MESO: Mesoscale Discussion 2117

ACUS11 KWNS 102240
SWOMCD
SPC MCD 102240
WIZ000-IAZ000-MNZ000-110245-

MESOSCALE DISCUSSION 2117
NWS STORM PREDICTION CENTER NORMAN OK
0440 PM CST FRI DEC 10 2010

AREAS AFFECTED...SRN MN...WRN WI...FAR NRN IA

CONCERNING...FREEZING RAIN

VALID 102240Z - 110245Z

A BAND OF FREEZING RAIN APPEARS LIKELY TO DEVELOP ACROSS SRN MN AND
FAR NRN IA THIS EVENING MOVING INTO WRN WI DURING THE OVERNIGHT
PERIOD. FREEZING RAIN RATES OF UP TO A TENTH OF AN INCH PER HOUR
WILL BE POSSIBLE WHERE THE HEAVIER PRECIPITATION OCCURS.

THE LATEST WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A WELL-DEFINED
VORTICITY MAX CURRENTLY LOCATED IN FAR SERN SD. THIS FEATURE ALONG
WITH LIFT ASSOCIATED WITH THE NOSE OF THE LOW-LEVEL JET IS HELPING
TO CREATE AN AREA OF PRECIPITATION IN THE MID-MO VALLEY LATE THIS
AFTERNOON. LIFT WILL INCREASE ACROSS THE MCD AREA AS THE VORTICITY
MAX MOVES EWD AND THE LOW-LEVEL JET STRENGTHENS THIS EVENING
RESULTING IN A GRADUAL INCREASE IN COVERAGE OF PRECIPITATION. SFC
TEMPS ARE ALREADY BELOW FREEZING FROM THE IA-MN STATE-LINE NWD AND
THE PRECIPITATION SHOULD MOVE ENEWD INTO THE SUB-FREEZING AIR.
FORECAST SOUNDINGS ACROSS THE MCD AREA THIS EVENING SUGGEST AN ABOVE
FREEZING LAYER MAY EXIST AROUND 850 MB WITH A SHALLOW SUB-FREEZING
LAYER NEAR THE SFC. THIS THERMODYNAMIC PROFILE SHOULD RESULT IN
FREEZING RAIN AS THE DOMINANT MODE OF PRECIPITATION OVER THE NEXT 3
TO 4 HOURS AT LEAST IN THE EARLY STAGES OF A DEVELOPING WINTER STORM
TO THE WEST. THE HEAVIEST RATES OF FREEZING RAIN SHOULD OCCUR ALONG
THE PATH OF THE VORTICITY MAX WHERE ICE ACCUMULATION OF .10 INCHES
PER HOUR SEEMS POSSIBLE ESPECIALLY IF A PERSISTENT BAND CAN SETUP.

..BROYLES.. 12/10/2010

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

ATTN...WFO...ARX...MPX...DMX...FSD...

LAT...LON 43229075 43369371 43629590 43989617 44389580 44589506
44659315 44539081 43889021 43229075

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