US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
423 PM EDT Mon Sep 14 2020
 
Valid Thursday September 17 2020 - Monday September 21 2020
 
Hazards:
- Heavy rain across portions of the Southeast, the Mid-Atlantic, the Southern Appalachians, and the 
Tennessee Valley, Thu-Fri, Sep 17-Sep 18.
- Flooding possible across portions of the Southeast, the Lower Mississippi Valley, and the 
Tennessee Valley.
- Flooding likely across portions of the Southeast.
- Much above normal temperatures across portions of the Central Rockies, the Central Great Basin, 
the Northern Rockies, and the Northern Great Basin, Thu, Sep 17.
- Much below normal temperatures across portions of the Great Lakes, the Ohio Valley, and the Upper 
Mississippi Valley, Fri-Sat, Sep 18-Sep 19.
- Much below normal temperatures across portions of the Great Lakes, the Mid-Atlantic, the 
Northeast, the Central Appalachians, and the Ohio Valley, Sat-Sun, Sep 19-Sep 20.
- Heavy precipitation across portions of mainland Alaska, Thu-Fri, Sep 17-Sep 18.
- Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Thu-Sat, Sep 
17-Sep 19.
- Heavy rain across portions of the Alaska Panhandle, Sat-Sun, Sep 19-Sep 20.
- High winds across portions of mainland Alaska, Thu-Fri, Sep 17-Sep 18.
 
Detailed Summary:

The remnants of Hurricane Sally will be among the hazards of note across the Lower 48 during the 
medium range period (Thurs. Sept 17 - Mon. Sept 21). Model guidance remains in different camps as 
to how progressive Sally is through the Southeast (the GFS & Canadian models have Sally in central 
Alabama 12Z Thurs; Euro near Mobile, AL; UKMET in southwest Georgia). All guidance agrees upon a 
swath of heavy rainfall, but the axis extends as far south as southern Georgia and the central 
Carolinas to as far north as the Tennessee Valley and southern Mid-Atlantic. Regardless, the 
mid-level center track with ensemble means does support upslope flow along the southern 
Appalachians does suggest the opportunity is there for copious amounts of rain. The current 
precipitation forecast suggests totals exceeding six inches are possible where the heaviest bands 
set up from central Alabama to North Carolina. Please see the latest advisory from the National 
Hurricane Center for additional and updated information. Resident's within Sally's reach should 
continue to monitor the its progress and follow the advice of local officials. Eventually the storm 
will be ushered into the northwest Atlantic as a large longwave trough over southeastern Canada 
steers the storm east this weekend.

Temperature-wise, the aforementioned upper trough swinging through southeast Canada late week will 
also send a fresh injection of cool Canadian air into the Great Lakes Thursday and Friday, then 
into the Northeast for the upcoming weekend. Temperatures look cold enough Friday and Saturday 
morning to develop frost and perhaps a freeze in parts of the Upper Great Lakes has high pressure 
moves overhead, leading to light winds, clear skies, and maximizing radiational cooling. The same 
chilly dome of high pressure slides over the Northeast this weekend and much of the northern 
Appalachians and interior New England could be looking at a widespread frost and/or freeze each 
morning this weekend and potentially into next Monday morning. Farther west, one day of much above 
normal temperatures is likely to transpire over the interior Northwest as high temps soar into the 
90s. A Pacific storm system should begin to cool things down in the Northwest and northern Rockies 
on Friday, allowing for seasonally cooler conditions to take shape by the weekend.

In Alaska, a powerful occluded storm system looks to slam into the Gulf Coast on Thursday. The 
moisture source out ahead of this storm extends all the way into the subtropics, and will result in 
heavy precipitation from the Kenai Peninsula on east to the upper Panhandle. This is also the case 
for the Alaska Range extending up towards Denali. Coastal areas and valleys can expect heavy 
rainfall while the higher elevations pickup heavy snow accumulations. In addition, strong winds are 
likely to occur across the northern Gulf of Alaska, along the Gulf coast, and as far west as Kodiak 
Island. A second storm system trailing behind the lead storm and heads for the Panhandle this 
weekend. The heavy rain threat is expected to extend down the Panhandle this where several inches 
of rain are possible.

Mullinax