000 FXUS65 KVEF 081806 AFDVEF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LAS VEGAS NV 1006 AM PST WED FEB 8 2012 .SYNOPSIS...CLOUDS WILL GRADUALLY CLEAR FROM NORTH TO SOUTH TODAY AS AN AREA OF LOW PRESSURE MOVES DOWN THE BAJA COAST. GUSTY NORTH WINDS ARE EXPECTED TO DEVELOP IN THE COLORADO RIVER VALLEY ON THURSDAY FOLLOWED BY LIGHTER WINDS AND TEMPERATURES SLIGHTLY ABOVE NORMAL FRIDAY. A CHANGE IN THE WEATHER PATTERN WILL THEN ALLOW A WEAK PACIFIC LOW PRESSURE SYSTEM TO DROP INTO SOUTHERN NEVADA SATURDAY FOLLOWED BY A STRONGER SYSTEM EARLY NEXT WEEK. && .UPDATE...THINGS HAVE CLEARED OUT THIS MORNING MUCH MORE THAN WHAT THE MODEL RELATIVE HUMIDITY PROGS SHOWED. SO PER THE LATEST SATELLITE IMAGES I HAVE GONE AHEAD AND MADE SOME ADJUSTMENTS TO THE SKY GRIDS FOR TODAY. LINCOLN COUNTY MAY SEE CLOUDS FILL IN SLIGHTLY AS SOME MID-LEVEL MOISTURE ROTATES BACK IN AND GETS ACCOMPANIED BY A WEAK PIECE OF VORTICITY AT 500 MB. MOHAVE COUNTY SHOULD ALSO STAY PARTLY CLOUDY ESPECIALLY IN NORTHERN AND EASTERN SECTIONS. THE ONLY OTHER CONCERN AT THIS TIME IS HIGH TEMPS FOR TODAY. MCCARRAN IS CURRENTLY AT 61 DEGREES AS OF WRITING AND WAS BEATING WHAT THE STATISTICAL GUIDANCE WAS FORECASTING AT 18Z BY ABOUT 4 DEGREES. HOWEVER I HAVE SEEN CASES WHERE WE JUMP UP BIG EARLY ON AND THEN LEVEL OFF WITH TEMPS AND WE WIND UP HITTING OUR FORECAST HIGH TEMP ANYWAYS. SO FOR NOW I WILL NOT ADJUST ANY HIGH TEMPS FOR TODAY. HOWEVER IF WE JUMP UP BIG IN ANOTHER HOUR I WILL LIKELY NEED TO ADJUST UP TEMPS AND SEND OUT ANOTHER UPDATE. && .AVIATION...MCCARRAN...VARIABLE HIGH CLOUDINESS TODAY THEN CLEARING OVERNIGHT. WINDS WILL TAKE ON A NORTHERLY DIRECTION GENERALLY UNDER 8KTS BY EARLY AFTERNOON AND LAST INTO THE EARLY EVENING THEN INCREASE TO AROUND 10KTS FROM THE NORTHWEST AS A WEAK FRONT PASSES THROUGH THE VALLEY. FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA...WINDS WILL GENERALLY BE OUT OF THE NORTH TODAY AND TONIGHT AS A WEAK COLD FRONT MOVES THROUGH THE AREA. LOCALLY GUSTY NORTH WINDS ARE POSSIBLE IN NORTHERLY WIND PRONE AREAS. CLOUD COVER WILL BE LIMITED TO VARIABLE HIGH CLOUDS OVER MUCH THE AREA EXCEPT FOR SOME SCT-BKN CLOUDS 10-15K FEET ACROSS THE FAR SOUTH. && .PREVIOUS DISCUSSION... ISSUED AT 343 AM PST WED FEB 8 2012 .SHORT TERM...TODAY THROUGH FRIDAY NIGHT...SATELLITE LOOPS SHOWED THE CENTER OF THE UPPER LOW PICKING UP SPEED AS IT SLID FROM THE SOUTHERN CALIFORNIA COAST TOWARD THE BAJA SPUR. A DEFORMATION ZONE ON THE NORTHERN PERIPHERY OF THE UPPER LOW COULD BE SEEN SETTING UP OVER SOUTHERN NEVADA AND IR IMAGERY REVEALED AN EXPANDING AREA OF COOLING CLOUD TOPS OVER LINCOLN COUNTY. HOWEVER...DUE TO THE LIMITED MOISTURE AND DRY LOW LEVELS...THIS SHOULD ONLY LEAD TO BRIEFLY ENHANCED CLOUD COVER OVER THE SOUTHERN HALF OF THE AREA BEFORE MID MORNING WITH SOME VIRGA AND MAYBE A FEW SPRINKLES. CLEARING WILL OCCUR FROM NORTHWEST TO SOUTHEAST THIS AFTERNOON AND EVENING AS THE UPPER LOW CONTINUES TO HEAD SOUTH. TEMPERATURES WILL BE SEVERAL DEGREES WARMER THIS AFTERNOON WITH MORE SUNSHINE AND INCREASING HEIGHTS AS THE EASTERN PACIFIC RIDGE BEGINS TO NOSE INLAND. A SHORTWAVE TROUGH THEN MOVES DOWN THROUGH UTAH TOWARD THE FOUR CORNERS REGION TONIGHT. THIS WILL LEAD TO AN INCREASING DEEP NORTHERLY FLOW ALONG WITH A MODERATELY STRONG NORTH-SOUTH SURFACE PRESSURE GRADIENT. THIS WILL SET THE STAGE FOR NORTH BREEZES TO DEVELOP ACROSS MUCH OF THE REGION BY THURSDAY MORNING WITH THE COLORADO RIVER VALLEY FAVORED TO SEE SUSTAINED WINDS OF 15 TO 25 MPH AND GUSTS UP TO 40 MPH NEAR LAUGHLIN AND BULLHEAD CITY THURSDAY AFTERNOON. A LAKE WIND OR WIND ADVISORY IS NOT OUT OF THE QUESTION...BUT LOCAL HIGH RESOLUTION 00Z MODEL RUNS WERE NOT AVAILABLE TO ADD CONFIDENCE AND THE NAM AND GFS GUIDANCE INDICATED SPEEDS GENERALLY BELOW ADVISORY LEVELS FOR MOST OF THE COLORADO RIVER VALLEY ZONES. THE PRESSURE GRADIENT IS FORECAST TO RELAX QUICKLY THURSDAY NIGHT LEAVING LIGHT WINDS FRIDAY AS THE RIDGE OVER THE GREAT BASIN BREAKS DOWN AND IS PUSHED EAST AHEAD OF AN APPROACHING SHORTWAVE TROUGH WHICH DROPS INTO NORTHERN CALIFORNIA AND WESTERN NEVADA FRIDAY NIGHT. .LONG TERM...SATURDAY THROUGH TUESDAY...AN ACTIVE PATTERN IS SHAPING UP FOR THE EXTENDED...ESPECIALLY IF THE LATEST OPERATIONAL GFS SCENARIO PLAYS OUT. THE RIDGING THAT HAS BEEN OVER THE AREA WILL BEGIN TO WEAKEN AND BE UNDERCUT IN SPLIT FLOW THAT HAS BEEN FORECAST TO OCCUR BEGINNING THIS WEEKEND. SATURDAYS TROUGH FORECAST HAS COME IN CLOSER AGREEMENT AMONG THE MODELS AND LOOKS TO BE DEEPER AND A MORE MOIST THAN THOUGHT EARLIER. DID EXPAND AND INCREASE THE POPS IN OUR NORTHERN ZONES FOR LATE SATURDAY AND EARLY SUNDAY. THE MODELS DO BRING A SHOT OF COLD AIR ALOFT WITH IT AND IT DOES CLOSE OFF. SO FAR...STABILITY PROGS KEEP THREAT OF THUNDER OUT. FUTURE FORECASTS MAY NEED NEED TO EXPAND PRECIPITATION COVERAGE AS I WENT A BIT CONSERVATIVE THIS PACKAGE. THE REST OF SUNDAY LOOKS QUIET AS THE SYSTEM DEPARTS AND BRIEF SHORT WAVE RIDGING MOVES THROUGH BEFORE THE NEXT SYSTEM QUICKLY COMES INTO THE AREA MONDAY. THE GFS IS THE MOST BULLISH ON THIS ONE. LEANED FORECAST MORE TOWARDS THE LESS ROBUST ECMWF. THE GFS ENSEMBLES ALSO LEAN TOWARDS THE ECMWF. HOWEVER THIS ONE IS GOING TO BE MORE POTENT THAN THE SATURDAY SYSTEM AND I EXPANDED THE PRECIPITATION AREAS FURTHER SOUTH. THIS ONE MAY BRING WITH IT INCREASED WINDS AND I DID INCREASE WINDS MONDAY BUT NOT TO HEADLINE LEVELS. TUESDAY WILL BE A TRANSITION DAY AS THE SYSTEM DEPARTS AND NORTHWEST FLOW COMES IN. LOOKING JUST BEYOND THE EXTENDED PERIOD INTO WEDNESDAY THERE IS A BIG DIFFERENCE IN MODELS AS THE ECMWF KEEPS THE AREA IN NORTHWEST TO NORTH FLOW WHILE THE GEM AND GFS WANT TO DROP ANOTHER LOW INTO OUR AREA FROM THE NORTHWEST YET AGAIN. WILL HAVE TO ADDRESS THIS ISSUE IN TOMORROW MORNINGS FORECAST PACKAGE. && .VEF WATCHES/WARNINGS/ADVISORIES... NV...NONE. AZ...NONE. CA...NONE. && $$ UPDATE...STACHELSKI AVIATION...SALMEN PREVIOUS...ADAIR/JACQUES HTTP://WEATHER.GOV/LASVEGAS