Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Fri Jul 10 2026
Day 2
Valid 12Z Sat Jul 11 2026 - 12Z Sun Jul 12 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE MS VALLEY TO THE CENTRAL APPALACHIANS...

...MS/OH/TN Valleys...
A shortwave trough is progged to extend from MO to OH by 12z
Saturday, likely featuring one or more embedded MCVs. Uncertainty
remains with the exact rack and strength of these mesoscale
features, which will play a large role in where the flash flood
threat is maximized.

Some high res guidance indicates an MCV moving towards WV Saturday,
which could interact with a southward dropping frontal boundary
and produce an area of enhanced convective coverage. Slow moving
convection near these features could maintain a flash flood threat
for portions of WV/OH/PA/MD/VA. Confidence is highest over WV,
where the Slight risk remains, with a Marginal risk maintained
further north and east.

Model consensus is trending towards a stronger shortwave/MCV
hanging back over IL/IN/KY, although guidance diverges on how
convection evolves around this feature. This evolution is
dependent on Friday's convective outcomes and the ultimate
strength/position of the shortwave. The RRFS/REFS/FV3/Gem reg
focus heavy convection over central/eastern TN and KY to the
southeast of the shortwave, a solution also generally supported by
the AIFS and AIGFS. Conversely, the GFS and ECMWF are displaced
further southwest, placing maximum rainfall over AR, MS and western
TN and showing lower values to the northeast.

At the moment, higher confidence is placed in the high res/AI
consensus favoring a maximum over central/eastern TN and KY. Given
that portions of this region will have seen heavy rainfall on day
1, a higher end Slight risk remains warranted due to the
possibility of increased hydrologic sensitivity. If models
converge on a repeatable heavy rainfall footprint over these areas,
a MDT risk upgrade may eventually be needed. Additionally, heavy
rainfall is also expected to extend westward across western TN, AR
and portions of MS and AL. The Slight risk has been expanded
westward into more of AR with this update, where the
RRFS/REFS/FV3/3km NAM all support heavier convection...with
northern AR potentially favored for training and backbuilding along
the southwestern flank of the broader convective regime.

...Southwest...
The terrain driven convective pattern continues as storms roll off
the higher elevations of AZ and into a pooling instability axis
across the southern portion of the state. Instability and PW
values are forecast to be higher than on day 1. The 00z REFS
neighborhood probabilities show a 40-60% chance of locally
exceeding 3" of rain, with the 3km NAM and FV3 also depicting
locally high totals. Given the favorable environmental ingredients
and a growing model QPF signal, southern AZ has been upgraded to a
Slight risk with this update.

Chenard


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