Strong Wind in Nevada, February 26, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
426 AM PST FRI FEB 26 2010

.UPDATE...HAVE UPDATED TO INCLUDE A LAKE WIND ADVISORY FOR PYRAMID
LAKE. GUSTY SOUTH TO SOUTHEAST WINDS THIS AFTERNOON AND EVENING
WILL CREATE CHOPPY LAKE WATERS. WINDS WILL ALSO BE GUSTY ACROSS
LAKE TAHOE...BUT WILL NOT BE ISSUING A WIND ADVISORY WITH A WINTER
WEATHER ADVISORY ALREADY IN EFFECT STARTING AT 1 PM PST. OTHERWISE
FORECAST REMAINS ON TRACK. DF

&&

.PREVIOUS DISCUSSION... /ISSUED 301 AM PST FRI FEB 26 2010/

SHORT TERM...
UPPER LEVEL LOW IS BEGINNING OT PUSH INTO NRN CA EARLY THIS
MORNING AS EVIDENT IN WATER VAPOR SAT IMAGERY. WEAK TO MODERATE
RADAR ECHOS ARE BEING PICKED UP ACROSS NRN CA AS OF 10Z AND ARE
EXPECTED TO SPREAD SOUTH AND EAST THROUGHOUT THE DAY AS THE SYSTEM
MOVES ONSHORE.

THE UPPER LOW IS PROGGED TO SPLIT AS IT MOVES INLAND AND THE COLD
FRONT APPROACHES FRIDAY EVENING. THE MOISTURE AND FORCING ALOFT
ARE BRIEFLY FAVORABLE FRIDAY AFTERNOON AND EVENING FOR THE TAHOE
BASIN...BUT THE TENDENCY FOR A SPLITTING SYSTEM WITH THE PARENT
LOW HEADING FOR SOUTHERN CA DOES NOT TREND TOWARDS SIGNIFICANT
ACCUMULATION EAST OF THE SIERRA CREST. THIS IS A FAIRLY WARM
SYSTEM WITH 700 TEMPS AROUND -2 C IN THE WARM SECTOR OF THE
STORM...WHERE THE MAJORITY OF THE PRECIP IS LOCATED...WHICH MEANS
SNOW LEVELS WILL BE AROUND 7000 FEET FOR MUCH OF THE EVENT. THE
SNOW THAT DOES FALL WILL BE HEAVY AND WET WITH LOW SNOW TO WATER
RATIOS. WILL CONTINUE THE WINTER WEATHER ADVISORY FOR THE TAHOE
BASIN ABOVE 7000 FEET WHERE 6 TO 12 INCHES OF SNOW IS LIKELY.

MONO COUNTY WILL BE HARDER HIT FROM THE SOUTHERN BRANCH OF THE
SPLITTING SYSTEM WITH BETTER DYNAMICS...OROGRAPHIC LIFT...AND
DECENT AMOUNTS OF QPF PROGGED ACROSS THE AREA. LOCALLY HEAVY
SNOWFALL IS POSSIBLE...ESP WEST OF HIGHWAY 395...OVERNIGHT INTO
EARLY SATURDAY MORNING. WILL CONTINUE THE WINTER STORM WARNING
ABOVE 7500 FEET FOR MONO COUNTY WITH UP TO A COUPLE OF FEET
POSSIBLE ABOVE 8000 FEET.

SOME PRECIP WILL SPILL OVER INTO WRN NV ON FRIDAY EVENING...BUT
AMOUNTS WILL BE LIMITED IN UNFAVORABLE SOUTHERLY FLOW. BEST
CHANCES FOR PRECIP WILL BE POST COLD-FRONTAL WHEN WINDS BECOME A
BIT MORE WESTERLY OVERNIGHT. THE ONLY PROBLEM IS THAT THE BEST
MOISTURE WILL HAVE PAST BY THIS TIME. SNOW LEVELS WILL DROP BEHIND
THE COLD FRONT...BUT NOT TO WRN NV VALLEY FLOORS. ANY ACCUMULATION
SHOULD BE LIMITED TO ABOVE 5000 FEET WITH ONLY 1-3 INCHES AT BEST
IN THE FOOTHILLS.

RIDGE WINDS ARE A SIGNIFICANT CONCERN WITH THIS SYSTEM WITH MODELS
INDICATING 700 MB WINDS SUSTAINED AROUND 70 MPH. WHILE THIS MAY BE
SLIGHTLY OVERDONE...RIDGE TOP GUSTS AROUND 100 MPH ARE LIKELY WITH
THE STRONGEST GUSTS FROM 21Z-06Z. VALLEYS WILL LIKELY SEE GUSTS
APPROACHING 40-45 MPH DUE TO A TIGHT SURFACE GRADIENT BUT THE
SOUTHERLY FLOW WILL NOT MAKE FOR THE TYPICAL DOWNSLOPE WIND EVENT.
LOCAL WIND PRONE AREAS COULD SEE HIGHER GUSTS...SUCH AS ALONG
HIGHWAY 395 SOUTH OF CARSON CITY WHERE OROGRAPHICS LEAD TO BETTER
WIND CHANNELING. THESE WINDS...COMBINED WITH THE SNOW...WILL
CREATE PERIODS OF WHITEOUT CONDITIONS IN THE HIGHER TERRAIN OF
MONO COUNTY OVERNIGHT.

LIGHT SHOWERS WILL LINGER THROUGH THE SIERRA SATURDAY IN THE
UNSTABLE COLD POOL IN THE WAKE OF THE TROUGH. THESE WILL TAPER OFF
INTO SUNDAY WITH A RIDGE STARTING TO BUILD ACROSS THE WEST SUNDAY
NIGHT INTO MONDAY. DF

LONG TERM...
UPPER LEVEL RIDGE STILL EXPECTED TO LINGER OVER THE GREAT BASIN
ON MONDAY. DRY AND MILD WEATHER IS EXPECTED TO CONTINUE...WITH
HIGH TEMPERATURES REACHING INTO THE MID TO UPPER 50S ACROSS THE
LOWER VALLEYS. SOME MID AND HIGH CLOUDS SHOULD BEGIN SPREADING
ACROSS THE REGION...AS OUR NEXT EPAC SYSTEM MOVES TOWARD THE WEST
COAST.

DEEP UPPER LOW IS SET TO DEVELOP OVER THE GULF OF AK MON-TUE. MODELS
ARE SHOWING A PIECE OF ENERGY SPLITTING FROM THE MAIN TROUGH AND
MOVING THROUGH NORTHERN CA/NV TUE-WED. EURO SEEMS MORE CONSOLIDATED
WITH THE LOW...KEEPING IT SMALLER AND RELATIVELY COMPACT...WHILE THE
GFS IS BROADER WITH THE LOW AND ASSOCIATED MOISTURE. BOTH MODELS DO
SHOW THE MOISTURE FEED GETTING CUT OFF BEFORE IT REACHES OUR
FORECAST AREA...WHICH COULD LIMIT QPF AMOUNTS FOR THE AREA. RIGHT
NOW...IT LOOKS AS THOUGH WE COULD SEE LESS THAN AN INCH QPF ALONG
THE SIERRA CREST. GENERALLY THIS WILL BE A COLDER SYSTEM...WITH SNOW
LEVELS EXPECTED TO DROP TO 4500-5000 FEET BY TUESDAY
NIGHT...POSSIBLY DOWN TO WESTERN NV VALLEY FLOORS EARLY WED MORNING.

COLD CORE CONVECTIVE SHOWERS WILL CONTINUE ACROSS THE REGION ON
WEDNESDAY...WITH THE UPPER LOW OVERHEAD. DEPENDING ON THE TIMING OF
THE LOW...THE SHOWER ACTIVITY COULD END EARLIER ON WEDNESDAY. RIDGING
IS EXPECTED TO BUILD OVER THE WEST COAST THROUGH THURSDAY...WITH
ANOTHER DEEP COLD LOW DROPPING FAST INTO THE PAC NW BY THE END OF
THE WEEK. WITH SOME DECENT MODEL AGREEMENT IN THE LATE WEEK
SYSTEM...WENT AHEAD AND TRENDED POPS HIGHER TO FINISH OUT THE WORK
WEEK.
HOON

AVIATION...
ALL SITES VFR THROUGH ABOUT 21-23Z FRI. WEATHER SYSTEM EXPECTED
TO PUSH THROUGH THE AREA BEGINNING THIS EVENING AND THROUGH FRIDAY
NIGHT. SOUTH-SOUTHWEST WINDS WILL INCREASE THIS AFTERNOON AT ALL
SITES...WITH GUSTS UP TO 35KTS POSSIBLE THROUGH 02Z. PRECIP WILL
START AS RAIN FOR THE SIERRA TERMINALS LATE THIS AFTERNOON...
BECOMING ALL SNOW AFTER 06Z. LIFR CIG/VIS EXPECTED FOR KTVL-KTRK
THROUGH MUCH OF THE NIGHT FROM 06-18Z FRI NIGHT.

STRONG WINDS AT RIDGE TOP WILL CAUSE SOME MODERATE LOW LEVEL
TURBULENCE AROUND THE SIERRA AND WESTERN NV AFT 15Z...SFC TO 160.

FOR KRNO...MAINLY VFR THROUGH THE PERIOD. -SHRA COULD MOVE IN
OVERNIGHT...LOWERING CIG/VIS TO MVFR AT TIMES. SHADOWING WILL LIMIT
ANY SIGNIFICANT MOISTURE FROM COMING DOWN INTO THE LOWER
ELEVATIONS.  HOON

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...LAKE WIND ADVISORY FROM 1 PM THIS AFTERNOON TO 8 PM PST THIS
     EVENING NVZ004.

     WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 10 AM PST
     SATURDAY ABOVE 7000 FEET FOR NVZ002.

CA...WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 10 AM PST
     SATURDAY ABOVE 7500 FEET FOR CAZ073.

     WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 10 AM PST
     SATURDAY ABOVE 7000 FEET FOR CAZ072.

&&

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