Special Weather Discussion: Monday Afternoon: Isolated Flash Flooding Possible

Heavy showers and isolated thunderstorms will continue
developing along an axis from the South Carolina Coast to the
North Carolina Blue Ridge rest of this afternoon. Rainfall of
2"/hr is likely to continue and expand in coverage with localized
totals exceeding 4" possible rest of this afternoon. Localized
flash flooding can be expected.

Discussion...Broad scale southerly flow is present over the
Southeast with a trough along the Carolina Coast. A somewhat
focused corridor of activity has developed from the SC coast north
of Charleston inland to the NC Blue Ridge which is ahead of a
mid-level vort lobe drifting north over southern SC per recent RAP
runs. Heavy thunderstorms moved through Charleston late morning
with continued development lifting along the coast. A new cluster
of thunderstorms have developed in the past hour over interior
northern SC and heavy showers continue from this morning from
around Charlotte west through the southern NC Blue Ridge (with
further growth possible through the diurnal max). Robust,
tropically sourced moisture is present over this corridor with
2.3" PW along the coast and 2" butting up against the Blue Ridge
which is around 2 sigma above normal across the region. SBCAPE of
1500-2500 J/kg along this corridor is allowing this development
and warm rain processes are maximizing rates with with recent
hourly rainfall of 1.5-2" in the heaviest activity.

Recent HRRR runs are a little subdued compared to reality, but
generally focus afternoon development along this corridor. Flash
flood guidance is 1.5-2"/hr in the Piedmont/foothills and
generally 2.5"/hr in the Coastal Plains. The combination of
extreme moisture and sufficient instability should allow for
localized extreme rainfall rates of up to 3"/hr which would cause
localized flash flooding rest of the afternoon.

Given the broad scale of the elevated moisture across the
Southeast, further consideration will be given to other areas
outside this corridor (which is purposefully just north of
vulnerable Columbia based on trends), but for now this appears to
be the most likely area for flash flood concern this afternoon.