####018008929#### FGUS73 KMQT 221426 ESFMQT MIC013-053-061-071-103-131-221500- Probabilistic Hydrologic Outlook National Weather Service Marquette MI 821 AM EST Thu Feb 22 2024 ...2024 SPRING FLOOD AND WATER RESOURCES OUTLOOK... This Spring Flood and Water Resources Outlook is for the rivers in western and east-central Upper Michigan. ...Flood Outlook Highlights... The overall flood risk this spring is much below-normal across all of Upper Michigan. The primary factors contributing to a below-normal flood risk is significantly below normal snowpack and the lack of river ice. ...Flood Terminology... The term minor flooding is used to indicate minimal or no property damage. However, some public inconvenience is possible. The term moderate flooding is used to indicate some inundations of structures and roads near streams. Some evacuations of people and/or transfer of property to higher elevations may be needed. The term major flooding is used to indicate extensive inundation of structure and roads. Significant evacuations of people and/or transfer of property to higher elevations will be needed. ...Probabilistic Outlook... The chance of minor flooding is less than 40% at all of the Upper Michigan forecast locations. The chance of moderate flooding is less than 20% at all of the Upper Michigan forecast locations. ...Past Precipitation... Precipitation last Fall was below normal across the area and this dry pattern has continued through the winter season. ...River Conditions... Streamflow across Upper Michigan was near to below-normal and persistently warm temperatures combined with episodes of snowmelt has removed most of the river ice. ...Soil Moisture and Frost Depths... Soil moisture is below-normal across Upper Michigan due to persistently warm and dry conditions since last fall. Frost depth in Negaunee Township was 3 inches on Feb 20th and hasn't changed much since mid-January when the seasonal snowpack was established. ...Snow Cover and Liquid Water Content... Current snow water equivalent values are much below-normal across all of Upper Michigan. Even though the UP winter is far from over, snowpack is currently near or at record lows and there aren't any major systems in the forecast at this time. ...River Ice Conditions... Well above normal temperatures this winter limited ice formation on rivers across Upper Michigan. Continued warm temperatures suggest reduced potential for ice jams and associated flooding. ...Weather Outlook... The single biggest factor affecting spring flood risks are the weather conditions during the period of snow melt. A slow snow melt with little or no rainfall would elinimate this years flood risks. On the other hand, a rapid warmup accompanied by heavy rain substantially increases flood risks for portions of Upper Michigan with several inches of snow water equivalent. At this time, the Climate Prediction Center's probabilistic forecast is for 30-50% chance of below normal precipitation and above-normal temperatures continuing through March. The current threat for springtime flooding is lower than normal, but much of the Spring Flooding Outlook hinges on weather conditions over the next 4 to 8 weeks. ...Definitions... In Table 1 below...the current (CS) and historical (HS) or normal probabilities of exceeding minor...moderate...and major flood stages 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 more 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: 02/19/2024 - 05/19/2024 : 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 -------- ----- ----- ----- : --- --- --- --- --- --- :Michigamme River Witch Lake 9.0 10.0 12.0 : <5 30 <5 17 <5 6 :Paint River Crystal Falls (Pa 7.0 8.0 9.5 : <5 18 <5 5 <5 <5 :Black River Bessemer 10.0 12.0 14.0 : <5 11 <5 <5 <5 <5 :Ontonagon River Rockland 25.0 26.0 28.0 : <5 <5 <5 <5 <5 <5 :Sturgeon River Sidnaw 12.0 15.0 17.0 : <5 <5 <5 <5 <5 <5 Alston 8.0 11.0 14.0 : 7 34 <5 <5 <5 <5 :Chocolay River Harvey 10.0 11.5 13.0 : <5 <5 <5 <5 <5 <5 :East Branch Escanaba River Gwinn 7.0 9.0 12.0 : <5 6 <5 <5 <5 <5 :Middle Branch Escanaba River Humboldt 6.5 8.0 9.0 : <5 12 <5 <5 <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: 02/19/2024 - 05/19/2024 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Michigamme River Witch Lake 4.2 4.5 5.1 5.8 6.9 7.9 8.4 :Paint River Crystal Falls (Pa 3.3 3.5 3.9 4.3 4.8 5.4 6.1 :Black River Bessemer 3.7 3.8 4.5 5.3 6.3 8.5 9.0 :Ontonagon River Rockland 8.9 9.2 10.3 11.7 14.2 16.2 18.0 :Sturgeon River Sidnaw 5.5 5.6 5.9 6.3 6.7 7.4 8.0 Alston 5.3 5.5 5.8 6.4 6.9 7.8 8.3 :Chocolay River Harvey 3.7 3.9 4.3 4.8 5.7 7.0 7.6 :East Branch Escanaba River Gwinn 2.5 2.8 3.3 3.8 4.4 5.2 5.5 :Middle Branch Escanaba River Humboldt 3.4 3.6 4.2 4.7 5.2 5.7 6.2 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: 02/19/2024 - 05/19/2024 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Michigamme River Witch Lake 2.8 2.8 2.7 2.7 2.7 2.6 2.6 :Paint River Crystal Falls (Pa 2.2 2.2 2.1 2.1 2.1 2.1 2.0 :Black River Bessemer 2.3 2.3 2.3 2.3 2.3 2.2 2.2 :Ontonagon River Rockland 5.8 5.8 5.7 5.7 5.7 5.5 5.4 :Sturgeon River Sidnaw 4.1 4.1 4.1 4.1 4.1 4.0 4.0 Alston 4.1 4.1 4.0 4.0 4.0 4.0 3.9 :Chocolay River Harvey 2.8 2.8 2.8 2.8 2.8 2.7 2.7 :East Branch Escanaba River Gwinn 0.7 0.6 0.6 0.6 0.6 0.5 0.5 :Middle Branch Escanaba River Humboldt 1.8 1.8 1.8 1.8 1.7 1.7 1.7 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/mqt for more weather and water information. The next outlook will be issued $$