US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
337 PM EST Mon Dec 14 2020
 
Valid Thursday December 17 2020 - Monday December 21 2020
 
Hazards:
- Heavy snow across portions of the Northeast, Thu, Dec 17.
- Heavy precipitation across portions of California, the Pacific Northwest, and the Northern Great 
Basin, Sat-Mon, Dec 19-Dec 21.
- Heavy snow across portions of the Northern/Central Rockies and the Northern/Central Great Basin, 
Thu, Dec 17 and Sat-Mon, Dec 19-Dec 21.
- High winds across portions of the Central Great Basin, the Northern/Central Rockies, and the 
Northern/Central Plains, Sat-Sun, Dec 19-Dec 20.
- Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Thu-Sat, Dec 
17-Dec 19.
- High winds across portions of mainland Alaska, Thu, Dec 17.
- Much below normal temperatures across portions of mainland Alaska, Thu-Mon, Dec 17-Dec 21.
 
Detailed Summary:

Throughout the medium range period (Thursday, Dec 17 - Monday, Dec 21), the main area of concern 
for hazards is the northwestern quadrant of the U.S. as multiple frontal systems approach and move 
through the region. On Thursday, one round of potentially heavy snow is forecast for mountainous 
areas of the interior West, including the Northern Rockies, Wind River Mountains/Tetons, and 
Wasatch associated with a front and an upper-level trough. Then on Friday, precipitation amounts in 
the West should lessen, but chances of heavy precipitation once again increase for the weekend as 
westerly flow increases, bringing in Pacific moisture. The Pacific Northwest and adjacent northern 
California can expect coastal rain and higher elevation (Coastal Range and Cascades) snow through 
early next week. Heavy snow is also likely to spread farther inland across the Northern Rockies and 
Wind River Mountains/Tetons again over the weekend and Monday. Additionally, gusty winds are 
possible across Washington and Oregon over the weekend, but even higher winds could be hazardous 
across northern/central portions of the Rockies and the northern High Plains.

Elsewhere, the nor'easter impacting the Mid-Atlantic and Northeast on Wednesday will be pulling 
away from the CONUS on Thursday, but snow should continue across eastern New England into Thursday 
before the low pressure system exits. Locally high/gusty winds are not out of the question either. 
Temperatures are forecast to be warmer than average by 10 to 25 degrees across the north-central 
U.S. through the period, with Sunday likely to be the warmest day, but hazards are not expected 
from these mild temperatures.

For Alaska, a low pressure system moving through the Gulf of Alaska through the latter part of the 
week may spread high winds to areas near the Cook Inlet, such as portions of Kodiak Island, the 
Bristol Bay region, and the Kenai Peninsula on Thursday. As the low tracks slowly eastward, it 
should spread borderline heavy precipitation across Southcentral and likely heavier amounts across 
the Panhandle through the end of the week. A round of precipitation may affect the Alaska Peninsula 
by early next week, but precipitation amounts are still in question at this point. 
Temperature-wise, much of the mainland is likely to see near to below average temperatures 
especially in terms of highs through the period. A hazard area was delineated for the eastern 
Interior, where low temperatures are predicted to be the most below normal, with dangerously cold 
temperatures in the -30s and -40s. 

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