FOUS30 KWBC 290820
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
420 AM EDT Sun Mar 29 2026

Day 1
Valid 12Z Sun Mar 29 2026 - 12Z Mon Mar 30 2026

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

Chenard


Day 2
Valid 12Z Mon Mar 30 2026 - 12Z Tue Mar 31 2026

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

An uptick in convective activity is expected Monday night into
Tuesday morning across portions of MI into western PA/NY. There is
a strong surge of moisture and instability, and thus locally heavy
rainfall is possible. Overall it seems like the better chance of
localized flash flooding is after 12z Tuesday as the duration of
rain makes hydrologic conditions more sensitive by then. So we 
will hold off on introducing any day 2 risk area and let the day 3
Marginal cover the threat. But we will continue to monitor trends 
as the event gets more in range of the high res models today.

Chenard


Day 3
Valid 12Z Tue Mar 31 2026 - 12Z Wed Apr 01 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY INTO NEW YORK AND VERMONT...

A stationary front positioned over NY will likely be a focus for 
scattered convection to start the period Tuesday morning. The 
front is not forecast to move much during the day, likely 
supporting periodic rounds of scattered showers and thunderstorms.
An area of low pressure riding along the front should increase 
forcing and convergence by Tuesday evening, resulting in an uptick 
in rainfall coverage.

Moisture parameters are impressive with this system...PWs are
forecast to be near late March to early April max values, and IVT
increases above the climatological 90th percentile. Instability is
more marginal, and will likely reduce max rainfall rate potential
and act as a limiting factor for flash flooding. However, there is
some instability forecast in the morning, and by evening the
increasing forcing/convergence could help offset decreasing
instability. Thus while not widespread, some localized hourly
rainfall around 1" seems plausible. 

Model consensus rainfall magnitudes are generally in the 1-2"
range, although with multiple rounds likely, there is a potential
for more localized swaths getting into the 2-4" range. These 
higher amounts are most likely over portions of far northeast OH, 
far northwest PA and into southwest NY...near the stationary front
and within a corridor where instability has a better chance of 
persisting. A bit farther northeast into upstate NY and VT, some 
snow melt contribution could also aid in minor runoff concerns. 
Farther southwest over IN and OH instability is higher supporting 
greater rainfall rates, but duration should be shorter with a 
quicker frontal progression. Soil and streamflow conditions are 
more conducive for flood impacts over portions of OH and IN, but 
dry out with southwest extent into IL and MO. Thus while convection
will extend into these latter areas as well, for now we will stop 
the Marginal risk near the IL/IN border.

Overall the primary threat is for localized flooding in areas 
where training, or multiple convective rounds, occur near the 
stationary front...or where higher short duration rates intersect 
sensitive urban areas.

Chenard

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