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000
FOUS30 KWBC 160742
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
342 AM EDT Tue Apr 16 2024

Day 1
Valid 01Z Tue Apr 16 2024 - 12Z Tue Apr 16 2024

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS EASTERN
PORTIONS OF THE NORTHERN PLAINS SOUTHWARD THROUGH MUCH OF THE
MISSISSIPPI VALLEY...

Showers and thunderstorm are expected to align near and north of
an east-west orientated warm frontal boundary that is stretched
across the eastern portions of the Plains and the Ohio Valley. The
highest rainfall rates and accumulation will likely be concentrated
along the Minnesota/Iowa border where instability will be most
supportive to produce 1-2"/hr rainfall over this area, which will
likely exceed 1hr FFG in spots. One limiting factor for flash
flooding will be the swift movement of cells, limiting the duration
of heavy rates. Training/backbuilding near the warm front could
help accumulations to reach or exceed 5 inches.

Although there may be some 1hr and 3hr FFG exceedance, the
coverage and magnitude of impacts are expected to remain below
Slight risk levels. The main threat will be to urban areas, where
the intense rates may lead to localized flash flooding. Outside of
urban areas the dry ground and limited green vegetation may allow
for some excess runoff, however these impacts are expected to
remain isolated as well. A Marginal Risk area spans from the
eastern Dakotas, Upper/Central Mississippi Valley and across parts
of the Mid-Mississippi Valley.

Campbell




Day 3
Valid 12Z Wed Apr 17 2024 - 12Z Thu Apr 18 2024

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE GREAT LAKES, OHIO VALLEY AND WESTERN PARTS OF THE NORTHEAST...

20z Update:
Only minor changes to the inherited Marginal risk. Convection
moving across the OH Valley will be strong and capable of producing
high rainfall rates, but should generally be progressive in nature.
There is less instability with eastward extent, which should result
in lower rainfall rates. But given the above average soil
saturation and streamflows over portions of PA and NY the Marginal
looks good.

Chenard

...Previous Discussion...

Showers and thunderstorms will shift east as the closed low and
fronts advance through the Ohio Valley toward the Mid-Atlantic.
Much of the guidance has 1 to 2 inches for this period for parts of
the Great Lakes, eastern Ohio Valley and portions of the Northeast.
This part of the country has much lower FFG guidance from
antecedent rain thus are more sensitive to additional rainfall. A
Marginal Risk spans from Michigan/Wisconsin south to Kentucky and
east into western New York, Pennsylvania and Maryland.

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