MESOSCALE DISCUSSION 2241
   NWS STORM PREDICTION CENTER NORMAN OK
   0640 PM CST WED DEC 19 2007
   
   AREAS AFFECTED...HIGHER ELEVATIONS OF NORTHERN CA
   
   CONCERNING...HEAVY SNOW 
   
   VALID 200040Z - 200515Z
   
   HEAVY SNOW WILL INCREASE ACROSS THE HIGHER ELEVATIONS OF NORTHERN CA
   THROUGH EARLY/MID EVENING...WITH LOWERING SNOW LEVELS LATER TONIGHT
   AND THE POSSIBILITY OF 2 IN/HR RATES ABOVE 5000 FT.
   
   LATEST SATELLITE IMAGERY FEATURES MOIST PLUME EXTENDING INTO THE
   PACIFIC NORTHWEST/NORTHERN CA DOWNSTREAM OF POTENT/COLD UPPER TROUGH
   CENTERED ABOUT 400 MILES OFF THE ORE COAST. INCREASING LARGE SCALE
   ASCENT WILL LEAD TO STEADILY INCREASING PRECIPITATION RATES/HIGHER
   ELEVATION SNOW THIS EVENING ACROSS NORTHERN CA...WITH A STRONG
   WEST-SOUTHWEST MID LEVEL JET /75-100 KT AT 500 MB/ CONSIDERABLY
   ENHANCING OROGRAPHIC LIFT INTO WEST-SOUTH FACING SLOPES. LATEST
   MESONET OBSERVATIONS FROM NORTHERN CA SUGGEST SNOW LEVELS ARE
   RUNNING AROUND 4000-4500 FT LATE THIS AFTERNOON...WITH A STEADY DROP
   /1000 FT OR MORE/ EXPECTED LATER TONIGHT /ESPECIALLY AFTER 06Z/ VIA
   THE ARRIVAL OF COLDER AIR ALOFT WITH -30C AT 500 MB. AMPLE
   LIFT/PACIFIC MOISTURE AND STEEPENING MID LEVEL RATES WITH CONVECTIVE
   SNOW POTENTIAL WILL FAVOR THE POSSIBILITY OF 2 IN/HR SNOW RATES
   ABOVE 5000 FT FROM THE SHASTA/SISKIYOU VICINITY INTO THE NORTHERN
   SIERRA.
   
   ..GUYER.. 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...MFR...STO...EKA...
   
   40642122 39462071 39462130 40212179 40862197 40832266
   40702337 41192364 41582381 41902352 41782273 41662190
   41362146