Spring 2012 Snowmelt Flood Potential Outllook

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE CHEYENNE WY
841 AM MST THU MAR 1 2012

...SPRING 2012 FLOOD AND WATER RESOURCES OUTLOOK NUMBER THREE...

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 ALONG THE
LITTLE SNAKE RIVER AND SAVERY CREEK AS OF MID FEBRUARY...
...LOW SPRING SNOWMELT FLOOD POTENTIAL IS EXPECTED FOR THE UPPER
NORTH PLATTE RIVER...LARAMIE RIVER...LITTLE LARAMIE
RIVER...ENCAMPMENT RIVER AND MEDICINE BOW RIVER AS OF MID FEBRUARY...

...ABNORMALLY DRY CONDITIONS EXIST AT LATE FEBRUARY FOR SOUTHERN
CARBON COUNTY...WITH MODERATE DROUGHT CONDITIONS OVER FAR SOUTHWEST
CARBON COUNTY. NO DROUGHT CONDITIONS CURRENTLY EXIST OVER THE
REMAINDER OF SOUTHEAST WYOMING AND THE WESTERN NEBRASKA PANHANDLE.
THOSE CONDITIONS ARE EXPECTED TO CONTINUE UNCHANGED THROUGH APRIL...

THIS OUTLOOK IS VALID THROUGH THE END OF JUNE.  THE NEXT SPRING 2012
PROBABILISTIC HYDROLOGY OUTLOOK WILL BE ISSUED IN MID MARCH.

     ...CURRENT HYDROLOGIC CONDITIONS...

MANY OF THE SMALLER STREAMS IN THE REGION NEAR THE MOUNTAINS WERE
EITHER FROZEN OR STREAM FLOW WAS AT OR BELOW AVERAGE FOR LATE
FEBRUARY.

FEBRUARY 2012 ACROSS SOUTHEAST WYOMING AND THE WESTERN NEBRASKA
PANHANDLE WAS ABOVE NORMAL FOR PRECIPITATION...ESPECIALLY OVER THE
LAST HALF OF THE MONTH.  MEANWHILE...TEMPERATURES FOR THE AREA IN
FEBRUARY WERE BELOW NORMAL.

THE RESULTING SNOWPACK FROM SNOTEL SITES AS OF MARCH 1 2012 WAS NOW
ABOVE NORMAL OVER SOUTHEAST WYOMING. AS OF THAT DATE...BASIN SNOW
WATER EQUIVALENT VALUES RANGED FROM 136 PERCENT IN THE LOWER NORTH
PLATTE BASIN TO 92 PERCENT IN THE SOUTH PLATTE BASIN.

      ...CLIMATOLOGICAL OUTLOOK...

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

LONG RANGE...THROUGH MAY...THE LA NINA PATTERN WILL CONTINUE TO
WEAKEN WITH NEUTRAL CONDITIONS EXPECTED IN THE SUMMER. THERE WILL BE
EQUAL CHANCES OF ABOVE...NEAR OR BELOW AVERAGE TEMPERATURES AND
PRECIPITATION OVER THE AREA THROUGH MAY.

...WATER SUPPLY OUTLOOK...NATIONAL WEATHER SERVICE/NATURAL RESOURCES
CONSERVATION SERVICE STREAMFLOW FORECASTS FOR SOUTHEASTERN WYOMING
AND THE NEBRASKA PANHANDLE AS OF FEBRUARY 1 2012.  THESE VALUES MAY
NOW BE HIGHER DUE TO THE ABOVE NORMAL SNOWFALL IN THE MOUNTAINS IN
FEBRUARY.

                                            MOST PROBABLE FORECAST

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

NORTH PLATTE RIVER
  NORTHGATE NEAR, CO          APR-SEP           152           56
SEMINOE RES INFLOW, WY        APR-JUL           455           57
SEMINOE RES INFLOW            APR-SEP           485           56

  GLENDO BLO, WY              APR-SEP           510           53
  GUERNSEY RES BLO, WY        APR-SEP           520           53
  ALCOVA TO ORIN, WY GAIN     APR-JUL           185          122
ALCOVA TO ORIN, WY GAIN     APR-SEP           196
122

DEER CREEK
  GLENROCK, WY                APR-SEP            44          119

ROCK CREEK
  ARLINGTON NEAR, WY          APR-SEP            41           72

LA PRELE CREEK
  LA PRELE RESERVOIR ABOVE    APR-SEP            25          104

ENCAMPMENT RIVER
  ENCAMPMENT NEAR, WY         APR-SEP           105           64

LARAMIE RIVER
  WOODS LANDING NEAR, WY      APR-SEP           115           85

LITTLE LARAMIE RIVER
  FILMORE NEAR, WY            APR-SEP            43           67

LITTLE SNAKE RIVER   XXX
  SLATER NR, CO               APR-JUL           110           69


      ...HYDROLOGIC OUTLOOK...

SNOW WATER EQUIVALENTS...SWES...ARE ABOVE NORMAL FOR LATE FEBRUARY.
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
ARE EXPECTED TO BE NEAR OR BELOW NORMAL LEVELS.  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
FEBRUARY...A LOW TO MODERATE RISK OF SPRING SNOWMELT FLOODING WILL
RESULT ON THE LITTLE SNAKE RIVER AND SAVERY CREEK...WITH A LOW RISK
OF SPRING SNOWMELT FLOODING ON THE REST OF THE RIVERS ORIGINATING IN
THE SIERRA MADRE...SNOWY AND LARAMIE RANGES.

       ...FLOOD POTENTIAL OUTLOOK...

AT MID FEBRUARY...THE LITTLE SNAKE RIVER AND SAVERY CREEK AND THEIR
TRIBUTARIES ARE ALL EXPECTED TO EXPERIENCE A LOW TO MODERATE
SNOWMELT FLOOD POTENTIAL LATE THIS SPRING AND EARLY THIS SUMMER.
THE OTHER RIVERS IN SOUTHEAST WYOMING AND THE WESTERN NEBRASKA
PANHANDLE ARE EXPECTED TO HAVE A LOW SNOWMELT FLOOD POTENTIAL LATE
THIS SPRING AND EARLY THIS SUMMER. THE FLOOD POTENTIAL OUTLOOK WILL
BE ADJUSTED WITH IN MID MARCH DUE TO THE RECENT ABVOVE NORMAL
SNOWFALL IN LATE FEBRUARY.

       ...ADDITIONAL INFORMATION...

FOR THE CURRENT WYOMING SPRING FLOOD POTENTIAL GRAPHIC...PLEASE REFER
TO...WWW.CRH.NOAA.GOV/RIW/HYDRO/FLOOD.PHP

FOR THE LATEST AVERAGE MONTHLY PRECIPITATION BY BASIN
GRAPHICS...REFER TO...WWW.CRH.NOAA.GOV/RIW/HYDRO/PRECIP.PHP

FOR THE CURRENT WYOMING WATER SUPPLY GRAPHIC...PLEASE REFER TO...
WWW.CRH.NOAA.GOV/RIW/HYDRO/WATER.PHP

FOR OTHER WEATHER AND RIVER INFORMATION IN SOUTHEAST WYOMING AND THE
WESTERN NEBRASKA PANHANDLE...REFER TO...WWW.WEATHER.GOV/CYS.

$$

WEILAND


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