MESOSCALE PRECIPITATION DISCUSSION 0935
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
805 AM EST SAT NOV 18 2017

AREAS AFFECTED...IL...IN...OH

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

VALID 181304Z - 181804Z

SUMMARY...INTENSE JET LEVEL OUTFLOW AND LOW LEVEL INFLOW COMBINED
WITH MODEST INSTABILITY WILL SUPPORT A RISK OF RAIN RATES
EXCEEDING FLASH FLOOD GUIDANCE THROUGH 18Z.

DISCUSSION...AN AMPLIFYING / MATURING MID LATITUDE CYCLONE WAS
BRINGING SEVERAL INGREDIENTS INTO PLACE FOR A FOCUSED PERIOD OF
MODERATE TO HEAVY RAINFALL ALONG THE NORTH EDGE OF A CAPE GRADIENT
AND BENEATH STRONGLY DIFLUENT UPPER FLOW OWING TO JET SPEEDS IN
EXCESS OF 110 KNOTS.

AT 1245 UTC...RAIN AND EMBEDDED HEAVY CONVECTIVE RAINS WERE LINED
UP FROM WEST TO EAST ACROSS CENTRAL IL TO CENTRAL/NORTHERN IN/OH.
DUAL POL WSR-88D IN THE REGION ESTIMATED HOURLY RATES ABOVE ONE
INCH...ESPECIALLY NEAR THE DEEPER FORCING AND STRONGER INSTABILITY
OVER ILLINOIS. THE PHASING OF DEEP LAYER ASCENT WITH INCREASING
INSTABILITY AND PARTICULARLY WITH CONVERGENT AND STRENGTHENING LOW
LEVEL JET INFLOW...WILL MIGRATE EASTWARD DURING THE MORNING AND
EARLY AFTERNOON. HI-RES MODELS INDICATE A CONSENSUS SWATH OF AT
LEAST 1 TO 2 INCH AREAL AVERAGE RAINFALL. THERE IS
POTENTIAL...HOWEVER...FOR HIGHER AMOUNTS WITH WEST TO EAST
TRAINING UNTIL THE SYNOPTIC WAVE FURTHER AMPLIFIES AND THE BACK
EDGE OF FORCING SWINGS THROUGH. THE 10Z HRRR AND 00Z NSSL WRF WERE
HANDLING THE EARLY MORNING ACTIVITY WELL...AND THE NSSL WRF BOOSTS
LOCAL EVENT TOTALS ABOVE 3 INCHES...MUCH OF WHICH MAY FALL IN ONLY
A 2 TO 4 HOUR PERIOD AT ANY GIVEN LOCATION. SOME FLASH FLOODING
MAY OCCUR.

BURKE

ATTN...WFO...CLE...DVN...ILN...ILX...IND...IWX...LOT...LSX...
PBZ...

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

LAT...LON   41178531 40988252 40598145 39928298 39638588
            39478959 40329089 40758900