Hydrometeorological Discussion
Issued by NWS North Central River Forecast Center

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AGUS73 KMSR 101645
HMDMSR

Hydrometeorological Forecast Discussion
NWS North Central River Forecast Center Twin Cities/Chanhassen MN
1045 AM CST Sat Dec 10 2016

...Precipitation...
Snow fell across a big portion of the NCRFC region during the past
24 hours. Water equivalents were generally just a trace to a few
hundredths except for Michigan where heavier lake effect snow
brought nearly three quarters of an inch.  Portions of the upper
peninsula and northern lower Michigan reported over a foot of new
snow while southern lower Michigan received a few tenths to a few
inches.

Snow is expected to intensify across the west today and spread
east Sunday. Water equivalents of a quarter to half inch today
across the eastern Dakotas...southern Minnesota...southern
Wisconsin and southern Michigan will bring up to six inches of
snow. Sunday into Monday another half to three quarters of an inch
water equivalent could bring another four to eight inches of snow
to southern Wisconsin and southern Michigan.

Arctic cold temperatures will remain across the region well into
next week when high temperatures will fight to rise above zero
degrees.  Nighttime lows...across the northwest especially...will
fall to 20 to 30 degrees below zero.

...Hydrologic Conditions...

Rain and melt from before the recent cold spell caused rivers to
rise across much of the region.  In Minnesota, slow responding
rivers have finally crested, including the Crow River - above
bankfull stage at Delano - and the Mississippi River, which is
causing bankfull conditions on the St. Croix at Stillwater.

While no flooding is expected on the major rivers, flows are well
above normal for this time of year.  The system is vulnerable to
future runoff, and, importantly with the cold air setting in, the
region is going into the freeze-up with high flows and wet soils,
which could contribute to high spring melt runoff.  The USGS lists
streamflows in the 90th and above percentiles for nearly all
tributaries north of a line from Des Moines to Quad Cities to
Milwaukee.  The Mississippi is above the 75th percentile all the
way to the confluence with the Ohio.

With very cold air finally moving in over the region, there will
be an increased potential for freeze-up ice jams in the next
several days and weeks.  Several rivers are already showing ice
affects at their gages, with either erratic readings or
indications of an ice bite reduction in flow/stage, or the
beginnings of an ice jam.  People with assets on or near rivers
that are prone to ice jamming should be aware and prepared.  Ice
jam flooding can happen fast with very little warning.

Additionally, the coming cold weather should generate an
"ice-bite" along the Mississippi River.  An ice-bite occurs as the
initial ice cover forms over the river.  When a stationary surface
cover of ice forms on the river, the water in that ice is taken
away from the flow routed downstream.  The result is a temporary
reduction in flow downstream of the area where ice is forming.  We
call this an "ice-bite".  We can expect this to occur possibly as
far south as Lock and Dam 25 during the next 10 days.

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: WES ... BAC ... RJW

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


$$

...rjw/bac...





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