Mesoscale Precipitation Discussion 0840
NWS Weather Prediction Center College Park MD
1212 PM EDT Fri Aug 01 2025

Areas affected...Southwest VA...Western NC...Northeast TN...

Concerning...Heavy rainfall...Flash flooding likely

Valid 011610Z - 012200Z

SUMMARY...Another round of slow moving, locally intense
thunderstorms capable of 1.75-2"/hr rates and localized 2-4"
totals.  Proximity to terrain suggest localized flash flooding is
possible.

DISCUSSION...16z surface analysis shows cold front has dropped
through much of the Piedmont and coastal plain of VA and NC.  A
weak surface low in Upstate SC connects to the easier defined cold
front straddling the southern base of the Cumberland Plateau and
Appalachians in N AL/GA.  However, mid-level weak down sloping has
cleared much of the post-frontal low clouds across E TN/SW VA into
Western Carolinas.  The surface pressure trof has become even more
striking in isobaric and wind fields with weak surface lows dotted
from Roanoke, VA to Boone, NC to Hickory, NC locally increasing
convergence.  Surface to boundary layer moisture remains
anafrontal given lack of mixing/rainfall across the area, so Tds
remain in the low 70s and cold air is fairly shallow to support
1.75-2" PWats within the central to southern Appalachians and
along the Blue Ridge.  

Goes-E Visible animation shows the erosion of the stratiform but
also the north to northeast flow banking the deeper layer moisture
into the upslope regions.  The clearing has resulted in solid
insolation with temperatures rising into the upper 70s and low
80s; supporting an inverted bulge of unstable air along the
inverted surface trough with SBCAPEs of 1000-2000 J/kg from SW VA
to Upstate SC to work with.  Deep layer flow is weak for slow cell
motions; though oblique connection to the right entrance of the
northern stream jet (30-40kts) across central VA will support some
outflow to help maintain updraft strength/organization.  Low level
confluence will help to keep back-building, prolonged upslope flow
to support additional development as slow propagation southward
along the terrain will be the domain cell motions over the
afternoon hours.

As such, cells capable of 1.75-2"/hr will have some solid duration
to support localized 2-3" totals and with possible upstream
redevelopment is not out of the realm of possibility a localized
spot or two may reach 4" totals. FFG values are much lower in the
higher terrain of NE TN/W VA and would be likely to be exceeded if
cells were to develop, but best deep layer moisture convergence is
along the Blue Ridge where values are about .5-1" higher in both
1/3hr FFG values.  Still, the deep amount of moisture and
efficiency will likely even exceed the higher FFG values given
spotty 2-4"/3hrs even on the eastern edges of the MPD area of
concern.  As such, focused/localized incidents of flash flooding
are considered likely through the afternoon.

Gallina

ATTN...WFO...GSP...MRX...RAH...RNK...

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

LAT...LON   37847994 37717912 37177885 36667906 36167957
            35648050 35358208 35488357 36258354 36908213
            37368098