Winter Storm Watch 1, NWS Reno, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
252 PM PST SUN FEB 13 2011

.SHORT TERM...
COMPLEX FORECAST AS ANOMALOUSLY COLD UPPER LOW (APPROXIMATELY 2.5
SDEV) DROPS DOWN OVER THE EPAC AND AFFECTS MUCH OF THE WESTERN U.S.
EARLY THIS WEEK. THE GFS HAS MAINTAINED THE MOST CONTINUITY WHILE
THE ECMWF HAS TRENDED A BIT MORE ELONGATED BUT ONLY SLIGHTLY SLOWER.
SO ONGOING FORECAST IS ON TRACK FOR STRONG WINDS...SNOW AND MUCH
COLDER TEMPERATURES.

LATEST WATER VAPOR IMAGERY SHOWED LEAD SHORTWAVE AROUND 35N/135W
BEGINNING TO GET PICKED UP AND PUSHED TOWARD THE CA-OR COAST AS MAIN
COLD UPPER LOW DROPPED SOUTH FROM THE GULF OF ALASKA. LEAD SHORTWAVE
HAS TAPPED SOME SUBTROPICAL MOISTURE AND WILL BE PULLING IT INTO
NORTHERN CA TONIGHT AND MON ALONG WITH INCREASING UPPER LEVEL WINDS.
MOST OF THE PRECIPITATION WITH THIS INITIAL WAVE WILL AFFECT MAINLY
THE CASCADES WITH SOME LIGHT QPF AMOUNTS REACHING THE NORTHERN
SIERRA MON-MON NIGHT. MAIN IMPACT FROM THIS FEATURE WILL BE
INCREASING WINDS AS 700MB FLOW JUMPS TO 50-60KT BY 12Z MON AND
SURFACE PRESSURE GRADIENT TIGHTENS IN RESPONSE TO DEEPENING SURFACE
LOW NEAR THE PACNW COAST. 12Z NAM SOUNDINGS CONTINUE TO SHOW
CRITICAL LAYER LATE MON MORNING INTO MON AFTERNOON WHICH WOULD BE
CONDUCIVE TO A PERIOD OF STRONG DAMAGING WINDS ALONG THE HIGHWAY 395
CORRIDOR FROM SUSANVILLE TO LEE VINING.

HIGH WINDS MAY BECOME A BIT MORE LOCALIZED MON NIGHT BEFORE MAIN
TROUGH AND COLD FRONT MOVE INTO CA ON TUE. STILL EXPECT WIDESPREAD
GUSTY WINDS WHICH WILL ONLY INCREASE AGAIN TUE MORNING AS WINDS
INCREASE ALOFT AND GRADIENTS TIGHTEN FURTHER. HAVE UPGRADED HIGH
WIND WATCH TO A NUMBER OF WIND WARNINGS AND ADVISORIES THAT WILL
COVER THE MON-TUE EVENING TIME FRAME.

ATTENTION THEN TURNS TO WINTER WEATHER AS THE MODELS REMAIN
AMAZINGLY CONSISTENT WITH FRONTAL TIMING AND QPF AMOUNTS. COLD FRONT
WILL SLOWLY PUSH INTO NORTHERN ZONES BY LATE TUE AS IT AWAITS MAIN
UPPER JET TO ROUND BASE OF LARGE SCALE TROUGH. NORTHEAST
CA-NORTHWEST NV WILL BE IN A MOST FAVORABLE POSITION FOR A PROLONGED
PERIOD OF HEAVY PRECIPITATION (12-18 HOURS) AS DYNAMICS FROM DUAL
JETS ENHANCE LIFT TO THE NORTH OF SURFACE COLD FRONT. AIRMASS WILL
BE QUITE COLD IMMEDIATELY BEHIND THIS BOUNDARY WITH SNOW LEVELS
PROJECTED TO BE DOWN TO ALL VALLEY FLOORS. AS MAIN UPPER JET SWINGS
THROUGH CENTRAL/SOUTHERN CA TUE NIGHT INTO WED...FRONT WILL TIGHTEN
(STRONG FRONTOGENESIS) AND BEGIN TO ACCELERATE ACROSS WESTERN NV AND
THE SIERRA. PLUME OF MOISTURE AHEAD OF FRONT WILL THEN WORK ITS WAY
SOUTH ALONG THE SIERRA CREST BRINGING A 12 HOUR PERIOD OF HEAVY SNOW
TO THE TAHOE BASIN DOWN INTO MONO COUNTY ALONG WITH A SHORT PERIOD
OF HEAVY SNOW ALONG THE FRONT AS MOISTURE SPILLS OVER ALONG FRONTAL
BOUNDARY ACROSS WESTERN NV. RIGHT NOW THE TIMING OF FRONTAL/SNOW
BAND PASSAGE FOR WESTERN NV APPEARS TO BE DURING THE LATE MORNING
INTO AFTERNOON TIME FRAME WED. WINTER STORM WATCHES HAVE BEEN POSTED
FOR ALL AREAS GIVEN THE DYNAMIC NATURE OF THIS SYSTEM AND GIVEN THE
FACT WE HAVE BEEN IN SUCH AN UNUSUALLY DRY AND WARM PERIOD.

TEMPERATURES TO REMAIN ABOVE NORMAL FOR A COUPLE MORE DAYS BEFORE
RETURNING TO MUCH COLDER CONDITIONS WEDNESDAY BEHIND FRONT. WINDS
WILL GENERALLY KEEP TEMPERATURES UP AT NIGHT ESPECIALLY MON AND TUE
NIGHT WITH HIGHS ON WED OCCURRING IN THE MORNING FOR SOME LOCATIONS
NORTH OF HIGHWAY 50. HOHMANN

.LONG TERM...THURSDAY THROUGH SUNDAY...
MEDIUM RANGE GUIDANCE IS IN DISARRAY WITH TIMING AND TRACK OF
SUBSEQUENT SHORTWAVES OR AREAS OF LOW PRESSURE ROTATING AROUND THE
MEAN TROF OVER THE WRN US LATER THIS WEEK AND INTO NEXT WEEKEND.
THE GFS STRAYED THE MOST FROM ITS PREV RUNS WITH A MAJOR SPLIT
DEVELOPING ACROSS THE REGION AND DIVERTING MOST OF THE SNOW
POTENTIAL TOO FAR NORTH AND SOUTH. THE ECMWF HAS SHOWED MORE
CONSISTENCY WITH A CLOSED LOW ROTATING INTO THE SIERRA BY THURS
NIGHT AND FRIDAY...GENERATING AN AREA OF ORGANIZED DEFORMATION ZONE
SNOW AIDED BY LOW LEVEL EAST FLOW AND COLD POOL ALOFT. GFS ENSEMBLE
MEMBERS VARY IN BETWEEN THESE SCENARIOS BUT IN GENERAL FAVOR SOME
PERIOD OF ORGANIZED PRECIP SOMETIME BETWEEN LATE THURSDAY AND FRIDAY
EVENING. THE NET RESULT OF THE VARYING GUIDANCE SOLUTIONS WILL BE
LITTLE CHANGE TO THE CURRENT FORECAST WHICH ORIGINALLY LEANED TOWARD
THE ECMWF...WITH BETTER CHANCES OF SNOW IN THE SIERRA AND FAR WRN NV
THURSDAY NIGHT AND FRIDAY.

FOR NEXT WEEKEND...CYCLONIC FLOW ALOFT AND LINGERING LOW LEVEL
MOISTURE WILL KEEP THE THREAT OF LIGHT SNOW SHOWERS ONGOING THRU
SATURDAY...BUT THE PROBABILITY OF A LONGER PERIOD OF STEADY
ACCUMULATING SNOW WILL BE LOWER. SNOW SHOWER ACTIVITY ON SUNDAY MAY
BE MINIMAL AS THE CYCLONIC FLOW TRANSITIONS TO A DRIER NORTHWEST
FLOW ALOFT...BUT ANOTHER COLD AND SNOWY PERIOD COULD RETURN ON OR
AFTER THE PRESIDENTS DAY HOLIDAY.

CONFIDENCE IS HIGHER FOR KEEPING BELOW NORMAL TEMPS OVER THE REGION
THRU NEXT SUNDAY. DESPITE THE DIFFERENCES MENTIONED ABOVE...ALL
MAJOR GUIDANCE SOURCES KEEP THE 700 MB TEMPS GENERALLY WITHIN THE
-10 TO -14 C RANGE. IF WIDESPREAD SNOW COVER IS PRESENT IN THE LOWER
ELEVATIONS WITH SUFFICIENT DAYTIME CLOUD COVER...TEMPS IN MANY AREAS
MAY NOT SURPASS 40 DEGREES ALL THE WAY THRU SUNDAY. MJD
&&

.AVIATION...
VFR CONDS WILL PREVAIL CONTINUE THRU MONDAY...BUT MUCH STRONGER
WINDS WITH PERIODS OF LLWS AND LEE SIDE MTN WAVES ARE EXPECTED
ACROSS THE REGION MONDAY THRU TUESDAY. CROSSWIND IMPACT CRITERIA
COULD BE REACHED FOR SHORT PERIODS AT KRNO FROM TUES AFTN THRU TUES
NIGHT. SMALLER AIRPORTS IN W-CNTRL NV COULD ALSO BE IMPACTED BY
REDUCED VSBY DUE TO BLOWING DUST. MOST PRECIP WILL REMAIN TRAPPED
ALONG AND WEST OF THE SIERRA CREST THRU MONDAY NIGHT BEFORE STARTING
TO SPREAD INTO NERN CA-NWRN NV BY TUESDAY. MJD
&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...HIGH WIND WARNING FROM 7 AM MONDAY TO NOON PST TUESDAY NVZ005.

     WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
     AFTERNOON NVZ005.

     HIGH WIND WARNING FROM 7 AM MONDAY TO 10 PM PST TUESDAY NVZ003.

     WIND ADVISORY FROM 7 AM MONDAY TO 4 PM PST TUESDAY NVZ002.

     WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
     AFTERNOON NVZ002.

     BLOWING DUST ADVISORY FROM NOON MONDAY TO 10 PM PST TUESDAY
     NVZ001-004.

     WINTER STORM WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY
     AFTERNOON NVZ001-003-004.

CA...HIGH WIND WARNING FROM 7 AM MONDAY TO NOON PST TUESDAY
     CAZ070-071.

     WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
     AFTERNOON CAZ070-071.

     HIGH WIND WARNING FROM 7 AM MONDAY TO 10 PM PST TUESDAY CAZ073.

     WINTER STORM WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY
     EVENING CAZ073.

     WIND ADVISORY FROM 7 AM MONDAY TO 4 PM PST TUESDAY CAZ072.

     WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
     AFTERNOON CAZ072.

&&

HTTP://WEATHER.GOV/RENO