[MCD] SWOMCD

[Mesoscale Convective Discussions]

ACUS11 KWNS 180814
SWOMCD
SPC MCD 180814 
CAZ000-181415-

MESOSCALE DISCUSSION 2579
NWS STORM PREDICTION CENTER NORMAN OK
0214 AM CST SUN DEC 18 2005

AREAS AFFECTED...CA SIERRA NEVADA MOUNTAINS

CONCERNING...HEAVY SNOW 

VALID 180814Z - 181415Z

HEAVY WET SNOW IS EXPECTED TO OVERSPREAD THE SIERRA RANGE IN THE
NEXT SEVERAL HOURS AS MOIST PACIFIC STORM SYSTEM MOVES INLAND.
SNOWFALL RATES AOA 6000 FEET COULD EXCEED 2 INCHES PER HOUR THIS
MORNING.

OVER THE NEXT SEVERAL HOURS...PRECIPITATION RATES WILL CONTINUE TO
INCREASE AND SPREAD INLAND FROM THE COAST AND ACROSS THE CNTRL
VALLEY OF CA AS POTENT PACIFIC PERTURBATION MOVES EAST ACROSS THE
NCNTRL CA COAST. OBSERVED RAINFALL RATES NEAR THE COAST WERE ALREADY
IN THE RANGE OF 0.10 TO 0.25 INCHES PER HOUR WITHIN WARM AIR
ADVECTION REGIME AHEAD OF THE STRONGER DYNAMIC FORCING. /REF
NFDSPENES WMO HEADER TXUS20/.

INTENSIFYING UPSLOPE FLOW AND DYNAMIC FORCING WITH THE MID/UPPER
LEVEL IMPULSE/WIND MAX...ALONG WITH ENHANCED MOISTURE TRANSPORT
ACCOMPANYING +1 INCH PW PLUME...WILL LEAD TO EXCESSIVE SNOWFALL
RATES DEVELOPING ACROSS THE HIGHER ELEVATIONS THROUGH 12Z. WHILE
SNOW LEVELS MAY INITIALLY CLIMB ABOVE 6000 FEET...FREEZING LEVELS
WILL BEGIN TO FALL LATER THIS MORNING AS ADIABATIC COOLING WITHIN
THE UPPER TROUGH AXIS SPREADS ACROSS THE AREA. WITH POTENTIAL FOR
EMBEDDED CONVECTION...AND DECENT AGREEMENT IN LATEST SHORT-TERM QPF
GUIDANCE FROM NAM AND RUC MODELS...SNOWFALL RATES OF 2-4 INCHES PER
HOUR APPEAR LIKELY NEAR AND SOUTH OF THE TAHOE AREA BEFORE 12Z.
WINDS ALSO INCREASING TO NEAR 50KT LATER THIS MORNING WILL PRODUCE
DRIFTING SNOW AND WHITE-OUT CONDITIONS.

..CARBIN.. 12/18/2005

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...VEF...REV...HNX...STO...

37021850 36771865 37371945 37972000 38232022 38682029
39242058 39532070 39762078 40232140 40502156 40502133
40442108 40292076 40112059 39902037 39672017 38932008
37431870 

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