MESO: Mesoscale Discussion 2241

ACUS11 KWNS 200040
SWOMCD
SPC MCD 200040
CAZ000-200515-

MESOSCALE DISCUSSION 2241
NWS STORM PREDICTION CENTER NORMAN OK
0640 PM CST WED DEC 19 2007

AREAS AFFECTED...HIGHER ELEVATIONS OF NORTHERN CA

CONCERNING...HEAVY SNOW

VALID 200040Z - 200515Z

HEAVY SNOW WILL INCREASE ACROSS THE HIGHER ELEVATIONS OF NORTHERN CA
THROUGH EARLY/MID EVENING...WITH LOWERING SNOW LEVELS LATER TONIGHT
AND THE POSSIBILITY OF 2 IN/HR RATES ABOVE 5000 FT.

LATEST SATELLITE IMAGERY FEATURES MOIST PLUME EXTENDING INTO THE
PACIFIC NORTHWEST/NORTHERN CA DOWNSTREAM OF POTENT/COLD UPPER TROUGH
CENTERED ABOUT 400 MILES OFF THE ORE COAST. INCREASING LARGE SCALE
ASCENT WILL LEAD TO STEADILY INCREASING PRECIPITATION RATES/HIGHER
ELEVATION SNOW THIS EVENING ACROSS NORTHERN CA...WITH A STRONG
WEST-SOUTHWEST MID LEVEL JET /75-100 KT AT 500 MB/ CONSIDERABLY
ENHANCING OROGRAPHIC LIFT INTO WEST-SOUTH FACING SLOPES. LATEST
MESONET OBSERVATIONS FROM NORTHERN CA SUGGEST SNOW LEVELS ARE
RUNNING AROUND 4000-4500 FT LATE THIS AFTERNOON...WITH A STEADY DROP
/1000 FT OR MORE/ EXPECTED LATER TONIGHT /ESPECIALLY AFTER 06Z/ VIA
THE ARRIVAL OF COLDER AIR ALOFT WITH -30C AT 500 MB. AMPLE
LIFT/PACIFIC MOISTURE AND STEEPENING MID LEVEL RATES WITH CONVECTIVE
SNOW POTENTIAL WILL FAVOR THE POSSIBILITY OF 2 IN/HR SNOW RATES
ABOVE 5000 FT FROM THE SHASTA/SISKIYOU VICINITY INTO THE NORTHERN
SIERRA.

.GUYER.. 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...MFR...STO...EKA...

40642122 39462071 39462130 40212179 40862197 40832266
40702337 41192364 41582381 41902352 41782273 41662190
41362146

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