MESO: Mesoscale Discussion 0193

ACUS11 KWNS 031819
SWOMCD
SPC MCD 031818
CAZ000-032215-

MESOSCALE DISCUSSION 0193
NWS STORM PREDICTION CENTER NORMAN OK
1218 PM CST TUE MAR 03 2009

AREAS AFFECTED...SIERRA NEVADA MOUNTAINS

CONCERNING...HEAVY SNOW

VALID 031818Z - 032215Z

SNOWFALL INTENSITY OVER NRN PORTIONS OF THE SIERRA NEVADA MOUNTAINS
IS EXPECTED TO INCREASE DURING THE AFTERNOON...WITH RATES UP TO 2
IN/HR POSSIBLE. HIGHER RATES MAY SHIFT SOUTH ALONG THE WINDWARD
SLOPES BY LATE AFTERNOON/EARLY EVENING.

12Z UPPER AIR OBSERVATIONS DEPICT STRONG MID/UPR LEVEL
WEST-SOUTHWESTERLY FLOW IS PRESENT ALONG THE BASE OF A DEEP UPR
TROUGH OFF THE COAST OF CA. THIS FLOW WILL CONTINUE TO IMPINGE UPON
THE WINDWARD SLOPES OF THE SIERRAS THROUGHOUT THE
AFTERNOON...RESULTING IN STRONG OROGRAPHIC ASCENT AND A PROLONGED
PERIOD OF SNOWFALL /ABOVE 4000-5000 FT MSL/. OBSERVED RAOB DATA AND
RUC FORECAST SOUNDINGS INDICATE A STEEP LAPSE RATE ENVIRONMENT IS
PRESENT ACROSS THE REGION...SUGGESTING THE POTENTIAL FOR
CONVECTIVELY ENHANCED SNOWFALL RATES UP TO 2 IN/HR. LIGHTNING
STRIKES ACROSS NRN CA FURTHER SUPPORT THIS. THE HEAVIEST SNOWFALL
WILL LIKELY OCCUR NORTH-NORTHWEST OF TVL THROUGH MID AFTERNOON.
HOWEVER...AS AN EMBEDDED DISTURBANCE ROUNDS THE BASE OF THE MAIN UPR
TROUGH AND APPROACHES CENTRAL CA LATER THIS AFTERNOON AND
EVENING...OROGRAPHIC LIFT WILL LIKELY REFOCUS FURTHER SOUTH ALONG
THE SIERRAS...WITH A CORRESPONDING SHIFT IN HEAVIER SNOWFALL RATES.

..GARNER.. 03/03/2009

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

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

LAT...LON 37921913 37581932 37691982 38282027 38972059 39502093
39952150 40622170 40822151 40442100 39472035 38721997
37921913

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