MESOSCALE PRECIPITATION DISCUSSION 0305
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
544 AM EDT THU AUG 21 2014
 
AREAS AFFECTED...CENTRAL AND SOUTHERN MN...WESTERN AND SOUTHERN
WI...NORTHEAST IA...NORTHERN IL...NORTHWEST IN 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 210940Z - 211400Z
 
SUMMARY...TRAINING CONVECTION AND A FEW CELL-MERGERS WILL FOSTER A
FLASH FLOOD THREAT THROUGH THE MID-MORNING HOURS.

DISCUSSION...THE LATEST IR SAT IMAGERY SHOWS A COLD-TOPPED MCS
IMPACTING CNTRL/SRN MN ATTM...WITH THE MCS BEGINNING TO ADVANCE
ESEWD TWD SERN MN. MEANWHILE...A NW/SE ORIENTED BAND OF ELEVATED
CONVECTION IS SEEN IMPACTING SWRN WI...WHICH IS CONNECTED TO A
GRADUAL INCREASE IN WARM ADVECTION VIA A MOIST/UNSTABLE SWLY LOW
LVL JET INVOF A FRONTAL ZONE. THIS DOWNSTREAM CONVECTION MAY WELL
BE GETTING INFLUENCED TO A DEGREE BY A DEVELOPING MCV ASSOCD WITH
THE MN CONVECTIVE SYSTEM.

OVER THE NEXT FEW HOURS...THE MCS OVER MN WILL ADVANCE ESEWD ALONG
AND JUST NORTHEAST OF A WARM FRONT...WITH ADDITIONAL BANDS OR
CLUSTERS OF CONVECTION EXPECTED TO ORGANIZE DOWNWIND OF THE MCS
INVOLVING ESP SRN WI...NERN IL AND POSSIBLY FAR NWRN IN. THE
LATEST VAD WIND PROFILER DATA INDICATES 30 TO 40 KTS OF SWLY LOW
LEVEL JET AND THIS WILL CONTINUE AT LEAST THROUGH ABOUT 12Z. THE
LARGER SCALE ENVIRONMENT WILL REMAIN CONDUCIVE FOR CELL MERGERS
AND TRAINING GIVEN THE ORIENTATION OF THE ONGOING CONVECTION AND
EXPECTED PROPAGATION.

THIS COUPLED WITH RAINFALL RATES OF UP TO 2 INCHES/HR WILL FAVOR
THE POTENTIAL FOR FLASH FLOODING AT LEAST THROUGH THE MID-MORNING
HOURS. HOWEVER...THE LATEST HI-RES GUIDANCE INCLUDING THE 00Z
NAM-CONEST AND 00Z NSSL-WRF WHICH BOTH HAVE A SOMEWHAT REASONABLE
HANDLE ON THE MN MCS...SUGGEST THAT THE CONVECTION WILL TEND TO
WEAKEN BEYOND 12Z. SO THE FLASH FLOOD THREAT SHOULD TEND TO
CONTINUE FOR A FEW MORE HOURS AND THEN SUBSIDE.

ORRISON

ATTN...WFO...IWX...LOT...ILX...MKX...DVN...DLH...ARX...MPX...
DMX...FSD...

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

LAT...LON   45139191 44179054 42868838 42088691 41498636 40808656
            40628772 40998942 41809130 42879293 43659460 44059525
            44809587 45429576 45989510 46329407 45889300 45139191