Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
410 PM EDT Sun Aug 9 2026
Day 3
Valid 12Z Tue Aug 11 2026 - 12Z Wed Aug 12 2026

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
MIDWEST AS WELL AS FOR SOUTHERN ARIZONA...

...Midwest...

20Z Update: Little change necessary from the previous forecast as
consensus grows for a period of locally significant heavy rainfall
over areas of IN/OH, extending into WV. This setup is favoring
significant rainfall on a northwest to southeast alignment as a
series of stronger mid-level disturbances migrate quickly through
the flow with the height field oriented from the Northern Plains
into the Central Appalachians. Both the ECENS and GEFS mean
vorticity forecast show 3 distinct vorticity maxima migrating out
of the Midwest into the Ohio Valley during the D3, bleeding into
the D4 time frame. Multiple MCSs will likely transpire over the
area extending from northwest IN down through OH into WV leading to
some areas seeing multiple rounds of heavy rain and increasing
flash flood prospects as each complex will prime the grounds as we
move forward in time. Areas of interest for more significant
impacts include those broad urban zones and the terrain influenced
areas of WV and eastern OH as flash flood potential is generally
higher due to higher run off capabilities and more enhanced
riverine issues that couple with the heavy rainfall rates
anticipated (1-2"/hr likely, locally higher). The previous high-end
SLGT remains in effect, but there is a better than normal chance at
an upgrade in future updates based on the proposed setup.

Kleebauer

..Previous Discussion..

A rinse-and-repeat pattern will unfold across the Midwest on
Tuesday. Any morning MCSs from Monday night will continue towards
the southeast into West Virginia from Ohio while the storms
generally weaken Tuesday morning. Additional rounds of storms will
likely follow in the form of fast moving lines, but still tracking
over many of the same areas from prior days, from northern Indiana
across much of Ohio, and weakening as they move into West Virginia
late in the day. Just as on prior days, the storms will establish a
cold pool/pseudo-front across Ohio that will act as a train track
for additional storms to form along and track along by Tuesday
night. That precise scenario will play out again Tuesday night, as
storms form either immediately in the wake of any afternoon lines
of storms or along their cold pool. Westerly flow of deep moisture
will support the individual storms rather fast southeasterly motion
from Indiana across Ohio and eventually into West Virginia.
However, training and backbuilding will be common, and along a
narrow corridor that could stretch from as far north as Pittsburgh
south through the southern tip of West Virginia.

It appears this training and repeating scenario will ramp up as
compared to previous days on Tuesday, resulting in more common,
stronger, and more persistent lines of storms developing and moving
southeastward along the front. Given the likelihood that prior
days' rains over these same areas will have saturated the soils by
Day 3, and the general very flashy nature of the rivers of West
Virginia, it appears a Moderate Risk upgrade will be probable in
this region in the coming days.

Wegman

...Southern Arizona...

20Z Update: Little to no change necessary for the SLGT and MRGL
risk placements across the Western U.S. for D3 as the general model
consensus maintains a consistent output compared to the previous
forecast.

Kleebauer

..Previous Discussion..

The strongest storms associated with the monsoon across southern
Arizona on Tuesday are expected to form closer to the Mexican
border as compared to prior days. Given the likelihood of flooding
rains in this same area on Monday, despite the relative lack of
rainfall expected on Tuesday as compared with Monday, a small
Slight Risk upgrade for along the Mexican border was introduced
with this update. Otherwise, expect a return to a "base state" as
far as storm coverage, notably a significant decrease as compared
to Monday, but similar to today/Sunday. This should allow some
areas to dry out due to lack of activity on Tuesday.

Wegman

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