MESOSCALE PRECIPITATION DISCUSSION 0570
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
710 PM EDT MON AUG 15 2016
 
AREAS AFFECTED...NORTHEASTERN ILLINOIS...NORTHERN
INDIANA....SOUTHERN MICHIGAN...EXTREME NORTHWESTERN OHIO 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 152308Z - 160500Z
 
SUMMARY...AN AREA OF MODERATE TO HEAVY STRATIFORM RAIN WITH
EMBEDDED ELEVATED CONVECTIVE CELLS PRODUCING HEAVY RAINFALL IS
EXPECTED TO PERSIST THROUGH THE NEXT SEVERAL HOURS AS IT MOVES
NORTHEASTWARD. FLASH FLOODING IS POSSIBLE.

DISCUSSION...HIGHLY MOIST (PWATS NEAR 2.25 IN) AIR CONTINUES TO BE
TRANSPORTED ACROSS A STATIONARY FRONTAL BOUNDARY INTO A REGION OF
STRATIFORM RAIN ACROSS NERN IL/NWRN IN. INSTABILITY IS WEAK IN
THIS AREA NORTH OF THE SURFACE FRONT, HOWEVER MODERATE INSTABILITY
(MLCAPE OF 1000-1500 J/KG) IS PRESENT IN THE INFLOW REGION JUST
SOUTH OF THE FRONT. RAINFALL RATES OF 1-1.5 IN/HR ARE OCCURRING AT
THIS TIME IN HEAVIER ELEVATED CONVECTIVE CELLS EMBEDDED WITHIN THE
LARGER RAIN AREA. COVERAGE OF THESE HEAVIER RAIN RATES IS FORECAST
TO INCREASE OVER THE NEXT FEW HOURS BY SEVERAL HI-RES MODELS
INCLUDING THE HRRR, HRRR-PARALLEL, HRRR-EXPERIMENTAL, AND WRF-ARW.
THE HRRR TIME-LAGGED ENSEMBLE ALSO INDICATES INCREASING
PROBABILITIES FOR HEAVIER RAIN RATES OVER THE OUTLINED AREA
THROUGH THE NEXT FEW HOURS. THIS APPEARS TO BE SUPPORTED BY A
SLIGHT STRENGTHENING FORECAST IN SOUTHWESTERLY LOW-LEVEL FLOW TO
40 KT CROSSING THE FRONTAL BOUNDARY, AND A RESULTANT INCREASE IN
LOW-LEVEL CONVERGENCE ALONG THE FRONT AHEAD OF THE NORTHEASTWARD
MOVING SURFACE LOW. MID AND UPPER-LEVEL DYNAMICS WILL IMPROVE
MODESTLY OVER THE NEXT FEW HOURS AS A SHORTWAVE TROUGH TO THE WEST
APPROACHES. THE REGION WILL ALSO REMAIN IN AN AREA OF MODERATELY
DIFFLUENT FLOW AS A DEPARTING JET STREAM IS CENTERED FARTHER NORTH
OVER CENTRAL/NORTHERN MICHIGAN.

THROUGH 05Z, RAINFALL AMOUNTS OF 1 TO 3 INCHES ARE FORECAST ACROSS
THE OUTLINED AREA BY A NUMBER OF HI-RES MODELS, WITH LOCALLY
HIGHER AMOUNTS POSSIBLE. THE FLASH FLOODING THREAT WILL BE
SOMEWHAT LIMITED BY MODERATE TO HIGH FLASH FLOOD GUIDANCE, BUT
WITH IMPRESSIVE MOISTURE AND IMPROVING FORCING, CANNOT RULE OUT
THE POSSIBILITY FOR ISOLATED FLASH FLOODING. 

RYAN

ATTN...WFO...DTX...GRR...IND...IWX...LOT...

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

LAT...LON   43078504 42898407 42318377 41728407 40818500 
            40258580 40168667 40508747 40668788 40908842 
            41308832 41778770 42758582