FXUS65 KREV 230534
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
934 PM PST TUE DEC 22 2009

.UPDATE...
BUOYS ON LAKE TAHOE HAVE INCREASED A BIT MORE AND KTVL CONTINUES
TO SHOW GUSTY WINDS AROUND 20KT. WINDS ATOP WARD PEAK HAVE ALSO
INCREASED A BIT WITH LATEST READINGS SHOWING GUSTS TO 70 MPH. ERLY
PRESSURE GRADIENT HAS INCREASED A BIT AND LATEST MODEL PROGS SHOW
THIS STRONGER GRADIENT CONTINUING INTO WEDNESDAY MRNG. WINDS IN
THE WRN NV AND SIERRA VALLEYS HAVE STARTED TO DECOUPLE AND WITH
SKIES CLEARING AND A LITTLE FRESH SNOW COVER TEMPS ARE FALLING A
BIT FASTER THAN FORECAST. WILL DROP TEMPS IN WRN NV AND SOME
SIERRA VALLEYS A FEW DEGREES TONIGHT BUT WILL LEAVE TEMPS NEAR THE
LAKE ESSENTIALLY AS IS. WILL SHOW A BIT MORE OF AN INCREASE IN
WINDS AND WAVE AT LAKE TAHOE TONIGHT AND EARLY WEDNESDAY BUT WILL
HOLD IT JUT BELOW LAKE WIND ADVISORY CRITERIA. MLF

&&

.PREVIOUS DISCUSSION... /ISSUED 711 PM PST TUE DEC 22 2009/ 

UPDATE...
SNOW SHOWERS THAT WERE OVER THE FAR WESTERN PORTIONS OF NEVADA AND
THE LAKE TAHOE AREA HAVE DISSIPATED BUT A FEW ISOLATED SHOWERS MAY
CONTINUE ACROSS PORTIONS OF MONO COUNTY AND EAST INTO MINERAL
COUNTY THROUGH THE EVENING HOURS. STILL DO NOT EXPECT MUCH
ACCUMULATION. WINDS ON LAKE TAHOE HAVE INCREASED AS NOTED ON BUOYS
MID LAKE. ALSO NOTED THAT WINDS AT WARD PEAK HAVE INCREASED FROM
THE NORTHEAST. WINDS AT KTVL HAVE ALSO INCREASED FROM THE
NORTHEAST. NOT ATYPICAL FOR LAKE WINDS TO INCREASE AT NIGHT WHEN
ERLY GRADIENT INCREASES. HAVE OPTED TO BUMP UP THE LAKE WINDS JUST
A BIT OVERNIGHT WITH A CORRESPONDING INCREASE IN WAVE HEIGHTS. WILL
KEEP LAKE WINDS JUST BELOW ADVISORY CRITERIA. OTHERWISE NO
FURTHER UPDATES...BUT WILL NEED TO KEEP A CLOSE EYE ON TEMPS THIS
EVENING AS SKIES CLEAR AND WINDS DECREASE. MLF

PREVIOUS DISCUSSION... /ISSUED 401 PM PST TUE DEC 22 2009/ 

SHORT TERM...
LINGERING -SHSN CONTINUE TO MOVE SOUTH ACROSS PARTS OF THE SIERRA
AND FAR WRN NV INCLUDING THE RENO METRO AREA AS LINGERING INSTBY
AND CYCLONIC FLOW CONTINUES OVER THE REGION. SOME LOCAL
ACCUMULATIONS OF AN INCH OR TWO MAY OCCUR IN UPSLOPE AREAS OF MONO
COUNTY AND NEAR SOUTH SHORES OF AREA LAKES THRU EARLY THIS
EVENING...BUT NOT EXPECTING ANY SIGNIFICANT SNOWFALL. COLD POOL
ALOFT WILL EXIT THE REGION LATER THIS EVENING AS AIR MASS
CONTINUES TO DRY OUT. WHILE WINDS WILL DECREASE IN THE LOW LEVELS
THIS EVENING...NE RIDGE WINDS WILL BECOME STRONG TONIGHT AT RIDGE
LEVEL WITH GUSTS NEAR 100 MPH POSSIBLE IN THE HIGH SIERRA. THE AIR
MASS HAS BEEN THOROUGHLY MIXED OUT TODAY AND WITH LITTLE MELTING
DURING THE DAY THE POTENTIAL FOR VALLEY FOG IS LOW FOR WED
MORNING.

FROM WED-FRI...RIDGE WILL BUILD OFF THE WEST COAST AND MOVE SLOWLY
INLAND...KEEPING THE REGION DRY WITH LIGHT WINDS. RIDGE LEVEL
WINDS WILL DIMINISH WEDNESDAY AND WED NIGHT. WHILE INVERSION
CONDITIONS WILL FORM AGAIN AS THE RIDGE APPROACHES...IT DOES NOT
LOOK AS STRONG AS THE PREVIOUS INVERSION. WHILE VALLEY FOG POTENTIAL
WILL INCREASE STARTING WED NGT AND CONTINUE THRU FRI NIGHT...THE
EXTENT AND PERSISTENCE OF THE FOG SHOULD BE MORE LIMITED IN
COMPARISON TO LAST WEEK.

MAX TEMPS WILL REMAIN BELOW NORMAL WITH SEVERAL COLD NIGHTS
EXPECTED WITH LOWS IN THE SINGLE DIGITS OR TEENS. A FEW OF THE
COLDER VALLEYS IN WRN NV WITH EXISTING SNOW COVER MAY DIP BELOW
ZERO DURING THE NEXT COUPLE OF NIGHTS...ALTHOUGH NEW SNOWFALL FROM
LAST NIGHT WAS LESS THAN 1 INCH AND WOULD PROBABLY NOT COMPARE TO
THE EXTREME COLD THAT OCCURRED ABOUT 2 WEEKS AGO. MJD

LONG TERM...SATURDAY THROUGH TUESDAY...
AN UPPER RIDGE WITH THE AXIS CENTERED OVER WASHINGTON AND OREGON 
WILL REMAIN IN PLACE UNTIL A CUT OFF LOW BEGINS TO ENCROACH FROM THE 
WEST. WITH THE RIDGE OVERHEAD...INVERSION CONDITIONS WILL LIKELY 
REMAIN THROUGH SATURDAY MORNING SO MENTION OF FZFG WILL REMAIN IN 
THE FORECAST. THE FOG MAY LIFT EARLIER SATURDAY MORNING THAN 
PREVIOUS DAYS DUE TO HIGH CLOUDS MOVING IN WITH THE APPROACHING LOW 
ALONG WITH SLIGHTLY STRONGER SOUTHWEST FLOW ALOFT. HOWEVER...WINDS 
DO NOT LOOK STRONG ENOUGH TO BREAK VALLEY INVERSIONS SO TEMPS WILL 
REMAIN BELOW NORMAL. 

IT IS STILL UNCLEAR WHETHER OR NOT WE WILL RECEIVE A GLANCING BLOW 
OF PRECIPITATION FROM THIS APPROACHING DISTURBANCE. THE ECMWF HAS A 
MORE PROGRESSIVE SOLUTION WITH A DEEPER AND MORE DEFINED LOW 
CENTERED OVER THE CENTRAL CALIFORNIA/NEVADA BORDER WITH A 
SOUTHEASTWARD TRACK BY SUNDAY AFTERNOON. THIS SOLUTION PRESENTS 
LIGHT QPF FOR THE WESTERN HALF OF THE CWA SUNDAY NIGHT INTO MONDAY 
AND IS SLIGHTLY COLDER WITH SNOW LEVELS REACHING VALLEY FLOORS. THE 
GFS OPERATIONAL AND ABOUT HALF OF THE ENSEMBLE MEMBERS SHOW THE 
CENTER OF THE LOW SLIDING DOWN THE CALIFORNIA/NEVADA BORDER WITH 
BARELY ANY QPF REPRESENTED SUNDAY NIGHT. HAVE MENTIONED SLIGHT 
CHANCE OF PRECIP SUNDAY NIGHT INTO MONDAY MORNING BUT WILL KEEP AN 
EYE ON THE LOW TRACK IN FUTURE MODEL RUNS. BOTH MODELS KEEP THE JET 
ASSOCIATED WITH THE LOW WELL SOUTH OF THE REGION...SO WINDS WILL NOT 
BE AN ISSUE THROUGH THE LONG TERM PERIOD. 

TEMPERATURES WERE LOWERED SLIGHTLY TO REFLECT THE TREND OF THE LOW 
DIGGING DEEPER THAN PREVIOUSLY THOUGHT. MAX TEMPERATURES WILL MOST 
LIKELY REMAIN BELOW NORMAL DUE TO INVERSION CONDITIONS BUT MINIMUM 
TEMPS WILL LIKELY NOT BE AS COLD DUE TO CLOUD COVERAGE ASSOCIATED 
WITH THE LOW. -LABELLE-

AVIATION...
FOR KTVL-KTRK-KLOL...ISOLATED SNOW SHOWERS ARE PASSING THROUGH THE 
REGION FROM THE NORTHEAST. ANY ADVERSE CONDITIONS WILL BE SHORT 
LIVED. WINDS WILL REMAIN LIGHT THROUGH TOMORROW AFTERNOON. 

FOR KRNO...ISOLATED SNOW SHOWERS ARE PASSING THROUGH FROM THE NORTH 
AND WILL MOST LIKELY BE SHORT LIVED. VFR CONDITIONS WILL RETURN  
BY 01Z. CEILINGS WILL LIFT AS THE SNOW SQUALL PASSES AND WINDS WILL 
REMAIN LIGHT FROM THE NORTH. SKIES WILL CLEAR BEFORE 12Z WITH 
VARIABLE WINDS THROUGH WEDNESDAY AFTERNOON. -LABELLE-

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
CA...NONE.
&&

$$

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