038
AWUS01 KWNH 050517
FFGMPD
OHZ000-MIZ000-INZ000-051100-
MESOSCALE PRECIPITATION DISCUSSION 1206
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
116 AM EDT SAT SEP 05 2026
AREAS AFFECTED...SOUTHERN MICHIGAN...NORTHEAST INDIANA...NORTHWEST
TO SOUTHEAST OHIO...
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 050520Z - 051100Z
SUMMARY...INCREASING CONVECTIVE ACTIVITY WITH CAPABILITY OF
1.5-1.75"/HR RATES AND FAVORABLE REPEATING/TRAINING ENVIRONMENT
FOR LOCALIZED STREAKS OF 2-3" TOTALS OVERNIGHT. ISOLATED TO
WIDELY SCATTERED FLASH FLOODING IS POSSIBLE.
DISCUSSION...05Z SURFACE ANALYSIS SHOWS A WEAK SURFACE LOW AT THE
SOUTHERN BASE OF LAKE MICHIGAN AT A WEAK INFLECTION THE STATIONARY
FRONT THAT IS MORE WEST TO EAST ALONG THE WI/IL STATE LINE BEFORE
ANGLING SOUTH-SOUTHEAST ACROSS NE IND INTO CENTRAL OH BEFORE
CROSSING INTO W PA. ALOFT, A 500MB JET SPEED MAX IS EXITING THE
LP ACROSS LAKE ERIE INTO THE MID-ATLANTIC RESULTING IN A BROAD
RIGHT ENTRANCE REGION ACROSS SW LP OF MI, WHERE ALSO A POCKET OF
COOLER AIR ALOFT (-6 TO -8C) RESIDES SLIDING EASTWARD INDICATIVE
OF SLIGHTLY ENHANCED LAPSE RATES FURTHER WEST. LOW LEVEL
925-700MB DEEP LAYER FLOW HAS RESPONDED WITH STILL MOSTLY
UNIDIRECTIONAL FLOW OUT OF THE WEST, BUT A SMALL VEERED LOW LEVEL
PROFILE WEAKLY OBLIQUE TO THE ISENTROPIC PLANE ASSOCIATED WITH THE
FRONTAL ZONE. IN ADDITION, RETROGRADING UPPER-LEVEL LOW OVER
EASTERN CANADA HAS STARTED TO RESULT IN INCREASING 925-850MB
NORTHEASTERLY FLOW WHICH IS SIGNIFICANTLY DRIER. THIS IS HELPING
TO STEEPEN ISENTROPES NEAR AND DOWNSTREAM OF THE WEAK SURFACE LOW
TO SUPPORT DEEP LAYER CONVERGENCE IN THE ISENTROPIC ASCENT FOR
CONVECTIVE INITIATION ACROSS S MI AT THIS TIME, COINCIDENT WITH
THE 500-300MB DIVERGENCE MAXIMA PASSING SOUTHEASTWARD.
THE OVERALL COVERAGE AND ORGANIZATION STILL REMAINS SCATTERED DUE
TO OBLIQUE/WEAK CONVERGENCE FORCING, BUT THE AMPLE DEEP LAYER
MOISTURE POOLED IN THIS REGION IS ABOUT 2" OF TPW. SLOW
ORGANIZATION AND INCREASINGLY CONFLUENT STEERING FLOW ACROSS NW
OH/SE MI MAY HELP TO ORGANIZE THUNDERSTORM ACTIVITY INTO A MORE
FAVORABLE ORIENTATION FOR REPEATING/TRAINING. STILL, MUCAPE IS
HIGHER FURTHER SOUTHWEST INTO NE IL/NW IND AROUND 4000 J/KG, BUT
REMAINS VERY CAPPED WITH 50-75 J/KG OF REMAINING CINH. RAP
ANALYSIS SUGGESTS WEAKER CAPPING (LESS THAN 25 J/KG) ALONG THE
NORTHEAST GRADIENT OF CAPE BUT STILL AROUND 1500-2000 J/KG TO
SUPPORT STRONG UPDRAFT VIGOR AND LOW LEVEL MOISTURE FLUX
CONVERGENCE FOR EFFICIENT RAINFALL PRODUCTION. BULK SHEAR IS A
BIT WEAK OVERALL FOR BETTER ORGANIZATION (CURRENTLY ABOUT
20-25KTS) BUT ANY IMPROVEMENT MAY ALLOW FOR BROADER UPDRAFTS AS
WELL, BUT GIVEN INFLOW OF 20-30KTS (ALSO 925MB NORTHEASTERLY FLOW
OF 15KTS) SHOULD ALLOW FOR FLUX CONVERGENCE TO SUPPORT 1.5-1.75";
THOUGH THIS COULD INCREASE WITH ANY IMPROVEMENT IN DEEPER SHEAR
PROFILE TOWARD 2"/HR.
SO WHILE REPEATING IS LIKELY TO BE REQUIRED TO OVERCOME THE HIGHER
FFG VALUES OF S MI/NE IND (CURRENTLY 1.8-2.3"/HR), THIS WILL
REDUCE ACROSS AREAS RECENTLY SATURATED BY ACTIVITY THOUGH THE LAST
FEW DAYS ACROSS SE MI/NORTHWEST OH, WHERE VALUES DROP TO 1.5-2"/HR
WITH SOME SPOTS EVEN BELOW 1.5" FURTHER SOUTHEAST; WITH 3HR VALUES
OF 2-2.5" ACROSS MUCH OF THE AREA OF CONCERN. SO WITH LOCALIZED
STREAKS OF 2-3" TOTALS, ISOLATED TO WIDELY SCATTERED INCIDENT(S)
OF FLASH FLOODING WILL BECOME POSSIBLE THOUGH THE EARLY MORNING
GALLINA
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...CLE...DTX...GRR...ILN...IWX...PBZ...RLX...
ATTN...RFC...MSR...TIR...NWC...
LAT...LON 42278604 42208477 41828342 40858144 40388109
39718116 39408225 39648332 40388494 41478645
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