FGUS73 KBIS 251925 ESFBIS NDC009-013-023-049-069-075-079-101-271900- Probabilistic Hydrologic Outlook National Weather Service Bismarck ND 225 PM CDT Thu Apr 25 2024 ...FLOOD AND WATER RESOURCES OUTLOOK... This Flood and Water Resources Outlook is for the Souris River Basin of North Dakota, covering the period of 29 April through 28 July, 2024. This is a monthly issuance of the 90-day flood risks for the Souris River Basin of North Dakota. These probabilities are updated on or around, the fourth Thursday of every month. 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... With essentially zero snowpack remaining in the North Dakota portion of the Souris River basin, the region has largely dodged normal amounts of spring time flooding. Without a significant snowpack, the basin is generally in the range of well below normal, to slightly below normal risk of flooding over the next 90s days. What risk is present in the below tables is due to the region now entering its summer, severe thunderstorm season where heavy rains can pose problems. However, in general the risks are still well below normal for this time of year. ...Snowpack Conditions... While there may be a few drifts of snow in protected areas, no signficant snowpack exists overall in the Souris River basin of North Dakota. ...Soil Conditions... Soil moisture values across the Souris River Basin are mostly near normal with the exception of the Turtle Mountain area where it is generally below the 30th percentile. ...Current Drought Conditions... Most of the Souris River basin of North Dakota is depicted as in D0 (Abnormally Dry), with a small sliver of western Long Creek watershed shown as in D1 (Moderate Drought) in the very northwest corner of the state. ...Reservoirs and Natural Wetlands... Lake Darling above Minot along with the Saskatchewan reservoir of Grant Devine are generally at their summertime full supply level. However, Rafferty and Boundary dams in Saskatchewan are not expected to reach their full supply level this summer without the help of some timely rainfall. The majority of natural wetlands and lakes also are at, or near normal water levels going into spring. ...Weather Outlook... Near term, as in the next few days, rain is expected over most of North Dakota. This should put the region on track to enter May with at least a stable position on the drought front. The 6-10 and 8-14 day outlooks favor an above normal temperature and precipitation pattern. The strength of this above normal temperature and precipitation pattern slightly wanes in the weeks 3-4 outlooks before all of the Souris River basin in North Dakota slides into the equal chances category for above normal, near normal, or below normal temperature and precipitation for the entirety of May and again in the 3-month outlook for May, June and July. ...Ice Conditions... No ice is known to exist along the Souris River and its tributaries in North Dakota. 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: 04/29/2024 - 07/28/2024 : 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 6 <5 <5 <5 <5 Foxholm 1573.0 1576.0 1578.0 : 8 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 10 <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 : 20 48 9 19 <5 <5 Bantry 1440.0 1441.0 1443.0 : 20 49 15 33 <5 <5 :Willow Creek Willow City 1442.0 1446.0 1448.0 : 12 35 7 10 <5 <5 :Souris Westhope 1414.0 1418.0 1420.0 : 13 47 6 20 <5 12 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: 04/29/2024 - 07/28/2024 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Des Lacs Foxholm 1639.5 1639.5 1639.5 1640.7 1642.4 1644.2 1645.7 :Souris Sherwood 1606.8 1606.9 1607.5 1610.0 1612.4 1618.0 1620.4 Foxholm 1567.9 1568.3 1569.0 1570.5 1571.0 1571.6 1574.5 Minot 1551.2 1551.4 1551.8 1553.6 1554.7 1556.1 1558.3 Minot 1541.5 1541.6 1541.6 1542.6 1543.1 1544.1 1544.8 Logan 1521.2 1521.8 1523.2 1525.7 1527.1 1531.5 1533.6 Sawyer 1507.9 1508.2 1509.5 1511.2 1512.5 1518.6 1520.0 Velva 1491.5 1492.0 1492.8 1495.3 1496.6 1504.2 1505.4 :Wintering Karlsruhe 1504.3 1504.3 1504.3 1504.5 1506.8 1508.1 1508.6 :Souris Towner 1449.8 1449.8 1449.8 1451.5 1453.1 1455.6 1456.3 Bantry 1436.0 1436.0 1436.0 1436.8 1439.0 1441.4 1441.9 :Willow Creek Willow City 1436.9 1436.9 1436.9 1437.1 1438.0 1444.3 1446.8 :Souris Westhope 1411.1 1411.1 1411.1 1411.8 1412.5 1415.5 1418.5 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: 04/29/2024 - 07/28/2024 LOCATION 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Des Lacs Foxholm 1639.4 1639.3 1639.1 1639.0 1638.9 1638.9 1638.9 :Souris Sherwood 1606.6 1606.4 1606.2 1605.8 1605.8 1605.8 1605.8 Foxholm 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 Minot 1551.0 1550.9 1550.9 1550.8 1550.7 1550.7 1550.7 Minot 1541.4 1541.3 1541.3 1541.2 1541.1 1541.1 1541.1 Logan 1520.5 1520.1 1520.0 1519.9 1519.8 1519.8 1519.8 Sawyer 1507.6 1507.2 1506.8 1506.7 1506.6 1506.6 1506.6 Velva 1491.3 1490.7 1490.2 1490.2 1490.2 1490.2 1490.2 :Wintering Karlsruhe 1504.0 1503.6 1503.2 1503.0 1503.0 1503.0 1503.0 :Souris Towner 1446.1 1446.0 1445.6 1445.1 1445.0 1444.9 1444.9 Bantry 1432.0 1431.9 1431.4 1431.0 1430.9 1430.8 1430.8 :Willow Creek Willow City 1436.7 1436.6 1436.1 1436.1 1436.1 1436.1 1436.1 :Souris Westhope 1410.8 1410.4 1410.1 1409.8 1409.7 1409.7 1409.7 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