Strong Wind in Nevada, January 12, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
241 AM PST TUE JAN 12 2010

.SHORT TERM...

NEXT 36 HRS WILL BE ACTIVE ACROSS THE REGION WITH A PAIR OF
INCOMING WX SYSTEMS. WITH THIS UPDATE WE'LL BE PUSHING UP START
TIME OF WINTER WX ADVISORY FOR THE SIERRA, POSTING WIND ADVISORIES
FOR PARTS OF THE SIERRA FRONT AND MONO CO FOR TODAY, AND ISSUING A
NEW WINTER WX ADVISORY FOR WRN MONO CO VALID FOR TNGT-WED MORNING.

SHALLOW INVERSIONS AROUND SVE AND NFL/LOL HELPING KEEP PATCHY
DENSE FOG GOING THROUGH THIS MORNING. THOUGH IMMEDIATELY ABOVE
THESE INVERSIONS, WINDS ARE INCREASING (E.G. GUSTS TO 45 MPH AT
SAND SPRINGS PASS EAST OF NFL, WITH LIGHT/VARIABLE WINDS IN DIXIE
VALLEY JUST TO THE EAST). WINDS TODAY ARE A CONCERN, WITH THE
STRONG FLOW ALOFT AND FAVORABLE STABILITY PROFILE FOR MTN WAVE
GENERATION, PER NAM/WRF. PRIMARY AREAS TO WATCH ARE THE TAHOE
BASIN, ALREADY GUSTING INTO THE 30S, AND ALONG SIERRA FRONT SOUTH
OF RENO INTO MONO CO. HIGH RES MODELS SHOWING BEST WIND POTENTIAL
IN THESE AREAS TODAY, WITH GUSTS ABOVE 45 MPH LIKELY, ESPECIALLY
ABOVE 5000-6000 FT. BELOW THAT, GUST POTENTIAL MORE UNCERTAIN
GIVEN NAM BUFR SOUNDINGS SHOWING ONLY MARGINAL LAPSE RATES.

COLD FRONTAL BAND WELL ESTABLISHED ON RADAR MOVING ACROSS NRN CA.
BASED ON RADAR TRENDS AND FRESH MODEL GUIDANCE, HAVE SPED UP ONSET
OF PRECIP AND INCREASED QPF AMTS FROM LASSEN CO SOUTH INTO TAHOE
BASIN FOR TODAY. STILL EXPECTING TWO DISTINCT SYSTEMS: 1) TODAYS
ASSOC WITH JET EXIT REGION AND DEEP MOIST PLUME, 2) LATE TNGT-WED
MORNING WITH SECONDARY SHORTWAVE AND VERY UNSTABLE ATMS. MODEL
CONSISTENCY THE PAST FEW DAYS YIELDS A HIGH CONFIDENCE WITH THE
OVERALL QPF/TIMING FORECAST.

WITH TEMPS IN THE 40S AT TVL/TRK, SNOW LEVELS ARE WELL ABOVE 8000
FT ATTM, BUT SHOULD DROP BACK DOWN TO BETWEEN 6000-7000 FT WITH
HVY PRECIP ONSET. HOWEVER, CONFIDENCE IN SNOW LEVEL FORECAST IS
ONLY MODERATE-LOW FOR TODAY, WITH DIFFS BETWEEN GFS AND NAM
THERMAL PROFILES AND HOW MUCH WET BULBING/COOLING WE'LL SEE IN HVY
PRECIP. EITHER WAY, MAIN PASSES THRU THE SIERRA WILL SEE ACCUM
SNOWS AND TRAVEL PROBLEMS, THEREFORE THE WW.Y START TIME IS
ACCELERATED. A FEW SHOWERS SHOULD SPILL OVER INTO WRN NV TODAY,
BUT MAIN SPILLOVER EVENT WILL BE TNGT-WED MORNING WITH INCREASING
INSTABILITY. SNOW LEVELS WILL FALL TNGT, HELPING GENERATE
WIDESPREAD ADVISORY LEVEL SNOWS IN THE SIERRA. MODEL FCST
SOUNDINGS KEEP PTYPE MAINLY RAIN IN WRN NV VALLEYS THOUGH
FOOTHILLS SHOULD SEE SOME SNOW.

CS

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

MODELS CONTINUE IN EXCELLENT AGREEMENT INTO EARLY NEXT WEEK WITH
EVOLUTION TO A MAJOR PATTERN CHANGE AND VERY ACTIVE WEATHER NEXT
WEEK. VERY HIGH CONFIDENCE FOR THIS TIME PERIOD DUE TO MODEL
AGREEMENT AND THE EXPECTED EVOLUTION OF THE TROPICS. CHGS MADE TO
CONTINUE TO SLOWLY INCREASE POPS FROM SUN NIGHT ONWARD. HAVE ALSO
BEGUN TO ADJUST TEMPS DOWNWARD AS JET WILL REMAIN SOUTH OF THE
AREA AND SNOW LEVELS LOOK TO REMAIN 5500 FEET OR LOWER MOST OF THE
TIME WITH A MAX OF 6000 FEET.

RIDGE WILL MOVE EAST FRI WITH TEMPS COOLING ALOFT AND A LITTLE
INCREASE IN WIND. SPLITTING WK SYSTEM STILL ON TRACK FOR SAT WITH
MAIN EFFECT CLOUDS AND COOLER TEMPS ALOFT. BY SUN NIGHT...FIRST OF
THE SERIES OF SYSTEMS LOOKS TO IMPACT THE AREA. GFS/EC CONTINUE TO
SHOW IT QUITE WET THIS TIME PERIOD INTO MONDAY. SNOW LEVELS MAY
START NEAR 6000 FEET BUT MORE LIKELY 5000-5500 FEET FOR MUCH OF
THE STORM.

LOOKING AHEAD...NEXT STORM TO ARRIVE TUE/TUE NIGHT BUT MAY BE
FOCUSED JUST SOUTH OF THE AREA. SYSTEMS TO ARRIVE QUICKLY
AFTERWARD THROUGH THE WEEK. WITH PERHAPS ONLY A 6-12 HR BREAK
BETWEEN EACH AS THEY RIDE THE 200+ KT PACIFIC JET. REGARDLESS OF
THE EXACT TRACK...THESE SYSTEMS ARE QUITE LARGE SO IT WILL BE
WET...JUST A QUESTION OF HOW MUCH. JET ALSO SHIFTS SOUTH FOR MID-
WEEK WHICH WOULD LIKELY ALLOW COOLER TEMPS AND LOWER SNOW LEVELS.
WALLMANN

&&

.AVIATION...

KRNO...SOME INCREASE IN WINDS THIS MORNING AND SOME LLWS LIKELY
AS WK MTN WAVE FORMS THROUGH 20Z. AROUND 20Z...INITIAL FRONT TO MV
THRU WITH SOME -RA BUT CIGS/VIS SHOULD REMAIN MVFR. WINDS REMAIN A
BIT GUSTY FROM 200 OR SO...BUT AS WINDS WEAKEN ALOFT SEE ONLY
MINOR LLWS <15 KTS SO WL NOT MENTION IN TAF. WINDS WL CONTINUE
OVERNIGHT WITH VFR CONDS. MAIN FRONT TO MV THRU AROUND 12-15Z WED
WITH MVFR CIGS/VIS PSBL IN RA.

KTRK/KTVL...SOME LLWS AT KTVL THIS AM DUE TO SOME DIRECTION AND
SPEED SHEAR BUT SHOULD ABATE AFT 18Z. RA TO SPREAD OVER THE
TERMINALS BY 18Z WITH MVFR CIGS/VIS IN RA. ABT 25 PCT CHC OF CIGS
BLO LANDING MINS AT KTVL THROUGH 00Z. BREAK WITH SOME MVFR CIGS
AFTERWARD THEN MORE -SN AFT 08Z TONIGHT AS MAIN SYSTEM MOVES IN
AND SNOW LEVELS LOWER. IFR/CIGS VIS EXPECTED AT THAT TIME BLO
AIRPORT MINS. WALLMANN

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WIND ADVISORY FROM 7 AM THIS MORNING TO 6 PM PST THIS EVENING
     FOR NVZ003.

     LAKE WIND ADVISORY UNTIL 6 PM PST THIS EVENING FOR NVZ002.

     WINTER WEATHER ADVISORY FROM 7 AM THIS MORNING TO 10 AM PST
     WEDNESDAY FOR NVZ002.

     LAKE WIND ADVISORY FROM 10 AM THIS MORNING TO 5 PM PST THIS
     AFTERNOON FOR NVZ004.

CA...WINTER WEATHER ADVISORY UNTIL 10 AM PST WEDNESDAY FOR CAZ071.

     WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 1 PM PST
     WEDNESDAY FOR CAZ073.

     WIND ADVISORY FROM 7 AM THIS MORNING TO 6 PM PST THIS EVENING
     FOR CAZ073.

     LAKE WIND ADVISORY UNTIL 6 PM PST THIS EVENING FOR CAZ072.

     WINTER WEATHER ADVISORY FROM 7 AM THIS MORNING TO 10 AM PST
     WEDNESDAY FOR CAZ072.

&&

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