MESOSCALE PRECIPITATION DISCUSSION 0639
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
600 PM EDT SUN SEP 04 2016
 
AREAS AFFECTED...SD INTO SERN ND 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 042159Z - 050359Z
 
SUMMARY...AN INCREASING COVERAGE OF CONVECTION ACROSS SD INTO SRN
ND THIS EVENING IS EXPECTED TO POSE A FLASH FLOOD THREAT WITH
RAINFALL RATES OF 2-3 INCHES IN 2-3 HOURS EXPECTED.

DISCUSSION...REGIONAL RADAR IMAGERY SHOWED INCREASING TRENDS IN
CONVECTIVE COVERAGE ACROSS PORTIONS OF WRN AND SRN SD AS OF
2130Z...AHEAD OF A WELL DEFINED SHORTWAVE TROUGH AND JET STREAK
NOTED OVER CNTRL WY/NRN CO ON WATER VAPOR IMAGERY. THE SPC
MESOANALYSIS PAGE INDICATED THE STORMS IN S-CNTRL SD WERE FORMING
IN AN ENVIRONMENT CONTAINING 2000-2500 J/KG MLCAPE WITH
PRECIPITABLE WATER VALUES OF 1.25 TO 1.5 INCHES OR ABOUT 1-2
STANDARDIZED ANOMALIES ABOVE THE MEAN. AT THE SURFACE...A
STATIONARY FRONT EXTENDED SW TO NE THROUGH A 1002 MB LOW SITUATED
JUST WEST OF PIR. 

A PRIMARY CONCERN FOR FLASH FLOODING IS THE FACT THAT STORM
MOTIONS ARE FORECAST TO LARGELY REMAIN PARALLEL TO THE SW-NE
ORIENTATION OF THE STATIONARY FRONT. ALSO OF CONCERN IS AN
EXPECTED INCREASE IN 850-700 MB FLOW FORECAST THROUGH 03Z TO REACH
THE 25-35 KT RANGE ACCORDING TO THE RAP. UPPER LEVEL DIFFLUENCE
OVER THE AREA TIED TO UPPER LEVEL JET STREAK CURRENTLY OVER THE
CNTRL HIGH PLAINS SHOULD ALSO WORK TO INCREASE COVERAGE OF STORMS
LATE THIS EVENING AS THE SHORTWAVE MOVES NEWD OVER SD AFTER 00Z.

GIVEN EXPECTED REPEATING CELLS AND CELL MERGERS...RAINFALL RATES
OF 1-2 IN/HR WITH 2-3 INCHES IN 2-3 HOURS CAN BE EXPECTED FROM
S-CNTRL SD...EVENTUALLY REACHING SRN/SERN ND. AS CONVECTION
INCREASES DURING THE 00-03Z TIME FRAME...AN OVERALL EWD
PROGRESSION TO THE COMPLEX OF RAINFALL IS EXPECTED...BUT TRENDS
WILL BE MONITORED FOR A CONTINUED FLASH FLOOD THREAT BEYOND 04Z.

OTTO

ATTN...WFO...ABR...BIS...FGF...UNR...

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

LAT...LON   46799838 45979803 44219941 43450063 43120166 
            43200274 43690300 44320277 44850161 45860048 
            46599939