Flood Potential Outlook
Issued by NWS Rapid City, SD

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000
FGUS73 KUNR 281452
ESFUNR
SDC055-063-085-093-103-105-123-137-041800-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
852 AM MDT FRI MAR 28 2014

...SPRING FLOOD AND WATER RESOURCE OUTLOOK...
...ABOVE AVERAGE FLOOD POTENTIAL THIS SPRING...

THIS SPRING FLOOD AND WATER RESOURCE OUTLOOK IS FOR THE RAPID CITY
HYDROLOGIC SERVICE AREA /HSA/ WHICH COVERS NORTHEASTERN WYOMING AND
WESTERN SOUTH DAKOTA. THE MAIN RIVER BASINS INCLUDE THE LITTLE
MISSOURI...EASTERN POWDER...BELLE FOURCHE...GRAND...MOREAU...
CHEYENNE...UPPER MISSOURI...WHITE AND KEYAPAHA RIVER BASINS.

.FLOOD OUTLOOK SUMMARY...
AT THIS TIME...THE POTENTIAL FOR FLOODING THIS SPRING IS ABOVE
AVERAGE DUE TO SATURATED SOIL CONDITIONS...LACK OF WATER STORAGE
AVAILABILITY...AND HIGHER THAN NORMAL STREAM FLOWS. HOWEVER SINCE
THERE IS LIMITED SNOW COVER RIGHT NOW...ADDITIONAL MOISTURE IS
NEEDED TO CAUSE THIS FLOODING.

FOR THE BLACK HILLS AND HIGHER ELEVATIONS...FLOODING FROM SNOWMELT
TYPICALLY BEGINS IN APRIL OR MAY. FLOODING ON THE PLAINS DUE TO
SNOWMELT AND ICE JAMS TYPICALLY OCCURS BETWEEN FEBRUARY AND MAY.

THE POTENTIAL FOR RAINFALL-INDUCED FLASH FLOODING IS NOT
QUANTIFIABLE BECAUSE THIS TYPE OF FLOODING IS USUALLY CAUSED BY
LOCALIZED THUNDERSTORMS DURING THE SPRING AND SUMMER.

THE FLOOD POTENTIAL IS STILL VERY DEPENDENT ON WEATHER CONDITIONS
FROM NOW UNTIL THE SPRING MELT. THE AMOUNT OF ADDITIONAL SNOW AND
RAIN...THE TIMING AND RATE OF THE SPRING THAW...AND THE TIMING OF
PEAK FLOWS WILL HAVE A SIGNIFICANT EFFECT ON THE FLOODING.

.SNOW COVER AND LIQUID WATER CONTENT...
CURRENT SNOWPACK IS CONFINED MOSTLY TO THE HIGHER ELEVATIONS IN THE
BLACK HILLS AND BEAR LODGE MOUNTAINS. SNOW COVER AT LOWER ELEVATIONS
IS MINIMAL.

SINCE OCTOBER 1...2013 PRECIPITATION HAS BEEN ABOVE AVERAGE...
ESPECIALLY SINCE OCTOBER WAS EXTREMELY WET. RUNOFF FROM THE OCTOBER
BLIZZARD AND LARGE RAINSTORMS THAT FOLLOWED...SATURATED THE SOIL AND
FILLED STOCK PONDS. THIS MOISTURE FROZE INTO THE GROUND DURING THE
WINTER AND HAS LEFT VERY LITTLE ROOM FOR SNOWMELT AND RAIN RUNOFF
THIS SPRING. ANY SIGNIFICANT PRECIPITATION THIS SPRING WILL MOST
LIKELY LEAD TO FLOODING.

.SOIL CONDITIONS AND FROST DEPTHS...
SOIL MOISTURE IS ABOVE AVERAGE ACROSS THE AREA. THE FROST IS
BEGINNING TO COME OUT OF THE GROUND AT THE LOWER ELEVATIONS ON THE
PLAINS WITH THE GROUND STILL FROZEN IN THE BLACK HILLS AND BEAR
LODGE MOUNTAINS. THE GROUND TYPICALLY THAWS BY THE END OF MARCH INTO
EARLY APRIL ON THE PLAINS AND TOWARD THE END OF APRIL INTO MAY FOR
THE HIGHER ELEVATIONS. THE FROZEN AND SATURATED SOIL CONDITIONS
INCREASE THE LIKELIHOOD OF FLOODING THIS SPRING.

.LAKE AND RIVER CONDITIONS...
MOST LAKES...RIVERS AND STREAMS ARE FREE OF ICE. STREAMFLOWS RANGE
FROM AROUND AVERAGE TO ABOVE AVERAGE.

.WEATHER OUTLOOKS...
AN UNSETTLED WEATHER PATTERN WILL CONTINUE INTO EARLY APRIL BRINGING
A MIXTURE OF WARM AND COOL TEMPERATURES AND A CHANCE FOR RAIN OR
SNOW TO THE NORTHERN HIGH PLAINS. OVERALL APRIL TEMPERATURES AND
PRECIPITATION ARE EXPECTED TO BE AROUND AVERAGE.

FOR APRIL...THE AVERAGE HIGH TEMPERATURE IS IN THE UPPER 50S AND THE
AVERAGE LOW TEMPERATURE IS AROUND 30 DEGREES. AVERAGE PRECIPITATION
IS AROUND TWO INCHES ON THE PLAINS WITH THREE AND A HALF INCHES FOR
THE BLACK HILLS AND BEAR LODGE MOUNTAINS.

.NUMERICAL RIVER OUTLOOKS...
THE FOLLOWING TABLE GIVES THE CHANCE OF REACHING FLOOD STAGE AT THE
GAUGES DURING THE VALID PERIOD MARCH 29 2014 UNTIL JUNE 27 2014.
THESE VALUES DO NOT REFLECT THE FLOODING POTENTIAL DUE TO ICE JAMS.

IN TABLE 1 BELOW...THE CURRENT (CS) AND HISTORICAL (HS) OR NORMAL
PROBABILITIES OF EXCEEDING MINOR...MODERATE...AND MAJOR FLOOD STAGES
ARE LISTED FOR THE VALID TIME PERIOD.

CS VALUES INDICATE THE PROBABILITY OF REACHING A FLOOD CATEGORY
BASED ON CURRENT CONDITIONS.

HS VALUES INDICATE THE PROBABILITY OF REACHING A FLOOD CATEGORY
BASED ON HISTORICAL OR NORMAL CONDITIONS.

WHEN THE VALUE OF CS IS MORE THAN HS...THE PROBABILITY OF EXCEEDING
THAT LEVEL IS HIGHER THAN NORMAL. WHEN THE VALUE OF CS IS LESS THAN
HS...THE PROBABILITY OF EXCEEDING THAT LEVEL IS LOWER THAN NORMAL.

TABLE 1--PROBABILITIES FOR MINOR...MODERATE AND MAJOR FLOODING
               VALID PERIOD:  3/29/2014 - 6/27/2014

                                       :    CURRENT AND HISTORICAL
                                       :     CHANCES OF EXCEEDING
                                       :       FLOOD CATEGORIES
                                       :      AS A PERCENTAGE (%)
                      CATEGORICAL      :
                   FLOOD STAGES (FT)   :   MINOR    MODERATE   MAJOR
LOCATION           MINOR   MOD   MAJOR :  CS   HS   CS   HS   CS   HS
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:LITTLE MISSOURI RIVER
CAMP CROOK          12.0   17.0   19.0 :  35   33   14    8    5    6
:MOREAU RIVER
FAITH               16.0   18.0   21.0 :  23    8    9   <5   <5   <5
:BELLE FOURCHE RIVER
WY-SD STATE LINE    15.0   16.0   18.0 :  20   <5   17   <5   <5   <5
STURGIS             15.0   17.0   19.0 :  21   18   15    8    8    6
ELM SPRINGS         19.0   22.0   24.0 :  14   <5    7   <5   <5   <5
:CHEYENNE RIVER
WASTA               14.0   16.0   17.0 :   6   <5   <5   <5   <5   <5
PLAINVIEW           16.0   17.0   19.0 :  47   36   41   24   21   12
:BAD RIVER
MIDLAND             21.0   24.0   25.0 :  16   24   <5   <5   <5   <5
:WHITE RIVER
KADOKA              13.0   15.0   19.0 :  43   35   29   26   <5   <5
WHITE RIVER         14.0   15.0   17.0 :  44   49   31   17   17   <5
OACOMA              15.0   20.0   25.0 :  41   51   14   19    6   <5

LEGEND
CS = CONDITIONAL SIMULATION (CURRENT OUTLOOK)
HS = HISTORICAL SIMULATION
FT = FEET

IN TABLE 2 BELOW...THE 95 THROUGH 5 PERCENT COLUMNS INDICATE THE
PROBABILITY OF EXCEEDING THE LISTED STAGE LEVELS (FT) FOR THE VALID
TIME PERIOD.

TABLE 2--EXCEEDANCE PROBABILITIES

                               CHANCE OF EXCEEDING STAGES
                                  AT SPECIFIC LOCATIONS
                          VALID PERIOD: 3/29/2014 - 6/27/2014
LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:LITTLE MISSOURI RIVER
CAMP CROOK            2.3    2.3    2.5    9.5   13.1   18.1   19.1
:MOREAU RIVER
FAITH                 3.9    4.9    8.0   10.5   14.7   17.9   18.5
:BELLE FOURCHE RIVER
WY-SD STATE LINE      4.9    4.9    4.9    8.5   12.4   16.6   16.9
STURGIS               5.4    5.7    7.3   10.3   13.2   18.3   21.9
ELM SPRINGS           6.4    6.6    7.9   11.1   14.5   20.4   22.9
:CHEYENNE RIVER
WASTA                 2.6    2.6    4.1    5.8    8.6   11.0   14.6
PLAINVIEW            11.1   11.4   12.6   13.9   18.2   21.3   21.7
:BAD RIVER
MIDLAND               3.5    3.5    5.6   12.2   17.6   21.8   22.6
:WHITE RIVER
KADOKA                4.0    4.3    5.5   10.1   15.2   16.4   16.6
WHITE RIVER           5.0    5.3    6.9   13.6   16.4   18.9   20.3
OACOMA                8.1    8.2    9.2   14.3   17.6   22.1   25.8

THESE LONG-RANGE PROBABILISTIC OUTLOOKS CONTAIN FORECAST VALUES THAT
ARE CALCULATED USING MULTIPLE SEASON SCENARIOS FROM 30 OR MORE YEARS
OF CLIMATOLOGICAL DATA...INCLUDING CURRENT CONDITIONS OF THE
RIVER...SOIL MOISTURE...SNOW COVER...AND 30 TO 90 DAY LONG-RANGE
OUTLOOKS OF TEMPERATURE AND PRECIPITATION. BY PROVIDING A RANGE OF
PROBABILITIES...THE LEVEL OF RISK ASSOCIATED WITH LONG-RANGE PLANNING
DECISIONS CAN BE DETERMINED. THESE PROBABILISTIC FORECASTS ARE PART
OF THE NATIONAL WEATHER SERVICE`S ADVANCED HYDROLOGIC PREDICTION
SERVICE.

THIS IS THE FOURTH SPRING FLOOD AND WATER RESOURCE OUTLOOK FOR 2014.
LONG-RANGE PROBABILISTIC OUTLOOKS ARE ISSUED NEAR THE MIDDLE OF THE
MONTH THROUGHOUT THE YEAR. THE NEXT SCHEDULED OUTLOOK FOR THESE
SITES WILL BE ISSUED TOWARD THE END OF APRIL.

VISIT OUR WEB SITE AT
HTTP://WWW.CRH.NOAA.GOV/AHPS2/INDEX.PHP?WFO=UNR FOR MORE WEATHER AND
RIVER INFORMATION INCLUDING GRAPHS OF PROBABILISTIC RIVER OUTLOOKS.

$$







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