US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 341 PM EDT Tue Apr 13 2021 Valid Friday April 16 2021 - Tuesday April 20 2021 Hazards: - Heavy rain across portions of the Southeast and the Lower Mississippi Valley, Fri-Sat, Apr 16-Apr 17. - Heavy rain across portions of the Southeast, Sat-Tue, Apr 17-Apr 20. - Flooding possible across portions of the Middle Mississippi Valley. - Flooding occurring or imminent across portions of the Middle Mississippi Valley and the Lower Mississippi Valley. - Flooding likely across portions of the Middle Mississippi Valley. - High winds across portions of the Northeast, Fri-Sat, Apr 16-Apr 17. Detailed Summary: During the medium range forecast period (Friday, April 16 through Tuesday, April 20), the main weather hazards will be found across the Lower Mississippi Valley and Southeast, as well as the Northeast. Starting in the northeastern U.S., a potent upper-level low and associated surface low pressure system is forecast to drift near and off the coast of southern New England on Friday and Saturday. Moderate rain and heavy higher elevation snow will be possible on Friday. At the moment, current precipitation amounts are forecast to remain below hazardous threshold as much of the region has experienced below normal rainfall over the last month. Any snow ongoing between Friday and early Saturday should be primarily focused to the Green and White Mountains of New England, with accumulations mainly occurring on grassy and elevated surfaces. High winds along coastal regions from southern Maine to Long Island will be a concern as the low pressure system pushes strong north-northeast winds onshore. Wind gusts could top 50 mph along Cape Cod, which could prompt coastal flooding/erosion. Precipitation and gusty winds are expected to relax across the region by Saturday evening. Meanwhile, a separate upper-level system located over the Central Rockies on Friday is forecast to interact with a stationary front draped across the northern Gulf of Mexico for much of the medium range period. Moderate-to-heavy mountain snow is a possibility across the Colorado and northern New Mexico Rockies on Friday and Saturday. Snowfall amounts up to 8 to 12 inches are not out of the question across the mountain peaks of this region, but no hazard area was added today given the impacts are mainly across higher elevations that experience this amount of snow often. An area of low pressure is forecast to develop across the Southern Plains on Friday as well, helping funnel moisture along an attached stationary front along the central Gulf Coast. As a result, showers and thunderstorms are expected to form between Louisiana and northern Florida/southern Georgia on Friday and Saturday. Rainfall amounts over 1 inch are possible across the region, with locally higher totals occurring where thunderstorms form. The Lower Mississippi Valley region (particularly southeast Louisiana and southern Mississippi) has experienced an abundance of rainfall over the last several weeks, therefore any additional rainfall could lead to enhanced flooding concerns. By late Saturday and into early Sunday, the system is expected to come to a crawl across northern/central Florida. This will lead to several rounds of showers and thunderstorms through early next week. Total rainfall amounts of 2 to 5 inches are forecast across northern Florida, extending as far south as Orlando and Tampa Bay. Isolated to scattered flash flooding will be possible for locations that experience repeating rounds of heavy rain. The temperature outlook across the Lower 48 during this time frame includes below normal temperatures across much of the Great Plains, with above normal temperatures found across the western United States. High Temperatures across the southern High Plains between Friday and this weekend are forecast to be around 20 degrees below average. Low temperatures are expected to continue dropping below freezing through early next week across the Northern Plains and portions of the central High Plains. This is not abnormal, as the average date for the last spring freeze across the Northern Plains and central High Plains is during the first half of May. For Alaska, no weather hazards are expected during this forecast period. Above normal temperatures are expected to continue across the North Slope, but are not considered hazardous at this time. Elsewhere, there is a growing signal for high winds across the Aleutian Islands by Tuesday, but high uncertainty remains and therefore no highlighted hazard area was added to today's graphic. Snell