MESOSCALE PRECIPITATION DISCUSSION 0337
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1054 PM EDT SUN AUG 31 2014
 
AREAS AFFECTED...WI...UP OF MI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 010254Z - 010624Z
 
SUMMARY...A BRIEF...UP TO 3 HOUR...PERIOD OF TRAINING CELLS WITH
HEAVY RAIN WAS ALREADY UNDERWAY...AND MAY PERSIST THROUGH 06 TO
07Z. RAIN RATES OF 1.5"/HOUR AND ISOLATED TOTALS AROUND 3 INCHES
ARE POSSIBLE...AND MAY LEAD TO FLASH FLOODING.

DISCUSSION...THIS REGION WAS NEAR A DEVELOPING INFLECTION POINT IN
THE UPPER LEVEL FLOW...WHERE DEEP LAYER FORCING WILL YIELD A
REGIONAL MAXIMUM OF HEIGHT FALLS THROUGH TONIGHT. THE RESULT IS
BACKING AND LARGELY UNIDIRECTIONAL MID LEVEL FLOW...AND A
FAVORABLE SETUP FOR SW TO NE TRAINING. THE SPC MESOANALYSIS AT
0230Z INDICATED AN ISLAND OF MODERATE MIXED LAYER CAPE...AROUND
2000 J/KG...OVER WISCONSIN AND DEVELOPING TOWARD THE UPPER
PENINSULA OF MICHIGAN. THIS SOURCE OF UNSTABLE AIR WAS SEPARATED
FROM THE LARGER SCALE CONVECTIVE ENVIRONMENT THAT WAS SUPPORTING A
LINEAR MCS TO THE SOUTH AND WEST. THIS ISLAND OF INSTABILITY
COMBINED WITH THE ONSET OF DEEP LAYER ASCENT...HAD ALREADY
SUPPORTED TRAINING CELLS...AND MAY DO SO THROUGH 06 TO 07Z. THIS
ACTIVITY WILL BE GRADUALLY OVERTAKEN BY THE LINEAR MCS.

DUAL POL DATA FROM DULUTH INDICATED SIZABLE SWATHS OF HEAVY RAIN.
WITH PW VALUES NEAR OR ABOVE 1.5 INCHES...AND LITTLE HAIL
INDICATED...THE 2 INCH PER HOUR ESTIMATED RAINFALL IN NORTHERN
BAYFIELD COUNTY MAY BE ACCURATE...AND IS INDICATIVE OF THE
ENVIRONMENT THAT WILL SUPPORT ISOLATED 3 INCH RAIN TOTALS IN A
SHORT TIME. ONE TO THREE HOUR FLASH FLOOD GUIDANCE VALUES ARE
LIKELY TO BE MET...AT LEAST ON AN ISOLATED BASIS.

BURKE

ATTN...WFO...MQT...GRB...DLH...ARX...MPX...

ATTN...RFC...NCRFC...

LAT...LON   47738797 46508792 45228903 44679094 45349252 46049249
            46829163 47838973 48038861 47738797