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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />4.3.6.8. Future trends/likelihood of occurrence Ble <br />The 2023 National Climate Assessment indicates that winter and spring precipitation is expected to <br />increase, while summer and fall precipitc <br />2070), the latest science suggests that <br />rainfall events that would ranking in <br />the top 2% for the period 1981-2010, <br />will become more common. Most of <br />Minnesota can expect, on average, an <br />additional day per year with these <br />events, which amounts to an <br />approximate doubling infrequency. <br />4.3.6.9. Indications and Forecasting <br />The Chanhassen Office of the National <br />Weather Service is the local authority <br />for extreme rainfall monitoring and <br />forecasting, and uses flash flood Additional days per year with upper 2% rainfall events by mid-century <br />(2041-2071). Source, 2014 National Climate Assessment, Midwest Chapter. <br />guidance, based on soil moisture and <br />land cover conditions, to evaluate whether expected and/or ongoing heavy rainfall poses a significant <br />flooding risk. Additionally, NOAA's Weather Prediction Center (WPC) has a legacy of advanced hydro - <br />meteorological monitoring and prediction and offers Excessive Rainfall Outlooks and Mesoscale <br />Precipitation Discussions that are comparable to the severe weather products offered by the Storm <br />Prediction Center. Unlike the Storm Prediction Center, however, the WPC does not issue Watches of any <br />sort. <br />Forecasters monitor and analyze numerical weather models and other predictive tools to ascertain <br />potential extreme rainfall and associated flash flooding threats. The following sequence of <br />products may then be used in an idealized situation, though it should be noted that extreme <br />rainfall threats may appear of disappear at any step in this timeline: <br />4+ days out: Chanhassen NWS Office highlights threat for heavy or extreme rainfall and flash flooding <br />potential in Hazardous Weather Outlook products. <br />1-3 days out: WPC issues Excessive Rainfall Outlook, indicating Marginal, Slight, Moderate, or High Risk of <br />excessive rainfall, according to the following probabilities: <br />126 <br />