Spring Snowmelt Flood Potential Outlook - April

...SPRING 2012 FLOOD AND WATER RESOURCES OUTLOOK NUMBER FIVE... THIS FLOOD OUTLOOK ENCOMPASSES THE NORTH PLATTE RIVER MAINSTEM AND
ITS TRIBUTARIES...THE LARAMIE AND MEDICINE BOW RIVERS...IN SOUTHEAST
WYOMING AND THE NEBRASKA PANHANDLE. LIKEWISE...IT ALSO INCLUDES THE
TRIBUTARIES TO THE MISSOURI RIVER...NIOBRARA AND WHITE RIVERS...IN
EXTREME NORTHWESTERN NEBRASKA.  FINALLY...IT ALSO INCLUDES THE LITTLE
SNAKE RIVER DRAINAGE OF SOUTH CENTRAL WYOMING.

...LOW TO MODERATE SNOWMELT FLOOD POTENTIAL IS EXPECTED ON THE CREEKS
AND STREAMS ON THE NORTH SIDE OF THE LARAMIE RANGE...INCLUDING DEER
CREEK...BOX ELDER CREEK AND ELKHORN CREEK...

...LOW TO MODERATE SNOWMELT FLOOD POTENTIAL ALSO EXISTS FOR THE UPPER
NORTH PLATTE RIVER NEAR SARATOGA AND THE ENCAMPMENT RIVER...

...ABNORMALLY DRY CONDITIONS EXIST AS OF MID APRIL FOR MOST OF FAR
SOUTHERN AND EASTERN WYOMING AS WELL AS ALL OF THE NEBRASKA
PANHANDLE.  MODERATE DROUGHT HAS DEVELOPED OVER LARAMIE AND EXTREME
SOUTHERN CARBON COUNTY...AS WELL AS PARTS OF THE CENTRAL NEBRASKA
PANHANDLE.  THESE CONDITIONS ARE EXPECTED TO CHANGE LITTLE THROUGH
JULY...

THIS OUTLOOK IS VALID THROUGH THE END OF JUNE.  THIS WILL BE THE LAST
SNOWMELT AND WATER RESOURCES OUTLOOK UNLESS CONDITIONS CHANGE.

     ...CURRENT HYDROLOGIC CONDITIONS...

THE RIVERS AND STREAMS IN SOUTHEAST WYOMING WERE AT OR BELOW AVERAGE
WATER LEVELS IN MID APRIL.

FROM OCTOBER 2011 THROUGH MID APRIL 2012...PRECIPITATION WAS ABOVE
NORMAL OVER MUCH OF SOUTHEAST WYOMING AND THE WESTERN NEBRASKA
PANHANDLE.  THE EXCEPTIONS WERE OVER SOUTHERN CARBON COUNTY AND THE
SOUTHERN NEBRASKA PANHANDLE...WHERE PRECIPITATION FOR OCTOBER 2011
THROUGH MID APRIL 2012 WAS BELOW NORMAL.  TEMPERATURES FOR THAT TIME
PERIOD WERE ABOVE NORMAL OVER MOST OF THE REGION...WITH SLIGHTLY
BELOW NORMAL VALUES OVER MUCH OF CARBON COUNTY.

MARCH 2012 THROUGH MID APRIL 2012 HAD WELL ABOVE NORMAL TEMPERATURES
AND MUCH BELOW NORMAL PRECIPITATION.

THE RESULTING SNOWPACK FROM SNOTEL SITES AS OF APRIL 25 2012 WAS NOW
MUCH BELOW NORMAL OVER SOUTHEAST WYOMING. AS OF THAT DATE...THE
LARGEST BASIN SNOW WATER EQUIVALENT VALUE WAS 74 PERCENT OF NORMAL
IN THE UPPER NORTH PLATTE RIVER BASIN. THE OTHER BASINS IN SOUTHEAST
WYOMING HAD EVEN LOWER VALUES.

      ...CLIMATOLOGICAL OUTLOOK...

SHORT RANGE...FOR THE NEXT 14 DAYS...SOUTHEAST WYOMING AND THE
WESTERN NEBRASKA PANHANDLE WILL AVERAGE ABOVE NORMAL TEMPERATURES
AND NEAR NORMAL PRECIPITATION

LONG RANGE...THROUGH JULY...THE LA NINA PATTERN HAS DISSIPATED AND
NEUTRAL CONDITIONS ARE EXPECTED THROUGH EARLY SUMMER.  THERE WILL BE
SLIGHTLY ENHANCED CHANCES FOR ABOVE NORMAL TEMPERATURES DURING THE
PERIOD OVER THE ENTIRE AREA.  SLIGHTLY ENHANCED CHANCES FOR BELOW
NORMAL RAINFALL EXIST OVER WYOMING WITH EQUAL CHANCES OF
ABOVE...NEAR OR BELOW AVERAGE PRECIPITATION OVER THE NEBRASKA
PANHANDLE.

...WATER SUPPLY OUTLOOK...NATIONAL WEATHER SERVICE/NATURAL RESOURCES
CONSERVATION SERVICE STREAMFLOW FORECASTS FOR SOUTHEASTERN WYOMING
AND THE NEBRASKA PANHANDLE AS OF APRIL 1 2012.

                                            MOST PROBABLE FORECAST

                                             VOLUME        PERCENT
STREAM AND STATION             PERIOD        1000 AF       OF AVG
_________________              ______        _______      _______

NORTH PLATTE RIVER
  NORTHGATE NEAR, CO          APR-SEP            57           21
SEMINOE RES INFLOW, WY        APR-JUL           245           31
SEMINOE RES INFLOW            APR-SEP           265           31

  GLENDO BLO, WY              APR-SEP           435           45
  GUERNSEY RES BLO, WY        APR-SEP           445           45
  ALCOVA TO ORIN, WY GAIN     APR-JUL           119           78
  ALCOVA TO ORIN, WY GAIN     APR-SEP           128           80

DEER CREEK
  GLENROCK, WY                APR-JUL            30           81
                              APR-SEP            31           84

ROCK CREEK
  ARLINGTON NEAR, WY          APR-SEP            38           67

LA PRELE CREEK
  LA PRELE RESERVOIR ABOVE    APR-SEP            14           58

ENCAMPMENT RIVER
  ENCAMPMENT NEAR, WY         APR-SEP            74           45

LARAMIE RIVER
  WOODS LANDING NEAR, WY      APR-SEP            92           68

LITTLE LARAMIE RIVER
  FILMORE NEAR, WY            APR-SEP            34           53

LITTLE SNAKE RIVER   XXX
  SLATER NR, CO               APR-JUL            80           50

      ...HYDROLOGIC OUTLOOK...

SNOW WATER EQUIVALENTS...SWES...ARE BELOW NORMAL FOR MID APRIL.
SNOW WATER EQUIVALENTS FROM THE MOUNTAIN SNOWPACK USUALLY PEAK
AROUND LATE APRIL TO EARLY MAY IN SOUTHEAST WYOMING. ALSO...30 TO 50
PERCENT OF THE TOTAL SWES USUALLY OCCUR IN MARCH THROUGH THE
BEGINNING OF MAY.  PEAK FLOW MAGNITUDES ARE VERY DEPENDENT UPON LATE
SPRING TEMPERATURES AND THE ENSUING MELT SCENARIO THAT DEVELOPS.
GIVEN THE AMOUNT OF SNOWPACK ALREADY IN THE MOUNTAINS ALONG WITH THE
CLIMATOLOGICAL PREDICTIONS FOR THE NEXT SEVERAL MONTHS...SWE PEAKS
HAVE OCCURRED IN MANY LOCATIONS AND HAVE OR WILL BE BELOW NORMAL.
AS OF APRIL 25 2012...THE SNOW HAS MELTED OUT AT ELEVATIONS BELOW
8800 FEET.

RUNOFF AND STREAMFLOW VOLUMES FOR THE LATE SPRING AND EARLY SUMMER
ARE LIKEWISE EXPECTED AT THIS TIME TO BE NEAR OR BELOW NORMAL
LEVELS.  AS OF MID APRIL...A LOW TO MODERATE RISK OF SPRING SNOWMELT
FLOODING WILL RESULT ON THE UPPER NORTH PLATTE RIVER NEAR SARATOGA
AND THE ENCAMPMENT RIVER.  LOW TO MODERATE RISK OF SNOWMELT FLOODING
ALSO IS EXPECTED ON THE STREAMS FLOWING OFF OF THE NORTHERN LARAMIE
RANGE.  A LOW RISK OF SPRING SNOWMELT FLOODING IS EXPECTED ON ALL
OTHER RIVERS AND STREAMS IN SOUTHEAST WYOMING.

       ...FLOOD POTENTIAL OUTLOOK...

AS OF APRIL 25...STREAMS AND CREEKS ON THE NORTH SIDE OF THE LARAMIE
RANGE ARE EXPECTED TO HAVE A LOW TO MODERATE SNOWMELT FLOOD
POTENTIAL LATE THIS SPRING AND EARLY THIS SUMMER.  THAT INCLUDES
DEER CREEK...BOX ELDER CREEK AND ELKHORN CREEK.  THE UPPER NORTH
PLATTE RIVER AT SARAYOGA AND THE ENCAMPMENT ALSO HAVE A LOW TO
MODERATE RISK OF SPRING SNOWMELT FLOODING.  THE OTHER RIVERS IN
SOUTHEAST WYOMING AND THE WESTERN NEBRASKA PANHANDLE ARE EXPECTED TO
HAVE A LOW SNOWMELT FLOOD POTENTIAL FOR LATE THIS SPRING AND EARLY
THIS SUMMER.



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