US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 322 PM EDT Thu Mar 28 2019 Valid Sunday March 31 2019 - Thursday April 04 2019 Hazards: - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Mon-Tue, Apr 1-Apr 2. - Heavy rain across portions of California and the Pacific Northwest, Mon, Apr 1. - Heavy rain across portions of the Southeast and the Mid-Atlantic, Mon-Tue, Apr 1-Apr 2. - Heavy snow across portions of the Central Rockies, the Central Great Basin, the Northern Rockies, the Northern Great Basin, and the Northern Plains, Tue-Wed, Apr 2-Apr 3. - Flooding possible across portions of the Central Plains, the Northern Plains, and the Northern Great Basin. - Flooding occurring or imminent across portions of the Central Plains, the Lower Mississippi Valley, the Northern Plains, the Tennessee Valley, the Middle Mississippi Valley, the Upper Mississippi Valley, the Great Lakes, and the Ohio Valley. - Flooding likely across portions of the Central Plains, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains. - High winds across portions of the Mid-Atlantic, Mon-Tue, Apr 1-Apr 2. Detailed Summary: A strong cold front moving across the eastern U.S. this weekend will stall out over the northern Gulf of Mexico and extend across the northern Florida peninsula by Sunday night/Monday morning. For the third consecutive day, model guidance is indicating surface low development along the front as a short wave trough tracks across the southeastern states early next week. The low will track across Florida, then strengthen as it tracks along or near the East Coast. While confidence in this coastal storm developing is increasing, there is still a lot of uncertainty in the timing, as well as how close to the coast it will track. At this time, model consensus suggests the best chance for heavy rain will stretch from eastern Georgia across southern South Carolina, then up along the Outer Banks Monday into Tuesday, so decided to introduce a heavy rainfall hazard for this period. Rainfall totals will likely range from 1-3 inches (and locally higher) over the hazard area, but a widespread extreme rain event is unlikely as the system is a fast-mover. In addition to the rainfall, the strong gradient between the strengthening low and high pressure to the north of it will bring the threat for high winds along the western side of the surface low track. Current thinking is that these winds will mainly be confined to coastal sections of North Carolina. Note that if the storm were to track closer to the coast, high winds and heavy rainfall would potentially extend into New England by mid-week. Farther west, a mid-level trough moving through the eastern Pacific will push into the West Coast next Tuesday. There's still uncertainty as to the latitude the system moves inland, but good agreement exists that it will be accompanied by a period of heavy precipitation next Monday and Tuesday. Current consensus suggests the best chance for significant accumulations will extend from western Oregon southward into northern California, where liquid equivalent totals of 1-3 inches are expected. Much of this will be rain, with snow mostly confined to the higher elevations of the Oregon Cascades and the Shasta/Siskiyous region. As this trough tracks inland Tuesday-Wednesday, it will bring widespread valley rain and mountain snow from the northern Intermountain region and central Great Basin eastward through the northern and central Rockies. Right now, it appears the heaviest precipitation will be across the higher elevations in western Wyoming, eastern Idaho and extreme southern Montana. Temperatures should be sufficiently cold to support mainly snowfall, so we've introduced a heavy snow hazard for this region covering April 2-3. However, confidence is relatively low as the exact track of the system may vacillate with later model guidance, and precipitation amounts are only borderline significant. Moderate to major flooding across the Mississippi and Missouri River Basins is expected to continue through the forecast period, The abovementioned trough which impacts the western states is expected to move out into the Plains during the middle of next week. Precipitation over the Plains and Mississippi Valleys will break out as this trough draws northward and interacts with increasing Gulf of Mexico moisture. While moderate to heavy rain is likely with this system, there wasn't enough confidence to narrow down where to place a hazard area given large variability among the model solutions. Alaska will again remain fairly quiet during the medium range period as upper ridging continues to dominate. The pressure gradient between high pressure over the state and Gulf of Alaska and a series of cyclones tracking south of the Aleutians may bring moderate winds and waves to parts of the Aleutian chain during the early-mid part of next week. At this time, neither appear strong enough to support hazard areas. Klein