US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
358 PM EDT Wed Apr 03 2019
 
Valid Saturday April 06 2019 - Wednesday April 10 2019
 
Hazards:
- Heavy precipitation across portions of California, the Pacific Northwest, and the Northern Great 
Basin, Sat-Mon, Apr 6-Apr 8.
- Heavy precipitation across portions of the Central Rockies, the Central Plains, the Northern 
Plains, and the Northern Rockies, Tue-Wed, Apr 9-Apr 10.
- Heavy rain across portions of California and the Pacific Northwest, Sat-Mon, Apr 6-Apr 8.
- Heavy rain across portions of the Southeast, the Middle Mississippi Valley, the Lower Mississippi 
Valley, the Southern Plains, and the Tennessee Valley, Sat-Sun, Apr 6-Apr 7.
- Heavy rain across portions of the Southeast, the Mid-Atlantic, and the Southern Appalachians, 
Mon, Apr 8.
- 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, and the Ohio Valley.
- Flooding likely across portions of the Upper Mississippi Valley and the Northern Plains.
- High significant wave heights for coastal portions of California and the Pacific Northwest, 
Sat-Sun, Apr 6-Apr 7.
- Heavy precipitation across portions of mainland Alaska and the Aleutians, Tue-Wed, Apr 9-Apr 10.
- High winds across portions of mainland Alaska and the Aleutians, Tue-Wed, Apr 9-Apr 10.
 
Detailed Summary:

Gulf of Mexico moisture streaming northward ahead of a cold frontal boundary moving across the 
Plains and Mississippi Valley will bring the threat for widespread moderate to heavy rainfall this 
weekend. The heaviest amounts should focus across the southern Plains (especially eastern Texas) on 
Saturday, progressing across the lower Mississippi Valley on Sunday where the warm, humid air mass 
will be most unstable. Rainfall totals will generally range from 1-3 inches through this region, 
with locally high amounts possible. On Monday, the front will continue its steady progression into 
the eastern U.S. There's a large amount of uncertainty among the model guidance with respect to 
forward speed and northward extent of the rainfall. The one area of general agreement exists over 
the southern Appalachians where a period of showers and thunderstorms will bring upwards of 1-2 
inches during the day Monday.

The weather pattern will remain quite active across the western U.S. this forecast period. During 
the latter part of Saturday into Sunday, a strong Pacific front will move inland across 
Washington/Oregon and northern California. This system will bring the potential for several 
hazards, including significant waves and heavy precipitation. Offshore and coastal winds will also 
be moderately strong, but overall do not appear significantly hazardous and are not expected to be 
especially long-lived. Regarding precipitation, am expecting the heaviest amounts, in the 2-4 inch 
range, to focus from the Washington/Oregon Cascades westward and extend southward across northern 
California (including the Klamath mountains and Shasta/Siskiyous). It's a fairly warm system, at 
least initially, so the best chance for heavy snow will be over the Washington Cascades where snow 
levels will be lower.

Another storm will be approaching the coast on Monday and is expected to bring a renewed uptick of 
precipitation to the West Coast Monday into early Tuesday. Some of the guidance indicates that this 
system will have a connection to moisture from the tropical Pacific, so the potential exists for 
some locally heavy rainfall...again likely focusing in the Pacific Northwest from the Cascades 
westward. As this system progresses inland and moves across the Rockies and High Plains during 
Tuesday-Wednesday, there are some indications that the system will intensify, with a combination of 
orographic lifting and upslope flow supporting moderate to heavy precipitation breaking out. 
There's a lot of uncertainty as to exactly where this will set up; we've drawn the hazard area 
across Wyoming and northern Colorado, but this may change as the event approaches.

Over the Southwest, an upper ridge will build in early next week, potentially bringing the first 
100 degree temperatures of the season to the Desert Southwest. While this is upwards of 10-15 
degrees above normal, it does not represent a significant hazard as the air mass is very dry and 
the warm temperatures will be short-lived, lasting just Monday and Tuesday before temperatures cool 
closer to normal on Wednesday.

The majority of Alaska will again remain fairly quiet during the medium range period. The exception 
will be the during the April 9-10 period over the Aleutians northward into St. Lawrence Island, the 
Alaska Peninsula, and sections of the southwest mainland. Here, a strong low pressure system 
developing over the northern Pacific will track into the Bering Sea by the middle of next week, 
bringing the potential for high winds and heavy precipitation.

Klein