MESOSCALE PRECIPITATION DISCUSSION 0372
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1136 AM EDT THU JUN 28 2018

AREAS AFFECTED...FAR SOUTHEAST MO INTO CENTRAL TN

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

VALID 281535Z - 282035Z

SUMMARY...CONVECTION DEVELOPING IN AN AXIS OF HIGH MOISTURE COULD
TRAIN...POSING A FLASH FLOOD THREAT THIS AFTERNOON.

DISCUSSION...REGIONAL RADARS SHOWED A SLOW INCREASE IN CONVECTIVE
CELLS STRETCHING FROM FAR SOUTHEAST MO ACROSS FAR WESTERN KY INTO
CENTRAL TN. THE GOES-16 CLEAN IR LOOP INDICATED COOLING TOPS WITH
THE CELLS... WITH THE COLDEST TOPS OVER CENTRAL TN. THE CONVECTION
WAS FORMING IN AN AXIS IF DEEP INSTABILITY...WITH THE MOST RECENT
RAP ANALYSIS SHOWING MUCAPE VALUES BETWEEN 3000-4000 J/KG (AND
THESE VALUES WERE SUPPORTED BY 12Z SOUNDINGS IN THE REGION).

THE CONVECTIVE IS TRACKING SOUTHEAST WITH THE 850-300 MB MEAN FLOW
ALONG AN AXIS OF 2.00 INCH PRECIPITABLE WATER AIR LOCATED
SOUTHWEST OF A WARM FRONT EXTENDING FROM SOUTHEAST MO INTO CENTRAL
TN. HOURLY RAINFALL RATES FROM THE KPAH RADAR WERE AS HIGH AS 2.00
INCHES OVER WILLIAMSON COUNTY TN...BUT DRY AIR IN THE MID LEVELS
(AS SEEN IN RAP MODEL SOUNDINGS) SUGGEST THAT HAIL COULD BE
CONTAMINATING THESE VALUES.

MODEL SOUNDINGS INDICATED MOST OF THE STRONG INSTABILITY STAYS
ELEVATED ABOVE A LOW LEVEL INVERSION...WITH DRY AIR REMAINING IN
PLACE IN THE MID LEVELS. THIS COULD ALLOW STORMS TO REMAIN WIND
AND HAIL PRODUCERS AS THEY TRACK SOUTHEAST ACROSS FAR WESTERN KY
INTO CENTRAL TN THIS AFTERNOON. THE PROPAGATION VECTORS SUGGEST
THAT THE TRAINING IS POSSIBLE AS THEY BECOME BETTER ALIGNED WITH
THE STEERING FLOW...INCREASING THE POSSIBILITY OF TRAINING.

THE MOST RECENT HRRR/EXPERIMENTAL HRRR AS NOT AS BULLISH AS SOME
OTHER 12Z HIGH RESOLUTION GUIDANCE WITH RESPECT TO RAINFALL
AMOUNTS...PRESUMING THE STORMS CONTINUE TO BE MAINLY WIND/HAIL
DOMINATED. HOWEVER...TRAINING IN THE HIGH MOISTURE ENVIRONMENT
COULD SUPPORT LOCAL 3.00 INCH RAINFALL AMOUNTS...EVEN IN THE
PRESENCE OF HAIL. THIS COULD RESULT IN A FLASH FLOOD THREAT THIS
AFTERNOON.

HAYES

ATTN...WFO...HUN...LMK...MEG...MRX...OHX...PAH...

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

LAT...LON   37578936 37528806 37508804 37268757 35898574
            35458514 35018493 35068679 35468763 36218897
            36878993 37238988