FXUS65 KREV 290621 AAB
AFDREV

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RENO NV
1021 PM PST SAT NOV 28 2009

.UPDATE...
EXTENDED LAKE WIND ADVISORY FOR TAHOE THROUGH 10 AM. WINDS WILL
CONTINUE ALL NIGHT WITH STG EAST GRADIENT KEEPING WINDS UP AND
FUNNELING THROUGH PASSES IN CARSON RANGE. EXPECT WINDS TO DIE OFF
MID-MORNING SUNDAY WITH CHOP DIMINISHING. WALLMANN

&&

.PREVIOUS DISCUSSION... /ISSUED 508 PM PST SAT NOV 28 2009/ 

UPDATE...
UPDATED FOR UPSLOPE SNOW SHOWERS IN MONO COUNTY THAT WILL CONTINUE
FOR ANOTHER 2-3 HOURS AT LEAST WEST OF 395 AND SOUTH OF LEE
VINING. TERRAIN INFLUENCE/POSSIBLE MONO LAKE ENHANCEMENT WILL
CONTINUE TO FAVOR JUNE LAKE AREA SO AN ADDITIONAL 3-4 INCHES IS
POSSIBLE THERE WITH UP TO AN INCH ELSEWHERE. WALLMANN

PREVIOUS DISCUSSION... /ISSUED 245 PM PST SAT NOV 28 2009/ 

SHORT TERM...CLOSED LOW THAT BROUGHT RAIN AND SNOW TO THE AREA
ON FRIDAY IS CONTINUING TO DIG SOUTHWARD AND AS OF 22Z IS CENTERED
OVER THE DESERT SOUTHWEST. MOISTURE TRAPPED IN THE DEFORMATION
ZONE CONTINUES TO BRING SCATTERED SHOWERS ACROSS MONO COUNTY.
ADDITIONAL ACCUMULATIONS THROUGH THIS EVENING WILL BE
LIGHT...TAPERING OFF LATE TONIGHT. DRIER AIR ADVECTING INTO THE
CWA WILL KEEP POPS OUT OF THE FORECAST THROUGH TUESDAY.

STRONG EASTERLY SURFACE GRADIENT ALONG WITH 40+ KTS AT 700 MB WILL
KEEP GUSTY WINDS ACROSS THE CWA THROUGH THIS EVENING. HAVE
CONTINUED THE LAKE WIND ADVISORY FOR TAHOE WITH GUSTS OF 35-40 KTS
THROUGH AROUND 10 PM PST. THE STRONGEST WINDS AND HIGHEST WAVES
WILL BE ALONG THE WESTERN SHORE OF THE LAKE...ESP BETWEEN TAHOE
CITY SOUTH TO EMERALD BAY. SEE RNONPWREV FOR ADDITIONAL DETAILS ON
THE ADVISORY. VALLEY WINDS WILL LIGHTEN OVERNIGHT...BUT THE
SIERRA RIDGES WILL CONTINUE TO GUST UP TO 60 KTS. GRADIENT SLOWLY
RELAXES SUNDAY INTO MONDAY BEFORE THE FLOW TURNS WESTERLY BY
MONDAY AFTERNOON.

THE ENE FLOW WILL INHIBIT MUCH WARMING OVER THE NEXT COUPLE OF
DAYS...WITH MANY VALLEYS LIKELY TO BE IN AN INVERSION. WARMING IS
ANTICIPATED BY TUESDAY WITH A RIDGE BUILDING IN OVER THE WEST.

SOME DIFFERENCES IN THE MODELS BEGIN TO CROP UP TUESDAY EVENING
WITH A SHORTWAVE POSSIBLY MOVING INTO THE WEST COAST.
IF...WHEN...AND WHERE IN THE WEST THIS HAPPENS VARIES MODEL TO
MODEL AND RUN TO RUN...THEREFORE CONFIDENCE IS LOW AT THIS POINT.
DF

LONG TERM...WEDNESDAY THROUGH SATURDAY...
MEDIUM RANGE MODELS ARE AGAIN OUT OF SYNCH THROUGH THIS PERIOD
ALTHOUGH THERE ARE SOME HINTS THAT SOME OF THE MODELS ARE CATCHING
ONTO AN ACTIVE TREND IN THE WESTERN/CENTRAL PACIFIC.

FOR MIDWEEK...WEDNESDAY...BOTH THE GFS AND EC CONTINUE TO SPLIT A 
WEAK PIECE OF ENERGY OFF OF A NORTHERN STREAM TROUGH. THE GFS SINKS 
THIS SOUTH OF 30N WHILE THE EC HAS FLIPPED FLOPPED...BRINGING A WEAK 
LOW NOW INTO THE PACNW AND SLIDING IT ACROSS NEVADA ON WED. THIS 
FEATURE WOULD LIKELY BE DRY AND SERVE TO INCREASE WINDS AND CLOUDS A 
BIT AND REINFORCE COOLER TEMPERATURES.

FOR LATER IN THE WEEK INTO NEXT WEEKEND THE MODELS SOLUTIONS ARE 
DRAMATICALLY DIFFERENT. HOWEVER... PER THE HPC EXTENDED DISCUSSION 
THE KEY TO WHAT HAPPENS ACROSS THE SIERRA AND GREAT BASIN MAY DEPEND 
ON EVOLUTION OF A STORM SYSTEM OUT NEAR THE DATELINE EARLY THIS 
WEEK. THE 12Z GFS/CANADIAN/UKMET ALL DEPICT A STORM SYSTEM WHICH 
COULD PUMP UP A STRONG RIDGE IN THE EASTERN PACIFIC. THIS IN TURN 
WOULD SUPPORT HEIGHT FALLS AND COLDER AIR INTO THE PACNW AND WESTERN 
US LATE IN THE WEEK. 

THE LATEST DETERMINISTIC GFS GENERATES AN UPPER LOW ACROSS THE PACNW 
AND RETROGRADES IT ACROSS THE GREAT BASIN OVER THE WEEKEND. THIS 
WOULD PUT US IN A COLD SHOWERY PATTERN WHILE THE LATEST EC SLIDES 
THE UPPER LOW EAST ALONG THE CANADIAN BORDER...PINCHING OFF THE
EASTERN PACIFIC HIGH AND ALLOWING ENERGY TO UNDERCUT THAT RIDGE
INTO THE WEST COAST. THIS WOULD RESULT IN A CHANCE OF SHOWERS FROM
TAHOE NORTH OVER THE WEEKEND AND MILDER TEMPERATURES. THE
UNDERCUTTING SCENARIO HAS BEEN HINTED AT BY SOME GFS ENSEMBLE
MEMBERS AS WELL BUT FOR LATER THAT FOLLOWING WEEK.

TELECONNECTIONS ARE EQUALLY INCONSISTENT. WHEN RUN ON HEIGHT 
ANOMALIES IN THE EASTERN ATLANTIC THE PATTERN POINTS TO A DRY AND 
COOL PERIOD. WHEN RUN ON WEAKER AND LESS DISTINCT ANOMALIES NEAR THE 
DATELINE THE PATTERN IS WETTER ALONG THE WEST COAST.    

SINCE THERE MAY BE A CLUSTERING OF MODEL SOLUTIONS BASED ON STORM 
EVOLUTION NEAR THE DATELINE WENT AHEAD AND INTRODUCED LOW 
CLIMATOLOGY POPS FOR SATURDAY AND SATURDAY NIGHT AND LOWERED 
TEMPERATURES A BIT FOR THE WEEKEND. JAH 

AVIATION...
VFR CONDITIONS ALL TAF ROUTES WITH LIGHT SURFACE WINDS THROUGH 
SUNDAY. EXPECT EASTERLY RIDGE WINDS OF 30KTS TONIGHT SO RETAINED 
MENTION OF LLWS AT BOTH KTVL AND KTRK THROUGH ABOUT 15Z SUNDAY AT 
WHICH TIME UPPER LEVEL WINDS BEGIN TO DECREASE. JAH

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...LAKE WIND ADVISORY UNTIL 10 AM PST SUNDAY FOR NVZ002.

CA...LAKE WIND ADVISORY UNTIL 10 AM PST SUNDAY FOR CAZ072.

&&

$$

HTTP://WEATHER.GOV/RENO