390
AWUS01 KWNH 181838
FFGMPD
MDZ000-VAZ000-NCZ000-SCZ000-190000-

Mesoscale Precipitation Discussion 0955
NWS Weather Prediction Center College Park MD
237 PM EDT Mon Aug 18 2025

Areas affected...Coastal Plain from Southeast Virginia through
Northeast South Carolina

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

Valid 181836Z - 190000Z

Summary...Showers and thunderstorms developing along a cold front
will expand and intensify through the afternoon. These storms will
be slow moving, and contain rainfall rates of 1-3"/hr. This could
produce 2-3" of rainfall with locally higher amounts, and
instances of flash flooding.

Discussion...The GOES-E day-cloud phase microphysics RGB this
afternoon is beginning to show rapid updraft growth from the
Tidewater region of Virginia through eastern NC. These storms are
developing along a slowly advancing cold front, with low-level
convergence along the boundary the primary ascent mechanism. Lift
along this front is occurring into robust thermodynamics to
support heavy rainfall. PWs measured by GPS are as high as 1.6
inches in southeast Virginia, and onshore northeast flow is
funneling a narrow corridor of PWs above 1.9 inches into eastern
NC. This elevated PW is overlapping MUCAPE of 2000-3000 J/kg
centered along this front, and developing convection within this
environment is producing radar-estimated rain rates that have
already exceeded 1.5"/hr according to KMHX.

The high-res CAMs are a little slow to capture the ongoing
development, but are generally in agreement that a narrow corridor
of thunderstorms will expand along this front through peak heating
of the aftn. This is reflected by relatively high EAS
probabilities for 1"/6hrs focused across eastern NC which reflect
the good CAM agreement. These storms will be generally slow moving
from N/NE to S/SW along the boundary, and cell motions progged by
propagation vectors the next several hours will be just around 5
kts. Additionally, these propagation vectors will remain aligned
to the front, suggesting training and repeating cells through the
aftn. With rain rates likely reaching 1-3"/hr (HREF neighborhood
probabilities for 2"/hr peaking above 60% coincident with HRRR
15-min rainfall above 0.75" suggesting brief 3"/hr rates), total
rainfall could reach 2-3" with locally as much as 5" possible as
shown by HREF neighborhood probabilities for 5"/6hrs as high as
20%.

This region has been quite wet recently as reflected by AHPS 7-day
rainfall that is above 300% of normal in most of the discussion
area. Although some of this rainfall has drained efficiently to
lower 0-10cm RSM to less than 50% and elevate 3-hr FFG to above
3", the forecast slow movement and training of these cells is
still causing HREF 3-hr FFG exceedance probabilities above 40%.
While this suggests the flash flood risk is generally confined to
where the most significant training can occur, it is possible that
any of these intense rain rates, especially if they occur atop an
urban area, could cause instances of flash flooding through the
aftn.


Weiss

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

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

ATTN...RFC...ALR...RHA...NWC...

LAT...LON   38027567 37737546 37347537 36607542 36067548
            35467578 34927611 34637662 34427735 34257805
            34137857 33977928 33897995 33938042 34098063
            34338052 34637978 34897904 35457818 36247740
            36977686 37587637 37897615