US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 458 PM EST Thu Feb 11 2021 Valid Sunday February 14 2021 - Thursday February 18 2021 Hazards: - Heavy rain across portions of the Southeast and the Mid-Atlantic, Sun, Feb 14. - Heavy snow across portions of the Pacific Northwest, Sun-Mon, Feb 14-Feb 15. - Heavy rain across portions of the Pacific Northwest and Northern California, Sun-Mon, Feb 14-Feb 15. - Heavy snow across portions of the Central/Southern Rockies, Mon-Tue, Feb 14-Feb 16. - Heavy snow across portions of the Northern/Central Great Basin and the Northern/Central Rockies, Sun-Tue, Feb 15-Feb 16. - Heavy snow across portions of the Southwest, the Southern Rockies, the Central/Southern Plains, and the Middle Mississippi Valley, Sun, Feb 14. - Heavy snow across portions of the Southern Plains, the Lower/Middle Mississippi Valley, the Tennessee Valley, the Ohio Valley, and the Great Lakes, Mon, Feb 15. - Heavy snow across portions of the Great Lakes, the Central Appalachians, the Mid-Atlantic, and the Northeast, Tue, Feb 16. - Heavy precipitation across portions of the Southern Plains, the Lower Mississippi Valley, the Tennessee Valley, the Ohio Valley, the Southern/Central Appalachians, the Mid-Atlantic, and the Northeast, Mon-Tue, Feb 15-Feb 16. - Heavy precipitation across portions of the Lower/Middle Mississippi Valley, the Tennessee Valley, the Southern/Central Appalachians, the Ohio Valley, the Mid-Atlantic, the Great Lakes, and the Northeast, Wed-Thu, Feb 17-Feb 18. - Heavy rain across portions of the Southeast, the Southern Appalachians, and the Mid-Atlantic, Thu, Feb 18. - Much below normal temperatures across portions of the Pacific Northwest, the Northern Great Basin, and the Northern Rockies, Sun, Feb 14. - Much below normal temperatures across portions of the Northern/Central/Southern Rockies, the Northern/Central/Southern Plains, the Upper/Middle/Lower Mississippi Valley, the Great Lakes, the Ohio Valley, and the Tennessee Valley, Sun-Thu, Feb 14-Feb 18. - Much below normal temperatures across portions of the Alaska Panhandle, Sun, Feb 14. Detailed Summary: During the medium range period (Sunday, February 14th - Thursday, February 18th) upper-level troughing over the central U.S. will act as a double whammy for the CONUS with respect to frigid temperatures and very active weather all across the country. On Sunday, a stationary frontal boundary straddling the Florida/Georgia border is expected to produce thunderstorms and heavy rain throughout the Southeast, with some areas possibly receiving up to 2 inches of rain over the course of 24 hours. On the other side of the country, a cold front passing through the Pacific Northwest on Sunday immediately followed by a moisture rich low pressure/frontal system moving onshore Monday will serve as the impetus for heavy snowfall in the Cascade and Olympic Mountains as well as heavy rain along coastal northern California and southern Oregon. The low pressure/frontal system is forecast to move southeast through the western terrain Monday into Tuesday, leaving a trail of snow in its wake. Higher elevation mountain ranges throughout the Great Basin and Rockies, extending from the Blue Mountains in the north to the San Juan Mountains in the south, will likely receive the heaviest snowfall. Shifting focus inland, a major winter storm is forecast to develop over the Southern Plains Sunday into Monday. With frigid temperatures permeating much of middle America, the stage is set for snow, sleet, and freezing rain to accompany the system. The heaviest snowfall will likely occur in eastern New Mexico, northern Texas, Oklahoma, and southern Kansas, while the greatest threat for freezing rain-laced mixed precipitation lies in central Texas, northern Louisiana and southern Arkansas. As upper-level shortwave energy guides the storm to the north and east Monday into Tuesday, the greatest heavy snow threat will shift to the Middle Mississippi River Valley, Ohio River Valley, and the lower Great Lakes, while the Lower Mississippi and Tennessee Valleys will carry the highest risk for icy conditions. Before exiting the CONUS, the storm system will give one final push on Tuesday, likely bringing heavy snow to the Central Appalachians and Northeast and inundating the I-95 corridor with mixed precipitation. Though only a few days out, forecast uncertainty still remains in regards to the exact path of the storm track as well as the location of the rain/snow line and heaviest snowfall. Even a small shift in the storm track can produce significant changes, however, the fact still remains that this multi-day storm will affect a large portion of the country and produce significant hazards that have the potential to impact travel, produce power outages, and threaten personal safety. As if one far reaching storm system in the medium range wasn't enough, a second system is expected to develop on Wednesday, following an almost identical track to the first. As two low pressure/frontal systems coalesce into one over Texas, shortwave energy over the Southern Plains and a warm front moving towards the Southeast are forecast to begin producing snow and rain, respectively. Guided by another upper-level shortwave, the newly formed low pressure/frontal system will propagate to the northeast Wednesday into Thursday, bringing snow, mixed precipitation and rain to the same areas hit a few days prior. While the models are currently in general agreement that the heaviest rain will likely fall over the Southeast on Thursday, there is still enough of a disparity in the storm track in the guidance that areas of snow and mixed precipitation cannot yet be determined. Therefore, the remaining area impacted by this second system is marked as heavy precipitation. As with the first storm, this system will also carry the potential to produce significant hazards and will continue to be watched over the coming days. Throughout the period, high pressure at the surface will continue its reign of bitter cold temperatures over the central U.S. While the Northern Great Basin will feel some relief after Sunday, temperatures well below normal will keep their grip over the Plains and Mississippi Valley. A final blast of cold air will begin a southward trek on Sunday, starting in the Northern Plains where low temperatures will hover in the negative 20s, up to 40 degrees below normal. On Monday and Tuesday, anomalously cold air is expected to settle in the Central and Southern Plains and break over 40 daily low record temperatures, as low temperatures dip to between 30 and 40 degrees below normal. By the end of the week, temperatures are expected to become more moderate throughout the central U.S., with daily low temperatures in most places reaching above zero and plateauing at approximately 10 to 20 degrees below normal. These widespread anomalously low temperatures can pose a threat to health and safety and should be taken seriously in all affected locations, particularly in the North/Central Plains and Mississippi Valley where low temperatures in the negative teens and 20s could cause frostbite on exposed areas of skin in a matter of minutes. Over Alaska, a series of deep low pressure/frontal systems are forecast to pass over the Aleutians early in the week, bringing some moderate rain to the region. Towards the end of the week, weaker systems will make their way through the Gulf of Alaska to the Mainland and Panhandle. While each of these regions will receive rainfall throughout the medium range period, none of it is expected to reach hazardous levels. On Sunday, a high pressure system positioned on the border of the Yukon and British Columbia will push cold arctic air into the Panhandle, dropping low temperatures well below freezing and up to 20 degrees below normal. Below normal low temperatures will also persist in the eastern Interior Sunday through Tuesday, however, these are not anticipated to be hazardous. Zavadoff