Sunday, January 6, 2008

MESO: Mesoscale Discussion 0012

ACUS11 KWNS 070141
SWOMCD
SPC MCD 070141
CAZ000-070715-

MESOSCALE DISCUSSION 0012
NWS STORM PREDICTION CENTER NORMAN OK
0741 PM CST SUN JAN 06 2008

AREAS AFFECTED...COASTAL MOUNTAINS OF SOUTHERN CA

CONCERNING...HEAVY SNOW

VALID 070141Z - 070715Z

MODERATE TO LOCALLY HEAVY SNOW IS EXPECTED TO DEVELOP/INCREASE
ACROSS THE COASTAL RANGE OF SOUTHERN CA THROUGH THE NIGHT...WITH
SNOW LEVELS GENERALLY FALLING AS LOW AS 3500-4500 FT. SNOW RATES
COULD REACH 2 IN/HR...ESPECIALLY IN THE HIGHER ELEVATIONS ABOVE 6000
FT LATE THIS EVENING/OVERNIGHT.

LATEST SATELLITE/RADAR IMAGERY REFLECTS INCREASING
MOISTURE/PRECIPITATION SPREADING INTO SOUTHERN CA AHEAD OF A LOW
AMPLITUDE SHORTWAVE TROUGH JUST OFF THE CENTRAL CA COAST. AS THIS
TREND CONTINUES...SHORT TERM NAM/RUC/GFS GUIDANCE SUGGEST THAT HEAVY
SNOW SHOULD DEVELOP/INCREASE ACROSS THE COASTAL MOUNTAINS OF
SOUTHERN CA THROUGH THE NIGHT. INITIALLY...THIS WILL BE THE CASE
ACROSS THE VENTURA/LOS ANGELES COUNTY MOUNTAINS/SAN GABRIELS THROUGH
03Z-06Z...WITH SNOW INCREASING TOWARD/AFTER 06Z ACROSS THE SAN
BERNARDINO/RIVERSIDE COUNTY MOUNTAINS. BOTH THE LATE AFTERNOON
OBSERVED VANDENBERG AFB AND MIRAMAR RAOBS REFLECT CONSIDERABLE
MOISTENING SINCE THIS MORNING...WITH THE WET BULB ZERO LEVELS
LOWERING SEVERAL HUNDRED FEET IN THAT SAME SPAN...TO AROUND 4300
FT/5200 FT AT VBG/NKX RESPECTIVELY AT 00Z. THESE SOUNDINGS AND
LATEST MESONET OBSERVATIONS IN ACCORDANCE WITH LATEST NAM/RUC
SOUNDINGS SUGGEST SNOW LEVELS COULD FALL AS LOW AS 3500-4500
FT...HIGHEST ACROSS SAN BERNARDINO/RIVERSIDE COUNTIES. AMPLE LARGE
SCALE ASCENT/OROGRAPHIC LIFT COINCIDENT WITH A HIGH PRECIPITABLE
WATER ENVIRONMENT /0.75-0.85/ WILL FAVOR MODERATE TO HEAVY
SNOW...WITH NAM/RUC SOUNDINGS REFLECTING SEVERAL HOURS OF AMPLE
OMEGA COINCIDENT WITH A FAVORABLE DENDRITIC GROWTH LAYER. IN
ADDITION...SNOW RATES MAY BE CONVECTIVELY ENHANCED LATER TONIGHT VIA
MODEST UPRIGHT/SLANTWISE INSTABILITY...ESPECIALLY ACROSS THE SAN
BERNARDINO/RIVERSIDE MOUNTAINS PER MARGINAL INSTABILITY PROGS AND
LATEST SREF CONVECTIVE PRECIP GUIDANCE.

.GUYER.. 01/07/2008

..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...SGX...HNX...LOX...

34801958 34891899 34761852 34381794 34381729 34491695
34121662 33451656 33361680 33671696 33991703 34111734
33991774 34261820 34561866 34531938 34671963

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