962 FXUS21 KWNC 171750 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT April 17 2026 SYNOPSIS: The mid-level pattern is anticipated to weaken throughout week-2 resulting in a quieter hazards period compared to yesterday, with many of them winding down by the onset of the period. Lee cyclogenesis may linger from the end of week-1 into week-2 over the lee of the Rockies, which may support enhanced wind speeds. This surface low pressure area may track from the central contiguous U.S. (CONUS) to the Great Lakes from the end of week-1 into the beginning of week-2. Heavy precipitation remains possible southward along the trailing front across parts of the eastern Southern Plains, Middle Mississippi, Tennessee, and Ohio Valleys, Southern Appalachians, and Southeast. Over the upper Midwest, flooding remains possible associated with above freezing temperatures accelerating spring snowmelt over the next two weeks. HAZARDS Slight risk of heavy precipitation for portions of the eastern Southern Plains, Middle Mississippi, Tennessee, and Ohio Valleys, Southern Appalachians, and Southeast, Sat-Sun, Apr 25-26. Slight risk of high winds for parts of the Great Plains,Sat, Apr 25. Possible flooding for parts of the Great Lakes region and Upper and Middle Mississippi Valley. DETAILED SUMMARY FOR MONDAY APRIL 20 - FRIDAY APRIL 24: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR SATURDAY APRIL 25 - FRIDAY MAY 01: During week-2, dynamical models continue to feature a transient 500-hPa height pattern. Anomalous mid-level troughing favored across the southwestern CONUS at the beginning of week-2 is anticipated to gradually weaken over the period. Meanwhile a mid-level short-wave trough is predicted to develop over the north-central CONUS and progress eastward across the eastern CONUS potentially lingering across the region towards the end of week-2. Multiple model ensemble guidance continues to indicate the development of an amplified ridge centered near the Davis Strait consistent with a transition towards a negative North Atlantic Oscillation (-NAO) circulation. This feature looks to peak at the end of week-1, gradually weakening throughout week-2. Negative height departures are anticipated to overspread much of the eastern CONUS favoring cooler temperatures shifting from the central to the northeastern CONUS during week-2. There continues to be good model agreement indicating increased potential of enhanced precipitation across parts of the interior eastern CONUS. Lee cyclogenesis in the Rockies from the end of week-1 is anticipated to transition to a surface low tracking northeastward to the Great Lakes at the beginning of week-2. The greatest potential for heavier rainfall is anticipated southward of the low associated with the trailing front. A slight risk of heavy precipitation lingering from the end of week-1 into week-2 is designated for portions of the eastern Southern Plains, Middle Mississippi, Tennessee, and Ohio Valleys, Southern Appalachians, and Southeast, Apr 25-26. As always, possible thunderstorms and accumulated precipitation combined with wet soils could support localized flooding including flash flooding. The moderate risk is not included in todays outlook due to much of the heavy precipitation anticipated to occur by the end of week-1. The Probabilistic Extremes Tools (PETs) indicate at least a 20% chance of 3-day precipitation (at the beginning of week-2) exceeding the 85th percentile climatologically and one inch in the designated risk area. Frozen precipitation including snow is possible across parts of the Upper Midwest on the Northwest side of the surface low. However, no associated snow hazard is posted due to high uncertainty regarding the details of the evolution of this system. The risk of heavy snow across the Rockies is discontinued due to the potential significantly decreasing with timing out of the supportive pattern. Lingering lee cyclogenesis across the Great Plains from the end of week-1 may support increased likelihood of episodic high winds at the beginning of week-2. The forecast pattern for week-1 would be more favorable for high winds compared to week-2. Multiple model tools and guidance including the PETs have significantly decreased probabilities of wind speeds reaching hazardous criteria. Therefore the moderate risk for high winds is discontinued, with a slight risk maintained for parts of the Great Plains for Apr 25. Gusty winds could increase wildfire risk especially across the Southern Plains where soils are dry and there are currently active wildfires. A flooding possible hazard continues to be posted for parts of the Great Lakes region and Upper and Middle Mississippi Valley. These areas have above-normal snowpack, with above freezing temperatures anticipated for weeks-1 and 2, in addition to precipitation anticipated for week-1 which would maintain flood conditions. Seasonal spring melt leading to saturated soils and subsequent current flood conditions. However, the threat of flooding is not limited to these areas alone, as lingering snow remains on the ground over portions of the High Plains as well. No hazard is issued for the Red River of the North or other watercourses in the region, although river rises are likely as snow melts and localized flooding may occur. Surface low formation in the Gulf of Alaska combined with anomalous cold temperatures and above normal precipitation predicted for Alaska, could support anomalously heavy late season snow for southern Mainland Alaska. No associated snow hazards are posted at this time with the expectation for totals to not reach hazardous criteria. Despite no associated flood hazards, flooding can occur this time of year with little or no notice during river ice breakup season. The colder temperatures in the Week-2 Outlook increase the chances of delayed river breakup in Alaska and increase the chances of ice jam flooding. Check the Alaska Pacific River Forecast Center (https://www.weather.gov/aprfc/breakupMap) for the latest conditions or advisories. FORECASTER: Melissa Ou $$