MESOSCALE PRECIPITATION DISCUSSION 0385
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
745 PM EDT SUN JUL 01 2018

AREAS AFFECTED...IN...IL..KY..TN

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

VALID 012345Z - 020345Z

SUMMARY...TRAINING OR BACKBUILDING ALONG A LINE OF CONVECTION
AHEAD OF A COLD FRONT COULD POSE A FLASH FLOOD THREAT THROUGH THE
EVENING HOURS.

DISCUSSION...REGIONAL RADARS SHOWED CONVECTION AHEAD OF A COLD
FRONT EXTENDING FROM WI INTO CENTRAL MO INCREASING IN AN AXIS OF
2000-3000 J/KG OF MLCAPE. THE GOES-16 CLEAN IR LOOP SHOWED BURSTS
OF COLDER CLOUD TOPS ALONG THE LINE...WITH CLOUD TOP TEMPERATURES
REACHING MINUS 70 DEGREES CELSIUS.

A 20 TO 30 KNOT LOW LEVEL SOUTHWEST FLOW (PER RECENT VWP
OBSERVATIONS) CONTINUE TO FUNNEL 2.00 INCH PRECIPITABLE WATER AIR
(WHICH IS ABOUT TWO STANDARD DEVIATIONS ABOVE THE MEAN) IN A
RIBBON COINCIDENT WITH THE ONGOING CONVECTION. THE MOST RECENT
HRRR MODEL SOUNDINGS SHOWED A MOISTURE COLUMN IN THE MOISTURE
RIBBON...AND THE KILX RADAR SHOWED HOURLY RAINFALL RATES NEAR 2.00
INCHES OVER MONTGOMERY AND MADISON COUNTIES IN IL.

THE CONVECTIVE LINE HAS BEEN PROGRESSIVE THUS FAR...ALONG WITH THE
20 KNOT 850-300 MB MEAN WIND. HOWEVER...THE CONVECTIVE LINE IS
EXPECTED TO SLOW AS THE MID LEVEL WINDS DROP OFF BELOW 10 KNOTS
OVER SOUTHERN IL/IN INTO WESTERN KY/WESTERN TN AFTER 02/00Z. IN
FACT...PROPAGATION VECTORS MAY BRIEFLY OPPOSE THE MEAN
WIND...WHICH COULD FOSTER TRAINING AND BACKBUILDING ALONG THE LINE
AS IT MOVES EAST.

MUCH OF THE HIGH RESOLUTION GUIDANCE IS SLOW TO PICK UP ON THE
CONVECTION IN PROGRESSIVE...AND DO NOT PRODUCE ENOUGH COVERAGE FOR
MUCH OF A FLASH FLOOD THREAT. AT THIS POINT...BASED ON
ENVIRONMENTAL CONDITIONS...THERE SEEMS TO BE ENOUGH FOR FLASH
FLOODING...THOUGH IF THE FRONT REMAINS PROGRESSIVE...AND LOCAL
TRAINING DOES NOT OCCUR...THE THREAT MAY NOT MATERIALIZE. BECAUSE
OF THIS...FLASH FLOODING IS ONLY CONSIDERED POSSIBLE.

HAYES

ATTN...WFO...ILX...IND...IWX...LMK...LOT...LSX...MEG...PAH...

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

LAT...LON   41408682 41098598 40148583 36528823 35948995
            36579070 38468973 40618836