MESOSCALE PRECIPITATION DISCUSSION 0885...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
745 AM EDT SAT OCT 14 2017

CORRECTED FOR SMALL TEXT FIXES

AREAS AFFECTED...SOUTHEAST IA...NORTHERN IL...NORTHERN
IND...SOUTHWEST MI

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 141130Z - 141730Z

SUMMARY...FAST MOVING/SHALLOW CONVECTION WITHIN REGENERATIVE
UPSTREAM ENVIRONMENT AND DEEP UNIDIRECTIONAL FLOW SUGGEST ISOLATED
FLASH FLOODING IS POSSIBLE WHERE PROLONGED TRAINING OCCURS. 

DISCUSSION...11Z SURFACE ANALYSIS DEPICTS A WELL DEFINED FRONT
EXTENDING FROM SE MI ACROSS S LK MI TO A WEAK INFLECTION IN SE
IA/NE MO...WITH GOES-16 TPW/CIRA LAYERED PW POOLED ALONG IT. 
GOES-16 3-CHANNEL WV LOOPS SHOW STRONG BUT RELATIVELY FLAT FLOW
PARALLEL TO AND JUST NORTH OF THE FRONTAL ZONE WITH BROAD ENTRANCE
TO 130-150KT 250MB JET SUPPORTING UPPER LEVEL EVACUATION TO THE
FRONTAL REGION.  ADDITIONALLY...A WEAK SHORTWAVE CAN BE SEEN
SPEEDING OFF INTO S MI ATTM WITH ASSOCIATED SCATTERED CONVECTIVE
CELLS MARCHING ACROSS N IND/SW MI ATTM.

AN ADDITIONAL WEAK WAVE IS ALSO DEPICTED ACROSS N MO WITHIN
INCREASED MID-ALTITUDE CLOUD SHIELD.  MOISTURE/INSTABILITY FIELDS
FROM THE RAP ANALYSIS DENOTE NOSE OF 1000-1500 J/KG MUCAPE AND
850MB MST ADVECTION IN ADVANCE OF THE WAVE AND WITH THE SHORTWAVE
RIDGING ALOFT BETWEEN THE WAVES...WEAK ASCENT AND THE LOW LEVEL
MST CONVERGENCE AS REINVIGORATED CONVECTIVE DEVELOPMENT ACROSS
CENTRAL NORTHERN IL JUST NORTH OF THE FRONTAL BOUNDARY. THOUGH
SHALLOW (-50C AND COOLING) THE WAA/MST AVAILABILITY WILL SUPPORT
MODEST TO HEAVY RAINFALL RATES UP TO 1.75"/HR.  DEEP MEAN FLOW IS
QUITE STRONG 40-50KTS LIMITING DURATION FOR ANY INDIVIDUAL
CELL...BUT GIVEN STRONG UPSTREAM FORCING STILL UPSTREAM
REDEVELOPMENT IS HIGHLY LIKELY EVEN IN THE SHORT TERM AND WITH
CLOUD BEARING FLOW QUITE UNIDIRECTIONAL... TRAINING IS LIKELY
ESPECIALLY ACROSS N IL AND PERHAPS DOWNSTREAM INTO NW IND/SW MI BY
MID-MORNING.  THIS COMBINED WITH THE EARLIER BOUT OF SHOWERS THIS
MORNING ACROSS N IL HAS A LOW CHANCE OF SETTING OFF LOCALIZED
FLASH FLOODING CONCERNS.

MUCH STRONGER/ROBUST MAIN WAVE IS CURRENTLY EXITING INTO THE
CENTRAL PLAINS...THIS WILL SUPPORT INCREASING AMPLIFICATION OF THE
UPPER LEVEL PATTERN THOUGH 15-18Z ACROSS THE AREA OF CONCERN. THIS
WILL SUPPORT STRONGER DPVA AND ENHANCED RIGHT ENTRANCE REGION
ASCENT...AS WELL AS STRENGTHENING WAA ACROSS THE W-E FRONTAL ZONE
AS IS CURRENTLY SEEN ON REGIONAL RADAR MOSAIC OCCURRING IN SW
IA/NW MO/NE KS.  THIS BETTER FORCING WILL TRACK ENEWARD WITH BEST
STRONGEST CORES TRAINING ALONG THE FRONTAL ZONE.  GREATER VERTICAL
DEPTH/STRONGER MST FLUX WILL SUPPORT RATES OF 2-2.25"/HR THOUGH
MORE LIKELY LEAD HOURLY TOTALS CLOSER TO 1.25-1.5" (DUE TO FORWARD
SPEED OF CELLS) POSSIBLE FROM SOUTH CENTRAL IA BY 15Z AND ACROSS N
IL THROUGH 17Z.  GIVEN DURATION OF TRAINING THERE ARE SOME
SUGGESTIONS OF A SWATH OF 2-5" THROUGH 18Z...WITH CURRENT TRENDS
THROUGH URBAN SECTIONS OF SOUTHERN CHICAGOLAND THERE IS AN
INCREASED RISK OF FLASH FLOODING.  THIS EVOLUTION IS BEST
PRESENTED IN HI-RES CAMS BY THE NSSL-WRF OR ARW2.

GALLINA

ATTN...WFO...DMX...DVN...GRR...ILX...IWX...LOT...

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

LAT...LON   42658621 42598517 41828489 40908740 40649295
            41219412 41769326 42279063 42438765