MESOSCALE PRECIPITATION DISCUSSION 0857
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
102 AM EDT TUE OCT 03 2017

AREAS AFFECTED...E-CNTRL NE/NWRN IA/SERN SD/MN/NWRN WI

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 030454Z - 031045Z

SUMMARY...AN ELONGATED AXIS OF TRAINING RAINFALL WITH RATES
GENERALLY BETWEEN 1-2 IN/HR WILL LIKELY CAUSE FLASH FLOODING FROM
E-CNTRL NE INTO PORTIONS OF THE UPPER MS VALLEY. MAXIMUM
ADDITIONAL RAINFALL OF 3-5 INCHES IS EXPECTED THROUGH 10Z.

DISCUSSION...REGIONAL MOSAIC RADAR IMAGERY AT 0430Z SHOWED A
BROKEN AXIS OF HEAVY RAINFALL EXTENDING FROM ERN NE INTO WRN
WI...TRAINING FROM SW TO NE. THIS ACTIVITY WAS OCCURRING VERY NEAR
THE 925 MB DEPICTION OF A FRONT EXTENDING THROUGH THE REGION AND
WAS LARGELY ELEVATED IN NATURE...EITHER ABOVE THE SURFACE FRONT OR
RESULTANT OUTFLOW BOUNDARY. INSTABILITY WAS ROUGHLY 500-1000 J/KG
ACROSS THE MPD THREAT AREA PER THE MOST RECENT SPC MESOANALYSIS
VALID 04Z.

A SEPARATE...NARROW LINE OF CONVECTION WAS IDENTIFIED MOVING
TOWARD THE EAST ALONG THE NE/KS BORDER NEAR THE 100TH MERIDIAN AT
0430Z. THE NARROW LINE APPEARS TO BE TIED TO HEIGHT FALLS
ASSOCIATED WITH A 700-500 MB SHORTWAVE SEEN MOVING INTO THE CNTRL
HIGH PLAINS ON WATER VAPOR IMAGERY. AHEAD OF THE SHORTWAVE WAS A
SPEED MAX OF 60-70 KT IN THE 850-700 LAYER...STRADDLING THE KS/NE
BORDER...AS SEEN IN RAP ANALYSES AND AREA VAD WIND PLOTS. A
SURFACE LOW OR TWO WAS ALSO EVIDENT IN SURFACE OBSERVATIONS FROM
04Z ON EITHER SIDE OF THE CNTRL KS/NE BORDER. THE REGION OF
STRONGER LOW LEVEL FLOW IS EXPECTED TO TRANSLATE TO THE
NNE...REACHING THE W-CNTRL MN/IA BORDER BY 10Z ACCORDING TO THE
RAP. GIVEN THE UNIDIRECTIONAL FLOW ABOVE THE LPL SEEN IN RAP
ANALYSIS AND FORECAST SOUNDINGS...AND THE SIMILAR MAGNITUDE OF LOW
LEVEL INFLOW TO THE CLOUD BEARING LAYER MEAN WIND...TRAINING IS
LIKELY TO CONTINUE THROUGH THE NIGHT ACROSS MUCH OF THE SAME
REGIONS BUT WITH A SURGE IN RAINFALL INTENSITY TIED TO THE 850-700
MB SPEED MAX.

CAPE IS EXPECTED TO REMAIN ABOVE 500 J/KG...SUFFICIENT TO SUSTAIN
HEAVY RAIN CORES OF 1-2 IN/HR AMID TOTAL PRECIPITABLE WATER VALUES
OF 1.50 TO 1.75 INCHES. WHILE MOST AREAS ARE EXPECTED TO SEE 1-3
INCHES...LOCALLY HIGHER VALUES OF 3-5 INCHES WILL BE POSSIBLE FROM
THE MISSOURI RIVER INTO S-CNTRL MN THROUGH 10Z. GIVEN WIDESPREAD
FFG VALUES OF 1.5 TO 2.5 INCHES IN 3 HOURS...FLASH FLOODING IS
CONSIDERED LIKELY.

OTTO

ATTN...WFO...DLH...DMX...FSD...GID...LBF...MPX...OAX...

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

LAT...LON   47139153 46939068 46459084 45589137 44569280
            43689396 42379568 40859807 40949913 41979864
            44009684 45559470 46809261