[MCD] SWOMCD

[MCD at goshenarc.org]

ACUS11 KWNS 051701
SWOMCD
SPC MCD 051700 
CAZ000-052100-

MESOSCALE DISCUSSION 2498
NWS STORM PREDICTION CENTER NORMAN OK
1100 AM CST SUN DEC 05 2004

AREAS AFFECTED...MTNS OF FAR SRN CA ABOVE 4500FT

CONCERNING...HEAVY SNOW 

VALID 051700Z - 052100Z

PERIOD OF CONVECTIVE SNOWFALL EXPECTED BETWEEN 05/19Z-06/00Z ABOVE
4500FT IN THE MTNS OF SAN DIEGO AND RIVERSIDE COUNTIES IN SRN CA.
SNOWFALL RATES BETWEEN 1-2IN/HR ARE LIKELY...PARTICULARLY IN MTNS OF
INTERIOR SAN DIEGO COUNTY.

SATELLITE IMAGERY INDICATES THAT STRONG OFFSHORE UPPER TROUGH
CONTINUES TO DIG SEWD TOWARD THE SRN CA/NRN BAJA CA COAST THIS
MORNING. WELL FORMED LEADING WARM CONVEYOR BELT IS AFFECTING COASTAL
POINTS AT 17Z...AND STRONG UPPER TROPOSPHERIC DIFFLUENCE IS EVIDENT
IN THE CLOUD FIELD ACROSS THE FAR SRN SAN JOAQUIN VALLEY. UPPER
DIVERGENCE SHOULD PROPAGATE SSEWD ACROSS THE MTNS OF SRN CA LATE
THIS MORNING INTO THIS AFTERNOON. MODELS SUGGEST 500MB TEMPERATURES
AROUND -25C WITH CENTER OF OFFSHORE LOW.

FRONTAL PRECIPITATION BAND APPROACHING SAN DIEGO COUNTY HAS AN EWD
COMPONENT OF MOTION AROUND 15KT...TAKING LEADING EDGE OF
PRECIPITATION INTO THE MTNS OF SAN DIEGO COUNTY AND SRN RIVERSIDE
COUNTY BETWEEN 19-20Z. EMBEDDED CONVECTION/LIGHTNING IS ONGOING AND
STEEP LAPSE RATES AROUND 7C/KM BETWEEN 700-500MB TRANSLATING INLAND
WITH COLD UPPER LOW SHOULD PROMOTE CONVECTIVE SNOWFALL AND ISOLATED
THUNDER SNOW OVER MTN AREAS THIS AFTERNOON. RUC AND ETA MODEL
SOUNDINGS FROM 12Z CYCLE SUGGEST SNOW LEVELS AROUND 4500 FT WITH UVV
DIMINISHING AROUND 06/00Z AS BAND OF PVA AND LOW-LEVEL WARM
ADVECTION MOVES EAST OF THE REGION. SLY LOW-LEVEL FLOW IS LARGELY
PARALLEL TO MTNS OF SAN DIEGO COUNTY SUGGESTING ONLY MODEST
OROGRAPHIC AUGMENTATION TO LIFT. HOWEVER...DYNAMICS WITH APPROACHING
SYSTEM AND PRESENCE OF STEEP LAPSE RATES SHOULD SUPPORT 4-5 HOURS OF
HEAVY SNOW WITH 1-2 IN/HR SNOWFALL RATES LIKELY IN THE MTNS.

..BANACOS.. 12/05/2004

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

...NOTICE...
SPC WINTER WEATHER MESOSCALE DISCUSSIONS WILL BE ISSUED ON A 
SCHEDULED BASIS...FOUR TIMES A DAY...BETWEEN 05-06 UTC...
11-12 UTC...17-18 UTC...AND 23-00 UTC AS SIGNIFICANT SHORT
RANGE WINTER WEATHER EVENTS UNFOLD.  THIS SCHEDULE WILL BE
USED FROM DECEMBER 1 THROUGH FEBRUARY 28 TO ALLOW PARTNERS
AND USERS TO BETTER ANTICIPATE THE TIMING OF SPC WINTER WEATHER
MESOSCALE DISCUSSIONS.

ATTN...WFO...SGX...

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33481635 33431641 33181636 

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