AWUS01 KWNH 151332
FFGMPD
VAZ000-WVZ000-TNZ000-KYZ000-INZ000-MSZ000-MOZ000-ARZ000-151930-

Mesoscale Precipitation Discussion 0038
NWS Weather Prediction Center College Park MD
830 AM EST Sat Feb 15 2025

Areas affected...Portions of the OH/TN Valleys and Mid-South

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

Valid 151330Z - 151930Z

SUMMARY...An expansive axis of heavy showers and thunderstorms
with strong cell-training concerns will be promoting a widespread
flash flood threat over the next several hours across portions of
the OH/TN Valley region and Mid-South.

DISCUSSION...The latest GOES-E IR satellite imagery shows an
expansive areas of heavy shower and thunderstorm activity
impacting areas of eastern AR up across central and western TN and
much of central and southern KY. Light to moderate stratiform
rains are noted north of here closer to the OH River and also into
the central Appalachians.

The convection that is organizing is associated with strong warm
air advection which is being aided by a powerful southwest
low-level jet of 50 to 60+ kts overrunning a strong frontal zone.
This is driving very strong moisture transport which is showing up
in an impressive fashion with the experimental CIRA-LVT (Layered
Vapor Transport) imagery as it is depicting SFC/850 layer LVT
magnitudes of 300+ kg/m/s. Meanwhile, a nose of MUCAPE values on
the order of 500 to 1000 J/kg is now oriented up across central to
northeast AR through western TN and western KY and this is helping
to facilitate the broader axis of elevated convection.

Over the next several hours, very strong warm air advection and
moisture transport will continue to support organizing bands of
convection that will be aligned with the deeper layer mean flow
and thus will be conducive for a substantial level of
cell-training. Increasing CAPE values with time along with
strengthening shear profiles will support stronger convective
elements that will yield increasingly heavy rainfall rates.

Rainfall rates with the stronger storms may reach as high as 1 to
1.5 inches/hour at least going through midday, but with
significant cell-training concerns, this may result in some
rainfall amounts by early afternoon alone of 2 to 4 inches. The
latest CAM guidance suggests areas of western/northern TN through
southern KY will have the heaviest totals going through the 18Z to
20Z time frame, with somewhat lesser amounts farther north.

Given the extremely sensitive/saturated soil conditions and
already elevated streamflows for many locations, these rainfall
totals over the next several hours are likely to begin resulting
in widespread flash flooding. Additional MPDs will be issued this
afternoon to update what should evolve into a high-impact and
life-threatening flash flood event in time.

Orrison

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