FXUS65 KREV 070040
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
440 PM PST SUN DEC 6 2009

.SHORT TERM...
A BAND OF MODERATE TO LOCALLY HEAVY SNOW DEVELOPED OVER SOUTHERN
LASSEN AND NORTHERN PLUMAS COUNTIES THIS MORNING IN AREA OF
CONVERGENCE CAUSED BY A SHORT WAVE ROTATING AROUND AN APPROACHING
UPPER LOW AND A GOOD H7 CONVERGENCE/H3 DIVERGENCE COUPLET. THIS
BAND OF SNOW PRODUCED UP TO 3 INCHES OF SNOW SOUTH OF SUSANVILLE
TO THE TAHOE AREA...AND UP TO AN INCH IN THE RENO AREA AS IT MOVED
THROUGH. 

THE LOW CENTER WAS ALONG THE CA/OREGON BORDER THIS AFTERNOON AND
MOVING SOUTH. A STRONG JET STREAM WAS OVER THE CWA AND WAS HELPING
TO PRODUCE VERY STRONG WIND GUSTS IN THE SIERRA. A WIND GUST OF 93
MPH WAS REPORTED AT THE MAMMOTH YOSEMITE AIRPORT JUST AFTER 2 PM
WITH GUSTS TO 66 MPH FARTHER NORTH AT BRIDGEPORT. RIDGE GUSTS HAVE
BEEN 90-100+ ALONG THE SIERRA FROM TAHOE TO MONO COUNTY. THESE
WINDS WILL REMAIN STRONG AND GUSTY INTO THE EVENING THEN DECREASE
AS HEAVIER PRECIPITATION MOVES INTO THE AREA. 

TIMING OF THE WINTER STORM WARNINGS WAS MOVED UP IN THE LASSEN
COUNTY TO TAHOE TO SIERRA FRONT AREAS AS THE SNOW BAND TODAY WILL
BE FOLLOWED BY ADDITIONAL SNOW MOVING INTO THE AREA EARLY THIS
EVENING. IN ADDITION...WINTER WEATHER ADVISORIES WERE ISSUED FOR
CHURCHILL AND PERSHING COUNTIES AS THE INCOMING SYSTEM SPREADS
SNOW OVER THE ENTIRE AREA TONIGHT AND MONDAY. THERE IS GOOD MODEL
AGREEMENT ON TIMING OF HEAVIER SNOW WITH THIS STORMS SYSTEM AS THE
HEAVIER SNOW IN THE NORTH SPREADS SOUTH TONIGHT AND THEN MOVES OFF
TO THE EAST LATER ON MONDAY WHEN THE NORTHERN CA LOW OPENS UP AND
MOVES EAST. 

NAM BUFKIT SOUNDINGS SHOW 18 INCHES OF SNOW DURING THIS STORM AT
SOUTH LAKE TAHOE WITH 5 INCHES AT THE RENO AIRPORT. HIGHER AMOUNTS
ARE EXPECTED AT UPPER ELEVATIONS IN THE SIERRA AND IN FOOTHILLS OF
EXTREME WESTERN NV. DETAILS ON THE WINTER WEATHER ADVISORIES AND
WARNINGS CAN BE FOUND IN THE RNOWSWREV PRODUCT ON OUR WEB SITE AT
WEATHER.GOV/RENO

TEMPERATURES WERE COLD TODAY AND MORE OF THE SAME IS EXPECTED
THROUGH WEDNESDAY. THE COLDEST READINGS ARE LIKELY TO OCCUR EARLY
WEDNESDAY MORNING AS CLEARING SKIES...LIGHT WINDS...AND SNOW COVER
ALLOW GOOD RADIATIONAL COOLING. TEMPS COULD BE NEAR OR BELOW ZERO
IN SOME WESTERN NV VALLEYS WITH EVEN COLDER READINGS IN THE
MOUNTAIN VALLEYS.

.LONG TERM...THURSDAY THROUGH SUNDAY...
SHORT TERM WEATHER ACTIVITY HAS TAKEN PRECEDENT...BUT ACTIVE WEATHER 
PATTERN IS LIKELY TO CONTINUE INTO NEXT WEEKEND. FOR THURSDAY...THE 
12Z GFS AND ECMWF CAME IN MUCH WEAKER WITH THIS SYSTEM...BUT NEARLY 
ALL OF THE GFS ENSEMBLE MEMBERS AND THE 18Z GFS RUN KEPT SOME PRECIP 
OVER MUCH OF THE REGION. THEREFORE THE POPS WERE MAINTAINED ALTHOUGH 
PRECIP AMOUNTS ARE NOT LOOKING AS IMPRESSIVE...QPF IN THE SIERRA NOW 
TOPPING OUT BTWN 0.50 AND 0.75 INCH ON THE ECMWF AND 18Z GFS WHICH 
IS LESS THAN HALF OF THE MAXIMUM THAT GUIDANCE INDICATED 24 HOURS 
AGO. PRECIP TYPE WITH THIS SYSTEM WILL BE VIRTUALLY ALL SNOW DUE TO 
THE COLD AIR MASS REMAINING LOCKED IN PLACE. MODEL SOUNDINGS KEEP 
VERTICAL PROFILES BELOW 700 MB LARGELY ISOTHERMAL...AND HELD BELOW 
FREEZING. 

FROM FRIDAY-SUNDAY...MOIST PACIFIC FLOW IS EXPECTED TO INCREASE AS A 
MORE SIGNIFICANT PRECIP EVENT IS BECOMING MORE LIKELY FOR THE SIERRA 
AND WRN NV. TIMING OF THE SHORTWAVES CARRYING THIS MOISTURE 
CONTINUES TO VARY BETWEEN GUIDANCE SOURCES SO THE CURRENT BEST 
ESTIMATE OF MAXIMIZING PRECIP THREATS FOR FRI NGT AND SATURDAY IS 
SUBJECT TO CHANGE. AS IS THE CASE FOR THE THURSDAY SYSTEM...THE SNOW 
LEVELS MAY STRUGGLE TO RISE MUCH ABOVE THE VALLEY FLOOR THRU NEXT 
WEEKEND IF THESE SHORTWAVES CONTINUE TO TRACK FAR ENOUGH SOUTH AND 
QUICKLY ENOUGH TO KEEP FLOW ALOFT FROM THE WEST INSTEAD OF 
SOUTHWEST. THEREFORE HAVE LOWERED MAX TEMPS BELOW MEX MOS GUIDANCE 
FOR NEXT WEEKEND. MJD    
   
&&

.AVIATION...
FOR KTVL/KTRK/KRNO...CURRENT IFR/LIFR CONDS DUE TO NARROW BUT MORE 
INTENSE SNOW BAND WILL LIKELY BE SHORT LIVED INTO EARLY THIS EVENING 
BY 02Z AS THE JET STREAK PRODUCING THIS BAND EXITS THE 
REGION...HOWEVER THE BREAK IN SNOW ACTIVITY MAY BE SHORT LIVED 
ESPECIALLY FOR THE TAHOE BASIN AS THE MAIN LOW AND STRONGER JET 
DYNAMICS ARRIVE LATER TONIGHT. ALL THREE SITES LIKELY TO SEE 
IFR/LIFR VSBY/CIGS IN STEADY SN NEARLY CONTINUOUSLY FROM 08Z TONIGHT 
THRU MOST OF MONDAY.  

FOR KLOL...MVFR CIGS/VSBY WITH OCNL IFR THRU 03Z THIS EVENING 
FOLLOWED BY A FEW HOURS OF IMPROVEMENT...BUT MVFR/IFR CONDS LIKELY 
IN STEADY -SN FROM 12Z EARLY MON MORNING AND THRU MOST OF MONDAY. 
MJD 

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WINTER STORM WARNING UNTIL 7 PM PST MONDAY FOR NVZ002.

     WINTER WEATHER ADVISORY UNTIL 4 PM PST MONDAY FOR NVZ005.

     WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 PM PST MONDAY 
     FOR NVZ003.

     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 PM PST 
     MONDAY FOR NVZ004.

CA...WINTER STORM WARNING UNTIL 7 PM PST MONDAY FOR CAZ071-072.

     WINTER WEATHER ADVISORY UNTIL 4 PM PST MONDAY FOR CAZ070.

     HIGH WIND WARNING UNTIL 10 PM PST THIS EVENING FOR CAZ073.

     WINTER STORM WARNING FROM 10 PM THIS EVENING TO 7 PM PST MONDAY 
     FOR CAZ073.

&&

$$

HTTP://WEATHER.GOV/RENO