND 
FOR NOW HAVE FOLLOWED THE 12Z ECMWF/GEM WHICH WERE MORE CONSISTENT 
AND SHOWED A SYSTEM PASSING BY TO THE NORTHEAST OF THE AREA. DUE TO 
THE TRAJECTORY OF THIS SYSTEM JUST EXPECT AN INCREASE IN HIGH LEVEL 
CLOUDS AND AN ENHANCEMENT OF WINDS ESPECIALLY OUT OF THE NORTH 
WEDNESDAY NIGHT ONCE THE SYSTEM PASSES BY. DRY NORTHWEST FLOW IS 
EXPECTED FOR THURSDAY AND FRIDAY HOWEVER HIGH TEMPS SHOULD BE RIGHT 
AT OR JUST BELOW NORMAL. 
&&

.AVIATION...FOR MCCARRAN...LIGHT AND VARIABLE WINDS THROUGH FRIDAY 
AFTERNOON. A CLEAR SKY TONIGHT WITH FEW-SCT CLOUDS AOA 25K FEET 
FRIDAY AFTERNOON. A STORM SYSTEM WILL APPROACH THE AREA ON SATURDAY 
BRINGING THE POSSIBILITY OF CLOUD LAYERS AS LOW AS 8K FEET AND EVEN 
THE POSSIBILITY OF A FEW SHOWERS TO SOUTHERN NEVADA.

FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST 
CALIFORNIA...MAINLY LIGHT WINDS TONIGHT FOLLOWING DIURNAL 
DIRECTIONAL TRENDS. FOR FRIDAY LIGHT WINDS ARE EXPECTED OVER THE 
MOJAVE DESERT WITH WINDS TURNING TO THE SOUTH AND GUSTING TO 15-20 
KTS AT TIMES OVER THE SOUTHERN GREAT BASIN BY THE AFTERNOON. FEW-SCT 
CLOUDS AOA 25K FEET TONIGHT IN THE NORTH WITH THESE CLOUDS SPREADING 
SOUTH INTO THE MOJAVE DESERT FRIDAY AFTERNOON. OVER THE SOUTHERN 
GREAT BASIN EXPECT SCT-BKN CLOUDS AOA 20K FEET WITH FEW-SCT CLOUDS 
AS LOW AS 15K FEET BY FRIDAY EVENING OVER THE WESTERN PART OF INYO 
COUNTY. A SYSTEM WILL APPROACH THE AREA FRIDAY NIGHT INTO SATURDAY 
BRINGING THE CHANCE OF SCATTERED SHOWERS TO THE AREA ESPECIALLY TO 
THE HIGHER ELEVATIONS.
&&

.CLIMATE...SO FAR THROUGH 2 PM THURSDAY THE AVERAGE TEMPERATURE FOR 
THE NOVEMBER AT MCCARRAN INTERNATIONAL AIRPORT HAS BEEN 59.8 
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.
&&

$$

JENSEN/MORGAN/STACHELSKI

HTTP://WEATHER.GOV/LASVEGAS