859
FGUS73 KBIS 241740
ESFBIS
NDC009-013-023-049-069-075-079-101-261745-
PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
1240 PM CDT THU APR 24 2025
..FLOOD AND WATER RESOURCES OUTLOOK
THIS FLOOD AND WATER RESOURCES OUTLOOK IS FOR THE SOURIS RIVER BASIN
OF NORTH DAKOTA, COVERING THE PERIOD OF 28 APRIL, 2025 THROUGH 27
JULY, 2025.
THE FOLLOWING MESSAGE HAS FOUR SECTIONS. THE FIRST PROVIDES SOME
TEXT ON THE HIGHLIGHTS OF THIS OUTLOOK AND CONDITIONS AFFECTING THE
LOCAL HYDROLOGY. THE SECOND SECTION GIVES THE CURRENT AND HISTORICAL
RISKS OF FLOODING AS DETERMINED BY THE ENSEMBLE STREAMFLOW FORECAST
MODEL OF THE NATIONAL WEATHER SERVICE. THE THIRD SECTION GIVES THE
CURRENT PROBABILITIES FOR REACHING FLOOD STAGE AT THE LISTED
FORECAST LOCATIONS. AND FINALLY, THE FOURTH SECTION COVERS THE RISK
OF THE RIVER SITES FALLING BELOW THE LISTED STAGES.
..FLOOD OUTLOOK HIGHLIGHTS
ALL FORECAST LOCATIONS ARE AT OR BELOW NORMAL FLOOD RISK FOR THIS
TIME OF THE YEAR. IN GENERAL THE RISKS BELOW ARE NOW PRIMARILY
ASSOCIATED WITH THE UPCOMING SEVERE THUNDERSTORM SEASON WHERE HEAVY
RAINS COULD CREATE LOCALIZED FLOODING.
..SNOWPACK CONDITIONS
WHAT APPRECIABLE SNOWPACK REMAINS IS ALL LOCATED IN THE NORTHERN
PORTION OF THE SOURIS RIVER BASIN OF SOUTHERN SASKATCHEWAN. IN THAT
SENSE, THE REMAINING SNOWPACK DOES NOT POSE MUCH OF A THREAT AS
RAFFERTY AND BOUNDARY DAMS ARE EXPECTED TO CAPTURE AND STORE MOST OF
THE REMAINING RUNOFF FROM MELTING SNOW, WHILE GRANT DEVINE IS NOT
EXPECTED TO FILL BASED ON HOW MUCH SNOW REMAINS.
..CURRENT DROUGHT CONDITIONS
NO SIGNIFICANT CHANGES HAVE OCCURRED WITH RESPECT TO DROUGHT
DESIGNATIONS OVER THE PAST MONTH. HOWEVER, DROUGHT REMAINS A CONCERN
ACROSS THE WESTERN HALF OF THE SOURIS RIVER BASIN OF NORTH DAKOTA
WITH UP TO A D2 (SEVERE) DROUGHT DESIGNATION.
..RESERVOIRS AND NATURAL WETLANDS
RAFFERTY, BOUNDARY, AND LAKE DARLING DAMS ARE ALL EXPECTED TO REACH
THEIR RESPECTIVE FULL SUPPLY LEVELS YET THIS SPRING. HOWEVER, GRANT
DEVINE IS NOT EXPECTED TO REACH FULL SUPPLY LEVEL WITHOUT GENEROUS
RAINFALL GOING FORWARD.
..SOIL CONDITIONS
SOIL MOISTURE VALUES ARE ROUGHLY NEAR NORMAL TO ABOVE NORMAL IN
SOUTHERN SASKATCHEWAN, BUT REMAIN BELOW NORMAL TO WELL BELOW NORMAL
ACROSS MUCH OF THE SOURIS RIVER BASIN OF NORTH DAKOTA. THIS
GENERALLY BELOW NORMAL SOIL MOISTURE IN NORTH DAKOTA WOULD BE
EXPECTED TO REDUCE RUNOFF FROM A GIVEN RAINFALL EVENT.
..WEATHER OUTLOOK
THE NEAR TERM 6-10 DAY WEATHER OUTLOOKS FAVORS ABOVE NORMAL
TEMPERATURES WITH NEAR NORMAL PRECIPITATION IN THE EASTERN PORTION
OF THE SOURIS RIVER BASIN, BUT WITH A SLIGHT FAVORING FOR BELOW
NORMAL PRECIPITATION IN THE WESTERN HALF OF THE BASIN. THE SLIGHTLY
LONGER TERM 8-14 DAY OUTLOOKS AGAIN FAVOR ABOVE NORMAL TEMPERATURES,
BUT WITH BELOW NORMAL PRECIPITATION. LOOKING OUT EVEN LONGER, THE
ONE-MONTH OUTLOOKS FOR MAY REFLECT THE EQUAL CHANCES DESIGNATION FOR
ABOVE NORMAL, NEAR NORMAL, OR BELOW NORMAL TEMPERATURES WITH A
SLIGHT FAVORING OF BELOW NORMAL PRECIPITATION. AND FINALLY, IN THE
3-MONTH OUTLOOKS COVERING MAY, JUNE AND JULY...THE SOURIS RIVER
BASIN IS AGAIN IN THE EQUAL CHANCES CATEGORY FOR TEMPERATURE, BUT
WITH A SLIGHT FAVORING FOR BELOW NORMAL PRECIPITATION.
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: 04/28/2025 - 07/27/2025
: 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
-------- ----- ----- ----- : --- --- --- --- --- ---
:DES LACS
FOXHOLM 1651.0 1653.0 1654.0 : <5 <5 <5 <5 <5 <5
:SOURIS
SHERWOOD 1623.0 1625.0 1630.0 : <5 6 <5 <5 <5 <5
FOXHOLM 1573.0 1576.0 1578.0 : <5 30 <5 12 <5 <5
MINOT 1562.0 1565.0 1570.0 : <5 8 <5 <5 <5 <5
MINOT 1551.0 1553.0 1557.0 : <5 <5 <5 <5 <5 <5
LOGAN 1536.0 1538.0 1540.0 : <5 11 <5 <5 <5 <5
SAWYER 1524.0 1526.0 1528.0 : <5 <5 <5 <5 <5 <5
VELVA 1507.0 1512.0 1517.0 : <5 9 <5 <5 <5 <5
:WINTERING
KARLSRUHE 1509.0 1511.0 1512.0 : <5 6 <5 <5 <5 <5
:SOURIS
TOWNER 1454.0 1456.0 1458.0 : 12 48 <5 19 <5 <5
BANTRY 1440.0 1441.0 1443.0 : 13 49 8 33 <5 <5
:WILLOW CREEK
WILLOW CITY 1442.0 1446.0 1448.0 : 9 38 6 10 <5 <5
:SOURIS
WESTHOPE 1414.0 1418.0 1420.0 : 11 48 <5 21 <5 13
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: 04/28/2025 - 07/27/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:DES LACS
FOXHOLM 1638.9 1638.9 1638.9 1639.7 1640.8 1641.8 1642.4
:SOURIS
SHERWOOD 1607.9 1607.9 1607.9 1609.4 1611.7 1616.2 1620.5
FOXHOLM 1566.5 1566.5 1566.5 1566.5 1570.9 1571.5 1572.3
MINOT 1550.8 1550.8 1550.9 1551.7 1554.1 1554.6 1555.5
MINOT 1541.2 1541.2 1541.4 1541.6 1542.8 1543.4 1543.8
LOGAN 1520.0 1520.0 1520.2 1523.2 1526.5 1528.2 1530.6
SAWYER 1506.8 1506.8 1507.6 1509.6 1512.0 1514.2 1517.1
VELVA 1490.2 1490.2 1491.5 1492.9 1496.0 1498.2 1502.6
:WINTERING
KARLSRUHE 1503.8 1503.8 1503.8 1504.2 1505.2 1507.9 1508.5
:SOURIS
TOWNER 1445.5 1445.5 1446.0 1448.9 1452.1 1454.9 1455.8
BANTRY 1431.2 1431.2 1431.8 1434.3 1437.6 1440.8 1441.5
:WILLOW CREEK
WILLOW CITY 1438.4 1438.4 1438.4 1438.4 1438.4 1441.6 1446.5
:SOURIS
WESTHOPE 1410.8 1410.8 1410.8 1411.3 1412.3 1414.6 1417.8
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: 04/28/2025 - 07/27/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:DES LACS
FOXHOLM 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:SOURIS
SHERWOOD 0.0 0.0 0.0 0.0 0.0 0.0 0.0
FOXHOLM 0.0 0.0 0.0 0.0 0.0 0.0 0.0
MINOT 0.0 0.0 0.0 0.0 0.0 0.0 0.0
MINOT 0.0 0.0 0.0 0.0 0.0 0.0 0.0
LOGAN 0.0 0.0 0.0 0.0 0.0 0.0 0.0
SAWYER 0.0 0.0 0.0 0.0 0.0 0.0 0.0
VELVA 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:WINTERING
KARLSRUHE 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:SOURIS
TOWNER 0.0 0.0 0.0 0.0 0.0 0.0 0.0
BANTRY 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:WILLOW CREEK
WILLOW CITY 0.0 0.0 0.0 0.0 0.0 0.0 0.0
:SOURIS
WESTHOPE 0.1 0.1 0.1 0.0 0.0 0.0 0.0
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/BIS FOR MORE WEATHER AND WATER
INFORMATION.
THE NEXT OUTLOOK WILL BE ISSUED BY THE END OF MAY.
SCHLAG
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