Graphic for MPD #0877

MESOSCALE PRECIPITATION DISCUSSION 0877
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1124 AM EDT SUN OCT 08 2017

AREAS AFFECTED...SOUTHERN IN...SOUTHERN OH...SOUTHWEST
WV...KY...FAR NORTHWEST TN

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

VALID 081520Z - 082120Z

SUMMARY...HEAVY RAINS ARE EXPECTED THROUGH THE AFTERNOON HOURS.
GIVEN THE RATHER CONCENTRATED AND PERSISTENT NATURE OF THE
RAINFALL...SOME RUNOFF AND/OR FLASH FLOODING CONCERNS WILL BE
POSSIBLE.

DISCUSSION...DEEP LAYER SOUTH TO SOUTHEAST FLOW WELL NORTH OF T.D.
NATE IS TRANSPORTING COPIOUS AMOUNTS OF TROPICAL MOISTURE UP
ACROSS THE TN/OH RIVER VALLEYS WHERE IT IS INTERACTING WITH A
WELL-DEFINED FRONTAL ZONE DRAPED ACROSS THE REGION. CIRA-LPW DATA
THROUGH 12Z SHOWS A VERY DEEP COLUMN OF ENHANCED MOISTURE
CONCENTRATION...WITH PWATS OF 2.0 TO 2.3 INCHES...WHICH IS LOCALLY
OVER 3 SIGMAS ABOVE NORMAL FOR THIS TIME OF YEAR.

THE LOW LEVEL FLOW OVER THE BOUNDARY HAS STRENGTHENED OVER THE
LAST FEW HOURS RESULTING IN STRONG ISENTROPIC LIFT AND THUS AN
EXPANSION OF HEAVY RAINFALL NORTHWEST OF THE FRONT. SOME OF THE
HEAVIEST RAINFALL IS CURRENTLY NOTED OVER CENTRAL AND WESTERN KY
AND IS APPROACHING FAR SOUTHERN IN ACROSS THE OH RIVER. FARTHER
EAST...SOME HEAVIER RAINS ARE ALSO BEGINNING TO DEVELOP OVER
NORTHEAST KY AND SOUTHWEST WV.

OVER THE NEXT SEVERAL HOURS...EVEN STRONGER ISENTROPIC ASCENT IS
EXPECTED AS T.D. NATE LIFTS UP ACROSS SOUTHERN TN. THIS COUPLED
WITH FAVORABLE RIGHT-ENTRANCE REGION JET DYNAMICS/UPPER DIVERGENCE
OVER THE OH VALLEY AND PRESENCE OF A WEAK SHORTWAVE TROUGH/VORT
CENTER OVER WESTERN TN (AS SEEN IN NON-OPERATIONAL GOES-16 RGB
AIRMASS IMAGERY) SHOULD FOSTER WIDESPREAD HEAVY RAINFALL.

INSTABILITY IS HIGHLY LIMITED WHICH WILL HELP KEEP THE RAINFALL
RATES RELATIVELY LOW...BUT WITH WARM RAIN PROCESSES IN PLACE...THE
EXPECTATION IS FOR PERSISTENT AND HIGHLY EFFICIENT STRATIFORM
RAINFALL WITH RATES THAT COULD BE AS HIGH AS 0.75 INCHES/HR. A
CONSENSUS OF THE LATEST HRRR AND HRRRX GUIDANCE SUGGESTS AS MUCH
AS 2 TO 3 INCHES OF ADDITIONAL RAIN WITH ISOLATED HEAVIER TOTALS
THROUGH 21Z.

GIVEN SOME OF THE HEAVY RAINFALL THAT OCCURRED SINCE LAST
EVENING...THE SOIL CONDITIONS ARE LOCALLY NOW SATURATED...AND ANY
ADDITIONAL HEAVY RAINFALL MAY ENCOURAGE SOME RUNOFF AND/OR FLASH
FLOODING CONCERNS.

ORRISON

ATTN...WFO...ILN...IND...JKL...LMK...MEG...OHX...PAH...RLX...

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

LAT...LON   39448378 39208224 38758166 38218150 37888175
            37628240 37418347 37098508 36718657 36348784
            36318862 36508898 37078889 37988785 38638686
            39308529


Last Updated: 1124 AM EDT SUN OCT 08 2017