US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
330 PM EDT Fri May 08 2020
 
Valid Monday May 11 2020 - Friday May 15 2020
 
Hazards:
- Heavy rain across portions of California and the Pacific Northwest, Mon-Tue, May 11-May 12.
- Heavy rain across portions of the Central/Southern Plains, the Mississippi Valley, the Great 
Lakes, and the Ohio Valley, Mon-Fri, May 11-May 15.
- Heavy rain across portions of the Southeast, Mon-Thu, May 11-May 14.
- Flooding possible across portions of the Northern Plains.
- Flooding occurring or imminent across portions of the Middle/Lower Mississippi Valley, the Great 
Lakes, and the Northern Plains.
- Flooding likely across portions of the Northern Plains.
- Much above normal temperatures across portions of the Central Great Basin, the Northern Rockies, 
and the Northern Great Basin, Mon, May 11.
- Much below normal temperatures across portions of the Plains, the Mississippi Valley, the 
Tennessee Valley, the Ohio Valley, the Central/Southern Appalachians, the Great Lakes, the 
Mid-Atlantic, and the Southeast, Mon-Tue, May 11-May 12.
- Much below normal temperatures across portions of the Northeast, the Central/Southern 
Appalachians, the Mid-Atlantic, the Upper Mississippi Valley, the Great Lakes, and the Ohio Valley, 
Mon-Wed, May 11-May 13.
- Much above normal temperatures across portions of mainland Alaska, Mon, May 11.
- Much above normal temperatures across portions of mainland Alaska, Mon-Tue, May 11-May 12.
 
Detailed Summary:

The medium range period will begin on Monday 5/11 with below normal upper-level heights persisting 
across central and eastern parts of the U.S., as a potent upper trough settles overhead with 
shortwave troughs progressing through. This will lead to continued below normal temperatures on 
Monday and Tuesday, with many record low maximum and minimum temperatures forecast from the 
Central/Southern Plains to the Northeast. Late frosts and freezes are expected in some areas. 
Temperatures should remain cool from the Midwest/Great Lakes to the Mid-Atlantic/Northeast through 
midweek underneath a surface high pressure system, but upper-level troughing will relax farther 
south and west, bringing temperatures to about normal in the Southern Plains and Gulf Coast states 
after Tuesday.

Meanwhile over the West, an upper-level ridge over the Great Basin on Monday should shift eastward 
and relax during the workweek. Above normal temperatures are expected under the ridge, and a few 
record high minimum temperatures could be set Monday. An upper-level low is forecast to approach 
the West on Monday and Tuesday, cooling down temperatures and leading to precipitation in the 
Pacific Northwest and northern California. Heavy rain is possible, with the best chance currently 
across northwestern California and southwestern Oregon. But some precipitation is forecast all 
across the Pacific Northwest toward the Cascades and Sierra Nevada, then spreading into the 
Northern Great Basin and Northern Rockies by Tuesday and Wednesday. Lower elevation precipitation 
should fall as rain, but higher elevations could see a few inches of snow.

A couple of frontal systems are expected to linger near southern Florida next week, leading to the 
potential for multiple rounds of locally heavy rain. Another area where heavy rain is possible is 
from the Central/Southern Plains toward the Mississippi and Ohio Valleys, as moisture interacts 
with a stationary front to the south which then becomes a warm front around midweek. Currently, 
rain and thunderstorms are currently forecast to spread from the Plains Monday and Tuesday 
northeastward to the Middle Mississippi Valley Wednesday and portions of the Ohio Valley Thursday. 
Then as a front pushes back southward, the Southern Plains could have another round of heavy rain 
by Friday. However, the timing and details like the extent (especially the eastward extent) and 
magnitude of the heavy rain are still uncertain and should continue to be monitored.

Over Alaska, much above normal temperatures are forecast to continue over portions of the mainland 
for the early part of the week, underneath upper-level ridging and south of the influence of the 
Arctic surface high pressure system over the North Slope. Temperatures should moderate from midweek 
on, though still remaining somewhat above normal over southern and western portions of the mainland 
in particular. Ice jam and snowmelt flooding will continue to be threats across some areas of the 
mainland where rivers have not yet opened up, particularly the Middle Yukon River.

Tate