Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Jul 25 2025 17:09:56

AWUS01 KWNH 251708
FFGMPD
PAZ000-MDZ000-WVZ000-OHZ000-252245-

Mesoscale Precipitation Discussion 0798
NWS Weather Prediction Center College Park MD
107 PM EDT Fri Jul 25 2025

Areas affected...Upper Ohio Valley into central Appalachians

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

Valid 251704Z - 252245Z

SUMMARY...Isolated flash flood potential will exist over sensitive
locations of the upper OH Valley into the central Appalachians
from 1 to 2 inches of rain in 30-60 minutes. The flash flood
threat will continue through the remainder of the afternoon with
potential for 2-4 inch totals.

DISCUSSION...Visible satellite and regional radar imagery at 1645Z
showed ongoing thunderstorms extending from southeastern OH into
north-central WV, partially tied to a vorticity max over far
southeastern OH noted on water vapor imagery within a mean
westerly flow. LPW imagery from OSPO showed this region was not
under the axis of highest moisture, which was positioned over
northern IL into northern PA, but a secondary axis noted along the
OH River into the central Appalachians. 12Z soundings showed PW
values at ILN and PIT of 1.78 and 1.71 inches (respectively), both
just over the 90th percentile for late July. SPC mesoanalysis data
from 16Z showed MLCAPE of 1500-2500 J/kg.

Additional cells are forecast to develop upstream, in the wake of
the departing vorticity max over southeastern OH over the next few
hours with movement from west to east. 850-925 mb winds as seen on
VAD wind plots were 10-15 kt from southern OH into southwestern
PA, and slightly weaker to the south as seen at KRLX in WV. While
low level flow was parallel to the mean steering flow, relatively
weak low level flow should not favor as strong of an upslope
response into the higher terrain of the Appalachians compared to a
stronger low level flow setup. Still, the high moisture
environment and plentiful CAPE in place could support brief
training and/or repeating of cells, capable of generating 1 to 2
inches of rain in 30 to 60 minutes, with isolated totals in the
2-4 inch range. The potential for these higher rates should remain
isolated but may generate excess runoff within typical low lying,
urban areas or across locally sensitive terrain.

Otto

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!9vOPY-XYQnn81z2ZCo2ztX0x4oHtjrgPQaQoaTBChxxPZfwq8SiE7BAsWhAUd0KKz1sa=
MIiot3LEvYZtpVIShEIL25Q$  for graphic product...

ATTN...WFO...CTP...ILN...LWX...PBZ...RLX...RNK...

ATTN...RFC...RHA...TIR...NWC...

LAT...LON   40767951 40697897 40477864 39687898 38947938=20
            38397981 38018045 37918091 37938131 38078182=20
            38308223 38478250 38708267 39188278 40058266=20
            40418169 40718045=20

=3D =3D =3D
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