AWUS01 KWNH 220951
FFGMPD
MDZ000-VAZ000-NCZ000-WVZ000-SCZ000-GAZ000-TNZ000-KYZ000-221530-

Mesoscale Precipitation Discussion 1353
NWS Weather Prediction Center College Park MD
550 AM EDT Tue Sep 22 2026

Areas affected...Central and Southern Appalachians...TN Valley

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

Valid 220950Z - 221530Z

SUMMARY...Locally slow-moving showers and thunderstorms with heavy
rainfall rates may pose an isolated threat for flash flooding this morning.

DISCUSSION...The latest radar and satellite imagery shows
scattered areas of locally heavy showers and thunderstorms still
impacting portions of the TN Valley and the central to southern
Appalachians, with some recent convective development noted as far
south as northern GA.

This convection continues to be supported by some surface low
activity riding along a wave frontal zone that is now generally
draped across eastern TN through western NC. However, there is a
well-defined inverted trough that extends north up across
southwest VA and into central and southern WV which is also a
facilitator for some of the activity.

The airmass remains moist and modestly unstable with PWs upwards
of 1.5+ inches, and MUCAPE values as high as 500 to 1000 J/kg. The
greatest instability is focused down across eastern TN, northern
GA, and southwest NC which is where generally the strongest
convection and cold cloud tops are focused.

Supporting the ongoing areas of showers and thunderstorms
continues to be the larger scale presence of right-entrance region
upper-level jet dynamics. This coupled with orographics and the
proximity of the front should tend to favor areas of showers and
thunderstorms persisting into the morning hours.

The latest hires model guidance suggests convection may become a
bit more expansive across areas of northern GA over the next few
hours, but overall, there should be at least a scattered threat
for showers and thunderstorms well to the north across the
southern and central Appalachians and adjacent areas of the Blue
Ridge and Piedmont east of the terrain. Portions of the TN Valley
and Cumberland Plateau region across eastern TN will also still
have potential for locally slow-moving convection.

Rainfall rates will be continue to be capable of reaching 1 to 2
inches/hour, and the relatively slow cell-motions near areas of
higher terrain may allow for some additional 2 to 3+ inch rainfall
amounts this morning. This may allow for some isolated areas of
flash flooding, and especially near areas of rugged terrain. It
should be noted that areas farther north across southwest VA and
especially through central WV have low FFGs, so this area has a
notably sensitive antecedent environment for runoff concerns.

Orrison

ATTN...WFO...FFC...GSP...JKL...LWX...MRX...OHX...PBZ...RLX...RNK...

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

LAT...LON   39448017 39187943 38507941 37347986 35578099 
            34618233 33928385 33958492 34598542 35678503 
            36978331 38058233 39078105 

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