MESO: Mesoscale Discussion 0073

ACUS11 KWNS 090516
SWOMCD
SPC MCD 090515
CAZ000-NVZ000-090915-

MESOSCALE DISCUSSION 0073
NWS STORM PREDICTION CENTER NORMAN OK
1115 PM CST SUN FEB 08 2009

AREAS AFFECTED...SIERRA NEVADAS

CONCERNING...HEAVY SNOW

VALID 090515Z - 090915Z

HEAVY SNOWFALL RATES OF 1 TO 2 INCHES/HR WILL LIKELY OCCUR OVER THE
SIERRA NEVADAS DURING THE LATE EVENING AND OVERNIGHT HRS. HEAVY
SNOWFALL RATES WILL OCCUR OVER THE NRN 2/3RDS OF THE AREA BEFORE
08Z. THEN THE HEAVIEST RATES WILL SHIFT SWD AND INCREASE IN
INTENSITY /2 INCHES PER HOUR/ AND MAINLY IMPACT AREAS ALONG AND S OF
LAKE TAHOE DURING THE 08-12Z PERIOD.

05Z SATELLITE IMAGERY SHOWS A POTENT MID-LEVEL VORTICITY MAXIMUM 60
MI SW EKA MOVING RAPIDLY SEWD TOWARDS THE BAY AREA. EXTENSIVE CLOUD
TOP COOLING HAS BEEN OBSERVED AHEAD OF THIS FEATURE...INDICATING
SUBSTANTIAL MOISTENING/LIFT IS OCCURRING. DYNAMIC DESTABILIZATION
AND ASSOCIATED COLD MID LEVEL TEMPERATURES /-32 C AT 500MB PER 00Z
NAM 6 HR FORECAST SOUNDING AT UKI/ HAVE HELPED LEAD TO SPORADIC
LIGHTNING THIS EVENING NEAR THE WRN SLOPES OF THE CENTRAL SIERRAS.
ADDITIONALLY...STRONG UPSLOPE FLOW WILL CONTINUE ON THE WRN SLOPES
OF THE CENTRAL/SRN SIERRAS. AS A RESULT...CONVECTIVELY ENHANCED
SNOW BURSTS WILL OCCUR AT TIMES MAINLY OVER THE TERRAIN FAVORED
AREAS OF THE SIERRAS THROUGH 12Z AS SNOW LEVELS FALL TO AROUND
2000-3000 FEET BY THE END OF THE PERIOD.

..SMITH.. 02/09/2009

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

...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...VEF...REV...HNX...STO...

LAT...LON 37551967 38272032 39172076 39662118 39762123 40032105
39932065 39702019 38881990 38021914 37151821 36041799
35901838 36711890 37551967

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