Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
252 PM EDT Wed May 14 2025
Day 3
Valid 12Z Fri May 16 2025 - 12Z Sat May 17 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OHIO AND TENNESSEE VALLEYS...

A potent shortwave trough will round the periphery of the
vertically stacked low over the northern Plains and upper Great
Lakes on Friday. This shortwave will tap into a low level jet of
Gulf moisture riding the prior low's occluded front. This will
reinvigorate the front, resulting in rather fast northeastward
moving storms across the risk area. Much of this area remains
saturated given elevated soil moisture anomalies on the latest NASA
SPoRT due to prior storms, so any training thunderstorms will be
capable of producing flash flooding. The trend over the past 12 hrs
is for a greater training threat within the confines of the west
to east oriented front aligned from the Mid-Mississippi Valley
through the Central Ohio Valley with a proxy close to the Ohio
River down into KY. With such a well-defined theta_E gradient and
mean flow becoming more parallel to the boundary orientation, the
threat for waves of convection to funnel over a general area has
risen with ensemble bias corrected output and ML QPF placement
actually a bit further south overall. There is some merit to the
front being located a bit further into KY as we move closer to the
event, a trend that has occurred quite often inside 48 hrs with the
best convection co-located near the better instability access. A
SLGT risk is now embedded within the broad MRGL from previous
forecast with the higher risk now running from the Mid-Mississippi
River basin, east through the Central Ohio Valley to far western
WV.

Wegman/Kleebauer

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt