US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
313 PM EST Wed Dec 23 2020
 
Valid Saturday December 26 2020 - Wednesday December 30 2020
 
Hazards:
- Heavy precipitation across portions of the Pacific Northwest, Sat-Sun, Dec 26-Dec 27, and Wed, 
Dec 30.
- Heavy precipitation across portions of California, Sun-Tue, Dec 27-Dec 29.
- Heavy snow across portions of the Northeast, Mon, Dec 28.
- Heavy precipitation across portions of the Central Plains and Middle/Upper Mississippi Valley, 
Tue, Dec 29.
- Heavy Rain across portions of the Central/Southern Plains and Middle Mississippi Valley, Tue, Dec 
29.
- Heavy Rain across portions of the Southern Plains, Middle/Lower Mississippi Valley, Tennessee 
Valley and Southeast, Wed, Dec 30.
- Heavy snow across portions of the Northeast, Mon, Dec 28.
- Flooding possible across portions of the Great Lakes, the Mid-Atlantic, the Northeast, the 
Central Appalachians, and the Ohio Valley.
 
Detailed Summary:

Parts of the Northeast, central and western U.S. will experience hazardous weather during the 
medium range period (Saturday, December 26th - Wednesday, December 30th). An upper-level low will 
tilt negatively as it moves into the eastern seaboard on Friday (Christmas day). Flooding remains a 
concern over parts of the Northeast as rising temperatures and a new low pressure  system generate 
rapid snowmelt through the weekend. Meanwhile, in the west, another deep upper-level low will 
generate heavy snowfall over the Olympic mountains and rainfall over the surrounding lower 
elevations. This disturbance will weaken to a mere shortwave as it crosses the lower 48 over the 
weekend before restrengthening and developing a potent area of surface low pressure. This low 
pressure system may go on to produce heavy snowfall over interior portions of the Northeast on 
Monday, particularly over the Adirondacks, but current guidance may trend a bit farther south with 
the highest precipitation amounts. Heavy snow remains a threat downwind of lake Ontario. Another 
low pressure system will enter the West coast on Monday, bringing with it the chance for heavy 
snowfall to the Sierra and rain for the surrounding low elevations. This system is also forecast to 
restrengthen and produce a strong low pressure system over the Southern Plains. Heavy precipitation 
is possible over the Central Plains and Middle Mississippi Valley while heavy rain is expected 
across the Central/Southern Plains and into the Middle Mississippi Valley. The focus for heavy rain 
is expected to shift eastward into the Lower/Middle Mississippi Valley and Southeast on Wednesday. 
Heavier snow may shift into the Midwest on Wednesday, but models haven't reached a consensus on 
this at the moment.

Most of Alaska will remain relatively quiet throughout the medium range period, while the Aleutians 
and mainland west coast may experience some high winds on Saturday and Sunday as a very deep area 
of low pressure moves itself into the Bering Sea.

Kebede