Thursday, December 20, 2007

MESO: Mesoscale Discussion 2243

ACUS11 KWNS 200534
SWOMCD
SPC MCD 200534
CAZ000-NVZ000-200930-

MESOSCALE DISCUSSION 2243
NWS STORM PREDICTION CENTER NORMAN OK
1134 PM CST WED DEC 19 2007

AREAS AFFECTED...NRN/CNTRL SIERRA MTNS OF CA

CONCERNING...HEAVY SNOW

VALID 200534Z - 200930Z

HEAVY SNOW WILL GRADUALLY SHIFT SWD OVERNIGHT WITH SNOWFALL RATES OF
1.5 TO 2 IN/HR LIKELY...MAINLY ABOVE 4000 FT THROUGH 12Z.

RECENT SATELLITE IMAGERY DEPICTS A SIGNIFICANT SHORT WAVE TROUGH
IMPINGING UPON THE NRN CA COAST. STRONG FORCED ASCENT AHEAD OF THIS
WAVE ALONG WITH SUBSTANTIAL LOW-LEVEL WARM/MOIST ADVECTION /INFERRED
FROM AREA VAD PROFILERS/ HAS AIDED IN POCKETS OF MODERATE RAINFALL
IN LOWER ELEVATIONS AND HEAVY SNOW IN HIGHER ELEVATIONS OF NRN CA.
AS MID-LEVEL COOLING INCREASES INVOF TROUGH AXIS...STEEPENING LAPSE
RATES WILL SUPPORT SHALLOW CONVECTION AND SHOULD HELP MAXIMIZE
SNOWFALL RATES ACROSS THE NRN/CNTRL SIERRA MTNS FROM 09-12Z GIVEN
CONTINUED FAVORABLE OROGRAPHIC ENHANCEMENT. TOWARDS 12Z...SNOWFALL
RATES SHOULD DIMINISH ACROSS THE NRN SIERRAS AS LOW/MID-LEVEL FLOW
WEAKENS AND VEERS. THIS IS CONSISTENT WITH LATEST MODEL GUIDANCE
INDICATING THE BULK OF HEAVIER QPF SHIFTING SWD EARLY THU MORNING.

.GRAMS.. 12/20/2007

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

39562020 38681974 37941916 37471911 37441947 37651981
38262049 39172091 40042152 40542160 40822134 40532079

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