Winter Weather in Nevada, December 12 to 13, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
238 PM PST WED DEC 12 2012

.SHORT TERM...
WATER VAPOR IMAGERY SHOWS UPPER LOW ALONG THE COAST SLOWLY
PROGRESSING SOUTHEAST WITH SOUTH TO SOUTHWEST FLOW ACROSS THE
SIERRA AND WESTERN NEVADA. SNOW SHOWERS CONTINUE IN THE SIERRA AND
MORE HAVE DEVELOPED IN WESTERN NEVADA THIS AFTERNOON. EXPECT THE
SNOW SHOWERS IN THE SIERRA TO SLOWLY WANE WHILE THE WESTERN NEVADA
SHOWERS CONTINUE INTO THE EVENING. MODELS IN REASONABLY GOOD
AGREEMENT FOR TONIGHT AND THURSDAY, BUT THE WEAK SYSTEM FRIDAY IS
STILL A MESS IN THE MODELS.

FOR TONIGHT, THE SHOWERS DEVELOPING ACROSS WESTERN NEVADA SUGGEST
THE GFS/EC ARE ON THE RIGHT TRACK. THEY SHOW WEAK DEFORMATION AND
CONVERGENCE NEAR HIGHWAY 50 THIS EVENING BEFORE IT SHIFTS EASTWARD
OVERNIGHT. WITH INCREASING CONFIDENCE HAVE INCREASED POPS OVER
MINERAL AND SOUTHEAST CHURCHILL COUNTIES TO CATEGORICAL WITH MORE
SCATTERED SHOWERS AS WESTWARD TO THE HWY 395 CORRIDOR. DID
CONSIDER ISSUING A WINTER WEATHER ADVISORY FOR MINERAL, BUT THE
FRONT REMAINS STALLED WITH SNOW LEVELS STILL 4500-5000 FEET NEAR
AND EAST OF HWY 95. MOST OF THE PRECIP WILL FALL THIS EVENING AND
EVEN THOUGH THE SNOW LEVELS WILL FALL TO THE VALLEY FLOORS, MUCH
OF THE SNOW WILL HAVE A HARD TIME STICKING INITIALLY. AT THIS
POINT, UP TO AN INCH OF SNOW FOR THE VALLEY FLOOR WITH LOCALLY UP
TO 2 INCHES ABOVE 4500 FEET APPEAR TO BE THE MOST LIKELY SCENARIO.

THE UPPER LOW WILL ONLY SLOWLY MOVE EAST THROUGH SOUTHERN
CALIFORNIA TOMORROW. THEREFORE, SCATTERED SNOW SHOWERS STILL
APPEAR POSSIBLY FOR MONO AND MINERAL COUNTIES WITH ISOLATED
SHOWERS POSSIBLE UP TO I-80. THESE SHOWERS SHOULD SLOWLY DIMINISH
THURSDAY EVENING.

FRIDAY NOW APPEARS TO BE A BIT OF A BREAK WITH THE NEXT SYSTEM
ONLY ARRIVING LATE IN THE AFTERNOON. MODELS AGREE WITH IT
SPLITTING, BUT WHERE EACH PORTION OF THE SPLIT WINDS UP IS
UNCERTAIN. HAVE KEPT A SLIGHT CHANCE OF SNOW SHOWERS NORTH OF
HIGHWAY 50 MORE FOR FRIDAY NIGHT, BUT IT MAY JUST BE COLD AND DRY
AS WELL. ANOTHER BREAK SATURDAY BEFORE THE NEXT SYSTEM IS SET TO
ARRIVE SATURDAY NIGHT. EC CONTINUES TO BE THE WETTEST AND FURTHEST
SOUTH WITH THAT ONE WHILE THE GFS/NAM ARE FURTHER NORTH. WHILE
GFS/SREF SUPPORT THE NORTHERN SOLUTION, THE 75 MEMBER EC ENSEMBLE
SHOWS MUCH MORE SPREAD. AT THIS POINT, WILL MAKE FEW CHANGES WHICH
CURRENTLY LEAN MORE TOWARDS THE WETTER AND MORE CONSISTENT EC.
WALLMANN

.LONG TERM...SUNDAY THROUGH WEDNESDAY...
LITTLE CHANGE TO THE EXTENDED FORECAST. THE UNSETTLED/PROGRESSIVE
PATTERN WILL CONTINUE NEXT WEEK WITH AN UPPER DISTURBANCE PASSING
THROUGH THE WEST EVERY COUPLE DAYS OR SO. THE TWO DISTURBANCES
EXPECTED TO AFFECT NORTHEAST CALIFORNIA AND WESTERN NEVADA DURING
THE EXTENDED FORECAST ARE DUE IN ON SUNDAY AND TUESDAY. BASED ON
LARGE MODEL SPREADS, BOTH SYSTEMS COULD EITHER BE A GLANCING BLOW
WITH MORE WIND/LESS PRECIPITATION OR A MORE DIRECT HIT FOR HEAVIER
AND MORE WIDESPREAD PRECIPITATION AND LESS OVERALL WIND.

PREFERENCE-WISE FOR SUNDAY'S SYSTEM, THE FORECAST STILL LEANS IN THE
ECMWF DIRECTION GIVEN MUCH MORE CONSISTENCY AND DUE TO THE FACT THAT
THE ECMWF HAS BEEN SETTLING ON AN IN-BETWEEN SOLUTION BETWEEN THE
FAR NORTH GFS SOLUTION AND THE ECMWF'S MORE SOUTHERLY PROG. WITH
THIS IN MIND, PRECIPITATION STILL LOOKS LIKELY IN THE NORTHERN
SIERRA AND OUT INTO FAR NORTHWEST NEVADA LATE SATURDAY NIGHT AND
SUNDAY AS A STRONG COLD FRONT WITH GOOD OROGRAPHIC FLOW (50+ KTS)
INTO THE SIERRA MOVES INTO THE REGION. HOWEVER, THE JET APPROACHING
THE BASE OF THE TROUGH IS PROGGED BY THE ECMWF TO REMAIN OVER FAR
NORTHERN CALIFORNIA AND NEVADA AND THE SYSTEM MOVES THROUGH VERY
QUICKLY SO PRECIP/SNOWFALL AMOUNTS LOOK MODEST AT THIS TIME.
WIND-WISE, THERE COULD BE A PERIOD OF GUSTY WINDS AHEAD OF THE COLD
FRONT. HOWEVER, THE SYSTEM BRINGS A GOOD AMOUNT OF MOISTURE WITH IT
AND IT IS FAIRLY COLD SO THE MIXING OF HIGHER WINDS ALOFT SHOULD BE
LIMITED (STILL WINDY AT RIDGETOPS).

THE SECOND SYSTEM TO AFFECT THE REGION IN THE EXTENDED PERIOD WILL
MOVE THROUGH TUESDAY AND BRING ANOTHER MODEST SHOT OF PRECIPITATION.
SNOW LEVELS ARE QUITE UNCERTAIN WITH THAT SYSTEM (GFS MUCH COLDER
THAN ECMWF) BUT SHOULD REMAIN LOW ENOUGH TO NOT BE OF HYDROLOGICAL
CONCERN.

TEMPERATURES ARE ALSO QUITE UNCERTAIN NEXT WEEK (ESPECIALLY SUNDAY
NIGHT AND MONDAY) AND WILL DEPEND ON HOW FAR SOUTH THE SYSTEM'S CAN
DIG WHICH WILL DETERMINE HOW FAR SOUTH COLD FRONTS WILL REACH INTO
NEVADA AND CALIFORNIA. THE ECMWF WOULD IMPLY HIGHS IN THE 30S FOR
LOWER VALLEYS MONDAY WHILE THE GFS (WHICH KEEPS COLD FRONT FAR
NORTH) WOULD BRING HIGHS WELL INTO THE 40S. SNYDER
&&

.AVIATION...
A COLD FRONT IS STALLED NEAR OR WITHIN SEVERAL DOZEN MILES SOUTH OF
HIGHWAY 50 IN WESTERN NEVADA THIS AFTERNOON. IN THE SIERRA AND NORTH
OF THE FRONT, SCATTERED TO NUMEROUS SNOW AND LOWEST ELEVATION
RAIN/SNOW SHOWERS ARE ONGOING AS AIR IS FORCED UP AND OVER THE
SURFACE FRONT.

TONIGHT AND EARLY THURSDAY, WIDESPREAD LIGHT SNOW IS EXPECTED TO
DEVELOP ESPECIALLY SOUTH OF HIGHWAY 50 IN CHURCHILL COUNTY AND EAST
OF ALT HIGHWAY 95 IN SOUTHERN LYON COUNTY WITH IFR CIGS/VIS AND
LIGHT SNOWFALL ACCUMULATIONS ABV 4500 FT MSL. HEAVIER ACCUMULATIONS
ARE EXPECTED OUT IN CENTRAL AND SOUTH-CENTRAL NEVADA. FOR AREAS
BELOW 4500 FT MSL (KNFL/KHTH), PRECIP LOOKS LIKE IT WILL BE A MIX OF
RAIN AND SNOW WHICH WILL LIMIT OR EVEN ELIMINATE SNOW ACCUMULATIONS.
HOWEVER, LOW CIGS AND VIS WILL STILL BE AN ISSUE INTO THURSDAY
MORNING.

ISOLD-SCT SNOW SHOWERS WILL CONTINUE THROUGH THURSDAY AFTERNOON
BUT LITTLE OR NO ACCUMULATION IS EXPECTED SO THE MAIN IMPACT WILL BE
OCCASIONALLY LOWERED CIGS/VIS WITH TERRAIN OBSCURATION. SNYDER
&&

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

FOR MORE INFORMATION FROM THE NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/RENO (ALL LOWER CASE)