US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 322 PM EST Wed Feb 27 2019 Valid Saturday March 02 2019 - Wednesday March 06 2019 Hazards: - Heavy precipitation across portions of the Northeast, the Central Appalachians, the Middle Mississippi Valley, the Mid-Atlantic, the Great Lakes, and the Ohio Valley, Sun-Mon, Mar 3-Mar 4. - Heavy rain across portions of California, the Central Great Basin, the Pacific Northwest, and the Southwest, Sat-Wed, Mar 2-Mar 6. - Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Mid-Atlantic, the Southern Appalachians, the Southeast, and the Ohio Valley, Sat-Sun, Mar 2-Mar 3. - Heavy snow across portions of the Northeast, the Central Great Basin, the Pacific Northwest, the Northern Great Basin, California, the Great Lakes, and the Southwest, Sat, Mar 2. - Heavy snow across portions of the Southern Rockies, the Central Rockies, the Central Great Basin, the Central Plains, and the Southwest, Sat-Sun, Mar 2-Mar 3. - Flooding possible across portions of the Southeast and the Mid-Atlantic. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Tennessee Valley, the Great Lakes, the Middle Mississippi Valley, the Mid-Atlantic, the Upper Mississippi Valley, the Southeast, the Pacific Northwest, and the Ohio Valley. - Flooding likely across portions of the Southeast, the Mid-Atlantic, and California. - Much below normal temperatures across much of the eastern two-thirds of the country including the interior sections of the Pacific Northwest, Sat-Wed, Mar 2-Mar 6. - High winds across portions of mainland Alaska and the Aleutians, Mon-Tue, Mar 4-Mar 5. - High winds across portions of the Aleutians, Sun-Mon, Mar 3-Mar 4. and Wed, Mar 6. - High significant wave heights for coastal portions of mainland Alaska, Mon-Tue, Mar 4-Mar 5. Detailed Summary: Arctic air is expected to dominate much of the eastern two-thirds of the country including the interior sections of the Pacific Northwest through the medium range period as a cold high pressure system from Canada is forecast to remain anchored across the region through early next week. The actual temperatures could be more than 40 degrees below normal over the northern and central High Plains, which would equate to high temperatures between -10 F and 10 F. A clipper low pressure system ahead of the arctic outbreak will bring a quick round of snow and some mixed precipitation across the Great Lakes on Saturday, followed by New England from Saturday night into Sunday. In the meantime, moisture from the next Pacific cyclone should reach California on Saturday. Rain could be heavy over the lower elevations while the Sierra Nevada will likely see heavy snow into Sunday. The moisture will be carried eastward rapidly across the Great Basin and into the central Rockies through the weekend, with the chance of heavy snow most likely over Colorado under strong upslope flow. By Sunday, models continue to show significant differences as well as run-to-run variability on the track and intensity of a low pressure system which is forecast to form over central/southern Plains. This low will have significant implications on whether a winter storm will impact areas from the Ohio/Tennessee Valley into the Mid-Atlantic and the Northeast from Sunday into Monday. Models have indicated a definite northward trend in the forecast track of this potential winter storm since yesterday. This is reflected on the latest WPC hazards chart with the area of heavy precipitation nudged farther to the north. Note that "heavy precipitation" is indicated instead of "heavy snow" to address the uncertainties in the forecast track, as well as the potential for the snow to change over to rain during this potential event. Farther to the south, potential exists for heavy rain and thunderstorms to impact the Deep South on Sunday ahead of the low pressure system. A strong cold front should then push the heavy rain into the Southeast Sunday night while ushering in colder air and ending the heavy rain for the Deep South. Behind the potential winter storm for parts of the eastern U.S., arctic air will once again dominate much of the eastern two-thirds of the country with well below normal temperatures spreading down into Florida. Meanwhile, moisture from the next Pacific cyclone is forecast to reach California on Tuesday (3/5), bringing the next round of heavy rain for the lower elevations with heavy snow once again for the Sierra Nevada. The rain should move into the Intermountain West on Wednesday (3/6) as mixed precipitation reaches the northern and central Rockies. For western Alaska and the Aleutians, high winds will be likely through the weekend, spreading into western Alaska on Monday into Tuesday thanks to a strong low pressure system moving into the Bering Sea. Significant waves can also be expected early next week near the coast of western Alaska as the next Pacific cyclone brings the next round of high winds into the western Aleutians by next Wednesday. Kong