Excessive Rainfall Discussion...UPDATED
NWS Weather Prediction Center College Park MD
424 PM EDT Thu Jun 4 2026
Day 2
Valid 12Z Fri Jun 05 2026 - 12Z Sat Jun 06 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
EASTERN NEBRASKA INTO THE MID-MISSISSIPPI VALLEY...

...21Z Outlook Update...

The Slight Risk in the previous D2 issuance has been shifted
southwestward and expanded slightly based on most recent model
trends. Fairly progressive convection should migrate across much of
Wisconsin and Lower Michigan in the morning/early afternoon hours.
During the latter parts of the forecast period (afternoon onward),
Additional, surface-based convection should redevelop near the
NE/IA border and migrate eastward toward the MS River/IA/IL border
region. This convection should be oriented favorably for local
training/backbuilding - and some of that convection (particularly
in Iowa) could fall on wet soils from prior-day anticipated
rainfall, creating more moist ground conditions favoring excessive
runoff. The current configuration of Slight reflects most recent
model depictions of heavy rainfall risk from deep convection.

Elsewhere, the overall forecast is generally on track, with small
spatial expansions of Marginal in New Mexico to account for
potential convection in higher terrain. Scattered thunderstorms
should move slowly across the entire Marginal Risk area from
NM/west Texas eastward to southeast Texas. Some consideration of
Slight was given for the Big Country/Hill Country with a nearly
stationary mid/upper trough upstream and copious moisture content
present. Instability and convective coverage were in question
though and will likely be dependent on prior-day convection and the
evolution of any potential complexes from west Texas that migrate
through the region during the early morning hours. After collab
with local WFOs, decision was made to wait another model cycle
before reconsideration of a potential upgrade.

Though specific timing is uncertain, a disturbance over the central
Gulf will begin to migrate slowly northwestward toward southeastern
Louisiana and pose heavy rainfall potential across that area and
adjacent areas of Mississippi. Wet soils from prior rainfall will
support excessive runoff should heavier rainfall/deep convection
materialize as suggested by models.

Cook

...Previous Discussion...

Upper Midwest...
Additional scattered thunderstorm activity is expected once again
ahead of a front making its way from Iowa into Wisconsin and
vicinity, spreading 1-2 inches of rain with local amounts reaching
4 inches. Storms in that area should be progressive in nature due
to 20-30 knot mid/upper level flow, though localized backbuilding
and mergers may increase totals locally.

The Marginal Risk surrounding the Slight Risk was largely
unchanged...although some of the territory was removed from the
northern part of Michigan now that timing of the boundary and low
level moisture fields have become handled better by the
models/ensembles.

Texas into New Mexico...
Weak mid/upper troughing across the southern Rockies and Texas
will promote another round of thunderstorm activity across a large
part of Texas and southern New Mexico, with attendant flash
flooding expected due to slow storm motions and abundant moisture.

Coastal Louisiana...
A trough of low pressure interacting with the higher moisture in
place will bring a higher coverage of thunderstorms with the
potential for intense rain rates and localized heavy rainfall.
Spaghetti plots show more ARW core members than NMMB...suggesting
that there could still be shifts in placement or QPF amounts
between now and the time the outlook verifies.

Bann

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