US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 434 PM EST Wed Feb 10 2021 Valid Saturday February 13 2021 - Wednesday February 17 2021 Hazards: - Heavy precipitation across portions of the Lower Mississippi Valley, the Central/Southern Appalachians, the Tennessee Valley, the Mid-Atlantic, the Southeast, the Southern Plains, and the Ohio Valley, Mon-Tue, Feb 15-Feb 16. - Heavy precipitation across portions of the Mid-Atlantic and the Northeast, Tue-Wed, Feb 16-Feb 17. - Heavy rain across portions of California and the Pacific Northwest, Sat, Feb 13 and Mon, Feb 15. - Heavy rain across portions of the Southeast and the Mid-Atlantic, Sat, Feb 13. - Heavy snow across portions of California, the Pacific Northwest, and the Northern Great Basin, Sat-Tue, Feb 13-Feb 16. - Heavy snow across portions of the Central/Southern Plains, the Central/Southern Rockies, the Central Great Basin, the Pacific Northwest, and the Southwest, Sun, Feb 14. - Heavy snow across portions of the Central Plains, the Rockies, the Central Great Basin, California, the Northern Great Basin, and the Southwest, Sat, Feb 13. - Heavy snow across portions of the Central/Southern Plains, the Middle/Lower Mississippi Valley, the Tennessee Valley, the Great Lakes, and the Ohio Valley, Mon, Feb 15. - Heavy snow across portions of the Great Lakes, the Mid-Atlantic, the Northeast, the Central Appalachians, and the Ohio Valley, Tue-Wed, Feb 16-Feb 17. - Much below normal temperatures across portions of the Pacific Northwest, the Northern Rockies, and the Northern Great Basin, Sat-Sun, Feb 13-Feb 14. - Much below normal temperatures across portions of the Plains, the Mississippi Valley, the Central/Southern Appalachians, the Tennessee Valley, the Great Lakes, the Northern/Central Rockies, the Southeast, and the Ohio Valley, Sat-Tue, Feb 13-Feb 16. Detailed Summary: Cold temperatures continue to be the predominant story and the precipitation type for the upcoming Day 3-7 period (Friday, Feb 12 to Tuesday, Feb 16). An area of cold high pressure builds south out of Western-Central Canada into the Northern Plains by Sunday. The high will move into the Upper/Middle Mississippi Valley by Monday, then into Southeastern Canada by Tuesday. The deeply entrenched arctic air mass brings below to well below normal temperatures widespread to many sections of the lower 48. The most significant impacts will be over the Central U.S., where temperatures will range from 25-45 degrees below normal through most of the period; this translates to temperatures remaining below zero over the Northern Plains on Saturday and Sunday. Sub-zero low temperatures will extend as far south as parts of the Texas Panhandle and eastward into Wisconsin/Northern Michigan/Illinois through Monday, with single digits reaching the Texas/Mexican border and Northeast. The temperatures will begin to moderate by Wednesday. Any winds will exacerbate the very cold air mass, leading to dangerously low wind chills for much of this area. Upper-level energy and moist onshore flow will help produce areas of heavy snow over parts of the Cascades on Friday into Tuesday. Heavy snow will develop over parts of the Central Rockies, Great Basin, and Northern Rockies on Saturday and again on Monday. The energy will also produce heavy snow over parts of the Sierra-Nevada Mountains on Saturday. On Sunday, the energy will move out of the Southwest and into Texas on Monday and into the Northeast by Wednesday. The energy will help produce heavy snow over parts of Central/Southern High Plains on Sunday, moving into Midwest on Monday and into the Northeast on Tuesday and Wednesday. Additionally, the energy will also produce heavy precipitation from the Western Gulf Coast northeastward into the Lower Mississippi and Tennessee Valleys into the Central Appalachians into the Mid-Atlantic on Monday and Tuesday. The heavy precipitation will move into parts of the Mid-Atlantic into Southern New England on Wednesday. This forecast's most challenging aspect is the precipitation type from the Western Gulf Coast northeastward into the Lower Mississippi and Tennessee Valleys into the Central Appalachians and then into the Mid-Atlantic on Monday and Tuesday. The current guidance suggests the potential for accumulating freezing rain over Mid-Atlantic/Central Appalachians sections into the Western Gulf Coast as the arctic air mass undercuts warmer temperatures aloft. However, there is still a lot of uncertainty concerning the current details. Some models have warm temperatures streaking northward into the Ohio Valley, while other models suggest the temperatures at the surface will remain very cold. Furthermore, there is a good signal for freezing rain and sleet to develop over the Mid-Atlantic into Southern New England on Tuesday into Wednesday. With that uncertainty continuing, WPC decided again to depict the area as heavy precipitation for the time being. Despite this depiction, there is one area over the East with a clear precipitation type. An area of heavy rain will develop over the Floridian area on Saturday due to a front. Across Alaska, an area of deep low pressure will move to near the Aleutians on Saturday into Wednesday. A plume of moisture will not make it as far as the Aleutians during the period. However, we will keep an eye out to see if conditions will change over the next few days to depict Alaska's hazard. Ziegenfelder