MESOSCALE PRECIPITATION DISCUSSION 0195
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
211 AM EDT TUE MAY 09 2017

AREAS AFFECTED...FAR SOUTHWEST WI...NORTHERN IL...FAR NORTHWEST IN

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

VALID 090600Z - 091000Z

SUMMARY...CONVECTION TRAINING NORTH OF A FRONTAL BOUNDARY COULD
PRODUCE A FLASH FLOOD THREAT EARLY THIS MORNING ACROSS PORTIONS OF
NORTHERN IL.

DISCUSSION...CONVECTION CONTINUES TO FORM/INTENSIFY ACROSS
PORTIONS OF WESTERN WI INTO NORTHERN IL EARLY THIS MORNING. IR
IMAGES FROM THE EXPERIMENTAL GOES-16 SHOWED SLOWLY COOLING TOPS IN
ADVANCE OF A JET STREAK DIVING SOUTHEAST ON THE BACK SIDE OF THE
CLOSED MID LEVEL LOW OVER EASTERN CANADA.

THE CONVECTION IS FORMING IN AN AXIS OF 500-1000 J/KG MUCAPE
AIR...WHERE PRECIPITABLE WATER VALUES RANGE NEAR 1.25 INCHES...PER
THE LATEST BLENDED TPW PRODUCT AND RAP ANALYSIS. THE KDVN RADAR
INDICATED HOURLY RAINFALL RATES NEAR 1.50 INCHES RECENTLY OVER
CARROLL AND OGLE COUNTIES IN NORTHERN IL...AN INDICATION OF THE
POTENTIAL FOR HIGH RAINFALL RATES IN THE ELEVATED CONVECTION.

AS THE JET STREAK DIVES SOUTHEAST INTO THE UPPER GREAT LAKES...IT
SHOULD PROVIDE SUFFICIENT LIFT IN THE BROAD WARM AIR ADVECTION
PATTERN TO FEED NARROW BANDS OF CONVECTION ACROSS MUCH OF NORTHERN
IL THROUGH 09Z. AS THE NARROW BANDS DEVELOP...THERE ARE EXPECTED
TO BECOME PARALLEL TO THE MID LEVEL FLOW...INCREASING THE THREAT
FOR TRAINING AND FLASH FLOODING.

THREE HOUR FLASH FLOOD GUIDANCE VALUES ACROSS PORTIONS OF NORTHERN
IL...AND MOST OF THE HIGH RESOLUTION MODELS SHOWED STRIPES OF 1.50
INCHES OF RAINFALL ACROSS NORTHERN IL THROUGH 10Z. IT IS POSSIBLE
THAT INSTABILITY BECOMES A LIMITING FACTOR FOR A MORE WIDESPREAD
FLASH FLOOD THREAT... BUT TRAINING SHOULD MAKE FLASH FLOODING
POSSIBLE EARLY THIS MORNING.

HAYES

ATTN...WFO...ARX...DVN...IWX...LOT...MKX...

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

LAT...LON   42678933 40998685 40538726 41228902 42029017
            42669050