917
FXUS65 KREV 091103
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
300 AM PST TUE FEB 9 2010
SHORT TERM
BAND OF LIGHT SNOW SHOWERS MOVED THROUGH THE RENO-TAHOE AREA AROUND
MIDNIGHT...PROGRESSING EAST OF THE RENO AREA. DIDN'T SEE MUCH OUT OF
THIS...BUT IT WAS ENOUGH FOR A DUSTING AT THE NWS OFFICE HERE AT
5000 FEET. IR IMAGERY IS SHOWING SOME COOLING CLOUD TOPS OVER
NORTHERN CA/WESTERN NV ASSOCIATED WITH DIFFLUENCE ALOFT FROM THE
UPPER LOW JUST OFF THE CALIFORNIA COAST...WHICH IS PROMISING FOR
SOME INCREASING SHOWERS THIS MORNING. THE LOW IS MOVING QUICKLY DOWN
THE COAST...AND MAY EVEN BE FASTER THAN SOME OF THE MODELS ARE
CURRENTLY SUGGESTING.
THE TRACK OF THE LOW HAS TRENDED FURTHER WEST OVER THE LAST 24
HOURS...WHICH HAS IN TURN PULLED INSTABILITY/FRONTOGENESIS AND
QPF/SNOW FURTHER WEST AS WELL. THIS WAS A POSSIBILITY THAT WE WERE
AWARE THAT COULD HAPPEN...AND NOW IT LOOKS LIKE WE AREN'T GOING TO
SEE MUCH AT ALL. INSTABILITY WILL BE LIMITED...ONLY LOOKING AT
MARGINAL INSTABILITY COMPARED TO WHAT WE WERE EXPECTING THE LAST
COUPLE DAYS. STILL ENOUGH TO SEE SOME NUMEROUS TO SCATTERED SHOWERS
THROUGH THE DAY...BUT DEFINITELY MUCH LESS THAN PREVIOUSLY FORECAST.
MOST OF THE SHOWER ACTIVITY WILL BE SOUTH OF HIGHWAY 50 THIS
AFTERNOON WITH VERY SPOTTY ACCUMULATIONS DUE TO THE CONVECTIVE
NATURE OF THE PRECIP. COULD SEE SOME ENHANCED ACCUMULATIONS IN THE
EASTERN SLOPES OF MONO COUNTY THIS AFTERNOON AND EVENING...WITH SOME
LIGHT EAST/UPSLOPE FLOW ENHANCING THE LIFT. BUT EVEN THAT DOESN'T
LOOK ALL THAT GOOD ANYMORE WITH ONLY 5-10 KTS EAST FLOW AT 700MB.
BOTTOM LINE...SNOW ACCUMULATIONS WILL BE VERY SPOTTY TODAY. SOME
LOCATIONS WILL SEE NO SNOW AT ALL. OTHERS WILL SEE AN INCH OR TWO IF
THEY GET UNDERNEATH ONE OF THE HEAVIER SHOWERS. AS FOR THE RENO
AREA...WE MAY NOT SEE MUCH AT ALL...WITH MOST OF THE SHOWER ACTIVITY
SHIFTING QUICKLY TO THE SOUTH BY AFTERNOON.
SHOULD SEE AN INCREASE IN SHOWER ACTIVITY ALONG THE SIERRA CREST
THROUGH MORNING...BUT THEN QUICKLY SHIFTING THE FOCUS SOUTHWARD THIS
AFTERNOON AS THE LOW PULLS SOUTH OF THE BAY AREA. LOWERED POPS THIS
AFTERNOON NORTH OF HIGHWAY 50...AS SHOWERS BECOME MORE SCATTERED TO
ISOLATED WITH THE DECREASING INSTABILITY. DAY SHIFT MAY NEED TO CUT
THESE COMPLETELY IF IT LOOKS LIKE THE LOW IS MOVING FASTER THAN
FORECAST. ALSO...INCREASED TEMPERATURES FOR TODAY AS THE COLDEST AIR
IS NOW EXPECTED TO REMAIN WELL TO THE WEST OF OUR AREA...BUT SNOW
LEVELS WILL STILL BE AROUND 4000-4500 FEET SO MOST VALLEYS WILL
STILL SEE SNOW SHOWERS EXCEPT FOR AROUND THE LOWEST VALLEYS SUCH AS
THE CARSON SINK WHERE IT WILL BE MIXED SHOWERS.
SHOULD SEE WARMER AND DRIER CONDITIONS BY WEDNESDAY AS A SHORT WAVE
RIDGE MOVES OVERHEAD. NEXT STORM SYSTEM APPROACHES THE CA/OR COAST
BY LATE THURSDAY...WITH INCREASING CLOUD COVER AND CHANCES OF PRECIP
IN THE SIERRA NORTH OF TAHOE. HOON
LONG TERM (THURSDAY NIGHT THROUGH MONDAY)
MEAN HGTS FOR PD POINT TO FLAT RDG ACRS THE WRN CONUS WITH PAC
SYSTEMS TO BE DEFLECTED INTO THE PACNW BYND FRI. MODELS HAVE BACKED
OFF A BIT ON THE SYST FRI WITH THE ECMWF MUCH DRIER AND FURTHER NWD.
THE FCST WAS KEPT CLOSER TO THE GFS WHICH MAINTAINED ITS PREV
THINKING ALTHOUGH PERHAPS A BIT SLOWER/FURTHER NORTH AND OPEN WITH
ITS S/W FEATURE. POPS WERE REDUCED MOST AREAS THU NGT AND IN SRN ZNS
FRI TO TREND IN THE DIRECTION OF THE ECMWF. NOT A BIG WEATHER MAKER
NONETHELESS WITH SNOW LVLS ABV LOWER VLY FLOORS AND ONLY BRIEF
IMPACTS TO TRAVEL ACRS THE SIERRA LATE THU NGT-FRI. RDG AND MUCH
WARMER AIRMASS OVR THE WEEKEND INTO EARLY NEXT WEEK WITH WK S/W
ENERGY AND LOW POPS STILL POSSIBLE ACRS THE NRN PART OF THE FCST
AREA. TEMPS NEAR OR SLIGHTLY BELOW NORMAL FRI WL FINALLY RISE THIS
WEEKEND WITH 40S AND 50S MANY AREAS. HOHMANN
AVIATION
COLD UNSTABLE SYSTEM DROPPING SWD ALG/JUST OFF W COAST THIS MRNG...
A BIT FURTHER WEST THAN PREV THINKING. THIS WL RESULT IN HEAVIEST
SHOWERS STAYING OVR CA AND WEST OF CREST WITH MORE SCATTERED AND
LIGHTER ACTVTY ACRS WRN NV/SIERRA. BAND OF SNOW OVR WRN NV THIS MRNG
WL CONT TO LIFT NWD AND SLOWLY DIMINISH THRU 15Z WITH LGT ACCUM
MAINLY ABV 5000 FT. AS UPR LOW TRACKS SWD THRU THE DAY EMPHASIS FOR
SHOWERS WL SHIFT TO THE ERN SIERRA OF MONO CO WHERE PDS OF IFR/MTS
OBSCUREMENT WL PREVAIL FOR ABOUT 6 HRS THIS AFTN.
FOR KRNO...PDS OF LGT SNOW WL TAPER EARLY THIS MRNG AND END BY 15Z.
FLIGHT RESTRICTIONS MAINLY MVFR WITH MT OBSCUREMENT. IMPROVING CONDS
15Z-18Z WITH SCT -SHSN/MT TOP OBSCUREMENT AND ONLY OCNL MVFR CONDS
18Z-00Z. NO SNOW ACCUM EXPECTED ON THE RUNWAY.
FOR KTVL/KTRK...SCT-NMRS -SHSN/MT OBSCUREMENT IN LOW CLOUDS TODAY
WITH OCNL IFR CONDS IN BRIEF HEAVIER SHSN. ONLY LGT SNOW ACCUM ON
RUNWAYS. CONDS WL IMPROVE RAPIDLY FROM N-S EARLY TNGT. CLEARING WL
ALLOW FOR PATCHY FZFG AT KTRK AFT 10/08Z WITH 3-5SM BR AT KTVL.
REV WATCHES/WARNINGS/ADVISORIES
NV...NONE.
CA...NONE.
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