Mesoscale Precipitation Discussion 0767
NWS Weather Prediction Center College Park MD
344 PM EDT Thu Sep 17 2020

Areas affected...Eastern Carolinas

Concerning...Heavy rainfall...Flash flooding likely

Valid 171837Z - 172330Z

Summary...Heavy rainfall associated with Sally tracking across
eastern South Carolina will move into southern North Carolina
through the rest of the afternoon. Hourly rain totals of 2-3" are
likely to continue into the evening. Localized 3-5" totals are
likely with flash flooding expected to continue to occur.

Discussion...A area of overlapping instability and tropical
moisture along a warm front, well ahead of the center of T.D.
Sally (which is over north-central GA at 19Z), has made for a
particularly heavy swath of thunderstorms to occur over eastern SC
this afternoon. Recent mesonet observations in east-central SC
along with estimates from KCAE depict a swath from Sumter to
Darlington with 4-6" in the past 3 hours with 5.38" measured just
west of Florence, SC with totals in the past hour generally 2 to
2.5". This axis of particularly heavy rain appears to be on a
gradient where MUCAPE is greater than 1200 J/kg per recent RAP
analysis.

This area of heavy rain will continue to progress along the warm
front into southern NC through the rest of the afternoon and reach
into east-central NC by this evening. The 15Z HRRRv4 does a decent
job depicting this activity and highlights areas downstream of the
current activity along the warm front in southern NC as the area
with the greatest potential for 4-6" through 23Z. 3-hr flash flood
guidance is generally 2.5-3.5" over this area.

The intensity and duration of this rainfall will continue to cause
flash flooding, particularly from northeastern SC well into
southern NC where the highest amounts are expected through 23Z.
Some of this flooding could be significant for any sensitive or
urban locations.

Jackson

ATTN...WFO...CAE...CHS...ILM...MHX...RAH...

ATTN...RFC...SERFC...NWC...

LAT...LON   35277845 35097767 34047845 33367950 33208006
            33298017 33987993 34417978 35047920