National Weather Service Text Product Display

Flood Potential Outlook
Issued by NWS Cheyenne, WY
Versions: 1 2 3
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FGUS75 KCYS 292300
ESFCYS

WYC001-007-009-015-021-027-031-NEC007-013-033-045-105-123-157-165-011440-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE CHEYENNE WY
359 PM MST FRI JAN 29 2010

...SPRING 2010 FLOOD AND WATER RESOURCES OUTLOOK NUMBER ONE...

THIS FLOOD OUTLOOK ENCOMPASSES THE NORTH PLATTE RIVER MAINSTEM AND
ITS TRIBUTARIES (THE LARAMIE AND MEDICINE BOW RIVERS) IN SOUTHEASTERN
WYOMING AND THE NEBRASKA PANHANDLE. LIKEWISE...IT ALSO INCLUDES THE
TRIBUTARIES TO THE MISSOURI RIVER (NIOBRARA AND WHITE RIVERS) OF
EXTREME NORTHWESTERN NEBRASKA.  FINALLY...IT ALSO INCLUDES THE LITTLE
SNAKE RIVER DRAINAGE OF SOUTH CENTRAL WYOMING.

...LOW TO MODERATE SPRING SNOWMELT FLOOD POTENTIAL EXPECTED ALONG THE
LARAMIE RIVER...
...BELOW AVERAGE VOLUME SPRING RUNOFF IS FORECAST FOR THE REST OF THE
BASINS...
...NO DROUGHT CONDITIONS CURRENTLY EXIST IN SOUTHEAST WYOMING OR THE
WESTERN NEBRASKA PANHANDLE WHICH IS EXPECTED TO CONTINUE UNCHANGED THROUGH
APRIL...

THIS OUTLOOK IS VALID FROM APRIL TO THE END OF JUNE.  THE NEXT SPRING 2010
PROBABILISTIC HYDROLOGY OUTLOOK WILL BE ISSUED BY THE END OF FEBRUARY.

     ...CURRENT HYDROLOGIC CONDITIONS...

MANY OF THE SMALLER STREAMS IN THE REGION WERE EITHER FROZEN OR STREAM FLOW
WAS NEAR AVERAGE IN THE LAST WEEK OF JANUARY.  THE STREAM FLOW FOR THE LARGER
RIVERS WAS ALSO LOW AW SNOW MELT AND RUNOFF HAS YET TO BEGIN.

MUCH OF THE REGION HAD SIGNIFICANT SNOWFALL IN OCTOBER 2009 AND AGAIN IN
DECEMBER.  IN FACT...THE MONTH OF OCTOBER 2009 HAD MUCH ABOVE NORMAL
PRECIPITATION AND IN SOME LOCATIONS...OCTOBER WAS ONE OF THE WETTEST IN
MANY YEARS.  THE LITTLE SNAKE...UPPER NORTH PLATTE AND CHEYENNE RIVER
BASINS HAD 137% TO 192% OF NORMAL PRECIPTIATION WITH THE REST OF SOUTHEAST
WYOMING AND THE WESTERN NEBRASKA PANHANDLE RECORDING OVER 193% OF NORMAL
PRECIPITATION.  AFTER A FAIRLY DRY NOVEMBER WITH THE ENTIRE REGION RECEIVING
LESS THAN 75% OF NORMAL PRECIPITATION, DECEMBER 2009 WAS AGAIN WET.  DECEMBER
2009 HAD 89% TO 160% OF NORMAL PRECIPITATION OVER THE SOUTHEAST WYOMING
BASINS.  JANUARY 2010 HAS BEEN SIMILAR TO NOVEMBER 2009 WITH BELOW NORMAL
PRECIPITATION OVER THE REGION.

THE RESULTING SNOWPACK FROM SNOTEL SITES IN THE SNOWY AND LARAMIE RANGES
OF SOUTHEAST WYOMING AS OF JANUARY 27 2010 WERE NEAR OR BELOW NORMAL AT MOST
LOCATIONS.  THE EXCEPTIONS WERE AT SITE IN THE SOUTHERN PORTION OF THE
SNOWY RANGE.  THOSE SITES FEED INTO THE LARAMIE AND LITTLE LARAMIE RIVERS
AND WERE BETWEEN 100% AND 110% OF NORMAL VALUES.

TEMPERATURES OVER SOUTHEAST WYOMING AND THE WESTERN NEBRASKA PANHANDLE WERE
WELL BELOW NORMAL.  NOVEMBER 2009 AND JANUARY 2010 HAD READINGS NEAR OR JUST
ABOVE NORMAL AND DECEMBER 2009 HAD TEMPERATURES THAT WERE AT OR JUST BELOW
NORMAL.

      ...CLIMATOLOGICAL OUTLOOK...

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

LONG RANGE...FEBRUARY THROUGH APRIL...THERE WILL BE SLIGHTLY INCREASED
CHANCES FOR THE TEMPERATURES TO AVERAGE ABOVE NORMAL OVER THE AREA.  THE
EL NINO PATTERN WILL CNTINUE DURING THAT TIME...BUT IS EXPECTED TO SLOWLY
WEAKEN.  SO THERE IS SOME UNCERTAINTY WITH THE PRECIPITATION OUTLOOK FOR
FEBRUARY THROUGH APRIL.  AT THIS TIME IT APPEARS THAT THERE ARE EQUAL
CHANCES OF PRECIPITATION AMOUNTS BEING ABOVE NORMAL...BELOW NORMAL OR
NEAR NORMAL.  IF THE CURRENT EL NINO STRENGTH CONTINUES THROUGH THE
SPRING...PRECIPITATION CHANCES MAY BE ABOVE NORMAL FOR FAR SOUTHEAST
WYOMING AND THE FAR SOUTHERN NEBRASKA PANHANDLE.

      ...HYDROLOGIC OUTLOOK...

SNOW WATER EQUIVALENTS...SWES...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 THREE
MONTHS...SWE PEAKS ARE EXPECTED TO BE AT OR JUST BELOW NORMAL LEVELS.
RUNOFF AND STREAMFLOW VOLUMES ARE LIKEWISE EXPECTED TO BE AT OR JUST BELOW
NORMAL LEVELS.  THE EXCEPTION MAY BE THE LARAMIE AND LITTLE LARAMIE RIVERS...
WHERE NOWPACK AT THIS TIME IS JUST ABOVE NORMAL FOR THOSE WATERSHEDS.
FOLLOWING IS THE RECENTLY ISSUED WATER SUPPLY OUTLOOK FOR SOUTHEAST WYOMING
AND THE WESTERN NEBRASKA PANHANDLE.

...WATER SUPPLY OUTLOOK...NATIONAL WEATHER SERVICE/NATURAL RESOURCES
CONSERVATION SERVICE STREAMFLOW FORECASTS FOR SOUTHEASTERN WYOMING
AND THE NEBRASKA PANHANDLE FOR JANUARY 2010.

                                             MOST PROBABLE FORECAST

                                             VOLUME        PERCENT
STREAM AND STATION             PERIOD        1000 AF       OF AVG

NORTH PLATTE RIVER
  NORTHGATE NEAR  CO          APR-SEP           200           74
  SEMINOE RES INFLOW          APR-JUL           650           81
                              APR-SEP           695           81
  GLENDO BLO  WY              APR-SEP           755           79
  GUERNSEY RES BLO  WY        APR-SEP           780           79
  ALCOVA TO ORIN  WY GAIN     APR-JUL           133           88
  ALCOVA TO ORIN  WY GAIN     APR-SEP           142           88

DEER CREEK
  GLENROCK  WY                APR-SEP            36           97

ROCK CREEK
  ARLINGTON NEAR  WY          APR-SEP            56           98

LA PRELE CREEK
  LA PRELE RESERVOIR ABOVE    APR-SEP            21           88

ENCAMPMENT RIVER
  ENCAMPMENT NEAR  WY         APR-SEP           148           90

LARAMIE RIVER
  WOODS LANDING NEAR  WY      APR-SEP           144          107

LITTLE LARAMIE RIVER
  FILMORE NEAR  WY            APR-SEP            66          103

LITTLE SNAKE RIVER
  SLATER NR  CO               APR-JUL           135           85
  DIXON NR  WY                APR-JUL           285           86


       ...FLOOD POTENTIAL OUTLOOK...

THE LARAMIE AND LITTLE LARAMIE RIVERS HAVE A LOW TO MODERATE RISK OF
FLOODING FROM SNOW MELT LATER THIS SPRING AND EARLY SUMMER.  OTHERWISE...
ALL OTHER BASINS CAN EXPECT A LOW POTENTIAL FOR FLOODING DUE TO
SPRINGTIME SNOWMELT.

       ...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
National Weather Service Weather Forecast Office
