US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
222 PM EST Tue Dec 01 2020
 
Valid Friday December 04 2020 - Tuesday December 08 2020
 
Hazards:
- Heavy precipitation across portions of the Appalachians, the Ohio Valley, the Great Lakes, the 
Mid-Atlantic, and the Northeast, Sat-Sun, Dec 5-Dec 6.
- Heavy rain across portions of the Appalachians, the Southeast, the Mid-Atlantic, and the 
Northeast, Fri-Sun, Dec 4-Dec 6.
- Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sat-Mon, Dec 
5-Dec 7.
- Heavy precipitation across portions of the Alaska Panhandle, Fri-Mon, Dec 4-Dec 7.
- High winds across portions of the Alaska Panhandle and mainland Alaska, Sat-Sun, Dec 5-Dec 6.
 
Detailed Summary:

During the medium range period (Friday, Dec 4 - Tuesday, Dec 8), the main feature to watch in the 
contiguous U.S. is the potential for a surface low pressure system to move from near the central 
Gulf Coast Friday northward across the Eastern Seaboard this weekend. The exact track of the low 
remains uncertain, with quite a bit of east to west spread in the model guidance, but it appears 
that the 12Z models are coming into better agreement with the track, which is starting to increase 
forecast confidence. With that pattern, precipitation is expected to spread northward across much 
of the eastern U.S. Friday through Sunday. On the warm eastern side in the Carolinas and along the 
I-95 corridor of the Mid-Atlantic/Northeast, precipitation should stay rain. While rain totals 
currently do not look to be terribly heavy, the rain could cause flooding issues in some areas, 
especially considering that streamflow is high from the recent rain event Sunday-Tuesday. Meanwhile 
on the backside of the low, at least some snow is a possibility farther north and west across the 
Appalachians, northern Mid-Atlantic, and the interior Northeast. The exact areas that will see 
rain, mixed precipitation, and snow will have to be further refined in future forecasts given the 
current uncertainty in the low track. 

Elsewhere, Florida could also see some light to moderate rain with that system over the weekend as 
a cold front comes through. The Pacific Northwest could see some precipitation come in by Monday 
and especially Tuesday ahead of a front, but other than that, conditions are expected to be mainly 
dry for much of the western and central CONUS. Temperatures should be generally warmer than average 
across north-central parts of the CONUS, with slightly cooler than average temperatures for the 
southern tier.

Over Alaska, an initial weak low pressure system could cause heavy precipitation in the southern 
part of the Panhandle on Friday. Then, a deeper surface low is forecast to move slowly across the 
Gulf of Alaska south of the Aleutians over the weekend and toward Southcentral Alaska Monday. 
Pacific moisture will stream in ahead of the low, leading to heavy precipitation from Southcentral 
to the Panhandle over the weekend into Monday before lessening Tuesday. Additionally, as the 
surface pressure gradient tightens, gusty winds are possible Saturday and especially Sunday in 
southeastern Alaska as a result.  

Tate