FXUS65 KREV 011020
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
220 AM PST MON NOV 30 2009

.SHORT TERM...A WEAK RIDGE REMAINS THE MAIN FEATURE TO 
NOTE...KEEPING LIGHT WINDS AND CLEAR SKIES AROUND FOR MOST OF THE 
SHORT TERM. VALLEY LOCATIONS WILL REMAIN UNDER AN INVERSION YET 
AGAIN TODAY...WITH FORECAST SOUNDINGS SHOWING EVEN WARMER 
TEMPERATURES AT 800MB THAN YESTERDAY...MAKING IT MORE DIFFICULT TO 
MIX OUT. THIS MAY RESULT IN SOME LOCATIONS AT HIGHER ELEVATIONS 
REACHING A DEGREE OR TWO WARMER THAN VALLEY LOCATIONS. A SHORTWAVE 
DISTURBANCE WILL PASS TO OUR NORTHEAST TODAY...SHIFTING THE WIND 
DIRECTION NORTH AND BRINGING IN SOME HIGH LEVEL CLOUDS. THE CLOUDS 
WILL BE SHORT LIVED HOWEVER AS THEY ARE EXPECTED TO DISSIPATE 
OVERNIGHT TONIGHT. AT THE SAME TIME THE NORTHERLY FLOW WILL USHER IN 
COOLER AIR RESULTING IN A SLIGHT COOLING TREND THROUGH THURSDAY. AS 
MENTIONED PREVIOUSLY...WINDS WILL REMAIN LIGHT ACROSS THE BOARD DUE 
TO THE LACK OF UPPER LEVEL SUPPORT. RIDGE TOP GUSTS MAY PICK UP 
SLIGHTLY ON THURSDAY MORNING AS THE JET FROM THE AFOREMENTIONED 
SHORTWAVE BRUSHES BY TO THE EAST OF NEVADA. LABELLE

.LONG TERM...FRIDAY THROUGH MONDAY...
THE LONGWAVE PATTERN IS STARTING TO COME INTO BETTER FOCUS THIS MRNG 
ALTHOUGH MODELS STILL HAVE A WAYS TO GO BEFORE A DETAILED SCENARIO 
CAN BE OBTAINED. UPR RDG IS STILL FCST OVR THE EPAC AT BEGINNING OF 
PD WITH MODELS A BIT FASTER NOW AT PINCHING THE HIGH OFF AND 
BRINGING UNDERCUTTING ENERGY INTO THE WEST COAST BY EARLY NEXT WEEK. 
THE OPERATIONAL GFS CONTS TO BE SEVERAL DAYS SLOWER IN BRINGING 
UNDERCUT ENERGY TO THE REGION AND INSTEAD CONTS TO BRING DOWN SOME 
COLD AIR ALTHOUGH MAIN TROF IS DECIDEDLY FURTHER EAST AND LESS 
RETROGRESSIVE OF PREV RUNS. IT WOULD YIELD A COLDER BUT MUCH DRIER 
SOLN EARLY NEXT WEEK. WHILE THERE WL BE A TENDENCY FOR COLD AIR TO 
WORK SWD TWD THE GREAT BASIN...BELIEVE THE OPERATIONAL GFS IS AN 
OUTLIER AND DECIDED TO SIDE CLOSER TO THE ECMWF AND CANADIAN WHICH 
ARE WETTER AND COLDER(ALTHOUGH NOT AS COLD AS THE GFS). THE ECMWF 
RETROGRADES UPR LOW WITH MORE WLY FLOW AND COLDEST AIR BOTTLED JUST 
TO OUR NORTH. A NUMBER OF GFS ENSEMBLES AND THE GEFS MEAN SEEMS TO 
LEND CREDENCE TO THIS SCENARIO. 

DRY AND MILD CONDS FRI-SAT WL GRADUALLY GIVE WAY TO COOLER AND 
WETTER WEATHER BY MON. POPS WERE KEPT AT THE SLGT CHC CATEGORY SUN 
AND INCREMENTED TO CHC MON. HOWEVER IF CONFIDENCE CONTS TO FAVOR THE 
ECMWF...THESE POPS MAY NEED TO BE RAISED SIGNIFICANTLY AND WE COULD 
HAVE A WINTER STORM ON HAND ESPECIALLY FOR THE SIERRA. AT THE SAME 
TIME TEMPS WERE BUMPED UP A BIT(TWD HI END OF MOS) FRI AS INCRG WLY 
FLOW AHEAD OF COLD FRONT MAY BE ENOUGH TO FINALLY MIX OUT THE VLY 
INVERSIONS. THEREAFTER HI TEMPS WERE COOLED BUT KEPT IN THE MIDDLE 
OF THE MOS ENSEMBLE RANGE DUE TO REMAINING UNCERTAINTY. IF THE ECMWF 
VERIFIES TEMPS MAY STILL BE APPROACHING 50 DEGREES INTO EARLY NEXT 
WEEK AS COLD AIR GETS BOTTLED UP JUST TO OUR NORTH. THE UNCERTAINTY 
IN TEMPS LEADS TO UNCERTAINTY IN SNOW LVLS AS WELL. CURRENT FCST 
WL LEAN ON LOW SNOW LVLS INIT AND THEN SLOWLY BRINGING THEM UP. 
OVRNGT LOWS SHOULD MODERATE WITH THE CLOUDS AND PCPN. HOHMANN
&&

.AVIATION...
VFR CONDS WITH LIGHT SFC WINDS. 

FOR KTRK...AIR MASS WL REMAIN DRY. THE DEW POINTS ARE SLIGHTLY 
HIGHER THIS MRNG AND LCL SHALLOW FZFG MAY FORM NR THE AIRPORT 
12Z-16Z. DEWPOINTS RISE A BIT MORE FOR LATE TNGT INTO TUE MRNG AND 
THE NAM MOS IS BEGINNING TO SHOW SOME INDICATION OF FZFG. HOWEVER 
THE GFS CONTS AN ELY SFC GRADIENT AND THIS WOULD TEND TO MITIGATE 
FORMATION. OVERALL CONFIDENCE REMAINS LOW. HOHMANN
&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
CA...NONE.
&&

$$

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