Mesoscale Precipitation Discussion 0582
NWS Weather Prediction Center College Park MD
131 PM EDT Thu Aug 02 2018

Areas affected...Central and Eastern North Carolina, Southern
Virginia

Concerning...Heavy rainfall...Flash flooding possible

Valid 021730Z - 022130Z

Summary...Locally heavy rainfall will be possible with a
concentrated area of thunderstorm activity this afternoon,
primarily in central and eastern North Carolina. Some of these
storms could produce rain rates of 2 in/hr or more, which could
lead to localized flash flooding.

Discussion...Regional radars showed a broken line of thunderstorms
extending from just west of Richmond VA to just west of Charlotte
NC. Earlier this morning, a more compact version of this line of
convection produced a narrow swath of heavy rainfall and flooding
from near Winston-Salem and Greensboro, and areas just to the
north. The line has since drifted to the east, but it remains
oriented nearly parallel to the deep layer mean flow. MLCAPE
values around 2000 j/kg (per RAP analysis) and PWATs approaching 2
inches (GSO 12Z sounding was 2.02 inches) should be enough to
sustain strong, organized convection with heavy rain rates to 2
in/hr or more. The primary difference with this morning is that
the rain band is now centered east of areas that have received
heavy rainfall recently, so the antecedent conditions are less
favorable to flash flooding. Nevertheless, the convection may
begin to train over some larger urban areas in the region this
afternoon, and 2 in/hr rain rates would be sufficient to cause
flash flooding in such areas. Further south, in far southern North
Carolina, a separate cluster of thunderstorms initiated off the
sea breeze near Cape Fear, and was pushing N/NW into interior
North Carolina. These storms were producing heavy rain rates as
well, and may coalesce with existing thunderstorm activity over
central North Carolina later this afternoon. Such a merger could
create a larger areal coverage of heavy instantaneous rain rates,
which would have the effect of prolonging the duration of heavy
rain in some locations. This may create more favorable conditions
for flash flooding, particularly if the storm mergers occurred in
the vicinity of the Triangle region.

Lamers

ATTN...WFO...AKQ...CAE...ILM...MHX...RAH...RNK...

ATTN...RFC...MARFC...SERFC...

LAT...LON   37437771 36787710 35587765 34467863 34348000
            35648015 37057872