MESO: Mesoscale Discussion 0080

ACUS11 KWNS 231827
SWOMCD
SPC MCD 231827
CAZ000-232130-

MESOSCALE DISCUSSION 0080
NWS STORM PREDICTION CENTER NORMAN OK
1227 PM CST WED JAN 23 2008

AREAS AFFECTED...THE SIERRA MADRE MOUNTAINS AND ADJACENT AREAS OF
SRN CALIFORNIA

CONCERNING...HEAVY SNOW

VALID 231827Z - 232130Z

HEAVY SNOW IS DEVELOPING ACROSS THE MOUNTAINS OF SANTA
BARBARA/VENTURA/NORTHWESTERN LOS ANGELES/SOUTHEASTERN SAN LUIS
OBISPO/AND SOUTHERN KERN COUNTIES. LOWERING SNOW LEVELS AND
INCREASING SNOW RATES...POSSIBLY IN EXCESS OF 2 INCHES PER
HOUR...ARE EXPECTED BY 21-23Z.

FORCING FOR UPWARD VERTICAL MOTION CONTINUES TO STRENGTHEN AHEAD OF
A VIGOROUS SHORT WAVE IMPULSE APPROACHING THE SOUTHERN CALIFORNIA
COAST. A BELT OF STRONGER ISENTROPIC ASCENT HAS BECOME
QUASI-STATIONARY ACROSS SOUTHERN CALIFORNIA COASTAL AREAS...TO THE
NORTHWEST OF THE LOS ANGELES BASIN...INLAND THROUGH THE CENTRAL/
NORTHERN SIERRA NEVADA. BUT...A GRADUAL EASTWARD ACCELERATION OF
THE SOUTHERN PORTION OF THIS BAND IS EXPECTED DURING THE MID TO LATE
AFTERNOON HOURS...AS THE UPPER IMPULSE TAKES ON AN INCREASINGLY
NEGATIVE TILT...TO THE SOUTH/SOUTHEAST OF THE CLOSED LOW WEST OF SAN
FRANCISCO BAY.

AS THIS OCCURS...THE LEADING EDGE OF THE MAIN PRECIPITATION BAND IS
EXPECTED TO SLOWLY SHIFT ACROSS THE SIERRA MADRE RANGE. OROGRAPHIC
LIFT IS ALREADY SUPPORTING INCREASING PRECIPITATION ON ITS
SOUTH/SOUTHWEST FACING SLOPES...AND WILL CONTINUE TO ENHANCE
PRECIPITATION RATES IN A SATURATED ENVIRONMENT WITHIN A MOISTURE
TONGUE CHARACTERIZED BY PRECIPITABLE WATER VALUES UP TO .7 INCHES.
WITH GRADUALLY COOLING MID-LEVELS...SNOW LEVELS MAY LOWER INTO THE
3500-4000 FOOT RANGE BY 21-23Z. AT THE SAME TIME...STRENGTHENING
MID-LEVEL FORCING IS EXPECTED TO INCREASE LIFT THROUGH THE MIXED
PHASE LAYER FAVORABLE FOR LARGE DENDRITIC ICE CRYSTAL GROWTH.
AND...SNOW RATES COULD EXCEED 2 INCHES PER HOUR.

.KERR.. 01/23/2008

..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...HNX...LOX...

34891990 35031962 34991900 34841853 34551842 34401875
34461913 34601983

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