####018012502#### FGUS73 KBIS 291912 ESFBIS NDC009-013-023-049-069-075-079-101-021715- Probabilistic Hydrologic Outlook National Weather Service Bismarck ND 112 PM CST Thu Feb 29 2024 ...SPRING FLOOD AND WATER RESOURCES OUTLOOK... This Spring Flood and Water Resources Outlook is for the Souris River Basin of North Dakota, covering the period of 4 March through 2 June, 2024. This is the second of a three-part Spring Flood and Water Resources Outlook series. 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 normal/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... The flood risks within the Souris River Basin of North Dakota remain well below normal across the North Dakota portion of the Souris River Basin, generally due to a well below normal Snow-Water Equivalent (SWE) in the snowpack. While the overall risk for widespread flooding is below normal, melting snow this winter across much of the North Dakota portion and at least extreme southern Saskatchewan portion of the basin has wetted the surface of the ground and created a near impermeable layer of frozen soil that should be expected to significantly enhanced runoff in the event of an early spring rain. This enhanced runoff potential will remain in place until such time as the soils begin to thaw, most likely in mid to late March. Overall though, without at least normal to above normal precipitation going forward, increased and expanded drought designations are more likely to be a concern than flooding. ...Snowpack Conditions... Overall SWE content of the snowpack across the Souris River Basin of North Dakota is below, to well below normal for this time of year. To a somewhat lesser degree, the same can be said for the Souris River Basin in Saskatchewan. Overall, most of the Souris River Basin has well under an inch of SWE with one-quarter to one-half of an inch common in North Dakota, and up to one inch across much of the Saskatchwan portion of the basin. That being said, all it would take is one significant snow storm to bring the SWE up to around 1.5 inches of water, which is roughly the low-end of normal for the Souris River Basin of North Dakota. Note: There is a system expected to be centered on the Canadian portion of the Souris River Basin next week that would most likely not bring it quite up to normal for this time of year, but it is likely to bring it within easy reach of normal if another similar event were to occur in the next few weeks. ...Soil Conditions... Soil moisture values across the Souris River Basin are very high in the soil down to about 4 inches (0-10 cm), but begin to fall rapidly the deeper one looks. By the time one averages out the soil moisture to a depth of around 40 inches (100 cm) the overall soil moisture is normal to slightly elevated. Frost depth is highly variable this year as a mix of very warm weather in December and a good part of January has helped prevent extensive freezing of the soil, but up to 30 inches of frost depth has been observed in some areas. ...Current Drought Conditions... The U.S. Drought Monitor reflects D0 (Abnormally Dry) in the western portion of the Souris River Basin of North Dakota which increases to D2 (Severe Drought) in Towner County. Given the time of year, no significant impacts are noted with the current drought designations. However, concerns with increased drought designations going into spring are warranted, especially since climate outlooks and near-term forecasts do not favor a change in existing trends anytime soon. ...Reservoirs and Natural Wetlands... Lake Darling above Minot along with the Canadian reservoirs behind Grant Devine and Rafferty Dams have their full flood control storage available for spring runoff. The majority of natural wetlands and lakes also are at, or near normal water levels for this time of year as the drier than normal latter half of summer and early fall took a toll on water levels in 2023. ...Weather Outlook... The Climate Prediction Center 6-10 day outlooks favor near normal in the western part of the state to warmer than normal temperatures for central and eastern North Dakota. Precipitation for the same period is expected to be below normal in the northwestern two-thirds of the state and slightly above normal in the southeastern one-third of the state. The weeks 3-4 outlooks favor above normal temperatures state-wide, with an equal chances designation for above normal, near normal, or below normal precipitation for all but the southeastern corner which has a slight favoring for above normal precipitation. Overall, North Dakota is favored for an above normal temperature outcome during March, with an equal chance for above normal, near normal, or below normal precipitation. The longer 3-month outlook for March, April and May combined favors above normal temperatures with an equal chance for above normal, near normal, or below normal precipitation. In general, this is consistent with the expectation that the El Nino affected winter season will fade into an ENSO neutral pattern by late spring to early summer. One trend in nearly all of the outlooks for temperature and precipitation is a sharp gradient from one extreme to the other, often right through the middle of the Souris River Basin. A slight shift (70 miles) one way or the other could have large impacts on the overall outcomes. ...Ice Conditions... After recent warm weather, not all rivers remain covered in ice. Lakes and wetlands are generally still ice covered, but thickness is generally less than normal and reports of an early softening of ice, especially near the shoreline, are common. 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: 03/04/2024 - 06/02/2024 : 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 -------- ----- ----- ----- : --- --- --- --- --- --- :Des Lacs Foxholm 1651.0 1653.0 1654.0 : <5 <5 <5 <5 <5 <5 :Souris Sherwood 1623.0 1625.0 1630.0 : <5 10 <5 5 <5 <5 Foxholm 1573.0 1576.0 1578.0 : 8 37 5 16 <5 <5 Minot 1562.0 1565.0 1570.0 : <5 16 <5 6 <5 <5 Minot 1551.0 1553.0 1557.0 : <5 <5 <5 <5 <5 <5 Logan 1536.0 1538.0 1540.0 : 7 19 <5 <5 <5 <5 Sawyer 1524.0 1526.0 1528.0 : <5 7 <5 <5 <5 <5 Velva 1507.0 1512.0 1517.0 : <5 16 <5 <5 <5 <5 :Wintering Karlsruhe 1509.0 1511.0 1512.0 : 5 14 <5 <5 <5 <5 :Souris Towner 1454.0 1456.0 1458.0 : 34 56 9 28 <5 <5 Bantry 1440.0 1441.0 1443.0 : 34 55 16 40 <5 8 :Willow Creek Willow City 1442.0 1446.0 1448.0 : 34 47 <5 19 <5 <5 :Souris Westhope 1414.0 1418.0 1420.0 : 9 49 <5 21 <5 17 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: 03/04/2024 - 06/02/2024 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Des Lacs Foxholm 1639.5 1639.7 1640.4 1641.5 1642.3 1644.4 1645.3 :Souris Sherwood 1608.3 1608.8 1610.2 1612.6 1616.2 1619.2 1620.2 Foxholm 1571.0 1571.0 1571.0 1571.0 1571.0 1571.4 1576.2 Minot 1554.1 1554.1 1554.1 1554.3 1554.8 1556.4 1561.8 Minot 1542.8 1542.8 1542.8 1542.9 1543.4 1544.2 1546.3 Logan 1526.6 1526.6 1526.6 1526.8 1528.2 1532.6 1536.8 Sawyer 1512.0 1512.0 1512.0 1512.4 1514.4 1520.4 1522.5 Velva 1496.0 1496.0 1496.0 1496.4 1498.7 1503.7 1506.9 :Wintering Karlsruhe 1503.6 1503.8 1504.0 1505.8 1507.5 1508.7 1509.0 :Souris Towner 1447.6 1448.2 1449.9 1452.7 1454.3 1455.7 1456.6 Bantry 1433.1 1433.4 1435.3 1438.4 1440.3 1441.5 1442.1 :Willow Creek Willow City 1437.4 1437.4 1437.5 1439.4 1443.7 1444.9 1445.7 :Souris Westhope 1410.7 1410.7 1411.0 1411.8 1412.7 1413.8 1415.7 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: 03/04/2024 - 06/02/2024 LOCATION 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Des Lacs Foxholm 1639.3 1639.2 1639.0 1638.9 1638.8 1638.7 1638.7 :Souris Sherwood 1606.5 1606.5 1606.4 1606.2 1606.1 1605.8 1605.8 Foxholm 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 Minot 1551.2 1551.0 1550.9 1550.8 1550.7 1550.6 1550.6 Minot 1541.5 1541.4 1541.3 1541.2 1541.1 1541.1 1541.0 Logan 1521.0 1520.2 1520.1 1520.0 1519.9 1519.8 1519.7 Sawyer 1507.9 1507.5 1507.2 1506.9 1506.6 1506.6 1506.5 Velva 1491.7 1491.5 1490.7 1490.2 1490.2 1490.2 1490.2 :Wintering Karlsruhe 1503.6 1503.4 1503.4 1503.2 1503.0 1503.0 1503.0 :Souris Towner 1444.4 1444.4 1444.4 1444.4 1444.4 1444.4 1444.4 Bantry 1430.4 1430.3 1430.2 1430.2 1430.2 1430.2 1430.2 :Willow Creek Willow City 1436.9 1436.9 1436.8 1436.7 1436.1 1436.1 1436.1 :Souris Westhope 1410.1 1410.0 1409.9 1409.8 1409.5 1409.3 1409.2 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 on 15 March. $$ Schlag