Spring Flood Outlook as of January 26th, 2011

The three graphics below represent the general probabilities of exceeding major, moderate, and minor flood levels based on ensemble streamflow prediction analysis.  The long-range probabilistic outlook contains forecast values that are calculated using multiple season scenarios from 30 or more years of climatological data including current conditions of the river, snow cover, and soil moisture.  Locations on the map colored in gray are not yet modeled in such a way to provide this information.  That is not to rule out the possibility of flooding due to future rainfall at these gray locations during the Spring Flood Outlook period. Please refer to text below for more information.

  

Probabilities of exceeding Major Flood Levels
(click on specific points to view probabilistic outlooks)


Probabilities of exceeding Moderate Flood Levels
(click on specific points to view probabilistic outlooks)


Probabilities of exceeding Minor Flood Levels
(click on specific points to view probabilistic outlooks)

                        
THIS SNOWMELT OUTLOOK IS FOR THE MISSOURI RIVER DRAINAGE WHICH

INCLUDES RIVERS IN MONTANA, WYOMING, COLORADO, NORTH DAKOTA, SOUTH
DAKOTA, MINNESOTA, NEBRASKA, KANSAS, IOWA, AND MISSOURI.

SIGNIFICANT SNOWPACK EXISTS ON THE MISSOURI RIVER BASIN PLAINS FROM

EASTERN MONTANA THROUGH NORTHERN MISSOURI. SNOWMELT, COUPLED WITH
ABOVE NORMAL SOIL MOISTURE CONDITIONS AND CLIMATOLOGICAL RAINFALL
THIS SPRING, IS LIKELY TO RAISE MANY RIVERS ABOVE FLOOD STAGE DURING
THE NEXT FEW MONTHS.

SOME MINOR ICE JAM FLOODING IS ALREADY OCCURRING OR HAS RECENTLY

OCCURRED. THIS HAS BEEN REPORTED IN MONTANA AND IN THE PLATTE RIVER
BASIN OF NEBRASKA. ADDITIONAL FLOODING RESULTING FROM ICE JAMS IS
LIKELY THROUGHOUT THE LATE WINTER AND EARLY SPRING.  

THERE IS POTENTIAL FOR MODERATE TO MAJOR FLOODING DUE TO SNOWMELT

THROUGHOUT THE JAMES IN BOTH NORTH AND SOUTH DAKOTA AND THROUGHOUT
THE BIG SIOUX BASIN OF SOUTH DAKOTA, NORTHWEST IOWA, AND SOUTHWEST
MINNESOTA.


MODERATE FLOODING DUE TO SNOWMELT IS MORE LIKELY IN THE APPLE BASIN

IN NORTH DAKOTA AND THE FLOYD BASIN IN IOWA.  THERE IS POTENTIAL FOR
MINOR TO MODERATE FLOODING IN THE LOWER MILK BASIN OF MONTANA.  


MINOR FLOODING IS MORE LIKELY IN THE NORTHERN TWO-THIRDS OF THE

BASIN'S PLAINS ALONG THE FOLLOWING RIVERS: THE GRAND, MOREAU, AND
LITTLE MISSOURI BASINS IN SOUTH DAKOTA; THE LITTLE SIOUX BASIN IN
IOWA; THE KNIFE, LITTLE MISSOURI, LITTLE MUDDY, BEAVER, AND
CANNONBALL BASINS IN NORTH DAKOTA; AND THE WAHOO AND SALT CREEKS
IN NEBRASKA.

REGARDING THE WESTERN MOUNTAINOUS AREAS OF THE BASIN, BASED ON THE

CURRENT SNOWPACK IN THE MOUNTAINS OF MONTANA, WYOMING AND COLORADO,
THE UPPER NORTH PLATTE AND LARAMIE RIVERS IN WYOMING, AND THE
GALLATIN, BIG HOLE, AND UPPER YELLOWSTONE BASINS IN MONTANA HAVE
POTENTIAL FOR MINOR FLOODING DUE TO SNOWMELT.   

IN THE SOUTHEASTERN THIRD OF THE MISSOURI RIVER BASIN, WITHIN THE

STATES OF NEBRASKA, SOUTHWEST IOWA, EASTERN KANSAS, AND MISSOURI, THE
SOILS ARE NEARLY SATURATED AND THE GROUND IS SNOW COVERED. IN THIS
AREA IT IS LIKELY THAT SPRING FLOODING WILL HAPPEN IF TYPICAL RAINFALL
EVENTS OCCUR. LONG LEAD-TIME OUTLOOKS FOR THIS TYPE OF EVENT ARE NOT
POSSIBLE. AHPS PROBABILISTIC FORECASTS, HOWEVER, ARE AVAILABLE FOR
SOME OF THESE AREAS, INDICATING THAT MINOR TO MODERATE FLOODING IS
LIKELY WITH NORMAL OCCURRENCES OF HEAVY RAINFALL EVENTS.

THIS OUTLOOK CONTAINS A GENERALIZED SUMMARY OF SPRING FLOOD POTENTIAL.

ABOVE NORMAL FUTURE SNOW, COMBINED WITH SIGNIFICANT RAINS AND RAPID
MELT, WILL INCREASE THE CURRENT FLOOD POTENTIAL WHILE BELOW NORMAL
FUTURE PRECIPITATION AND GRADUAL OR INTERMITTENT FREEZING AND THAWING
WILL DECREASE THE MAGNITUDE OF THE CURRENT ASSESSMENT. IN ADDITION,
WHEN MANY OF THE FROZEN RIVERS AND STREAMS THAW, ICE JAMS CAN OCCUR
CAUSING HIGHER RIVER LEVELS AND POSSIBLE FLOODING.

THESE PROJECTIONS OF RIVER STAGES AND RESERVOIR LEVELS ARE BASED

ON CURRENT OBSERVED OR ESTIMATED STATES OF STREAMFLOW, SOIL MOISTURE,
AND SNOW PACK. THESE ANTECEDENT CONDITIONS ARE COUPLED WITH FUTURE
PRECIPITATION AND TEMPERATURE PATTERNS AND ANTICIPATED OPERATIONAL
HYDROLOGIC CHANGES, SUCH AS RESERVOIR RELEASES AND CANAL DIVERSIONS,
TO COMPILE THE OUTLOOK. "OUTLOOKS" ARE PROVIDED FOR LONG-RANGE (WEEKS
TO MONTHS) PROJECTIONS BASED ON CLIMATOLOGICAL PATTERNS OF
PRECIPITATION AND TEMPERATURE. "FORECASTS" ARE PROVIDED FOR
SHORT-TERM(DAYS) PROJECTIONS BASED ON FUTURE FORECASTED PATTERNS OF
PRECIPITATION AND TEMPERATURE. THE UNCERTAINTY OF THESE PRODUCTS
VARIES FROM SEASON TO SEASON AND SITE TO SITE. IN RECENT YEARS,
OUTLOOK CRESTS HAVE BEEN ABOVE THE OBSERVED CREST ABOUT AS OFTEN AS
THEY HAVE BEEN BELOW THE OBSERVED CREST.  THE UNCERTAINTY OF
FORECASTS TEND TO BE LESS THAN THE UNCERTAINTY OF OUTLOOKS DUE TO
THEIR SHORTER LEAD TIME. USERS OF THESE PRODUCTS ARE ENCOURAGED TO
CONTACT THEIR NEAREST NATIONAL WEATHER SERVICE FORECAST OFFICE FOR
CONTINUED UPDATES OF METEOROLOGICAL CONDITIONS WHICH CAN HAVE
SIGNIFICANT IMPACTS ON FLOOD PLANNING AND FLOOD MITIGATION ACTIVITIES.

OUTLOOK NUMBERS FOR LOCATIONS NOT REPRESENTED IN AHPS PRODUCTS ARE

NOT BEING ISSUED WITH THIS TEXT PRODUCT.  HOWEVER, THOSE LOCATIONS IN
NEBRASKA, KANSAS AND MISSOURI NOT INCLUDED IN THE AHPS PRODUCTS THAT
NORMALLY FLOOD NEARLY EVERY SPRING WILL LIKELY FLOOD THIS YEAR.
IN ADDITION, MINOR FLOODING IS LIKELY WITH THE ADDITION OF HEAVY
SPRING RAINS FOR RIVERS, LIKE THE MISSOURI RIVER, THAT HAVE INCREASED
FLOW FROM UPSTREAM SNOWMELT RUNOFF. FOR ADDITIONAL QUANTITATIVE
INFORMATION PLEASE REFER TO AHPS PRODUCTS FOR PROBABILISTIC FORECASTS
OF POTENTIAL FLOODING. REFER TO FLOOD FORECASTS, IF ANY ARE CURRENTLY
ISSUED, FOR INFORMATION ABOUT ONGOING OR ANTICIPATED FLOODING.

THE NEXT SPRING OUTLOOK IS SCHEDULED FOR RELEASE ON FEBRUARY 16TH.


ADDITIONAL RIVER INFORMATION CAN BE FOUND IN THE DAILY HYDROLOGIC

ACTIVITIES DISCUSSION, FLOOD FORECASTS FOR RIVERS NEAR OR ABOVE
FLOOD STAGE, DAILY RIVER FORECASTS, AHPS PRODUCTS AND THE MONTHLY
WATER SUPPLY OUTLOOK, ALL ISSUED BY THIS OFFICE.


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