Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
422 AM EDT Wed Jun 17 2026
Day 2
Valid 12Z Thu Jun 18 2026 - 12Z Fri Jun 19 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHEAST...

...Southeast...

Very heavy rain associated with what will be the remnants of PTC1
will be ongoing at the start of the period over most of southern
Mississippi and likely extending into southwestern Alabama. These
storms will be fueled by a strong low level jet pumping deep
tropical moisture into a corridor that covers much of the Moderate
Risk area. By around midday, the rapidly increasing instability and
the typical weakening of the low level jet will allow the
widespread convection to transition into training lines of storms
that track east with time, as the line gradually drifts south
towards the greatest instability and moisture source that is the
Gulf. Thus, the greatest focus of heaviest rain now appears to set
up from southeastern Mississippi east across the southern tier of
Alabama and far western Georgia. 3+ inch/hour rainfall rates from
individual storms will combine with multiple hours of rain as the
storms train along the east-west oriented lines. Storm total
rainfall for the day could easily exceed 8 inches in spots. Mobile,
AL will be the biggest city in the crosshairs of the heaviest
rainfall.

With this rather dramatic southward shift in the guidance of where
the heaviest rainfall totals are expected, the Moderate Risk
inherited was trimmed significantly on the north side, while
expanded across southeast Alabama, the western Florida Panhandle,
and far southwestern Georgia. The Moderate Risk was downgraded out
of both the Birmingham and Atlanta metros as those areas see
leftover heavy rains from the much more potent and heavy rain
producing storms much closer to the Gulf Coast. Nonetheless,
periodic convection and a long duration of light to moderate rain
is still expected over those metros, so the higher-end Slight
remains in effect. Convective coverage greatly decreases Thursday
night over all of the Southeast, but isolated to widely scattered
storms could persist through the night in some areas.

...Ohio/Tennessee Valleys...

Further north from the Gulf Coast along the Ohio and Tennessee
Valleys, a cold front will start the day following roughly parallel
to the Ohio River. The front will slowly sink southward over
Kentucky through the day. Meanwhile, daytime heating and
unidirectional southwesterly flow ahead of the front is expected to
generate a long line of storms. The storms will be training and
backbuilding along the KY/TN border and extending into West
Virginia. Guidance has shifted a bit further south, especially with
the western end of the line, so the higher-end Slight now follows
the entire length of the KY/TN border, and now includes Nashville,
while the Ohio River has largely been removed from the risk area.
With nightfall and the loss of daytime heating, the flash flooding
risk from storms will also diminish.

...Arkansas/Oklahoma...

On Thursday night, the westernmost extension of the low-level jet
over Texas will run into the same stalled out front that extends
east into Kentucky. This clash of air masses is likely to result in
the development of an MCS over eastern Oklahoma, which will then
propagate southeastward into western Arkansas. Here too the soils
are wetter than normal from multiple bouts of heavy rain in recent
weeks, so a Slight Risk remains in place over the area with few
changes.

Wegman


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt