US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
252 PM EST Wed Dec 02 2020
 
Valid Saturday December 05 2020 - Wednesday December 09 2020
 
Hazards:
- Heavy precipitation across portions of the Central Appalachians, the Great Lakes, the Ohio 
Valley, the Mid-Atlantic, and the Northeast, Sat-Sun, Dec 5-Dec 6.
- Heavy rain across portions of the Mid-Atlantic and the Northeast, Sat, Dec 5.
- Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sat-Mon, Dec 
5-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 (Saturday, Dec 5 - Wednesday, Dec 9), the main feature to watch in 
the contiguous U.S. is the potential for a surface low pressure system to move northeastward 
near/over the Mid-Atlantic and Northeast this weekend. The exact track of the low remains 
uncertain, as model spread in both the timing and placement of the low is still pretty broad for 
this forecast timeframe. But it appears that with this pattern, precipitation is expected to spread 
across the northeastern quadrant of the U.S. over the weekend. Precipitation should stay rain in 
lower elevations and along the I-95 corridor of the Mid-Atlantic/Northeast on the warm eastern side 
of the low pressure system. 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 early this week. 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 versus mixed precipitation and/or snow are yet to be 
determined, and will depend on the low track and the amount of cold air in place. There may be less 
cold air filtering into the region than with the system earlier this week, leading to possibly more 
areas of mix or rain than snow; the Adirondacks and higher elevations of northern New England may 
stay snow, however.

Elsewhere, Florida could also see some light to moderate rain with that low pressure system over 
the weekend as its cold front comes through. The Pacific Northwest can expect increasing 
precipitation to modest amounts by Monday and especially Tuesday ahead of a front, with light 
amounts in the Northern Rockies Tuesday and Wednesday. But other than that, conditions are expected 
to be mainly dry for much of the western and central CONUS. Temperatures should be generally quite 
a bit warmer than average across north-central parts of the CONUS, with highs in the 50s to as much 
as 60 degrees as far north as the Dakotas around Tuesday. These temperatures are likely be welcomed 
rather than hazardous.

Over Alaska, a relatively weak surface low pressure system is forecast to be over the Gulf of 
Alaska Sunday, and then get absorbed by a deep surface low tracking eastward toward it by Monday. 
This deeper low should move toward Southcentral Tuesday and spin down. Pacific moisture will stream 
in ahead of the lows, leading to heavy precipitation across the Panhandle Saturday and spreading 
into Southcentral Sunday and Monday. Additionally, as the surface pressure gradient tightens, gusty 
winds are possible Saturday and especially Sunday in southeastern Alaska as a result. Some 
precipitation remains in the forecast Tuesday and Wednesday, but with likely lesser amounts given 
the weakening low. 

Tate