US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 318 PM EDT Mon Mar 22 2021 Valid Thursday March 25 2021 - Monday March 29 2021 Hazards: - Heavy precipitation across portions of the Northeast, Mon, Mar 29. - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, the Great Lakes, and the Ohio Valley, Thu-Fri, Mar 25-Mar 26. - Heavy rain across portions of the Northeast and the Great Lakes, Fri, Mar 26. - Heavy snow across portions of the Southern Rockies, the Central Rockies, the Central Great Basin, and the Southwest, Thu-Fri, Mar 25-Mar 26. - Severe weather across portions of the Southeast, the Lower Mississippi Valley, the Southern Plains, and the Tennessee Valley, Thu, Mar 25. - Flooding possible across portions of the Central Plains and the Middle Mississippi Valley. - Flooding occurring or imminent across portions of the Central Plains, the Middle Mississippi Valley, the Southern Plains, and the Ohio Valley. - Flooding likely across portions of the Lower Mississippi Valley. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sat, Mar 27. - High winds across portions of mainland Alaska and the Aleutians, Sun-Mon, Mar 28-Mar 29. Detailed Summary: The medium-range forecast period (Thursday, March 25th to Monday, March 29th) is expected to include multiple rounds of active weather across the eastern third of the country. Starting on Thursday, a negatively tilted shortwave trough is forecast to lead to the potential for severe thunderstorms and heavy rain from the Central Gulf Coast States to the Lower Great Lakes. The Storm Prediction Center has specifically highlighted the region from far east Texas to Alabama as having the greatest chances for severe weather. As thunderstorms develop and the system progresses to the Northeast, a swath of heavy rain (greater than 1 inch) is expected to stretch northward throughout the Tennessee/Ohio Valleys and possibly into Lower Michigan between Thursday and Friday. The region most likely to experience flooding due to repeating rounds of showers and thunderstorms is located between northern Alabama/Mississippi and Kentucky. This area has experienced above average rainfall during the last 30 days and could see localized rainfall totals up to 4 inches. Heavy rain is also possible across the Interior Northeast on Friday as the system strengthens before exiting the area on Saturday. The combination of seasonably warm temperatures (10 to 25 degrees above average) and heavy rain could lead to flooding and river rises throughout the region as snow melt combines with rainfall runoff. Cooler air will enter the Northeast by the weekend. By Saturday yet another storm system is forecast to swing into the Eastern U.S. and bring the potential for heavy rain across the Southeast, as well as snow across portions of New England. No heavy rain areas were added to the hazards graphic today regarding this system due to model spread remaining relatively high. The greatest chances for heavy rain stretch from Mississippi to the Carolinas between Saturday and Sunday. A highlighted area may be warranted here in future outlooks. Farther northeast, confidence is higher that heavy precipitation will be found across northern New England/coastal Maine on Monday as the system enters the region. Due to the possibility of accumulating snow, the area was given a heavy precipitation label, as opposed to heavy rain. Across the western United States, relatively quiet weather can be expected as the end of March approaches. A progressing cold front will bring chances for mountain snow and lower elevation rain showers on Thursday and Friday. Higher snowfall totals (possibly as much as a foot) will be possible across the Central Rockies and more specifically the San Juan Mountains of southwest Colorado. Otherwise, much of the region will experience cooler than average temperature to start the forecast period, switching to slightly above average by the end of the weekend. By Monday, a strengthening storm system located in southern Alberta, Canada could bring gusty winds to the northern High Plains, but ultimately a hazard area was not drawn today given the spread in timing and magnitude. For Alaska, an area of low pressure is forecast to push into the Alaska Panhandle on Saturday and bring heavy coastal rain, interior and higher elevation snow. Upwards of 4 inches of total liquid precipitation will be possible as the storm exits on Sunday. Meanwhile, a separate storm system entering from the Bering Sea is expected to bring the potential for wind gusts greater than 50 knots to the Aleutian Islands on Sunday and Monday. This same system will bring the possibilities of light-to-moderate snow across western and Interior portions of the state between Sunday and Monday as well. Snell