998
AWUS01 KWNH 200950
FFGMPD
OHZ000-MIZ000-INZ000-WIZ000-ILZ000-IAZ000-201400-
MESOSCALE PRECIPITATION DISCUSSION 1341
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
548 AM EDT SUN SEP 20 2026
AREAS AFFECTED...FAR EASTERN IA...NORTHERN IL...FAR SOUTHERN
WI...FAR SOUTHWEST LOWER MI...NORTHERN IN...NORTHWEST OH
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 200948Z - 201400Z
SUMMARY...CLUSTERS OF SHOWERS AND THUNDERSTORMS WITH LOCALLY HIGH
RAINFALL RATES WILL CONTINUE INTO THE MORNING HOURS. ADDITIONAL
AREAS OF FLASH FLOODING WILL REMAIN POSSIBLE FOR AT LEAST A FEW
MORE HOURS AS A RESULT.
DISCUSSION...THE LATEST GOES-E IR SATELLITE IMAGERY SHOWS AN
ELONGATING AXIS OF COLD-TOPPED CONVECTION EXTENDING FROM FAR
EASTERN IA THROUGH NORTHERN IL AND ALSO NOW INTO AREAS OF NORTHERN
IN. REGIONAL RADAR DATA ALSO CONFIRMS SOME LOCALIZED CORRIDORS OF
CELL-TRAINING, AND ALL OF THIS CONVECTION CONTINUES TO BE DRIVEN
LARGELY BE THE ADVANCE OF A WAVE OF LOW PRESSURE AND ASSOCIATED
SHORTWAVE ACROSS THE MIDWEST.
THE DOWNSTREAM ADVANCE OF WARM AIR ADVECTION AND DEEPER LAYER
MOISTURE TRANSPORT IN CONJUNCTION WITH A WARM FRONT LIFTING
NORTHWARD SHOULD ALLOW SOME OF THE STRONGER CONVECTIVE ACTIVITY
OVER NORTHERN IL TO BECOME A LITTLE MORE CONCENTRATED ACROSS PARTS
OF NORTHERN IN IN THE NEAR-TERM WITH PERHAPS SOME OF THIS
SPREADING INTO NORTHWEST OH.
A SOUTHWEST LOW-LEVEL JET OF 30 TO 40 KTS SHOULD GRADUALLY VEER A
BIT MORE THIS MORNING AND EVENTUALLY START TO WEAKEN, BUT THIS
COMBINED WITH THE REMAINING ELEVATED INSTABILITY POOL AND HIGH PW
ENVIRONMENT SHOULD CONTINUE TO FAVOR LOCALLY HIGH RAINFALL RATES
OF 1 TO 2 INCHES/HOUR. MUCAPE VALUES ALONG THE ADVANCING WARM
FRONT ARE STILL CLOSE TO 1000 J/KG WITH PWS OF 1.75 TO 2.0 INCHES.
THE LATEST HRRR GUIDANCE SUGGESTS SOME ADDITIONAL LOCALIZED SWATHS
OF 2 TO 3 INCH RAINFALL AMOUNTS, WITH AREAS OF NORTHERN IL AND
NORTHERN IN MOST LIKELY TO SEE THE GREATER CONCENTRATIONS OF THESE
RAINFALL AMOUNTS.
GENERALLY, THE LARGER SCALE CONVECTIVE FOOTPRINT SHOULD BEGIN TO
WEAKEN BY MID-MORNING, BUT THE ADDITIONAL RAINS IN THE NEAR-TERM
SHOULD STILL FAVOR A CONCERN FOR SOME ADDITIONAL AREAS OF FLASH
FLOODING.
ORRISON
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...CLE...DTX...DVN...GRR...ILN...IWX...LOT...MKX...
ATTN...RFC...MSR...TIR...NWC...
LAT...LON 42888824 42728692 42458559 42068462 41618396
41068385 40678446 40718573 40908678 41188805
41298873 41379008 41839074 42409059 42758977
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