SWOMCD
SPC MCD 050039
CAZ000-050545-
MESOSCALE DISCUSSION 0007
NWS STORM PREDICTION CENTER NORMAN OK
0639 PM CST FRI JAN 04 2008
AREAS AFFECTED...CA
CONCERNING...HEAVY SNOW
VALID 050039Z - 050545Z
INTENSE WINTER STORM WILL CONTINUE TO PRODUCE EXTREME SNOWFALL RATES
OF 2-4 INCHES PER HOUR AT HIGHER ELEVATION ACROSS THE SIERRA NEVADA
RANGE TONIGHT. SNOW LEVELS /NOW IN THE RANGE OF 6500-8000 FEET ABOVE
MSL/ WILL FALL FROM NORTH TO SOUTH AS COLDER AIR MASS MOVES IN OVER
THE NEXT SEVERAL HOURS.
BACK EDGE OF DEEP-LAYER BAROCLINIC CLOUD BAND IS EVIDENT ON VISIBLE
SATL IMAGERY AND RADAR DATA FROM NEAR SFO NNEWD ACROSS NRN CA. TO
THE SOUTH OF THIS ZONE...INTENSE OROGRAPHIC FORCING AIDED BY 40-60KT
LLJ...AND PRONOUNCED MOISTURE TRANSPORT...WILL CONTINUE TO SUPPORT
HEAVY MOUNTAIN SNOW FROM THE LAKE TAHOE AREA SWD TO YOSEMITE. SNOW
LEVELS IN THE NORTH PART OF THIS ZONE HAVE BEGUN TO FALL BELOW 6500
FEET. MEANWHILE...FARTHER SOUTH...THE FREEZING LEVEL WILL FALL BELOW
8000 FEET AS THE HEAVIER PRECIPITATION SPREADS SWD/SEWD THROUGH
TONIGHT.
HIGH RESOLUTION NMM AND ARW MODELS...AS WELL AS THE MESOSCALE 12KM
NAM...ALL INDICATE THE SEWD SHIFT IN THE ZONE OF STRONGEST FORCING
FOR ASCENT OVER THE NEXT SEVERAL HOURS. PRECIPITATION RATES WITHIN
THIS BAND MAY LOCALLY EXCEED 1 INCH OF LIQUID QPF PER HOUR WITH MOST
LOCATIONS LIKELY TO EXPERIENCE A PERIOD OF AT LEAST 0.50 INCH PER
HOUR. SREF SNOWFALL GUIDANCE INDICATES A MEAN 3-HOURLY SNOWFALL IN
EXCESS OF 9 INCHES /3 INCH PER HOUR RATES/ ALONG THE CREST OF THE
CNTRL SIERRA RANGE THROUGH EARLY SATURDAY BEFORE RATES START TO
DIMINISH.
COLDER/UNSTABLE AIR NOW SPREADING INTO AREAS NRN CA WITHIN THE
TROUGH AXIS WILL RESULT IN FAIRLY RAPID DROP IN TEMPERATURES ACROSS
THESE AREAS NEXT FEW HOURS. WHILE SLIGHTLY DIMINISHED LARGE SCALE
ASCENT MAY SUGGEST A WANE IN PRECIPITATION RATES... OROGRAPHIC
ENHANCEMENT IN A LOW STATIC STABILITY ENVIRONMENT SHOULD CONTINUE TO
SUPPORT LOCALLY HEAVY...POSSIBLY CONVECTIVE...SNOWFALL IN
MOUNTAINOUS TERRAIN WELL INTO THE NIGHT.
.CARBIN.. 01/05/2008
..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...
38781998 38601968 38361938 37991901 37411848 36591808
35821803 35661818 35681832 35791844 36041864 36631875
36881884 37331941 37821980 38212016 38602045 39432068
39502049
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