Hydrometeorological Discussion
Issued by NWS North Central River Forecast Center

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AGUS73 KMSR 271733
HMDMSR

HYDROMETEOROLOGICAL FORECAST DISCUSSION
NWS NORTH CENTRAL RIVER FORECAST CENTER TWIN CITIES/CHANHASSEN MN
1130 AM CST THU NOV 27 2014

...PRECIPITATION...

DURING THE PAST 24-HOURS...LIGHT SNOW FELL ACROSS MUCH OF THE
NCRFC REGION WHERE 1-2 INCHES OF NEW SNOW WAS REPORTED. A HEAVIER
POCKET OF 4-7 INCHES WAS REPORTED IN SOUTHERN MINNESOTA AND ON THE
SOUTHERN SHORES OF LAKE SUPERIOR IN THE UPPER PENINSULA OF
MICHIGAN.

DURING THE NEXT 24-HOURS...MORE SNOW IS IN THE FORECAST FOR NORTH
DAKOTA...MINNESOTA...WESTERN WISCONSIN AND THE GREAT LAKES AREA OF
MICHIGAN. SNOWFALL TOTALS OF 2-4 INCHES POSSIBLE WITH ISOLATED
HIGHER AMOUNTS.

...HYDROLOGIC CONDITIONS...

MINOR FLOODING IS FORECAST FOR A SITE IN NORTHERN INDIANA AS A
RESULT OF WEEKEND RAINS AND SNOWMELT.

THIS HAS BEEN A CHALLENGING EVENT TO FORECAST FOR A NUMBER OF
REASONS..

   - PRECIPITATION GAGE QUALITY CONTROL

     QUALITY CONTROL OF TIPPING BUCKET PRECIPITATION GAGES HAS
     BEEN DIFFICULT BECAUSE WARM TEMPERATURES HAVE MELTED SNOW
     THAT ACCUMULATED IN THEM.

     OTHER GAGES HAVE BEEN COVERED
     AND REPORTED ZEROS.  IN EITHER CASE.. THEY DO NOT REPRESENT
     THE AMOUNT OF RAIN THAT FELL.

   - RIVER ICE

     MANY RIVERS WERE ELEVATED COMING INTO THIS WEEKEND DUE TO
     FREEZE-UP ICE JAMS. IT IS DIFFICULT TO DETERMINE THE
     EFFECTS OF THAT ICE ON THE RATING CURVE DURING THE RISE.

     WE HAVE ALSO SEEN SOME RIVER GAGES SPIKE UP AS BREAK-UP
     ICE JAMS FORM AND RELEASE.  WE MUST BE CAREFUL NOT TO ROUTE
     THAT SPIKE DOWNSTREAM BECAUSE IT IS NOT A TRUE
     REPRESENTATION OF THE FLOW HYDROGRAPH.

   - COLD TEMPERATURE FORECAST

     AIR TEMPERATURES ARE FORECAST TO DROP SIGNIFICANTLY DURING
     THE NEXT FEW DAYS.  THE SUB-FREEZING TEMPERATURES MAY FREEZE
     RUNOFF EN ROUTE TO THE RIVERS CAUSING RIVER LEVELS TO DROP
     MORE QUICKLY THAN EXPECTED.

     CONVERSELY.. AT LOCATIONS PRONE TO FREEZE-UP ICE JAMS..
     RIVER LEVELS MAY RISE HIGHER THAN EXPECTED AS THE COLD
     TEMPERATURES AND RELATIVELY HIGH STREAMFLOWS CAN COMBINE TO
     FORM FREEZE-UP ICE JAMS.



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: RJW  DAM   RHR

IF NO RESPONSE FROM THIS LIST... CALL THE DOH...SCH OR HIC.


$$

...JCH/BAC...





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