929
FGUS73 KUNR 141417
ESFUNR
PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
816 AM MST THU MAR 14 2024
..SPRING FLOOD AND WATER RESOURCE OUTLOOK
..BELOW-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,
BAD, WHITE, AND KEYA PAHA.
FLOOD OUTLOOK SUMMARY
THE FLOOD POTENTIAL THIS SPRING IS BELOW AVERAGE ACROSS ALL OF
NORTHEASTERN WYOMING AND WESTERN SOUTH DAKOTA.
ICE COVER THAT IS ON THE HIGHER ELEVATION LAKES WILL CONTINUE TO
MELT OVER THE NEXT FEW WEEKS. ICE JAM FLOODING IS NOT EXPECTED THIS
YEAR.
RIVER-ICE BREAKUP AND THE POTENTIAL FOR ICE-JAM FLOODING USUALLY
OCCURS IN LATE FEBRUARY AND MARCH. FLOODING FROM SNOWMELT ON THE
PLAINS TYPICALLY OCCURS BETWEEN MARCH AND MAY, WHILE SNOWMELT
FLOODING IS LATER IN THE BLACK HILLS. 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
THIS SPRING. THE AMOUNT OF ADDITIONAL SNOW AND RAIN, AS WELL AS THE
TIMING OF PEAK RIVER AND STREAM FLOWS, WILL HAVE A SIGNIFICANT
EFFECT ON THE SEVERITY OF FLOODING.
TEMPERATURES AND PRECIPITATION
TEMPERATURES SO FAR THIS WINTER HAVE BEEN VERY WARM AND ABOVE
AVERAGE. TO DATE, RAPID CITY IS THE 6TH WARMEST ON RECORD WITH AN
AVERAGE TEMPERATURE OF 37.3 DEGREES. THE AVERAGE TEMPERATURE IN
GILLETTE HAS BEEN 35.1 DEGREES, MAKING IT THE 5TH WARMEST WINTER.
PRECIPITATION SINCE DECEMBER HAS BEEN SLIGHTLY BELOW AVERAGE.
SNOWFALL THIS WINTER SEASON FOR RAPID CITY HAS BEEN 13.1 INCHES AND
13.3 INCHES IN GILLETTE.
SNOW COVER AND LIQUID WATER CONTENT
SNOW COVER ACROSS THE AREA IS BELOW AVERAGE. THERE IS STILL A LITTLE
SNOW IN THE BLACK HILLS, BUT AMOUNTS ARE MINIMAL. SNOW WATER
EQUIVALENT IS MORE THAN HALF OF AVERAGE FOR THIS TIME OF YEAR.
THE HALFWAY POINT OF THE SNOW SEASON WAS FEBRUARY 1, BUT MARCH AND
APRIL ARE TYPICALLY SNOWY MONTHS, WHICH IS WHEN A THIRD OF THE
ANNUAL SNOWFALL OCCURS. THE MEDIAN PEAK SNOW WATER EQUIVALENT IN THE
BLACK HILLS USUALLY OCCURS AROUND APRIL 1.
SOIL CONDITIONS AND FROST DEPTHS
MELTING SNOW ALONG WITH THE THAWED GROUND HAS HELPED TO REPLENISH
MOISTURE IN THE TOP LAYERS OF THE GROUND. SOIL MOISTURE IS SLIGHTLY
ABOVE AVERAGE ACROSS SOUTH-CENTRAL SOUTH DAKOTA, WITH BELOW-AVERAGE
SOIL MOISTURE IN MODERATE AND SEVERE DROUGHT AREAS. THE ONLY FROST
REMAINING IN THE GROUND IS OVER NORTHWESTERN SOUTH DAKOTA AND HIGHER
ELEVATIONS OF THE BLACK HILLS. FROST DEPTHS IN THESE AREAS ARE LESS
THAN A FOOT. IN A TYPICAL YEAR, THE FROST USUALLY COMES OUT OF THE
GROUND BY THE END OF MARCH.
LAKE AND RIVER CONDITIONS
ICE THICKNESS ON RIVERS, STREAMS AND LAKES RANGES FROM OPEN WATER TO
AROUND 14 INCHES OF ICE AT DEERFIELD. THE COOL NIGHTS AND WARM DAYS
WILL SLOWLY DETERIORATE THE ICE OVER THE NEXT FEW WEEKS.
WEATHER OUTLOOKS
WATER TEMPERATURES IN THE TROPICAL EASTERN PACIFIC OCEAN ARE ABOVE
AVERAGE AT THE SURFACE; HOWEVER, SUBSURFACE WATER TEMPERATURES HAVE
TRENDED TO NEAR AVERAGE. THIS MEANS EL NIñO SOUTHERN OSCILLATION
(ENSO) NEUTRAL CONDITIONS ARE EXPECTED TO DEVELOP BY LATE SPRING.
HISTORICALLY, THERE IS A TENDENCY FOR LA NIñA TO FOLLOW STRONG EL
NIñO EVENTS. IF THIS DOES OCCUR, IT WILL LIKELY DEVELOP IN THE JUNE-
JULY TIME FRAME. THIS WEATHER PATTERN TYPICALLY FAVORS DRIER
CONDITIONS ACROSS NORTHEASTERN WYOMING AND WESTERN SOUTH DAKOTA
THROUGH THE SUMMER. TEMPERATURES ARE OFTEN A LITTLE COOLER THAN
AVERAGE IN THE SPRING, BUT WARMER THAN AVERAGE IN THE SUMMER.
NUMERICAL RIVER OUTLOOKS
IN TABLE 1 BELOW, THE CURRENT (CS) AND HISTORICAL (HS) OR NORMAL
PROBABILITIES OF EXCEEDING MINOR...MODERATE...AND MAJOR FLOOD STAGE
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 GREATER 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: 3/16/2024 - 9/30/2024
: 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 : 9 41 <5 20 <5 6
:MOREAU RIVER
FAITH 16.0 18.0 21.0 : <5 21 <5 12 <5 6
:BELLE FOURCHE RIVER
WY-SD STATE LINE 15.0 16.0 18.0 : <5 16 <5 <5 <5 <5
:SOUTH BELLE FOURCHE RIVER
STURGIS 15.0 17.0 19.0 : 20 26 11 18 7 9
:BELLE FOURCHE RIVER
ELM SPRINGS 19.0 22.0 24.0 : 9 16 <5 <5 <5 <5
:CHEYENNE RIVER
WASTA 13.0 15.0 16.0 : <5 7 <5 <5 <5 <5
PLAINVIEW 17.0 19.0 20.0 : 27 44 16 27 12 17
:BAD RIVER
MIDLAND 21.0 24.0 25.0 : 20 36 <5 5 <5 <5
:WHITE RIVER
KADOKA 15.0 16.0 19.0 : 32 53 17 45 6 16
WHITE RIVER 14.0 15.0 17.0 : 26 47 24 36 18 22
OACOMA 15.0 20.0 25.0 : 41 66 12 23 <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: 3/16/2024 - 9/30/2024
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:LITTLE MISSOURI RIVER
CAMP CROOK 1.9 1.9 1.9 3.0 6.1 11.9 13.4
:MOREAU RIVER
FAITH 1.9 3.0 4.7 6.7 8.9 11.2 12.5
:BELLE FOURCHE RIVER
WY-SD STATE LINE 4.4 4.4 4.4 4.5 7.1 10.9 12.7
:SOUTH BELLE FOURCHE RIVER
STURGIS 3.5 3.6 4.9 7.6 12.4 17.1 19.5
:BELLE FOURCHE RIVER
ELM SPRINGS 4.8 4.9 6.1 9.5 14.5 18.3 21.0
:CHEYENNE RIVER
WASTA 0.6 0.7 1.1 4.4 6.0 7.0 8.4
PLAINVIEW 8.8 8.8 10.5 13.7 17.5 20.5 21.0
:BAD RIVER
MIDLAND 4.5 4.8 5.4 11.3 20.3 22.6 22.9
:WHITE RIVER
KADOKA 6.3 7.2 9.2 13.1 15.3 17.8 21.5
WHITE RIVER 6.5 7.6 10.2 12.0 14.5 18.2 21.1
OACOMA 10.0 10.6 12.4 14.0 18.8 20.3 22.1
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: 3/16/2024 - 9/30/2024
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:LITTLE MISSOURI RIVER
CAMP CROOK 1.8 1.8 1.7 1.6 1.5 1.5 1.5
:MOREAU RIVER
FAITH 0.7 0.7 0.7 0.7 0.7 0.7 0.7
:BELLE FOURCHE RIVER
WY-SD STATE LINE 3.2 3.2 3.2 3.2 3.1 3.1 3.1
:SOUTH BELLE FOURCHE RIVER
STURGIS 2.2 2.2 2.2 2.2 2.2 2.2 2.2
:BELLE FOURCHE RIVER
ELM SPRINGS 3.2 3.2 3.2 3.2 3.2 3.2 3.2
:CHEYENNE RIVER
WASTA 0.5 0.5 0.4 0.3 0.3 0.3 0.2
PLAINVIEW 8.4 8.4 8.3 8.3 8.3 8.2 8.2
:BAD RIVER
MIDLAND 2.9 2.9 2.7 2.7 2.7 2.7 2.7
:WHITE RIVER
KADOKA 4.6 4.5 4.2 4.0 4.0 4.0 4.0
WHITE RIVER 4.3 4.2 4.1 4.0 3.9 3.9 3.9
OACOMA 8.4 8.3 8.1 8.0 7.9 7.8 7.8
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.
VISIT OUR WEB SITE WEATHER.GOV/UNR FOR MORE WEATHER AND WATER
INFORMATION.
OUTLOOK SCHEDULE
THIS IS THE FINAL SPRING FLOOD AND WATER RESOURCES OUTLOOK FOR THE
SEASON.
SMITH
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