The severity of flooding is also dependent on antecedent conditions (soil moisture and soil type), land-use (urban vs. Users should be aware that this product does not consider antecedent conditions and should not be used as a sole indicator for impacts from flooding. Furthermore, precipitation ARIs are used in the design of hydrologic and flood-control structures and can be more relatable to emergency managers and key decision makers rather than absolute rain estimates alone. The value in recasting the QPF in the context of each ARI is that it allows the user to measure the climatological significance or 'rarity' of a forecasted or observed rain event for any location. See the table below for more specific information. These forecast products will be updated four times per day approximately 60-75 minutes after If the QPF for the given period is not expected to exceed the 1-yr ARI (or 4% AEP) anywhere in the domain, the text at the center of the graphic will read 'WPC X-hr QPF NOT EXPECTED TO EXCEED THE 1-YR ARI (or 4% AEP)'. The 1' inch contour is included on the imagery with a gray outline for reference to higher QPF amounts. Each contour level represents an ARI (or AEP) forecasted to be equaled or exceeded for the given time period. Users can select from WPC's deterministic or 90th percentile probabilistic QPF for comparison. This product is generated with the WPC's Days 1-3 Quantitative Precipitation Forecasts (QPFs) for the 6-, 24-, and 72-hr periods. The Extreme Precipitation Monitor displays exceedances for ARIs between 1 and 100 years and AEPs between 4% and 1%. The following table shows the equivalent AEP for ARIs ranging from 1-100 years. For example, precipitation thresholds that have a 100-yr ARI have a 1% AEP (i.e., a 1-in-100 chance of occurring in any given year). For values greater than or equal to 25 years, ARIs are inversely proportional to the Annual Exceedance Probability (AEP), which describes the probability of a particular event occurring at any one location in any given year. ARIs describe the expected amount of time (e.g., years) between periods of rainfall exceedances (usually in inches) at a given location.

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