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| Mesoscale Discussion 269 |
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MESOSCALE DISCUSSION 0269
NWS STORM PREDICTION CENTER NORMAN OK
0724 PM CDT SUN MAR 10 2013
AREAS AFFECTED...SERN MN...W-CNTRL AND N-CNTRL WI
CONCERNING...HEAVY SNOW
VALID 110024Z - 110530Z
SUMMARY...AN AREA OF HEAVY SNOWFALL WILL EXPAND INTO PARTS OF SERN
MN AND CNTRL WI AS A DEEP-LAYER CYCLONE PROGRESSES NEWD. HOURLY
SNOWFALL RATES ARE FORECAST TO INCREASE TO 1-1.5 INCH ACROSS SERN MN
BY 02Z AND INTO N-CNTRL WI BY 05Z.
DISCUSSION...A SWATH OF PRECIPITATION DEVELOPING WITHIN A
DEFORMATION ZONE N OF A CLOSED MID-LEVEL CYCLONE WILL EXPAND NWD
INTO PORTIONS OF SERN MN AND W-CNTRL WI OVER THE NEXT SEVERAL HRS. A
PRONOUNCED DRY SLOT /NOTED ON WATER VAPOR IMAGERY/ WAS ADVANCING NWD
ACROSS WRN IL...BUT IS EXPECTED TO GENERALLY REMAIN E OF THE
HIGHLIGHTED AREA IN CONJUNCTION WITH THE NEWD PROGRESSING LOW. SFC
OBSERVATIONS INDICATE TEMPERATURES ACROSS THIS AREA ARE CURRENTLY IN
THE LOW-MID 30S...BUT THE COMBINATION OF MODEST WET-BULB AND DYNAMIC
COLUMNAR COOLING...ALONG WITH LOW-LEVEL CAA...WILL RESULT IN
CONDITIONS BECOMING INCREASINGLY FAVORABLE FOR ACCUMULATING
SNOWFALL. VERTICAL ASCENT WILL BE MAXIMIZED WITHIN A LAYER OF
ISENTROPIC LIFT WITHIN THE WRN BRANCH OF A WARM CONVEYOR
BELT...WHICH WILL BECOME FOCUSED ACROSS SRN WI INTO SERN MN.
SHORT-TERM MODEL OUTPUT /INCLUDING 22Z RAP AND 21Z WRF-HRRR/ AND
OBSERVATIONAL TRENDS SUGGEST HEAVY SNOWFALL WILL SPREAD INTO FAR
SERN MN BY 02Z...AND CONTINUE SPREADING NEWD INTO N-CNTRL WI BY 05Z.
SNOWFALL RATES ARE EXPECTED TO PEAK NEAR 1-1.5 INCH PER HR ACROSS
MUCH OF THE HIGHLIGHTED AREA...WITH THE POSSIBILITY OF LOCALLY
HIGHER RATES WITHIN EMBEDDED SNOW BANDS.
..ROGERS.. 03/11/2013
ATTN...WFO...GRB...DLH...ARX...MPX...
LAT...LON 45248870 44348954 43659065 43579121 43619179 43609304
44229283 44889195 45559103 45749034 45818965 45658876
45248870
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