US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
245 PM EDT Mon Sep 20 2021
 
Valid Thursday September 23 2021 - Monday September 27 2021
 
Hazards:
- Heavy rain across portions of the Great Lakes, the Mid-Atlantic, the Northeast, and the Central 
Appalachians, Thu-Fri, Sep 23-Sep 24.
- Flooding occurring or imminent across portions of the Tennessee Valley.
- Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Thu-Fri, Sep 
23-Sep 24and Sun-Mon, Sep 26-Sep 27.
- High winds across portions of mainland Alaska and the Aleutians, Sat-Mon, Sep 25-Sep 27.
 
Detailed Summary:

The medium range forecast period (Thursday, Sept. 23 to Monday, Sept. 27) will feature mostly 
tranquil weather across CONUS, with the main precipitation hazard found across the Northeast by the 
end of this week. A strong upper-level low is expected to swing across the Ohio Valley and Great 
Lakes on Thursday before eventually reaching southern Ontario, Canada. As a result, a surge of 
moisture should race northward ahead of this system and associated cold front, providing a ripe 
environment for heavy rain from the Mid-Atlantic to the Northeast. As the front reaches the warm 
western Atlantic, it may slow and lead to additional rounds of rainfall into Friday. Model guidance 
has been inconsistent regarding the timing of the heavy rainfall, therefore the highlighted hazard 
area includes both Thursday and Friday. However, it's entirely possible that the heavy rain lingers 
an additional day across parts of New England. Widespread rainfall amounts over 1 inch are possible 
and could fall over areas that have experienced an extremely wet summer. Elsewhere, scattered 
thunderstorms and heavy rain may impact central and southern Florida during the medium range time 
frame as the cold front stalls over the area. The Southwest will also have chances for rain as an 
upper-level low dances around southern California.

No hazardous temperatures are currently forecast during the medium range period. Outside of New 
England, fall esque weather and slightly below average temperatures are expected across the eastern 
United States. Patchy frost is not out of the question across the Upper Great Lakes and parts of 
the Appalachians between Thursday and Saturday. Meanwhile, above average temperatures are set to 
return to the Intermountain West, Rockies, and Great Plains by Saturday, with highs into the 90s 
remaining confined to the Desert Southwest and Southern Plains.   

Across Alaska, multiple storm systems and atmospheric rivers are forecast to dump heavy 
precipitation along the south-central coast and Panhandle. The first system is set to arrive on 
Thursday and last through Friday, with heavy snow found in the higher elevations of south-central 
Alaska and heavy rain along the coast and Panhandle. Widespread liquid precipitation amounts over 2 
inches are expected. By Sunday and Monday a separate system is forecast to produce similar hazards, 
as well as high winds as early as Saturday across the Aleutian Islands. For the mainland, 
temperatures around 10 to 15 degrees below average are likely to remain locked over the region 
along with chances for scattered snow showers. 

Snell