MESOSCALE PRECIPITATION DISCUSSION 0263
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1248 AM EDT TUE MAY 23 2017

AREAS AFFECTED...NORTHEAST AL INTO SOUTHERN APPALACHIANS

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

VALID 230444Z - 230914Z

SUMMARY...EMBEDDED CONVECTIVE ELEMENTS WITHIN A BROADER STRATIFORM
RAIN AREA ARE PRODUCING LOCALLY HEAVY RAINFALL RATES ACROSS THE
AREA.

DISCUSSION...AS OF 04Z A CONVECTIVELY INDUCED LOW WAS EVIDENT OVER
NORTHERN AL...MOVING NORTHEASTWARD. OUT OF AHEAD OF THIS FEATURE A
LARGE AREA OF STRATIFORM RAINFALL IS CURRENTLY IMPACTING PORTIONS
OF NORTHERN AL/GA INTO EASTERN TN AND SOUTHWEST NC. GIVEN THE LACK
OF INSTABILITY...RAINFALL RATES ARE GENERALLY NOT IMPRESSIVE WITH
THIS ACTIVITY. HOWEVER HAVE NOTICED EMBEDDED CONVECTIVE ELEMENTS
PRODUCING SOME IMPRESSIVE RAINFALL AMOUNTS AND RATES. THE FORCING
MECHANISM FOR THESE EMBEDDED CONVECTIVE ELEMENTS IS A BIT
UNCLEAR...AS UPRIGHT INSTABILITY IS PRETTY MUCH NON EXISTENT. BUT
CLEARLY GETTING SOME LOCALIZED AREAS OF ENHANCED LIFT AND LOW
TOPPED CONVECTIVE ELEMENTS EMBEDDED WITHIN THE BROADER STRATIFORM
RAIN AREA. A SITE IN CROSSVILLE ALABAMA HAS RECEIVED 4.8" OF RAIN
IN THE LAST THREE HOURS FROM THIS ACTIVITY..WHICH CORROBORATES
RADAR ESTIMATES.

RECENT RADAR TRENDS SHOW A CONTINUATION OF THESE HEAVIER
CONVECTIVE ELEMENTS STRETCHING FROM NORTHEAST AL NORTHEASTWARD
TOWARDS THE TN/NC BORDER NEAR A FRONTAL BOUNDARY EXTENDING
NORTHEAST FROM THE AL LOW. UNCLEAR HOW LONG THESE HEAVIER CORES
WILL PERSIST AND AM BEGINNING TO SEE SOME EASTWARD
PROGRESSION...BUT RECENT TRENDS SUGGEST THAT A SHORT TERM
LOCALIZED FLASH FLOOD RISK WILL EXIST ACROSS THE MPD AREA. THE LOW
TOPPED NATURE OF THE CONVECTIVE ELEMENTS SUGGESTS THAT EFFICIENT
WARM RAIN PROCESSES ARE LIKELY DOMINANT...RESULTING IN THE HEAVY
RAINFALL RATES. POCKETS OF 3-5" EMBEDDED WITHIN A BROADER LIGHTER
AREA OF RAINFALL IS LIKELY.

CHENARD

ATTN...WFO...BMX...FFC...GSP...HUN...MRX...

ATTN...RFC...LMRFC...SERFC...

LAT...LON   35608358 35268336 34698419 34168518 34068574
            34658606 34978547 35298467