US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
153 PM EST Thu Dec 31 2020
 
Valid Sunday January 03 2021 - Thursday January 07 2021
 
Hazards:
- Heavy precipitation across portions of California, the Pacific Northwest, and the Northern Great 
Basin, Sun-Wed, Jan 3-Jan 6.
- Heavy precipitation across portions of the Central Great Basin, California, and the Southwest, 
Mon, Jan 4 and Wed-Thu, Jan 6-Jan 7.
- Heavy rain across portions of the Southeast, the Lower Mississippi Valley, and the Southern 
Plains, Wed-Thu, Jan 6-Jan 7.
- Heavy snow across portions of the Northern Rockies and the Northern Great Basin, Sun-Thu, Jan 
3-Jan 7.
- Heavy snow across portions of the Central Rockies and the Northern Rockies, Mon-Tue, Jan 4-Jan 5.
- Heavy snow across portions of the Mid-Atlantic and the Northeast, Sun-Mon, Jan 3-Jan 4.
- Flooding possible across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, 
the Southern Plains, and the Ohio Valley.
- High winds across portions of the Central Plains, the Northern Plains, and the Northern Rockies, 
Sun, Jan 3.
- High significant wave heights for coastal portions of California and the Pacific Northwest, 
Tue-Wed, Jan 5-Jan 6.
- High significant wave heights for coastal portions of the Pacific Northwest, Sun, Jan 3 and 
Tue-Wed, Jan 5-Jan 6.
 
Detailed Summary:

The medium range period (Sunday, January 3rd to Thursday, January 7th) will be fairly active across 
both the western and eastern United States. Starting in the East, an area of low pressure is 
forecast to move up the Mid-Atlantic and just off the New England coastline Sunday and Monday. As a 
result, precipitation to the northwest of the low could fall as snow from central Pennsylvania to 
Maine. The highest chance for heavy snow (greater than 4 inches) will be from northeast 
Pennsylvania to eastern Maine, where temperatures should remain below freezing. Forecast models 
have been trending northwest with this system over last few days, but overall confidence still 
remains relatively low and a trend back to the southeast is not out of the realm of possibility. 
Given the latest guidance and potential impacts, a highlighted area was added to the hazards 
graphic today.

Across the Pacific Northwest, multiple storm systems will make for an unsettled start to 2021. 
Large scale upper-level troughing will be responsible for the extended period of active weather and 
high elevation snow, with several smaller scale systems bringing locally hazardous weather. Several 
inches of rain are forecast along coastal sections of the Northwest and northern California, with 
potentially feet of snow falling across the Sierra and Cascade mountains between Sunday and 
Wednesday. Significant waves could lead to coastal hazards across the Northwest during this time 
period as well. Heavy snow is also forecast to enter the northern Rockies of Idaho and Montana 
through next week. As energy ejects into the northern Plains on Sunday, high winds with gusts over 
50 mph could reach the surface across the northern High Plains.

By Wednesday, an area of low pressure is forecast to enter the central Plains, with warm/moist air 
surging ahead of an associated cold front. Showers and thunderstorms could bring areas of heavy 
rain/flash flooding from eastern Texas to the Lower Mississippi Valley. Further north, snow will be 
possible across the central Plains and Midwest.

Weather across Alaska will remain fairly quiet through early next week. Heavy precipitation (rain 
along the coast/lower elevations and snow inland/higher elevations) will remain a concern across 
the North Gulf Coast by Tuesday as a storm churns to the south. Total snowfall amounts appear 
marginal at the moment, therefore a highlighted area was not added today.

Snell