MESOSCALE DISCUSSION 0018
   NWS STORM PREDICTION CENTER NORMAN OK
   1225 PM CST MON JAN 03 2005
   
   AREAS AFFECTED...MTN OF SRN CA...SRN SIERRA NEVADA
   
   CONCERNING...PRECIPITATION TRENDS...WINTER PRECIPITATION 
   
   VALID 031825Z - 032330Z
   
   HVY SNOW OVER SAN GABRIEL MTNS OF SRN CA ABOVE 4000 FT WILL 
   DIMINISH IN INTENSITY THROUGH 20Z...WITH HVY SNOW DIMINISHING OVER
   THE SAN GABRIEL AND SAN DIEGO CTY MTNS ABOVE 5000 FT BETWEEN 20-22Z.
   HRLY ACCUMULATIONS ABOVE 2 INCHES WILL REMAIN LIKELY THROUGH THESE
   TIMES. FARTHER NORTH...HVY SNOW IS ANTICIPATED TO DEVELOP OVER THE
   KERN COUNTY MTNS AND SRN SIERRA NEVADA THROUGH 00Z. HOURLY
   ACCUMULATION ON SOUTH FACING SLOPES GREATER THAN 2 INCHES CAN BE
   EXPECTED.
   
   DOUBLE BARRELED UPPER LOW OFF THE CA COAST WILL CONTINUE TO SLOWLY
   PROGRESS EWD THROUGH THE AFTERNOON. STRONG UPPER DIVERGENCE ON THE
   ERN SIDE OF THE UPPER TROUGH COMBINED WITH LOW-MID LEVEL CONVERGENCE
   AHEAD OF A LEAD TROUGH AXIS WILL MAINTAIN A WELL DEVELOPED
   PRECIPITATION AREA OVER SRN AND PORTIONS OF CENTRAL CA. STRONG
   CONVERGENCE AHEAD OF A LOW-MID LEVEL TROUGH WILL CONTINUE TO SUPPORT
   HVY SNOWFALL OVER THE MTNS OF SRN CA THROUGH 20-22Z TIME.
   PROGRESSIVE NATURE OF THIS TROUGH EVIDENT BY RECENT KVTX VWP DATA
   AND SAT TRENDS INDICATE THAT FOCUSED CONVERGENCE WILL CONTINUE TO
   SHIFT FURTHER INLAND OVER THE HIGH DESERT AND SRN SIERRA NEVADA.
   SNOW LEVELS RANGING FROM AROUND 4000 FT IN THE NRN SAN GABRIEL MTNS
   TO AROUND 5000 FT IN THE MTNS OF SAN DIEGO COUNTY SHOULD FALL
   SLIGHTLY AFTER THE TROUGH PASSAGE.
   
   FARTHER NORTH...AS THE LEAD MID LEVEL TROUGH PROGRESSES INTO THE
   HIGH DESERT AND SRN SAN JOAQUIN VALLEY...EXPECT HVY SNOW TO CONTINUE
   TO DEVELOP OVER THE SRN SIERRA NEVADA/KERN COUNTY MTNS ABOVE 4000
   FT. DEEP/MODERATE SSELY FLOW WILL SUPPORT ADDITIONAL UPSLOPE
   COMPONENT TO VERTICAL MOTION AND 2 IN/HR RATES ON S/SE FACING
   SLOPES.  AS MAIN UPPER TROUGH CONTINUES TO DIG SLOWLY OFF THE CA
   COAST...THE SRN SIERRA NV IS LIKELY TO BE THE LOCATION OF A
   DEVELOPING MID LEVEL DEFORMATION ZONE. THUS...THERE EXIST THE
   POTENTIAL FOR A PROLONGED 1-2 IN/HR HVY SNOW EVENT WELL INTO THE
   EVENING HOURS.
   
   ..CROSBIE.. 01/03/2005
   
   
   ...NOTICE...
   SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A 
   SCHEDULED BASIS...FOUR TIMES A DAY...BETWEEN 00-01 UTC...
   06-07 UTC...12-13 UTC...AND 18-19 UTC AS SIGNIFICANT SHORT
   RANGE WINTER WEATHER EVENTS UNFOLD.  THIS SCHEDULE WILL BE
   USED FROM DECEMBER 1 THROUGH FEBRUARY 28.
   
   ATTN...WFO...VEF...SGX...HNX...LOX...
   
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