MESOSCALE DISCUSSION 0240
   NWS STORM PREDICTION CENTER NORMAN OK
   0123 PM CDT SUN MAR 20 2011
   
   AREAS AFFECTED...MOUNTAINS OF SWRN CA
   
   CONCERNING...HEAVY SNOW 
   
   VALID 201823Z - 202230Z
   
   SNOWFALL RATES OF 2 IN/HR ARE EXPECTED TO DEVELOP OVER THE MOUNTAINS
   OF SWRN CA THIS AFTERNOON...GENERALLY IMPACTING ELEVATIONS AOA 5500
   FT.
   
   A POWERFUL DEEP-LAYER TROUGH OVER THE ERN PACIFIC IS ASSOCIATED WITH
   A COLD FRONT THAT WILL MOVE EWD ACROSS SWRN CA THIS AFTERNOON INTO
   TONIGHT. AN ATTENDANT PLUME OF DEEP-LAYER PACIFIC MOISTURE EXTENDS
   INLAND...WITH THE BLENDED AMSU-SSMI TPW PRODUCT INDICATING PWAT
   VALUES IN EXCESS OF 0.65 INCH ACROSS THE DISCUSSION AREA /AOA 150
   PERCENT OF NORMAL/. THIS MOISTURE...ALONG WITH STRONG DEEP-LAYER
   ASCENT /DCVA/ ASSOCIATED WITH THE TROUGH...AND FRONTAL CONVERGENCE
   WILL YIELD INCREASING PRECIPITATION RATES THIS AFTERNOON. COOLING
   TEMPERATURES ALOFT ASSOCIATED WITH THE AMPLIFICATION OF THE TROUGH
   WILL ALLOW SNOW LEVELS TO FALL...WITH SNOWFALL RATES OF 2 IN/HR
   ANTICIPATED OVER THE SWRN CA MOUNTAINS...GENERALLY OVER ELEVATIONS
   AOA 5500 FT. THESE RATES WILL FIRST IMPACT THE MOUNTAINS OF NRN
   VENTURA AND SRN KERN COUNTIES...BEFORE SPREADING EWD/SEWD AND
   IMPACTING THE MOUNTAINS OF LOS ANGELES AND SAN BERNARDINO COUNTIES.
   THE HIGHEST SNOWFALL RATES WILL OCCUR ON SOUTH- AND SOUTHWEST-FACING
   SLOPES...WHERE MOIST UPSLOPE CONDITIONS WILL BE FAVORED...AS
   INTENSIFYING LOW/MID-LEVEL FLOW /700-MB S-SWLY FLOW OF 50 TO 60 KT
   ACCORDING TO THE GFS MODEL/ IMPINGES ON THE HIGHER TERRAIN. THE
   HEAVIEST PRECIPITATION IS FORECAST TO PERSIST INTO THIS EVENING
   WHILE GRADUALLY SHIFTING SWD...BEFORE TAPERING OFF LATER TONIGHT.
   
   ..COHEN.. 03/20/2011
   
   
   ATTN...WFO...SGX...HNX...LOX...
   
   LAT...LON   34041675 34081691 34161705 34241726 34211751 34241769
               34291778 34291791 34251803 34351816 34401829 34591846
               34621879 34561907 34571928 34641939 34771938 34911927
               34941908 34961880 35141856 35261836 35291825 35271818
               35181817 35071827 34951845 34841864 34721850 34661828
               34471765 34401737 34421710 34381680 34291656 34181652
               34071664 34041675