Flood Potential Outlook
Issued by NWS Cheyenne, WY

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000
FGUS75 KCYS 191930 CCA
ESFCYS
WYC001-007-009-015-021-027-031-NEC007-013-033-045-105-123-157-165-
201928-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE CHEYENNE WY
1228 PM MST THU FEB 19 2015

...SPRING FLOOD AND WATER RESOURCES OUTLOOK...

THIS OUTLOOK COVERS THE CHEYENNE HYDROLOGIC SERVICE AREA (HSA) WHICH
EMCOMPASSSES 7 COUNTIES ACROSS SOUTHEAST WYOMING AND 7 COUNTIES
ACROSS WESTERN NEBRASKA. THIS OUTLOOK COVERS THE NORTH PLATTE RIVER
MAINSTEM AND ITS TRIBUTARIES (THE LARAMIE AND MEDICINE BOW RIVERS) IN
SOUTHEAST WYOMING AND THE WESTERN NEBRASKA PANHANDLE. LIKEWISE, IT ALSO
INCLUDES THE TRIBUTARIES TO THE MISSOURI RIVER (NIOBRARA AND WHITE
RIVERS) OF EXTREME NORTHWEST NEBRASKA AND THE LITTLE SNAKE IN SOUTHEAST
WYOMING.

...NORMAL TO SLIGHTLY WETTER THAN NORMAL SOIL MOISTURE CONDITIONS
EXIST...

...NORMAL TO BELOW NORMAL RISK FOR FLOODING DUE TO SNOW MELT THIS
SPRING RUNOFF SEASON ACROSS THE CHEYENNE HSA...

CURRENT RIVER LEVELS ARE RUNNING NEAR TO SLIGHTLY ABOVE NORMAL. MINOR
FLUCTUATIONS WERE OBSERVED AT SOME OF THE FORECAST POINTS ON THE NORTH
PLATTE RIVER DUE TO ICE.

AUTUMN RAINFALL AND MODERATE AMOUNTS OF WINTER PRECIPITATION HAVE KEPT
SOIL MOISTURE VALUES AT NORMAL TO SLIGHTLY WETTER THAN NORMAL FROST DEPTHS
WERE GENERALLY FROM ONE-HALF FOOT TO A FOOT.

CURRENT SNOW CONDITIONS ACROSS THE EASTERN WYOMING PLAINS RANGED FROM
2 TO 4 INCHES...WITH LESS THAN 2 INCHES FOR WESTERN NEBRASKA PANHANDLE.
MOUNTAIN SNOWPACK CONDITIONS WERE AVERAGING 85 TO 95% OF NORMAL.

THE SPRING WATER SUPPLY OUTLOOK FOR THE SOUTHEAST WYOMING AND WESTERN
NEBRASKA PANHANDLE MAIN STEM RIVERS AND TRIBUTARIES INDICATES 75 TO 90%
OF AVERAGE FLOW.

PRECIPITATION SINCE JANUARY 1 HAS AVERAGED BELOW NORMAL ACROSS THE
CHEYENNE HSA.

THE 90-DAY OUTLOOK ISSUED FEBRUARY 19 FOR MARCH THROUGH MAY INDICATES
EQUAL CHANCES OF ABOVE...BELOW AND NORMAL TEMPERATURES AND ABOVE NORMAL
PRECIPITATION.


...TABLE 1--PROBABILITIES FOR MINOR...MODERATE AND MAJOR FLOODING...
                    VALID PERIOD:  2/21/2015 - 9/30/2015

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:ENCAMPMENT RIVER
ENCAMPMENT           6.5    7.5    8.5 :   5   13    5    5   <5   <5
:NORTH PLATTE RIVER
SARATOGA             8.5    9.5   10.5 :  24   20    6    7   <5   <5
SINCLAIR             9.0   10.0   11.0 :  11   27    6   15    5    5
:MEDICINE BOW RIVER
HANNA                6.0    7.0    8.0 :  <5   <5   <5   <5   <5   <5
:NORTH PLATTE RIVER
GLENROCK            10.0   11.0   12.0 :  <5   <5   <5   <5   <5   <5
ORIN                 8.0    9.0   10.0 :  <5    6   <5   <5   <5   <5
:LARAMIE RIVER
WOODS LANDING        6.0    6.5    7.0 :  <5   <5   <5   <5   <5   <5
LARAMIE              5.0    6.0    7.0 :  11   39   <5   19   <5   <5
BOSLER               7.5    8.5    9.5 :  <5   <5   <5   <5   <5   <5
FORT LARAMIE         7.0    8.0    9.0 :  <5   16   <5    5   <5   <5
:NORTH PLATTE RIVER
HENRY                5.5    6.5    7.5 :   7   18    5   13   <5   11
MITCHELL             7.5    8.5    9.5 :  10   19    6   17    5   12
MINATARE             7.5    8.5    9.5 :   6   27   <5   17   <5    9
BRIDGEPORT           9.5   10.0   10.5 :  <5    9   <5    6   <5   <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: 2/21/2015 - 9/30/2015
LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:ENCAMPMENT RIVER
ENCAMPMENT            4.1    4.2    4.6    5.0    5.3    5.9    7.1
:NORTH PLATTE RIVER
SARATOGA              6.6    6.7    7.4    7.8    8.5    8.9    9.9
SINCLAIR              5.8    5.9    6.8    7.4    8.4    9.0   10.8
:MEDICINE BOW RIVER
HANNA                 3.7    3.9    4.1    4.5    4.8    5.4    5.7
:NORTH PLATTE RIVER
GLENROCK              2.8    2.8    2.9    3.0    3.5    4.9    6.0
ORIN                  4.8    4.8    4.8    4.9    5.5    6.2    7.4
:LARAMIE RIVER
WOODS LANDING         2.1    2.2    2.6    3.0    3.4    4.0    4.7
LARAMIE               1.3    1.8    2.6    3.2    3.7    5.0    5.8
BOSLER                1.5    1.8    2.7    3.9    5.1    6.1    6.6
FORT LARAMIE          3.6    3.6    3.9    4.2    4.9    6.1    6.5
:NORTH PLATTE RIVER
HENRY                 3.7    3.8    3.8    4.0    4.2    4.8    6.7
MITCHELL              4.0    4.0    4.0    4.1    5.1    7.0    9.8
MINATARE              4.4    4.4    4.6    4.9    5.3    6.6    8.1
BRIDGEPORT            5.3    5.3    5.3    5.6    5.9    6.9    8.2


IN TABLE 3 BELOW...THE 95 THROUGH 5 PERCENT COLUMNS INDICATE THE
PROBABILITY OF FALLING BELOW THE LISTED STAGE LEVELS (FT) FOR THE
VALID TIME PERIOD.

TABLE 3--NONEXCEEDANCE PROBABILITIES...

                            CHANCE OF FALLING BELOW STAGES
                                 AT SPECIFIC LOCATIONS
                          VALID PERIOD: 2/21/2015 - 9/30/2015
LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:ENCAMPMENT RIVER
ENCAMPMENT            1.9    1.9    1.9    1.8    1.8    1.8    1.7
:NORTH PLATTE RIVER
SARATOGA              4.7    4.7    4.6    4.6    4.6    4.5    4.5
SINCLAIR              3.5    3.4    3.4    3.3    3.3    3.2    3.2
:MEDICINE BOW RIVER
HANNA                 2.2    2.2    2.1    2.0    2.0    2.0    2.0
:NORTH PLATTE RIVER
GLENROCK              1.0    1.0    0.9    0.8    0.8    0.7    0.7
ORIN                  3.6    3.6    3.6    3.5    3.4    3.4    3.4
:LARAMIE RIVER
WOODS LANDING         1.3    1.2    1.1    0.9    0.3    0.3    0.3
LARAMIE               0.5    0.4    0.4    0.3    0.3    0.3    0.3
BOSLER                1.1    1.1    1.0    0.9    0.8    0.8    0.8
FORT LARAMIE          3.2    3.2    3.2    3.2    3.2    3.2    3.2
:NORTH PLATTE RIVER
HENRY                 2.1    2.0    2.0    2.0    2.0    2.0    1.9
MITCHELL              0.7    0.5    0.2    0.2    0.2    0.2    0.2
MINATARE              2.1    1.9    1.6    1.4    1.4    1.3    1.3
BRIDGEPORT            3.6    3.5    3.4    3.3    3.2    3.2    3.2

THESE LONG-RANGE 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 PROBABALISTIC FORECASTS ARE PART OF THE NATIONAL WEATHER SERVICE`S
ADVANCED HYDROLOGIC PREDICTION SERVICE (AHPS).

VISIT OUR WEB SITE AT WWW.WEATHER.GOV/CHEYENNE FOR MORE WEATHER
AND RIVER INFORMATION INCLUDING GRAPHS OF PROBABLILISTIC RIVER
OUTLOOKS.

$$



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