MESOSCALE PRECIPITATION DISCUSSION 0465
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
453 PM EDT SAT AUG 22 2015
 
AREAS AFFECTED...WEST/SOUTHWEST IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 222052Z - 230252Z
 
SUMMARY...THUNDERSTORMS HAVE BEGUN TO FORM ACROSS WESTERN IA. 
HOURLY RAIN RATES UP TO 2" COULD LEAD TO FLASH FLOODING.

DISCUSSION...THUNDERSTORMS HAVE BEGUN TO FORM IN AN AREA OF ERODED
CIN ALONG A WEAK PRE-FRONTAL WAVE NEAR THE NE/IA BORDER.  THEY ARE
FORMING WITHIN A POOL OF MLCAPES IN THE 3000-4000 J/KG RANGE. 
INFLOW AT 850 HPA IS 25-30 KTS PER VAD WIND PROFILES, WHILE
PRECIPITABLE WATER VALUES OF 1.5-1.75" ARE INDICATED BY RECENT RAP
RUNS.  WHILE INDIVIDUAL CELL MOTION IS NORTHEAST AT 30-35 KTS,
THERE HAS BEEN SOME INDICATION OF STORMS EITHER BACKBUILDING OR
FORMING FARTHER DOWN THE SURFACE BOUNDARY.

FORWARD PROPAGATING CONVECTIVE VECTORS ALONG WITH THE 1000-850 HPA
THICKNESS PATTERN IN THE REGION INDICATE A SOUTH-SOUTHEAST TO
SOUTHEAST MOTION AT 20-25 KTS WHICH IS ROUGHLY ALONG A VAGUE
SYNOPTIC SCALE STATIONARY FRONT.  TOWARDS THE END OF THE PERIOD,
CONVECTION MAY TRY TO BECOME MORE ELEVATED OVER THIS BOUNDARY AS
CIN REDEVELOPS.  PERIODS OF CELL TRAINING ARE EXPECTED TO BE THE
MAIN CONCERN.  OVERALL, LIKED THE 12Z CANADIAN REGION QPF FOR THE
IA/SOUTHERN MN AREA THE MOST OF THE AVAILABLE CAM GUIDANCE -- THE
18Z NAM CONEST APPEARED TOO FAR WEST ACROSS EASTERN NE.  LOCAL
AMOUNTS OF 2-4" ARE INDICATED BY THE MESOSCALE GUIDANCE, WHICH
COULD FALL QUICKLY, AS AVAILABLE MOISTURE SUPPORTS HOURLY RAIN
RATES UP TO 2".  THE 12Z SSEO NEIGHBORHOOD PROBABILITIES INDICATE
THAT THIS EVENT SHOULD MATURE IN THE 02-04Z TIME FRAME.  FLASH
FLOODING IS POSSIBLE.

ROTH

ATTN...WFO...DMX...EAX...FSD...OAX...

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

LAT...LON   43089534 42219409 41099359 40549406 40569502 
            40979606 41689642 42349597