Winter Storm Watch 2, NWS Reno, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
424 AM PST WED JAN 2 2008

.SHORT TERM...
NUDGED BACK PRECIP TIMING WITH THE LATE THURSDAY AFTERNOON/THURSDAY
NIGHT SYSTEM AND TWIDDLED SLIGHTLY WITH SNOW LEVELS...OTHERWISE FEW
CHANGES TO SHORT TERM GRIDS.

CLOUDS WILL GRADUALLY THICKEN AND LOWER TODAY AHEAD OF THURSDAY
NIGHTS OPENING ROUND SYSTEM. THURSDAY NIGHTS SYSTEM WILL BRING
MODEST SNOWFALL TOTALS TO THE SIERRA...WITH PERHAPS ISOLATED/MINIMAL
SNOW ADVISORY AMOUNTS NEAR THE CREST INTO FRIDAY MORNING.

FRIDAYS SYSTEM IS STILL WELL ON TRACK TO DUMP 2 TO 4 FEET OF SNOW
IN THE SIERRA BY SATURDAY MORNING (WITH MUCH MORE BY THE TIME ALL IS
SAID AND DONE THIS WEEKEND). HOWEVER...THE MAIN STORY CONTINUES TO
BE THE EXPECTED WINDS WITH FRIDAYS SYSTEM (THIS IS NO GARDEN
VARIETY STORM). AT LAKE TAHOE LEVEL...THE ONE THING THAT WILL SPARE
THE LAKE POSSIBLE BLIZZARD CONDITIONS FRIDAY WILL BE SNOW LEVELS.
SNOW LEVELS ARE EXPECTED TO RISE TO AROUND 7000 FEET FRIDAY
AFTERNOON ON THE HEELS OF 70-85 KT WARM ADVECTION BETWEEN 700-550 MB
(OF COURSE THIS WILL BE OFFSET BY JET DYNAMICS TRYING TO COOL THE
ATMOSPHERE). SNOW LEVELS ARE EXPECTED TO SHARPLY PLUMMET TO LAKE
LEVEL FRIDAY EVENING AS A STRONG COLD FRONT MOVES THROUGH. THIS IS
THE MOST DANGEROUS TIME FOR LAKE TAHOE...WHEN STRONG WINDS COMBINE
WITH HEAVY SNOW FOR POTENTIAL WHITEOUT CONDITIONS. THE DAYSHIFT MAY
HAVE TO CONSIDER A BLIZZARD WATCH FOR AT LEAST THE LAKE TAHOE ZONE
FOR FRIDAY NIGHT.

NOW FOR THE WIND SIDE OF THINGS FRIDAY. MESOSCALE WRF MODEL RUNS
CONTINUE TO SUPPORT POSSIBLE WIND GUSTS OVER 60 MPH FRIDAY MORNING
IN THE LEE OF THE SIERRA (ESPECIALLY RENO SOUTH TO MONO COUNTY).
THIS MAKES SENSE WITH PRECIPITATION LOADING AIDING AN ALREADY
OUTRAGEOUS SURFACE PRESSURE GRADIENT OVER WESTERN NEVADA (AT LEAST
20 MB FROM TONOPAH TO ALTURAS) FRIDAY MORNING. DESPITE LITTLE
EVIDENCE OF A CRITICAL LAYER NEAR MOUNTAIN TOP (THE INVERSION LOOKS
TO SET UP WELL ABOVE MOUNTAIN TOP WITH THE BEST WARM ADVECTION)...AN
ANOMALOUS PRESSURE GRADIENT AND A SOUTHERLY WIND PROFILE EXCEEDING
60 KNOTS BELOW MOUNTAIN TOP SHOULD SUPPORT HIGH WINDS FOR RENO AND
MANY OTHER AREAS IN THE LEE OF THE SIERRA. STAY TUNED FOR MORE
DETAILS.

BY THE WAY...CHECK OUT OUR WINTER STORM...HIGH WIND...AND SPECIAL
WEATHER STATEMENTS FOR MORE DETAILS OF THE UPCOMING BUSY WEATHER
PATTERN AS MY TIME FOR DISCUSSION WRITING HAS RUN OUT SNYDER

.LONG TERM...SATURDAY THROUGH TUESDAY...
THE DETERMINISTIC RUN OF THE GFS IS SLIGHTLY SLOWER WITH INITIAL
SYSTEM PRIOR TO THIS PERIOD AND AGREES WITH TELECONNECTIONS/SLOWER
ECMWF RUN WHICH KEEPS FLOW OVER THE CENTRAL PACIFIC FLATTER/LESS
AMPLIFIED. THE ECMWF HAS BEEN CONSISTENT WITH THIS SLOWER SCENARIO
AND IS THE PREFERRED SOLUTION THROUGH THE WEEKEND. THIS MEANS THAT
DETAIL IN FEATURES MOVING THROUGH MEAN TROUGH WILL FAVOR A SLIGHTLY
MORE NORTHERN TRACK AND CONTINUE LONGER INTO THE WEEKEND. MOIST
STEEP LAPSE RATES AND VERY COLD AIRMASS WILL FAVOR VERY GOOD SNOW
PRODUCTION. SNOW SHOWERS WILL BE ALMOST CONTINUOUS IN THE SIERRA
THROUGH SUNDAY AND POSSIBLY EARLY SUNDAY NIGHT WITH PERIODS OF
HEAVIER SNOW ASSOCIATED WITH EMBEDDED SHORTWAVES/ADDITIONAL LIFT
WHICH WILL SPILL OVER INTO LOCAL AREAS OF WESTERN NEVADA. TIMING OF
THESE SHORTWAVES AND LOCATION OF MESOSCALE BANDS ARE VERY TRICKY AT
THIS POINT. GENERALLY...SEVERAL INCHES OF SNOW ARE PROBABLE FOR
LOWER VALLEYS WITH 6 TO 8 INCHES IN THE FOOTHILLS. AN ADDITIONAL
COUPLE OF FEET ARE POSSIBLE AT THE CREST ONCE THE STORM FRIDAY NIGHT
AND SATURDAY MORNING WINDS DOWN. SHORTWAVE RIDGE WILL BRING AN
OVERALL BREAK TO PRECIPITATION MONDAY AND TUESDAY ALTHOUGH SOME
LIGHT PRECIPITATION IS STILL POSSIBLE IN WARM ADVECTION...ESPECIALLY
NORTH. IT WILL REMAIN CONSIDERABLY CLOUDY AND COOL WITH TEMPERATURES
KEPT BELOW MOS BOTH DAYS. HOHMANN
&&

.AVIATION...
LIGHT SOUTH WINDS AT SFC WITH INCREASING WINDS/CLOUDS ALOFT THROUGH
03/12Z AS UPPER TROUGH APPROACHES THE WEST COAST. RIDGE WINDS WILL
INCREASE TO 25-35KT/GUSTS 70KT BY THIS AFTERNOON WITH FURTHER
INCREASE TONIGHT AND THURSDAY. INVERSIONS WILL LIKELY HOLD FOR ONE
MORE NIGHT AND MAY RESULT IN A PERIOD OF LLWS 03/06Z-03/18Z AT KRNO
AND LAKE TAHOE AREA TAF SITES. HOHMANN
&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...HIGH WIND WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY
     AFTERNOON FOR NVZ001-003-005.

     WINTER STORM WATCH FROM FRIDAY MORNING THROUGH SATURDAY MORNING
     FOR NVZ002.

CA...WINTER STORM WATCH FROM FRIDAY MORNING THROUGH LATE FRIDAY NIGHT
     FOR CAZ071.

     HIGH WIND WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY
     AFTERNOON FOR CAZ070.

     WINTER STORM WATCH FROM FRIDAY MORNING THROUGH SATURDAY MORNING
     FOR CAZ072-073.
&&

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