FXUS65 KREV 112318
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
318 PM PST FRI DEC 11 2009

.SHORT TERM...
SHOWERS DECREASING IN COVERAGE ACROSS THE SIERRA AND WESTERN
NEVADA FOR THE EVENING COMMUTE. HOWEVER A BAND OF MODERATE TO
HEAVY PRECIP EAST SFO AND MONTEREY BAY WILL REACH THE SIERRA
NORTH OF SONORA PASS THIS EVENING AND TRACK INTO WESTERN NEVADA
TONIGHT. ADDITIONAL LIGHT ACCUMULATIONS WILL OCCUR WITH THIS BAND.

MAIN CONCERN CONTINUES TO BE THE SATURDAY AFTERNOON/SATURDAY
EVENING PERIOD AS AN ALMOST PERFECT SET UP FOR A HEAVY SNOW STORM
MOVES INTO THE SIERRA AND WESTERN NEVADA. DEEP MOISTURE AHEAD OF
THE LOW WITH SUPPORT FROM JET AND MID AND UPPER LEVEL WAVES WILL
HAVE TO POTENTIAL TO PRODUCE VERY HIGH SNOWFALL RATES. HOWEVER
FAST MOVING WAVE WILL ONLY PRODUCE HEAVY AMOUNTS FOR A 6 HOUR
PERIOD. 12Z AND 18Z RUNS HAVE REMAINED CONSISTENT WITH AN INCH OF
QPF IN THE SIERRA AND AMOUNTS OF 0.25 TO 0.50 FOR THE RENO-CARSON
CITY AREA BETWEEN 4 AND 10PM SATURDAY. 

WATCHES FOR THE RENO-CARSON AREA AND SOUTHERN LYON AND MINERAL
HAVE BEEN UPGRADED TO WINTER STORM WARNINGS. TOTAL ACCUMULATIONS UP TO
6 INCHES ON VALLEY FLOORS...WITH AMOUNTS UP TO 10 INCHES IN THE
FOOTHILLS. TOTALS IN THE SIERRA OF 1-3 FEET REMAIN ON TRACK.
FARTHER NORTH AND EAST FOR GERLACH...LOVELOCK AND FALLON...AMOUNTS
WILL BE LIGHTER AS THE MAIN DYNAMICS ARE SOUTH AND WEST OF THESE
AREAS. THUS HAVE ISSUED WINTER WEATHER ADVISORIES FOR THOSE AREAS.

DURING THIS TIME HEAVY SNOW WILL MAKE TRAVEL VERY DANGEROUS WITH
WHITEOUT CONDITIONS...ESPECIALLY OVER THE SIERRA PASSES.
SIGNIFICANT TRAVEL DELAYS ARE LIKELY WITH A GOOD CHANCE AT ROAD
CLOSURES DUE TO THE RAPID SNOW ACCUMULATIONS. THIS STORM IS ALSO
WARMER THAN THE PREVIOUS...WITH LOWER SNOW RATIOS. THIS WILL
PRODUCE A HEAVIER WET SNOW ON A LESS DENSE SNOW PACK AND POTENTIAL
AVALANCHE CONDITIONS.

ONCE THE MAIN WAVE PASSES LIGHT TO MODERATE SNOW WILL CONTINUE IN
THE SIERRA AND WESTERN NEVADA INTO SUNDAY. MODELS KEEP MOISTURE
STREAMING INTO THE SIERRA UNTIL SUNDAY EVENING...SO SHOWERS AND
ACCUMULATING SNOW ARE LIKELY TO CONTINUE WELL INTO SUNDAY.  BRONG

.LONG TERM...MONDAY THROUGH FRIDAY...

MODELS CONTINUE TO SHOW RIDGING BUILDING INTO THE SOUTHWEST STATES 
NEXT WEEK AFTER THE MAJOR TROUGH MOVES TO THE EAST. HOWEVER...RIDGE 
MAY NOT BE VERY STRONG INITIALLY AS LOW PRESSURE IN THE GULF OF 
ALASKA CONTINUES TO SEND ENERGY INTO THE PAC NW. THESE SHORTWAVES 
ARE NOT EXPECTED TO AFFECT OUR AREA IN A BIG WAY...BUT WE MAY SEE 
SOME BRUSH-BY SYSTEMS THROUGH THE WEEK. CONTINUE TO ADVERTISE A 
CHANCE OF RAIN/SNOW FOR THE NORTHERN SIERRA MAINLY NORTH OF TAHOE. 
BEST CHANCE LOOKS TO BE THE TUE-WED TIME FRAME...AS THE GULF OF AK 
LOW SENDS A SHORTWAVE INTO NORTHERN CA.

THE BIG QUESTION REMAINS FOR THE LONG TERM...HOW MUCH SNOWFALL THE 
REGION WILL GET FROM THIS WEEKEND'S STORM...AND HOW STRONG WILL THE 
RIDGE BUILD IN FOR NEXT WEEK. IF THE RIDGE BUILDS IN STRONGER...WITH 
A DEEP SNOWPACK ACROSS THE WESTERN NV VALLEYS...WE COULD SEE A 
PROLONGED PERIOD OF BELOW NORMAL TEMPERATURES...FREEZING FOG...HAZE 
AND SMOG IN THE LOWER VALLEYS AS HIGH PRESSURE BRINGS LIGHT WINDS... 
SUBSIDENCE AND VALLEY INVERSIONS.  HOON

&&

.AVIATION...

SCATTERED SNOW SHOWERS CONTINUE ACROSS THE REGION...WITH PERIODS
OF MVFR-IFR CIG/VIS AFFECTING LOCAL TERMINALS THROUGH 06Z.

MAJOR WINTER STORM STILL ON TRACK TONIGHT THROUGH SATURDAY NIGHT. 
SIGNIFICANT OPERATIONAL IMPACTS EXPECTED AT ALL LOCAL TERMINALS DUE 
TO HEAVY SNOW AND PERIODS OF IFR-LIFR CIG/VIS BEGINNING BETWEEN 
06-09Z. PERIODS OF MODERATE AND HEAVY SNOW ESPECIALLY SATURDAY 
AFTERNOON AND EVENING IN THE SIERRA. 10 TO 20 INCHES OF NEW SNOW 
EXPECTED AT KTRK AND KTVL BY SUNDAY MORNING.

KRNO...UP TO 6 INCHES OF HEAVY WET SNOW EXPECTED THROUGH EARLY 
SUNDAY MORNING. PERIOD OF IFR AFTER 12Z SAT. HEAVIEST SNOWFALL 
BETWEEN AFTER 00Z SUN (4PM SATURDAY) WITH A FEW HOURS LIKELY OF 
<1/4SM +SN.  HOON

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WINTER WEATHER ADVISORY FROM 4 PM SATURDAY TO 4 AM PST SUNDAY 
     FOR NVZ004-005. 

     WINTER STORM WARNING FROM 10 PM THIS EVENING TO 4 AM PST SUNDAY 
     FOR NVZ002. 

     WINTER STORM WARNING FROM 1 PM SATURDAY TO 4 AM PST SUNDAY FOR 
     NVZ001. 

     WINTER STORM WARNING FROM 1 PM SATURDAY TO 4 AM PST SUNDAY FOR 
     NVZ003. 

CA...WINTER STORM WARNING FROM 10 PM THIS EVENING TO 4 AM PST SUNDAY 
     FOR CAZ071. 

     WINTER WEATHER ADVISORY FROM 4 PM SATURDAY TO 4 AM PST SUNDAY 
     FOR CAZ070. 

     WINTER STORM WARNING FROM 10 AM SATURDAY TO 10 AM PST SUNDAY FOR 
     CAZ073. 

     WINTER STORM WARNING FROM 10 PM THIS EVENING TO 4 AM PST SUNDAY 
     FOR CAZ072. 

&&

$$

HTTP://WEATHER.GOV/RENO