Hydrometeorological Discussion
Issued by NWS North Central River Forecast Center

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Hydrometeorological Forecast Discussion
NWS North Central River Forecast Center Twin Cities/Chanhassen MN
112 PM CDT Fri Apr 28 2017

...Significant Flooding Event Imminent for Parts of the Area...


...Precipitation...

In the last 24 hours, rain and snow exited Wisconsin and upper
Michigan leaving up to about an inch of water equivalent in
central and northern Wisconsin.  Light showers fell near our
boundaries in NE Missouri and SE Michigan dropping about a quarter
inch.

In the next 24 hours, a convective boundary will move into the
southern edged of the NCRFC area in Missouri and Illinois,
dropping up to an inch and a half for the first 24 hours.  The
boundary will continue on days two and three - waving further
north in Missouri, all of Illinois and across lower Michigan.
Storm total rainfalls over three days will likely exceed 3 inches
in a broad region over the aforementioned areas.  Local totals
will likely be up to 7 inches, with the heaviest amounts currently
expected to fall in St. Louis and surrounding areas.

Confidence is relatively high in a heavy rain event occurring in
the general vicinity from the Oklahoma/Arkansas border through
Missouri and Illinois to the borders with Indiana and Michigan.
Exact placement of the heaviest totals is still uncertain.

...Hydrologic Conditions...

In the Hudson Bay Drainage, flooding continues to diminish along the
Souris River from Towner and Bantry downstream to near the Westhope
area.

Meanwhile, as advertised for days...a large spring storm will bring
heavy rainfall to portions of Missouri, Illinois, Indiana, and
Michigan. The widespread and heavy rainfall will result in a large
number of rivers rising significantly, with flooding becoming likely.
Per coordination, today`s forecasts utilized 72 hours of QPF, to
capture the bulk of this rain event. This resulted in several
forecasts for minor to moderate flooding, with nearly two dozen
locations potentially reaching the major level. In fact, some
forecast points could reach record levels if the rainfall plays out
as currently forecast, with the most severe flooding expected from
Missouri into Illinois. Some simulations are suggesting similar
flows on the Illinois mainstem river as were seen in April 2013.

NCRFC will be utilizing 48 hours of QPF for Saturday morning`s
forecasts, but beyond that we will return to the normal 24 hour QPF
input. NCRFC will also go to 24-hour operations starting Saturday.

As always, we will continue to monitor the forecast rainfall and
the potential for any forecasts or forecast updates as necessary.

For additional and more in-depth information concerning river
forecasts, precipitation and all hydrometeorological information
in the NCRFC area of responsibility, please refer to the NCRFC
web page at:     http://www.weather.gov/ncrfc

Emergency Call Back List: LLD... BAC... MAW... JMP

If no response from this list, call the DOH, SCH or HIC.


$$

...JMP/MAW...





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