Mesoscale Precipitation Discussion 0705
NWS Weather Prediction Center College Park MD
1234 AM EDT Wed Jul 16 2025

Areas affected...Southern Appalachians...

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

Valid 160435Z - 160930Z

SUMMARY...Slow moving/stationary cells with ample deep layer
moisture may generate localized 1.5"/hr and 2-3" totals over
rugged terrain resulting in possible widely scattered incidents of
flash flooding for the next few hours.

DISCUSSION...GOES-E 10.3um loop shows a scattering of developing
smaller core thunderstorms across the southern Appalachians.  CIRA
LPW shows SW to NE oriented subtropical band of moisture
(associated with retrograding TUTT cell); SFC-850mb layer is noted
as 99th percentile within the last 20years of record for the
product.  Solid upslope flow of 925-850mb still remains at
15-20kts per VWP before veering northeast across the spine of the
Appalachians, increasing moisture flux along it.  So while loss of
heating has reduced instability (500-1000 J/kg) and updraft vigor,
there remains sufficient forcing to develop these widely scattered
cells.  Aloft, the band is within the core of the deep layer ridge
and though steering and cell motions are near zero there is
directional divergence for some modest outflow to help at least
allow for a few up/downdraft cycles before dissipation.  However,
one limiting factor is the narrower core width likely resulting in
broad enough moisture loading for extreme rainfall rates and
totals (even with slow drift).  However,  spotty 1.5-2"/hr rates
and localized 2-3" totals in rugged terrain will maintain a widely
scattered risk of localized flash flooding, with greater potential
along the eastern side of the terrain.  

Gallina

ATTN...WFO...FFC...GSP...MRX...RNK...

ATTN...RFC...ALR...ORN...TIR...NWC...

LAT...LON   36848218 36818158 36518106 35788113 34848264
            34378339 34038440 34398498 35538427 35988380
            36348342 36638299