Latest Mountain Snowmelt Flood Potential Outlook

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE CHEYENNE WY
239 PM MDT WED MAY 8 2013

...SPRING 2013 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 SNOWMELT FLOOD POTENTIAL IS EXPECTED FOR ALL RIVERS AND STREAMS
IN SOUTHEAST WYOMING AND THE WESTERN NEBRASKA PANHANDLE...

...DRY CONDITIONS PERSIST AS OF EARLY MAY FOR SOUTHEAST WYOMING AND
THE WESTERN NEBRASKA PANHANDLE. BENEFICIAL MOISTURE IN APRIL OVER
THE AREA EASED THE DROUGHT CONDITIONS. MOST OF SOUTHEAST WYOMING IS
IN MODERATE TO SEVERE DROUGHT AS OF MAY 1...WITH THE WESTERN NEBRASKA
PANHANDLE IN EXTREME DROUGHT CONDITIONS. THROUGH JULY...SOME MINOR
IMPROVEMENT IN THE DROUGHT CONDITIONS OVER MUCH OF SOUTHEAST WYOMING
AND THE WESTERN NEBRASKA PANHANDLE.

THIS OUTLOOK IS VALID THROUGH EARLY JUNE AND WILL LIKELY BE THE LAST
SNOWMELT AND WATER RESOURCES OUTLOOK FOR THIS YEAR.

     ...CURRENT HYDROLOGIC CONDITIONS...

THE RIVERS AND STREAMS IN SOUTHEAST WYOMING WERE AT OR BELOW AVERAGE
WATER LEVELS FOR EARLY MAY.

FROM OCTOBER 2012 THROUGH EARLY MAY 2013...PRECIPITATION WAS BELOW
NORMAL OVER SOUTHEAST WYOMING AND THE WESTERN NEBRASKA PANHANDLE AND
RANGED FROM 50 PERCENT TO 90 PERCENT. APRIL 2013 WAS ONE OF THE
SNOWIEST AND WETTEST OVER THE AREA SINCE RECORDS HAVE BEEN KEPT.

TEMPERATURES FOR THAT TIME PERIOD WERE NEAR NORMAL OVER THE REGION.
AFTER A MILD OCTOBER THROUGH DECEMBER...JANUARY THROUGH APRIL 2013
HAVE BEEN BELOW NORMAL. APRIL 2013 WAS WELL BELOW NORMAL AND WAS ONE
OF THE COLDEST SINCE RECORDS HAVE BEEN KEPT.

THE RESULTING SNOWPACK FROM SNOTEL SITES AS OF MAY 1 2013 WAS JUST
BELOW THE 30 YEAR NORMAL. THE SIGNIFICANT SNOWFALL IN APRIL INCREASED
THE SNOWPACK IN THE MOUNTAINS CONSIDERABLY. ALL OF THE RIVER BASINS
IN SOUTHEAST WYOMING HAD BETWEEN 85 PERCENT AND 100 PERCENT OF THE
30 YEAR NORMAL VALUES OF SNOW WATER EQUIVALENT AS OF MAY 1.

      ...CLIMATOLOGICAL OUTLOOK...

SHORT RANGE...FOR THE NEXT 14 DAYS...ODDS FAVOR ABOVE NORMAL
TEMPERATURES AND BELOW NORMAL PRECIPITATION ACROSS SOUTHEAST WYOMING
AND THE WESTERN NEBRASKA PANHANDLE.

LONG RANGE...THROUGH THE SUMMER...THE MAJORITY OF THE STATISTICAL AND
DYNAMICAL MODELS ARE PREDICTING ENSO-NEUTRAL CONDITIONS. THE CLIMATE
PREDICTION CENTER INDICATES ENHANCED CHANCES FOR ABOVE NORMAL
TEMPERATURES AND BELOW NORMAL PRECIPITATION.

...WATER SUPPLY OUTLOOK...NATIONAL WEATHER SERVICE/NATURAL RESOURCES
CONSERVATION SERVICE STREAMFLOW FORECASTS FOR SOUTHEASTERN WYOMING
AND THE NEBRASKA PANHANDLE AS OF MAY 1 2013.

                                            MOST PROBABLE FORECAST

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

NORTH PLATTE RIVER            MAY-JUL           155           83
  NORTHGATE NEAR, CO          MAY-SEP           174           83
SEMINOE RES INFLOW, WY        MAY-JUL           420           68
SEMINOE RES INFLOW            MAY-SEP           460           69

  GLENDO BLO, WY              MAY-JUL           460           69
  GLENDO BLO, WY              MAY-SEP           485           69
  GUERNSEY RES BLO, WY        MAY-JUL           480           72
  GUERNSEY RES BLO, WY        MAY-SEP           515           74
  ALCOVA TO ORIN, WY GAIN     MAY-JUL            26           27
  ALCOVA TO ORIN, WY GAIN     MAY-SEP            28           27

DEER CREEK
  GLENROCK, WY                MAY-JUL           M             M
                              MAY-SEP           M             M
ROCK CREEK
  ARLINGTON NEAR, WY          MAY-JUL            37           77
  ARLINGTON NEAR, WY          MAY-SEP            39           76

LA PRELE CREEK
  LA PRELE RESERVOIR ABOVE    MAY-SEP           M             M

ENCAMPMENT RIVER
  ENCAMPMENT NEAR, WY         MAY-JUL            91           77
  ENCAMPMENT NEAR, WY         MAY-SEP            98           77

LARAMIE RIVER
  WOODS LANDING NEAR, WY      MAY-JUL            95           88
  WOODS LANDING NEAR, WY      MAY-SEP           105           88

LITTLE LARAMIE RIVER
  FILMORE NEAR, WY            MAY-JUL            36           75
  FILMORE NEAR, WY            MAY-SEP            39           75

LITTLE SNAKE RIVER
  SLATER NR, CO               MAY-JUL            86           62

LITTLE SNAKE RIVER
  DIXON NR, WY               MAY-JUL            158           54

      ...HYDROLOGIC OUTLOOK...

SNOW WATER EQUIVALENTS...SWES...ARE JUST BELOW NORMAL FOR EARLY MAY.
SNOW WATER EQUIVALENTS FROM THE MOUNTAIN SNOWPACK HAVE PEAKED AS OF
MAY 8 WITH SNOWMELT UNDERWAY. PEAK FLOW MAGNITUDES ARE VERY DEPENDENT
UPON LATE SPRING TEMPERATURES AND RAINFALL AND THE ENSUING MELT
SCENARIO THAT DEVELOPS.

RUNOFF AND STREAMFLOW VOLUMES FOR THE LATE SPRING AND EARLY SUMMER
ARE LIKEWISE EXPECTED AT THIS TIME TO BE AT BELOW NORMAL LEVELS.
AS OF EARLY MAY...A LOW RISK OF SPRING SNOWMELT FLOODING WILL RESULT
ON ALL RIVERS AND STREAMS IN SOUTHEAST WYOMING.

       ...FLOOD POTENTIAL OUTLOOK...

AS OF MAY 1...STREAMS AND RIVERS ACROSS SOUTHEAST WYOMING ARE
EXPECTED TO HAVE A LOW SNOWMELT FLOOD POTENTIAL LATE THIS SPRING AND
EARLY THIS SUMMER.

       ...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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