US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 238 PM EST Wed Feb 17 2021 Valid Saturday February 20 2021 - Wednesday February 24 2021 Hazards: - Heavy precipitation across portions of the Pacific Northwest, Sun-Mon, Feb 21-Feb 22. - Heavy snow across portions of the Pacific Northwest and the Northern Great Basin, Sat-Wed, Feb 20-Feb 24. - Heavy snow across portions of the Central Great Basin, the Pacific Northwest, and the Northern Great Basin, Sat, Feb 20. - Heavy snow across portions of the Northern Rockies, Sun-Tue, Feb 21-Feb 23. - Flooding possible across portions of the Mid-Atlantic. - Flooding occurring or imminent across portions of the Southeast and the Mid-Atlantic. - Flooding likely across portions of the Southeast and the Mid-Atlantic. - High winds across portions of the Central Rockies, the Central Plains, the Central Great Basin, the Northern Plains, and the Northern Rockies, Sun-Mon, Feb 21-Feb 22. - Much below normal temperatures across portions of the Central Plains, the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Great Lakes, the Middle Mississippi Valley, the Southern Appalachians, the Upper Mississippi Valley, the Southeast, the Southern Plains, and the Ohio Valley, Sat, Feb 20. - Much below normal temperatures across portions of the Northeast, the Central Appalachians, the Mid-Atlantic, the Southern Appalachians, the Great Lakes, and the Ohio Valley, Sun, Feb 21. - Heavy precipitation across portions of the Alaska Panhandle, Sat-Mon, Feb 20-Feb 22. - Much below normal temperatures across portions of mainland Alaska, Sat-Tue, Feb 20-Feb 23. Detailed Summary: The medium range period (Saturday, February 20th - Wednesday, February 24th) is expected to be much warmer and less active across the Lower 48 compared to current conditions. Saturday is expected to be the last day with widespread temperatures well below average from the Southern Plains to the Ohio and Tennessee valleys. The Mid-Atlantic and Central Appalachians will likely wake up to a cold morning on Sunday, with low temperatures in the single digits and low teens. This is partly due to fresh snowfall and a cold arctic high pressure system parked across the region. Otherwise, the beginning of next week will feature temperatures generally closer to average across the country as bitter cold dissipates, with widespread above average highs in the Northern Plains and Southwest. This equates to high temperatures above freezing for much of the Great Plains and other regions that have recently experienced multiple rounds of snowfall. Rivers and small lakes that are currently frozen or partially frozen will likely begin to thaw and slowly fill with melted snow. The current sun angle is also similar to that of October, therefore any sunshine will greatly increase melting. Regarding hazardous precipitation, multiple rounds of mountain snow are expected across the Pacific Northwest and Northern Rockies during the medium range time frame. Snowfall amounts greater than 8 inches are particularly likely across the Cascades and portions of northern Idaho and northwest Montana before a cold front pushes through on Tuesday. Ahead of this same cold front, gusty winds are possible across the Northern High Plains. These downsloping winds will also be responsible for the warmer temperatures forecast across the region. Meanwhile, heavy coastal/lowland rain will be possible with the system across the Pacific Northwest on Sunday and Monday, total rainfall amounts could add up to over 2 inches. The biggest uncertainty remains with an area of low pressure forecast to exit the Central Rockies on Saturday, before racing across the Central Plains on Sunday while moving towards the Great Lakes and New England early next week. Heavy snow will be possible across the mountainous terrain of Utah and localized sections of western Colorado on Saturday. East of the Rockies, rain and snow associated with the system are expected to remain below hazardous threshold. Lake effect snow could add up downwind of Lake Ontario and across isolated portions of Upstate New York on Monday and Tuesday, however this area is currently too small to be added to the hazards graphic. For Alaska, a busy pattern over the Gulf of Alaska will lead to a long duration heavy coastal rain and inland snow event throughout the Panhandle between Saturday and Monday. Liquid precipitation amounts over 2 inches will be possible, with over a foot of snow likely in the higher elevations. The greatest chances for impactful precipitation remain across far southern regions of the highlighted area. Additionally, daily low temperatures are expected to be much below normal for portions of the Interior beginning on Saturday. With temperatures reaching as low as -30F, extreme caution should be taken when traveling outdoors to prevent frostbite and illness. These temperatures will begin to slowly increase back to near normal across southwest portions of the state by Tuesday, as warmer air starts to advect from the Bering Sea and Bristol Bay. Snell