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
1110 AM CST Fri Dec 9 2016

...Precipitation...
Cyclonic flow around the large storm complex over southeast Canada
was finally shifting away from the region, as high pressure was
building in from the west. Diminishing northwest winds were still
bringing in cold air from the Canadian provinces, resulting in
continued light snow and flurries for much of the area, with lake
effect snows in the favored lee locations. The majority of the
Upper Midwest saw little if any accumulation, with mainly trace
amounts or perhaps a few hundreths. But in the lake effect belts,
snow amounts of 2 to 5 inches were more common, with an isolated
report of just over 11 inches at Wetmore in the UP of Michigan.
Water equivalent in that snow ranged from just over a tenth to as
much as three tenths of an inch.

Looking ahead to the weekend, the Canadian system will continue to
slowly pull away, but a disturbance will track across South Dakota
early Saturday, across Minnesota and Iowa by Saturday evening, and
into the Great Lakes States on Sunday. This system will bring a
band of significant snowfall, with 4 to 8 inches possible
generally along and south of Interstate 90.

...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.

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.


$$

...MAW/BAC...





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