029
AWUS01 KWNH 111744
FFGMPD
VAZ000-NCZ000-SCZ000-112300-

Mesoscale Precipitation Discussion 0607
NWS Weather Prediction Center College Park MD
143 PM EDT Thu Jul 11 2024

Areas affected...Coastal Plain from far southeast VA through
northeast SC

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

Valid 111743Z - 112300Z

Summary...Slow moving showers and thunderstorms will continue to
regenerate and begin to drift westward through the afternoon.
Rainfall rates of 2-3"/hr are expected, which could produce 2-3"
of rain with locally up to 5". Flash flooding is possible.

Discussion...The GOES-E visible satellite imagery this afternoon
shows a very unique setup across the coastal plain from southeast
VA through northeast SC. In this area, convective Cu is
continuously regenerating along a hybrid cold front/outflow
boundary, with high-level convective debris shifting west into the
Piedmont. Storms are regenerating along this axis due to modest
easterly low-level flow impinging into the boundary to drive
ascent, while concurrently drawing extreme thermodynamics
characterized by near-record PWs above 2.3 inches and SBCAPE above
3000 J/kg westward into the boundary. The persistent ascent into
these thermodynamics has fueled a narrow corridor of nearly
stationary storms this morning, which have resulted in
radar-estimated rainfall rates above 3"/hr, and MRMS measured
rainfall as much as 7" in parts of eastern NC.

Confidence in evolution the next few hours is somewhat limited due
to variable CAM solutions, but the ingredients will continue to
support a heavy rain threat through the evening. A mid-level wave
of low pressure off the NC coast will begin to retrograde
westward, shedding weak impulses onshore coincident with an
increase in moist advection/IVT. This should finally begin to push
the cold front westward, aided by the sea breeze circulation,
while still continuing to be a focus for locally enhanced ascent
through convergence. With PWs remaining at near record values, and
higher SBCAPE spreading westward behind the front, the environment
will remain supportive of rainfall rates exceeding 2"/hr as
reflected by HREF and REFS probabilities reaching 30-50%. At the
same time, the Corfidi vectors are progged to remain nearly
anti-parallel to the mean 0-6km winds, suggesting storms will
continue to backbuild along the front as it advects west,
resulting in a longer duration of these rates. The focus is not
expected to be as narrow as it has so far today since the
instability gradient will weaken as the front pivots towards the
Piedmont, but the HREF probabilities and HREF/REFS 6-hr PMM still
suggest additional rainfall of 2-4" with locally higher amounts in
some areas.

Rainfall today has already been 2-3" with locally much higher
amounts, and this has saturated the soils in a narrow corridor.
While this region will be most sensitive to additional heavy rain
leading to instances of flash flooding, the slow movement of these
intense rain rates have a 15-35% chance of exceeding 3-hr FFG
according to the HREF as far west as I-95 through this evening.
This indicates the continued potential for flash flooding anywhere
across the coastal plain, but the greatest risk will continue to
be in urban areas or atop already saturated soils.

Weiss

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...AKQ...ILM...MHX...RAH...

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

LAT...LON   36987643 36957594 36537573 36007612 35257664
            34677684 34137734 33777801 33627853 33417901
            33357923 33477931 34077907 34757897 35627877
            36537817 36847727