SNOWMELT FLOOD OUTLOOK ISSUED ON MARCH 6TH, 2013



   SNOWMELT FLOOD OUTLOOK                                              
                                                                       
BELOW AVERAGE FALL STREAMFLOW AND PRECIPITATION, DRIER THAN
NORMAL SOIL MOISTURE CONDITIONS, AND THE LACK OF AN APPRECIABLE
SNOWPACK ACROSS MUCH OF THE PLAINS HAVE RESULTED IN A DIMINISHED
CHANCE FOR SIGNIFICANT FLOODING DUE TO SMOWMELT ALONE IN THE
PLAINS AREA OF THE MISSOURI BASIN THIS YEAR.  LONG RANGE
PROJECTIONS INDICATE AN OVERALL DECREASE FOR THE RISK OF FLOODING
AS COMPARED TO NORMAL FOR NEARLY THE ENTIRE PLAINS AREA. AN
EXCEPTION TO THIS GENERAL STATEMENT IS THE MILK RIVER BASIN IN
MONTANA, WHICH HAS A NEAR NORMAL RISK FOR FLOODING THIS YEAR.
NEAR NORMAL RISK SUGGESTS THAT LOCATIONS WHICH TYPICALLY
EXPERIENCE SPRING FLOODING MAY FLOOD AGAIN THIS YEAR. LOCATIONS
THAT DO NOT NORMALLY EXPERIENCE FLOODING ARE NOT PROJECTED TO
FLOOD THIS YEAR. BY THE SAME TOKEN, AREAS HAVING A LESS THAN
NORMAL RISK FOR FLOODING CAN STILL BE PROJECTED TO FLOOD, ALBEIT
AT A DIMINISHED RISK AS COMPARED TO NORMAL.

MINOR TO MODERATE FLOODING IS POSSIBLE IN THE LOWER PORTION OF
THE MILK RIVER BASIN IN MONTANA. THE BIG SIOUX RIVER BASIN IN
SOUTH DAKOTA MAY ALSO EXPERIENCE MINOR FLOODING.  MINOR FLOODING
IS ALSO POSSIBLE ON THE NORTH PLATTE RIVER AT NORTH PLATTE.

CONVECTION, NOT SNOWMELT, IS OFTEN THE PRIMARY DRIVER OF SPRING
FLOODING IN THE LOWER ONE-THIRD OF THE MISSOURI RIVER BASIN.
MINOR FLOODING HAS ALREADY BEEN EXPERIENCED ALONG SOME STREAMS
OF CENTRAL MISSOURI DUE TO RAINS IN LATE JANUARY AND FEBRUARY.
THE TWO HEAVY SNOW EVENTS OCCURING IN THE LAST PART OF FEBRUARY
PLACED A CONSIDERABLE AMOUNT OF MOISTURE INTO THE GROUND ACROSS
WIDE PORTIONS OF KANSAS AND MISSOURI.  THIS WILL ENHANCE THE
RUNOFF POTENTIAL OF FUTURE SPRING EVENTS. MINOR TO MODERATE
FLOODING IS PROJECTED AT SOME LOCATIONS IN THE GRAND RIVER BASIN
IN MISSOURI, AND ALONG SOME OF THE SMALLER STREAMS AND RIVERS
IN EXTREME EASTERN KANSAS AND ACROSS THE STATE OF MISSOURI. THE
CHARITON RIVER IM MISSOURI MAY EXPERIENCE MINOR FLOODING THIS
SPRING, AS MIGHT CERTAIN LOCATIONS ALONG THE LOWER PORTION OF THE
MISSOURI RIVER.

ANTECEDENT FALL CONDITIONS IN THE MOUNTAINOUS WEST COUPLED WITH
THE CURRENT GENERALLY LOWER THAN NORMAL SNOWPACK CONDITION HAS
RENDERED UNLIKELY THE POTENTIAL FOR SIGNIFICANT FLOODING DUE TO
MOUNTAIN SNOWMELT ALONE THIS YEAR. LONG RANGE PROJECTIONS
INDICATE AN OVERALL DECREASE IN THE RISK FOR FLOODING AS COMPARED
TO NORMAL FOR ALL MOUNTAIN BASINS. AGAIN, BELOW NORMAL RISK DOES
NOT NECESSARILY MEAN THAT FLOODING IS NOT PROJECTED, OR CANNOT
OCCUR, BUT SIMPLY MEANS THAT THE RISK FOR FLOODING IS DIMINISHED
AS COMPARED TO NORMAL. CURRENTLY NO SNOWMELT FLOODING IS
PROJECTED IN THE MOUNTAINOUS WEST.

THIS OUTLOOK CONTAINS A GENERALIZED SUMMARY OF SNOWMELT FLOOD          
POTENTIAL.  ABOVE NORMAL FUTURE SNOW ACCUMULATIONS COMBINED            
WITH HEAVY 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. MINOR ICE JAM FLOODING HAS ALREADY
BEEN EXPERIENCED THIS SEASON ALONG THE LOUP RIVER AND NORTH PLATTE
RIVER IN NEBRASKA.  ICE JAM FLOODING WILL CONTINUE TO BE A THREAT
FOR SOME LOCATIONS THROUGHOUT THE REMAINER OF THE LATE WINTER AND
SPRING.                                        
                                                                       
THESE PROJECTIONS OF RIVER STAGES AND RESERVOIR LEVELS ARE BASED       
ON CURRENT OBSERVED STATES OF STREAMFLOW, SOIL MOISTURE, AND SNOW      
PACK, COUPLED WITH FUTURE PRECIPITATION AND TEMPERATURE PATTERNS       
AND ANTICIPATED OPERATIONAL HYDROLOGIC CHANGES SUCH AS RESERVOIR       
RELEASES AND CANAL DIVERSIONS.  "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 FIGHTING ACTIVITIES.                          
                                                                       
OUTLOOK NUMBERS FOR LOCATIONS NOT REPRESENTED IN AHPS PRODUCTS ARE     
NOT BEING ISSUED WITH THIS TEXT PRODUCT. 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.         
                                                                     
THIS IS THE LAST SCHEDULED SPRING OUTLOOK OF THE SEASON. IF
SIGNIFICANT CHANGES OCCUR SUBSEQUENT TO THIS PRODUCT, ADDITIONAL
OUTLOOKS CAN BE RELEASED TO ADDRESS NEEDS.                           
                                                                       
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.
_______________________________________________________________________                 
                                                                       
   CURRENT SNOW CONDITIONS                                             
THE CONDITIONS LISTED BELOW ARE BASED ON OBSERVATIONS AND MODEL DATA   
AS OF TUESDAY MORNING, MARCH 5TH.       
                                                                       
MONTANA PLAINS                                                         

THERE IS STILL MINIMAL SNOW BEING REPORTED ON MOST OF THE MONTANA
PLAINS, WITH THE EXCEPTION OF THE MILK RIVER BASIN. CURRENTLY,
LOCATIONS OUTSIDE OF THE MILK ARE GENERALLY REPORTING 2-5 INCHES WITH
SNOW WATER EQUIVALENT AMOUNTS BEING LESS THAN 0.75 INCHES. SNOW DEPTHS
IN THE MILK BASIN WITHIN CANADA, AND ALONG THE BORDER, ARE 5-10 INCHES
GENERALLY. SNOW WATER EQUIVALENTS IN THE MILK RANGE FROM 1.5-4.0
INCHES.                                            
                                                                       
WYOMING PLAINS                                                         

MANY LOCATIONS IN EASTERN WYOMING ARE REPORTING 4 INCHES OF SNOW OR    
LESS. GENERALLY, WATER EQUIVALENT IN THE WYOMING PLAINS IS LESS THAN
AN INCH.     
                                                                       
COLORADO PLAINS                                                        

CURRENTLY THERE IS VERY LITTLE SNOW BEING REPORTED IN THE COLORADO
PLAINS. ISOLATED STATIONS ARE REPORTING 1-3 INCHES.
                                                                       
MOUNTAINOUS WEST

SNOWPACK CONDITIONS IN THE MOUNTAINOUS AREAS OF THE BASIN CAN
GENERALLY BE CATEGORIZED AS SLIGHTLY BELOW NORMAL FOR THIS TIME
OF YEAR (ABOUT 80-95% OF NORMAL). NOTABLE EXCEPTIONS TO THAT ARE THE
GALLATIN, ST MARY, MILK, SMITH, JUDITH AND MUSSELSHELL BASINS, ALL OF
WHICH HAVE SLIGHTLY ABOVE NORMAL SNOW WATER EQUIVALENT VALUES (RANGING
FROM 105% TO AS MUCH AS 115%). THE NORTH AND SOUTH PLATTE AND LARAMIE
BASIN SNOWPACKS ARE ALSO EXCEPTIONS, WITH ALL HAVING SNOW WATER
EQUIVALENTS MUCH BELOW NORMAL FOR THIS TIME OF YEAR. CURRENTLY THESE
BASINS ARE REPORTING ABOUT 70-80% OF NORMAL SNOW WATER EQUIVALENT.
TYPICALLY, ABOUT 80% OF THE AVERAGE SNOW WATER EQUIVALENT IN THE
MOUNTAINOUS WEST HAS BEEN RECEIVED BY THIS POINT IN THE CALENDAR YEAR.
                                                                       
NORTH DAKOTA                                                           

ALL OF THE STATE WITHIN THE MISSOURI RIVER BASIN IS REPORTING SNOW,
HOWEVER, THE AMOUNTS IN THE SOUTHWEST ARE NEGLIGIBLE. SOUTH CENTRAL
PARTS OF THE STATE CURRENTLY HAVE 3-6 INCHES OF SNOW ON THE GROUND
WITH THREE-QUARTERS TO ONE AND A HALF INCHES OF WATER EQUIVALENT.
ELSEWHERE, STATIONS ARE REPORTING 10-15 INCHES OF SNOW WITH TWO TO
TWO AND A HALF INCHES OF WATER EQUIVALENT.
                                                                       
SOUTH DAKOTA                                                           

MOST OF THE SNOW BEING REPORTED IN SOUTH DAKOTA IS EITHER IN THE       
BLACK HILLS OR THE EASTERN HALF OF THE STATE. STATIONS IN THE BLACK
HILLS ARE REPORTING UP TO TWO FEET OF SNOW AND ANYWHERE FROM TWO TO
FIVE INCHES OF WATER EQUIVALENT. SNOW DEPTHS IN THE EASTERN HALF OF
THE STATE GRADUALLY INCREASE FROM SOUTH TO NORTH. NORTHEASTERN SOUTH
DAKOTA IS REPORTING SNOW DEPTHS RANGING FROM 9-15 INCHES WITH SNOW
WATER EQUIVALENTS OF 2-3.5 INCHES. SNOW WATER EQUIVALENTS IN THE
SOUTHEASTERN CORNER OF THE STATE ARE GENERALLY LESS THAN AN INCH.                                           
                                                                       
IOWA                                                                   

THE MAJORITY OF IOWA THAT FALLS WITHIN THE MISSOURI BASIN HAS SOME
SNOW ON THE GROUND. THE LARGEST REPORTED AMOUNTS ARE IN THE SOUTHERN
COUNTIES. COUNTIES ALONG THE MISSOURI BORDER PRESENTLY HAVE 6-10
INCHES OF SNOW DEPTH AND UP TO 1.5 INCHES OF SNOW WATER EQUIVALENT.
ELSEWHERE, IN THE WEST CENTRAL AND NORTHWESTERN PORTIONS OF THE STATE,
SNOW DEPTH IS 2-4 INCHES WITH UP TO A HALF OF AN INCH OF WATER
EQUIVALENT.
                                                                       
NEBRASKA                                                               

INSIGNIFICANT SNOW AMOUNTS ARE BEING REPORTED IN SOUTHERN AND EASTERN
PARTS OF THE STATE. GENERALLY, 3-5 INCH DEPTHS ARE THE LARGEST
AMOUNTS CURRENTLY MEASURED. SNOW WATER EQUIVALENTS IN THOSE AREAS ARE
GENERALLY LESS THAN TWO-THIRDS OF AN INCH.                                                        
                                                                       
KANSAS                                                     

ASIDE FROM FAR EASTERN KANSAS, THE REMAINDER OF THE STATE IS REPORTING
VERY LITTLE SNOW. THERE ARE A FEW REPORTS OF 1-2 INCHES IN CENTRAL
KANSAS, BUT THOSE AMOUNTS WILL HAVE NO IMPACT ON HYDROLOGIC
CONDITIONS. AFTER LAST WEEK'S WINTER STORMS, EASTERN TIER COUNTIES ARE
STILL REPORTING 4-8 INCHES OF SNOW ON THE GROUND. SNOW WATER
EQUIVALENTS IN THIS PORTION OF THE STATE ARE LESS THAN AN INCH AND A
QUARTER.

MISSOURI

ALTHOUGH A GOOD PORTION OF THE STATE IS STILL REPORTING SNOW ON THE
GROUND, THE SIGNIFICANT AMOUNTS ARE IN THE NORTHERN TWO-THIRDS OF
MISSOURI. 6-10 INCH REPORTS ARE COMMON, WITH MANY MODEL ESTIMATES,
OR FIELD MEASUREMENTS, OF 1.5 INCHES OF SNOW WATER EQUIVALENT.    
                                                                       
_________________________________________________________________________
                                                                       
   CURRENT SOIL MOISTURE CONDITIONS                                    
                                                                       
WITH THE SIGNIFICANT RECENT PRECIPITATION IN THE SOUTHEASTERN THIRD OF
THE BASIN, SOIL MOISTURE LEVELS IN THAT AREA HAVE GREATLY INCREASED IN
THE LAST TWO WEEKS. THIS REPRESENTS A SUBSTANTIAL IMPROVEMENT TO AN
AREA THAT WAS HIT HARD BY THE DROUGHT LAST SUMMER AND FALL. THROUGHOUT
THE REGION, THE U.S. DROUGHT MONITOR INDICATES THAT NEARLY ALL OF THE
MISSOURI RIVER BASIN IS STILL CLASSIFIED AS BEING IN DROUGHT STATUS.
FAR NORTHERN MONTANA AND NORTHWESTERN NORTH DAKOTA ARE CURRENTLY THE
ONLY EXCEPTIONS TO THAT CLASSIFICATION. ISOLATED FROST DEPTH REPORTS
INDICATE THAT SOILS IN THE NORTHERN STATES HAVE FROST PENETRATION UP
TO 30 INCHES DEEP.                                        

__________________________________________________________________________
                                                                       
   CURRENT RIVER CONDITIONS                                            
                                                                       
MANY RIVERS IN THE SOUTHERN PART OF THE BASIN CURRENTLY HAVE FLOWS     
THAT ARE BELOW NORMAL IN COMPARISON TO LONG TERM MEDIANS. EXCEPTIONS
INCLUDE THE SMALLER RIVERS IN EASTERN KANSAS AND THE WESTERN HALF OF
MISSOURI WHERE LAST WEEK'S SNOWS HAVE STARTED TO MELT AND RAINFALL
PRECEDED THE SNOW. IN THE NORTHERN TIER STATES OF MONTANA, WYOMING AND
THE DAKOTAS, FLOWS ARE GENERALLY NEAR NORMAL FOR THIS TIME OF YEAR.
MOST RIVERS IN THE NORTHERN HALF OF THE BASIN REMAIN ICE-COVERED.                       
                                                                       

These graphics represent the general probabilities of exceeding minor, moderate, and major 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. Go to WFO AHPS pages to view more detailed probabilistic information for each river location.

  

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)


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