Strong Wind in Nevada, March 24 to 25, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
320 PM PDT WED MAR 24 2010

.SHORT TERM...
TWO FAST MOVING SHORTWAVES SPAWNING FROM A LOW PRESSURE SYSTEM
CENTERED OFF THE COAST OF WA WILL MOVE ACROSS THE AREA TONIGHT AND
TOMORROW...BRINGING GUSTY WINDS AND LIGHT PRECIPITATION THROUGH MOST
OF THE SHORT TERM PERIOD. THE CENTER OF THE LOW WILL MOVE OVER
THE NORTHWESTERN STATES BY TOMORROW EVENING.

WINDS WILL BE THE MAIN STORY OF THIS EVENT AS THEY INCREASE THIS
EVENING AS THE FIRST TROUGH APPROACHES THE COAST TONIGHT. THE LOCAL
ARW MODEL RUN ALONG WITH THE NAM AND GFS INDICATE STRONG SURFACE
WINDS BEGINNING TONIGHT AND PERSISTING THROUGH TOMORROW MORNING. THE
PROGGED WIND DIRECTION IS COMMON FOR A DOWNSLOPE EVENT BUT THE CROSS
SECTION ANALYSES DO NOT INDICATE A CRITICAL LAYER DEVELOPING OVER
THE CREST. HAVE ELECTED TO GO WITH AN ADVISORY TONIGHT THROUGH
TOMORROW MORNING ALONG THE SIERRA AND AREAS EAST. WINDS WILL
CONTINUE TO BE GUSTY THROUGH TOMORROW EVENING AS THE SECOND...WEAKER
SHORTWAVE PUSHES THROUGH.

PRECIP WITH THIS SYSTEM WILL BE LIMITED TO NORTHEASTERN CA AND THE
SIERRA FROM TAHOE NORTHWARD AS THE FIRST SHORTWAVE MOVES THROUGH. 2
TO 4 INCHES EXPECTED ALONG THE CREST WITH TRACE AMOUNTS POINTS
EAST. WESTERN NEVADA COULD SEE SOME LIGHT SHOWERS OR FLURRIES DUE
TO THE STRONG WINDS PUSHING SHOWERS FURTHER EAST...BUT THEY WILL
MOST LIKELY BE SHORT LIVED. A CHANCE OF ISOLATED SHOWERS LINGERS
THROUGH TOMORROW AFTERNOON HOWEVER...AS THE LEFT EXIT REGION OF
THE UPPER LEVEL JET COULD PROVIDE SOME FORCING ACROSS THE WESTERN
ZONES. TEMPERATURES WILL DROP CONSIDERABLY TOMORROW MORNING
FOLLOWING THE COLD FRONT...DROPPING SNOW LEVELS TO AROUND 4500
FEET BY SUNRISE. THE SECOND WAVE WILL BRING ANOTHER LIGHT BOUT OF
PRECIP THURSDAY EVENING TO THE SIERRA...BUT QPF WILL AGAIN BE
LIMITED.

THE LOW WILL DEPART TO THE EAST FRIDAY MORNING AS A LONGWAVE RIDGE
BUILDS IN BEHIND IT. TEMPERATURES WILL HAVE A CHANCE TO REBOUND
THROUGH THE WEEKEND WITH SUNNY CONDITIONS AND LIGHT WINDS. LABELLE

.LONG TERM...SATURDAY THROUGH WEDNESDAY...
RIDGE IN PLACE FOR SATURDAY WILL MOVE INTO THE ROCKIES SUNDAY AS
PACIFIC JET NEARS THE WEST COAST.  AS USUAL GFS IS FASTER TO BREAK
DOWN THE RIDGE...AND HAS LESS AMPLIFIED PATTERN OVER THE PACIFIC AND
NORTH AMERICA WITH UNUSUALLY DEEP LOWS OVER THE THE BERING
SEA...GULF OF ALASKA AND EASTERN CANADA.  THUS WILL LEAN TOWARD THE
MORE AMPLIFIED ECMWF THROUGH THE PERIOD.

WEEKEND TO BE WARM AND DRY WITH BREEZY CONDITIONS POSSIBLE WITH THE
JET NORTH OF THE AREA.  THERE IS ONE SYSTEM THAT MAY BRUSH AREAS
NORTH OF SUSANVILLE-GERLACH ON SUNDAY...BUT WITH DRY CONDITIONS
BELOW 10000 FEET THE CHANCE OF RAIN IS VERY LOW.  TEMPERATURES WILL
WARM INTO LOW 70S FOR WESTERN NEVADA SUNDAY AND MONDAY WITH
INCREASED MIXING.

A FEW CONCERNS FOR THE TRANSITION TO A COOLER/WETTER PATTERN TUESDAY
AND WEDNESDAY.  GFS ENSEMBLE SPREADS ARE VERY HIGH IN THE CENTRAL
PACIFIC...DUE TO VARYING AMPLITUDES OF THE RIDGE FORECAST TO DEVELOP
NEAR 160W.  THIS WILL DETERMINE THE TRACK OF THE COLD GULF OF ALASKA
SYSTEM...AS A JET SHOULD DEVELOP ON THE BACK SIDE OF THE TROUGH.
12Z ECMWF IS MIDDLE OF THE ROAD WITH TRACK AND TIMING...WHERE THE
12Z GFS IS TOO PROGRESSIVE DUE TO A LACK OF AMPLIFICATION.  06Z GFS
AND A FEW 12Z GFS ENSEMBLES SPLIT ENERGY DOWN THE CALIFORNIA COAST.
THIS WOULD LIMIT THE AMOUNT OF ENERGY/LIFT FOR THE SIERRA AND
PRODUCE LESS QPF.

HAVE FOLLOWED THE ECMWF TUESDAY AND WEDNESDAY WHICH BRINGS RAIN/SNOW
INTO THE NORTHERN SIERRA TUESDAY WITH THE FRONT AND COLD POOL
PASSING OVER WESTERN NEVADA TUESDAY NIGHT AND WEDNESDAY. IF THE COLD
POOL PASSES OVERHEAD SNOW LEVELS SHOULD EASILY LOWER TO VALLEY
FLOORS TUESDAY NIGHT/WEDNESDAY MORNING.

FOR THE SIERRA...QPF AMOUNTS UP TO AN INCH ARE POSSIBLE WHICH COULD
TRANSLATE INTO A SIGNIFICANT AMOUNT OF SNOW TUESDAY NIGHT AND EARLY
WEDNESDAY. STRONG WINDS ALSO A CONCERN WITH THE JET OVERHEAD.

ACROSS WESTERN NEVADA AND THE EASTERN SIERRA...INITIAL CONCERN IS A
POTENTIAL DOWNSLOPE WIND EVENT WITH THE JET AND FRONT DROPPING
TEMPERATURES 20-25 DEGREES FROM MONDAY TO WEDNESDAY.  RAIN/SNOW IS
POSSIBLE WITH THE FRONTAL PASSAGE AND COLD POOL ALOFT TUESDAY NIGHT
AND WEDNESDAY.  BRONG

&&

.AVIATION...

WINDS ARE THE MAIN CONCERN TONIGHT AS TROUGH PASSES OVERHEAD.
SUSTAINED RIDGE WINDS OF 45-60 KTS LIKELY 03Z-12Z...WITH GUSTS OF
35-45KTS IN THE LOWER VALLEYS.  MOUNTAIN WAVES LIKELY TO DEVELOP AS
THE FLOW ALOFT IS PERPENDICULAR TO THE SIERRA CREST.  ALSO POTENTIAL
LLWS AT THE TERMINALS 09Z-12Z AS THE FRONT NEARS.

FOR KTVL AND KTRK...GOOD CONFIDENCE A BURST OF SNOW ALONG THE FRONT
08Z-12Z WILL DROP VISIBILITIES DOWN TO 1 MILE OR LESS.  BEFORE THE
SNOW ARRIVED GUSTS TO 40 KTS ARE POSSIBLE.

FOR KRNO...SUSTAINED SOUTH-SOUTHEAST WINDS COULD EXCEED 25KTS WITH
GUSTS AS HIGH AS 40-45KTS AHEAD OF THE FRONT.  AS THE FRONT
APPROACHES 09Z-12Z...FLOW ALOFT SHIFTS TO THE WEST AND INCREASES THE
POTENTIAL FOR LOW LEVEL WIND SHEAR.  WINDS TO REMAIN GUSTY THROUGH
THURSDAY AFTERNOON.  BRONG

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WIND ADVISORY FROM 8 PM THIS EVENING TO 8 AM PDT THURSDAY
     NVZ002-003.

CA...WIND ADVISORY FROM 8 PM THIS EVENING TO 8 AM PDT THURSDAY
     CAZ072-073.

&&

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