MESOSCALE DISCUSSION 0104
   NWS STORM PREDICTION CENTER NORMAN OK
   0717 PM CST TUE FEB 15 2011
   
   AREAS AFFECTED...NRN-SRN SIERRA NEVADA MOUNTAINS
   
   CONCERNING...HEAVY SNOW 
   
   VALID 160117Z - 160715Z
   
   SNOWFALL RATES OF 2 IN/HR ARE FORECAST TO DEVELOP AT ELEVATIONS
   ABOVE 5000 FT OVER THE NRN SIERRA NEVADA MOUNTAINS BY 03-06Z. THESE
   SNOWFALL RATES WILL THEN SPREAD INTO THE SRN SIERRA NEVADA MOUNTAINS
   DURING THE 06-12Z PERIOD.
   
   RECENT WV IMAGERY SHOWS AN UPPER TROUGH MOVING SEWD TOWARD THE PAC
   NW...WHILE AN EMBEDDED IMPULSE AT THE BASE OF THE TROUGH IS
   PROGRESSING EWD TOWARD CA. STRONG W-SWLY MIDLEVEL FLOW /700 MB
   SPEEDS AROUND 50 KT/ LOCATED ALONG THE PERIPHERY OF THE UPPER TROUGH
   EXTENDED E-NEWD ACROSS NRN CA AND ORE AT 00Z. AS THE UPPER TROUGH
   CONTINUES TO DROP SWD...THE STRONGER MIDLEVEL FLOW...WHICH IS
   COINCIDENT WITH A PLUME OF HIGHER PWAT VALUES /AROUND 0.6-0.9 IN.
   PER GPS PW GUIDANCE/...WILL BEGIN TO IMPINGE UPON THE NRN SIERRAS BY
   03-06Z. THIS WILL LEAD TO STRENGTHENING UPSLOPE FLOW...WITH ASCENT
   BEING FURTHER ENHANCED DURING THE OVERNIGHT HOURS BY THE APPROACHING
   S/W IMPULSE. THE COMBINATION OF STRONG MOIST ASCENT...MODERATELY
   STEEP LAPSE RATES...AND TEMPERATURE PROFILES COOLING TO SUB-FREEZING
   ABOVE 5000 FT...WILL LEAD TO SNOWFALL RATES AROUND 2 IN/HR OVER THE
   NRN SIERRA NEVADA MOUNTAINS BY 03-06Z. THE MOIST UPSLOPE FLOW REGIME
   WILL THEN SHIFT SWD INTO PORTIONS OF THE SRN SIERRA NEVADA MOUNTAINS
   DURING THE 06-12Z PERIOD...WHERE 2 IN/HR SNOWFALL RATES CAN ALSO BE
   EXPECTED.
   
   ..GARNER.. 02/16/2011
   
   
   ATTN...WFO...REV...HNX...STO...
   
   LAT...LON   39582023 38981984 37721911 37411950 37872008 38812061
               39312089 39802139 40082164 40372170 40652142 40352087
               39582023