000 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