Mesoscale Precipitation Discussion 0805
NWS Weather Prediction Center College Park MD
353 PM EDT Sun Aug 04 2024
Areas affected...Southeast VA...Central/Eastern NC...Much of
SC...Eastern GA
Concerning...Heavy rainfall...Flash flooding possible
Valid 041953Z - 050153Z
SUMMARY...Multiple clusters of heavy showers and thunderstorms
will continue to evolve this afternoon and early this evening
across the coastal plain of the southern Mid-Atlantic and
Southeast. Some isolated to widely scattered instances of flash
flooding will be possible, including sensitives locally to the
urban centers.
DISCUSSION...The mid-afternoon GOES-E GeoColor satellite imagery
in conjunction with dual-pol radar shows an elongated and broken
axis of heavy showers and thunderstorms oriented in a southwest to
northeast fashion across areas of eastern GA and central SC up
through central and eastern NC and into some portions of southeast
VA.
Strong diurnal heating has contributed to MLCAPE values of 1500 to
2500 J/kg, and the region is very moist/tropical in nature with
PWs of 2.0 to 2.25 inches in place based off the latest NESDIS
Blended-TPW data. This moisture and instability meanwhile is seen
focusing along an elongated surface trough across the interior of
the Southeast, which will provide a general focus for additional
expansion of heavy shower and thunderstorm activity going through
the afternoon and early evening hours.
There is also proximity of a weak mid-level shear axis over the
Southeast and southern Mid-Atlantic region which is helping to
yield as much as 30 kts of effective bulk shear. This coupled with
the instability may favor some locally stronger and persistent
updrafts for more organized convection.
Rainfall rates will be likely reaching 2.0 to 2.5 inches/hour with
the stronger storms, and the cell-motions are expected to be
relatively slow-moving which will potentially favor some scattered
storm totals of 3 to 4+ inches.
Isolated to widely scattered instances of flash flooding will be
possible where these heavier rains focus, and this will include
the more urbanized locations such as Columbia, SC and the
Raleigh-Durham, NC vicinity.