MESOSCALE PRECIPITATION DISCUSSION 0878
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
131 PM EDT SUN OCT 08 2017

AREAS AFFECTED...NORTHEAST GA...NORTHWEST SC...WESTERN NC...FAR
EASTERN TN

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

VALID 081730Z - 082330Z

SUMMARY...VERY HEAVY RAINS ARE EXPECTED OVER THE NEXT SEVERAL
HOURS OVER THE HIGHER TERRAIN OF THE SOUTHERN APPALACHIANS. SOME
FLASH FLOODING WILL BE POSSIBLE.

DISCUSSION...T.D. NATE CONTINUES TO LIFT QUICKLY NORTH-NORTHEAST
UP ACROSS WESTERN AL AND SHOULD MOVE UP ACROSS SOUTHERN TN BY
AROUND 21Z. THERE CONTINUES TO BE A VERY STRONG INFLUX OF DEEP
TROPICAL MOISTURE ALONG WITH ENHANCED SURFACE CONVERGENCE AROUND
THE EASTERN SEMICIRCLE OF NATE...WITH MULTIPLE BANDS OF WELL
ORGANIZED CONVECTION. THE STRONGEST CONVECTIVE BAND EXTENDS FROM
FAR SOUTHEAST TN SOUTHWARD DOWN ACROSS MUCH OF CENTRAL GA WITH A
LINEAR AXIS OF VERY INTENSE RAINFALL RATES. THE INDIVIDUAL CELL
MOTION IS RAPIDLY OFF TO THE NORTH...BUT THERE IS A BRIEF PERIOD
CELL-TRAINING OCCURRING AS THE OVERALL BAND SHIFTS GRADUALLY TO
THE NORTHEAST.

THE LATEST RAP GUIDANCE FAVORS A SOUTHEAST LOW LEVEL JET OF 50 TO
60 KTS AIMING INTO THE HIGHER TERRAIN OF THE SOUTHERN APPALACHIANS
THIS AFTERNOON WITH AN EMPHASIS ON NORTHEAST GA...NORTHWEST SC AND
WESTERN NC WHILE THE CENTER OF NATE BEGINS TRACKING UP THROUGH THE
TN VALLEY. THE CIRA-LPW DATA SHOWS AND ALREADY VERY MOIST
ENVIRONMENT WITH PWATS JUST OVER 2 INCHES...BUT THESE VALUES WILL
LIKELY INCREASE FURTHER WITH A NOSE OF 2.25 TO 2.5 INCH PWATS
EXPECTED TO NOSE UP ACROSS THE SOUTHEAST PIEDMONT AND INTO THE
FAVORED SOUTHEAST FACING TERRAIN THROUGH MID TO LATE AFTERNOON.
THERE IS MUCH GREATER INSTABILITY ALSO NOTED ACROSS THE SOUTHEAST
COASTAL PLAIN WITH THE LATEST RAP ANALYSIS SHOWING A NOSE OF
MLCAPE VALUES EXCEEDING 1500 J/KG LIFTING UP ACROSS EASTERN GA
AHEAD OF THE AFOREMENTIONED CONVECTIVE BANDING.

THE MOISTURE AND INSTABILITY TRANSPORT WILL BE QUITE STRONG AND
WILL FAVOR SUSTAINABLE CONVECTIVE BANDS WITH RAINFALL RATES THAT
MAY APPROACH 3 INCHES/HR. THIS WILL BE AIDED BY OROGRAPHIC ASCENT.
DESPITE QUITE HIGH FFG VALUES...THE INTENSE RAINFALL RATES OVER
THE HIGHER TERRAIN WILL ENCOURAGE SOME RAPID RUNOFF AND MAY RESULT
IN SOME ENHANCED SHORT-TERM FLASH FLOODING CONCERNS. EXPECT
RAINFALL TOTALS THROUGH 00Z OF AS MUCH AS 4 TO 6+ INCHES. WILL
CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...CAE...FFC...GSP...MRX...RNK...

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

LAT...LON   36598154 36328112 35368137 34458186 33698287
            33658368 34028420 34558448 34828463 35088463
            35378439 35598404 35718372 35838338 36008310
            36128287 36288223 36348194