MESOSCALE DISCUSSION 2243
   NWS STORM PREDICTION CENTER NORMAN OK
   1134 PM CST WED DEC 19 2007
   
   AREAS AFFECTED...NRN/CNTRL SIERRA MTNS OF CA
   
   CONCERNING...HEAVY SNOW 
   
   VALID 200534Z - 200930Z
   
   HEAVY SNOW WILL GRADUALLY SHIFT SWD OVERNIGHT WITH SNOWFALL RATES OF
   1.5 TO 2 IN/HR LIKELY...MAINLY ABOVE 4000 FT THROUGH 12Z.
   
   RECENT SATELLITE IMAGERY DEPICTS A SIGNIFICANT SHORT WAVE TROUGH
   IMPINGING UPON THE NRN CA COAST. STRONG FORCED ASCENT AHEAD OF THIS
   WAVE ALONG WITH SUBSTANTIAL LOW-LEVEL WARM/MOIST ADVECTION /INFERRED
   FROM AREA VAD PROFILERS/ HAS AIDED IN POCKETS OF MODERATE RAINFALL
   IN LOWER ELEVATIONS AND HEAVY SNOW IN HIGHER ELEVATIONS OF NRN CA.
   AS MID-LEVEL COOLING INCREASES INVOF TROUGH AXIS...STEEPENING LAPSE
   RATES WILL SUPPORT SHALLOW CONVECTION AND SHOULD HELP MAXIMIZE
   SNOWFALL RATES ACROSS THE NRN/CNTRL SIERRA MTNS FROM 09-12Z GIVEN
   CONTINUED FAVORABLE OROGRAPHIC ENHANCEMENT. TOWARDS 12Z...SNOWFALL
   RATES SHOULD DIMINISH ACROSS THE NRN SIERRAS AS LOW/MID-LEVEL FLOW
   WEAKENS AND VEERS. THIS IS CONSISTENT WITH LATEST MODEL GUIDANCE
   INDICATING THE BULK OF HEAVIER QPF SHIFTING SWD EARLY THU MORNING.
   
   ..GRAMS.. 12/20/2007
   
   
   ...NOTICE...
   SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A
   SCHEDULED BASIS FROM DECEMBER 1 THROUGH FEBRUARY 28...FOUR
   TIMES A DAY...AROUND 00 UTC...06 UTC...12 UTC...AND 18 UTC
   FOR SIGNIFICANT SHORT RANGE WINTER WEATHER EVENTS.
   
   ATTN...WFO...REV...HNX...STO...
   
   39562020 38681974 37941916 37471911 37441947 37651981
   38262049 39172091 40042152 40542160 40822134 40532079