Snow Advisory 5, NWS Reno, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
345 AM PST TUE FEB 14 2006

.SHORT TERM...
INITIAL WEAK SURFACE FRONT CURRENTLY MOVING ACROSS NRN NEVADA
KICKING UP SOME CLOUDS AND POSSIBLY VIRGA SHOWERS AS WELL AS
INCREASING NW WINDS. WINDS WILL INCREASE LATER TODAY CWA-WIDE AS
DIURNAL EFFECTS HELP TO ORGANIZE THE MAIN COLD FRONT W-E OVER THE
NRN ZONES WHICH WILL TIGHTEN GRADIENTS SIGNIFICANTLY. MODELS ARE
TRYING TO COME TO A CONSENSUS ON TIMING OF THE FRONT WITH THE LATEST
SOLUTIONS PUSHING THE FRONT ACROSS THE NRN ZONES THIS EVENING AND
INTO THE RENO AREA RIGHT AROUND SUNRISE TOMORROW MORNING. MOISTURE
ALONG THE FRONT REMAINS SHALLOW UNTIL UPPER FORCING MOVES OVER THE
NRN ZONES THIS EVENING ENHANCING UPWARD MOTION. LATEST MODEL RUNS
HAVE MORE FAVORABLE JET DYNAMICS AND ARE SLOWLY INCREASING QPF WITH
EACH RUN...SO WILL ISSUE SNOW ADVISORY FOR NRN WASHOE AND THE
SURPRISE VALLEY FOR TONIGHT. ALSO CONCERNED ABOUT SNOW ALONG THE
INTERSTATE 80 CORRIDOR DEPENDING ON WHERE THE BEST SURFACE GRADIENT
SETS UP BUT WILL LET DAY SHIFT LOOK INTO IT.

WINDS ACROSS THE NRN HALF OF THE CWA WILL BE GUSTY TONIGHT RIGHT
ALONG THE FRONT BUT NOT EXPECTING WIDESPREAD ADVISORY LEVELS AT THIS
TIME WITH NOCTURNAL FRONTAL PASSAGE. WINDS OVER MONO AND MINERAL
COUNTIES ARE MORE OF A CONCERN DURING THE DAY WEDNESDAY JUST AHEAD OF
THE FRONT. WIND STATEMENTS MAY BE NEEDED IN THOSE ZONES DEPENDING
ON WHEN THE FRONT MOVES THROUGH. PRECIP IS NOT MUCH OF A CONCERN
SOUTH OF HIGHWAY 50 WITH LITTLE UPPER SUPPORT. SHOWERS WILL TAPER
OFF THURSDAY NIGHT AND FRIDAY IN BETWEEN UPPER WAVES...SO TRIMMED
POPS BACK DURING THOSE PERIODS. LONGWAVE TROUGH ORIENTS ITSELF
NEARLY E-W OVER THE NRN CONUS WITH THE NEXT BATCH OF SHORTWAVE
ENERGY MOVING INTO NRN CALIFORNIA THURSDAY NIGHT BRINGING INCREASING
CHANCES FOR PRECIP. JORDAN
&&

.LONG TERM...FRIDAY THROUGH MONDAY...
PATTERN REMAINS VERY COLD AND UNSETTLED THROUGH THE WEEKEND INTO
MONDAY. POTENTIAL FOR SIGNIFICANT SNOW IN THE SIERRA AND WESTERN
VALLEYS EXISTS FOR SAT-SUN TIMEFRAME. AMOUNTS WILL BE DETERMINED BY
THE EVENTUAL POSITION OF THE UPPER LOW OFF OF THE PACNW COAST AND
THE RESULTANT FETCH OFF OF THE EASTERN PACIFIC.

OVERALL THROUGH THE PERIOD THE ECMWF AND GFS ARE IN THE BEST
AGREEMENT. UKMO IS THE OUTLIER. SATURDAY ECMWF/GFS POSITION COLD
DEEP UPPER LOW NORTH AND WEST OF SFO WITH THE ECMWF INDICATING
HIGHER HEIGHTS. UKMO HAS TROF FURTHER EAST/INLAND WITH VIRTUALLY NO
FETCH OFF THE PACIFIC. BY SUNDAY THE ECMWF/GFS OPEN UP THE UPPER LOW
AND MOVE A POSITIVELY TILTED TROUGH ACROSS THE GREAT BASIN. CORE OF
TROUGH IS RIGHT OVER TAHOE AREA WITH 500MB TEMPS AROUND -34C AND
700MB TEMPS -14C.  VERY STEEP 700MB-500MB LAPSE RATES ASSOCIATED
WITH UPPER LOW EXCEEDING 8C/KM SAT AND ESPECIALLY SUNDAY AS
UPPER TROUGH MOVES ACROSS AREA.

MAIN QUESTION FOR HEAVY SNOW IN WESTERN VALLEYS IS WHERE UPPER LOW
SETS UP. CURRENT RUNS RETROGRADE LOW TO 40N/128W BY EARLY SATURDAY
MORNING WHICH IS SOUTH OF FAVORED POSITION FOR HEAVY SNOW IN RENO
AREA. IN ADDITION THE EASTERN PAC RIDGE IS MORE POSITIVELY TILTED
WHICH WOULD INHIBIT THE MOISTURE FETCH ACROSS THE
PACIFIC...ENTRAINING COLD DRIER AIR FROM WESTERN CANADA INTO THE
SYSTEM. NEVERTHELESS...DYNAMICS WITH UPPER LOW WILL BE STRONG ENOUGH
FOR SIGNIFICANT PRECIPITATION BOTH SIERRA AND VALLEYS. SATURDAY
DIVERGENCE ALOFT IN ADVANCE OF LOW WILL PROVIDE SOME LIFT...ALTHOUGH
EXPECT STRONGEST LIFT SATURDAY NIGHT INTO SUNDAY AS UPPER LOW MOVES
ACROSS AREA. JAH
&&

.AVIATION...
VFR WITH LIGHT WINDS THROUGH TUESDAY AFTERNOON. STRONG ARCTIC COLD
FRONT WILL MOVE FROM NORTHERN NV THROUGH TAHOE AND RENO AREAS BY 12Z
WED. EXPECT A PERIOD STRONG GUSTY WINDS AHEAD OF AND WITH THE FRONT
WITH POSSIBLE BRIEF MVFR/IFR CONDITIONS IN SNOW. JAH
&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...SNOW ADVISORY FOR ZONE 005 FROM 7 PM TO 7 AM PST TONIGHT.
CA...SNOW ADVISORY FOR ZONE 070 FROM 7 PM TO 7 AM PST TONIGHT.
&&

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