FXUS65 KREV 022348
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
348 PM PST WED DEC 2 2009

.SHORT TERM...
NORTH TO NORTHEAST FLOW ALOFT WILL KEEP HIGH TEMPERATURES SEASONABLE
THROUGH FRIDAY. LOWS WILL REMAIN QUITE COLD AND A BIT BELOW AVERAGE
WITH VERY DRY AIR (ALLOWING SUPERB RADIATIONAL COOLING) EXPECTED TO
MOVE INTO THE REGION TONIGHT THROUGH FRIDAY.

LATE FRIDAY NIGHT AND SATURDAY MORNING...A VERY SHARP COLD FRONT
WILL BLAST THROUGH THE REGION. UNFORTUNATELY...THE 12Z GFS AND NAM
LOOKED VERY DIFFERENT FROM THE ECMWF LEADING TO UNCERTAINTIES WITH
POSSIBLE FRONTAL PRECIP AND TEMPERATURES SATURDAY. HOWEVER...I AM
SIDING WITH THE FURTHER WEST UPPER LOW IN THE ECMWF AS THE 18Z GFS
AND NAM HAVE COME TOWARDS THE ECMWF SOLUTION...WHICH HAS BEEN VERY
CONSISTENT FOR THE LAST COUPLE RUNS. IN ADDITION...THERE IS A
LARGE STANDARD DEVIATION ON THE WEST SIDE OF THE SREF 500 MB
HEIGHTS OVER OREGON...IMPLYING THAT THERE ARE MEMBERS FURTHER WEST
THAN THE SREF ENSEMBLE MEAN. 

WITH THE FURTHER WEST SOLUTION OF THE ECMWF (AND NOW THE 18Z GFS) 
...SATURDAY WILL FEATURE THE VERY STRONG FROPA SATURDAY MORNING
ALONG WITH A 100-110 KT JET NOSE ROUNDING THE UPPER LOW'S BASE
INTO THE LAKE TAHOE VICINITY. THIS WILL PROVIDE STRONG LIFT ALONG
THE FRONT...BRINGING A FAST-MOVING BAND OF SNOW OR SNOW SHOWERS
THROUGH THE REGION ON SATURDAY. OF CONCERN IS THE FACT THAT WITH
VERY COLD AIR MOVING IN...SNOW RATIOS WILL PROBABLY BE AT LEAST 20
TO 1 SO A COUPLE INCHES OF SNOW IS POSSIBLE IF A SHORT-LIVED
HEAVY BURST OF PRECIPITATION DEVELOPS. THERE IS STILL MUCH
UNCERTAINTY IN THE SMALLER-SCALE DETAILS SATURDAY SO STAY WITH US
FOR FORTHCOMING INFORMATION. 

FINALLY...WITH THE VERY STRONG FRONT USHERING IN -16C TO -18C AIR
AT 700 MB AND A BAND OF SNOW POSSIBLE SATURDAY...HIGH TEMPERATURES
COULD COME IN THE EARLY TO MID MORNING WITH FALLING TEMPS
THEREAFTER. SNYDER 

.LONG TERM...SUNDAY THROUGH WEDNESDAY...
GOOD AGREEMENT OVERALL WITH LOW PRESSURE OVER THE WESTERN STATES
THIS WEEKEND. A PIECE OF ENERGY WILL SWING OUT AND RETROGRADE TO
THE WEST...OUT OVER THE PACIFIC ON SUNDAY...THEN SLAM BACK INTO
NORTHERN CA BY SUNDAY NIGHT THROUGH MONDAY.

EURO HAS BEEN PRETTY CONSISTENT OVER LAST COUPLE DAYS ALONG WITH 
GEFS/CANADIAN ENSEMBLES...LEADING TO BETTER CONFIDENCE OVERALL... 
12Z/18Z GFS NOW COMING BETTER IN-LINE AS WELL. A STRONG 
JET...INSTABILITY AND LIFT WITHIN THE DENDRITIC GROWTH 
ZONE...MOISTURE FROM A FAVORABLE FETCH OVER THE EASTERN PAC ALL LOOK 
FAVORABLE TO GIVE THE AREA A DECENT AMOUNT OF MOISTURE AND SNOW. 
EURO IS MUCH WETTER WITH THIS SUN NIGHT-MONDAY STORM...SHOWING A 
GOOD POSSIBILITY OF SPILLOVER AND ACCUMULATING SNOWFALL DOWN TO THE 
WESTERN NV VALLEYS BY MONDAY. BOTH GFS AND EC ARE SHOWING VERY COLD 
TEMPERATURES INITIALLY...WHICH COULD LEAD TO SOME HIGHER SNOW RATIOS 
AND ENHANCED ACCUMULATIONS. TIMING OF THIS STORM WILL BE 
CRITICAL...DUE TO THE POSSIBILITY OF SNOWFALL DURING/BEFORE THE 
MONDAY MORNING COMMUTE.

FOR THE TUE-WED FORECAST...CONTINUED TO RAISE POPS ACROSS THE ENTIRE 
FORECAST AREA. MODELS HAVE BEEN SHOWING A MUCH WETTER AND MILDER 
PATTERN...WITH HIGHER SNOW LEVELS...THROUGH THE SECOND HALF OF THE 
WEEK. HOON
&&

.AVIATION...
HIGH PRESSURE...LIGHT WINDS...VFR CONDS. CHANCE OF FREEZING FOG IN 
SOME COLDER SIERRA VALLEYS TONIGHT. DID NOT INCLUDE IN THE TAF IN 
KTRK DUE TO LIGHT EASTERLY WINDS ALOFT KEEPING FOG FROM FORMING.  
HOON
&&

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

$$

HTTP://WEATHER.GOV/RENO