Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
320 AM EST Sun Dec 28 2025

Day 1
Valid 12Z Sun Dec 28 2025 - 12Z Mon Dec 29 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
WESTERN NEW YORK...

...New York...

The warm front associated with a rapidly deepening low that will
track from the central Plains to the northern mitten of Michigan
today will move into western New York later this morning. This warm
front will advect much warmer air behind it, to its south, which in
turn will change over any wintry precipitation ahead of it to
plain rain. Dynamics associated with the rapidly deepening low,
including well above normal amounts of atmospheric moisture, some
instability, and slow northward movement, will all allow rain,
heavy at times, to persist from when it starts later this morning
through into tonight, when the trailing cold front sweeps across
western New York, ending any warm precipitation, as much colder
Canadian air rushes in behind the cold front. This extended period
of warm rainfall will occur over a below-normal, but still fairly
robust snow pack at the higher elevations of the Southern Tier, to
the amount of 1-4 inches of snow water equivalent. Thus, the
combination of rain and snow melt should rapidly increase stream,
creek, and river levels across western New York. Thus, the flooding
threat has increased and a Slight Risk for portions of western New
York, generally west of Rochester and north of the PA State Line,
remains in place. Urban and small stream flooding look to be the
types of flooding that are most likely, but any flood-prone area
will be susceptible today and especially into tonight.

...Midwest...

A Marginal Risk extends from northern Illinois across much of
southern Michigan. The warm front with embedded elevated convection
will persist through the entire day in the Marginal Risk area. The
cold front will swing west to east from late this afternoon in
Illinois to this evening across Michigan. This will effectively end
the flooding threat as much colder air turns any lingering
precipitation tonight over to snow, and the lakes help with
localized enhancement across western lower Michigan. Urban and
small stream flooding are possible in the Chicago area, Detroit,
and any smaller urbanized areas in between. Due to relatively dry
conditions across the Midwest prior to today, any instances of
flooding should be isolated.

The rain has already started out this early morning to the
southwest of the Marginal Risk area across portions of Missouri,
Iowa, and western Illinois. For these areas, even drier soils prior
to this storm should keep the flooding threat below the 5% Marginal
Risk threshold, but the area will be monitored for overperformance
and any potential need to extend the Marginal Risk south and west
for the morning into these areas.

Wegman

Day 2
Valid 12Z Mon Dec 29 2025 - 12Z Tue Dec 30 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Wegman

Day 3
Valid 12Z Tue Dec 30 2025 - 12Z Wed Dec 31 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Wegman


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt