US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
330 PM EST Mon Nov 15 2021
 
Valid Thursday November 18 2021 - Monday November 22 2021
 
Hazards:
- Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, 
Thu-Fri, Nov 18-Nov 19.
- Heavy precipitation across portions of the Pacific Northwest, Thu, Nov 18.
- Heavy rain across portions of the Southeast and the Pacific Northwest, Thu, Nov 18.
- Heavy snow across portions of the Northern Rockies and the Northern Great Basin, Thu-Fri, Nov 
18-Nov 19.
- Heavy snow across portions of the Northern Rockies, Fri, Nov 19.
- Flooding occurring or imminent across portions of the Pacific Northwest and the Northern Great 
Basin.
- Heavy precipitation across portions of the Alaska Panhandle, Sun-Mon, Nov 21-Nov 22.
- Much below normal temperatures across portions of mainland Alaska, Thu-Mon, Nov 18-Nov 22.
- Much below normal temperatures across portions of mainland Alaska, Thu-Fri, Nov 18-Nov 19.
 
Detailed Summary:

The medium range period (Thurs. Nov 18 - Mon. Nov 22) starts off as a fairly progressive pattern as 
one robust upper trough tracking through the Great Lakes on Thursday races through the Northeast on 
Friday. The occluded low associated with thus trough will track through Quebec and its cold front 
will race east. Given its fast progression, it should limit rainfall totals to fall shy of heavy 
rainfall thresholds. Farther south, a weak upper level disturbance tracking through the Gulf of 
Mexico looks to aid in the development of heavy showers and thunderstorms over South Florida. 
Precipitable water levels in excess of 2" (roughly 2 STDs above normal) and modest instability 
should lead to excessive rainfall rates Thursday and into Thursday night. Meanwhile in the West, 
another Pacific storm system ushers in another atmospheric river to the Pacific Northwest. Heavy 
mountain snow will extend from the Olympics and Cascades on Thursday to the northern Rockies by 
Friday. The valleys and coastal areas of western Washington and northwest Oregon can expect more 
heavy rainfall, which on top of overly saturated soils, could lead to more flooding concerns to 
close out the week. Temperature-wise, no notable much below or above normal temperatures are 
currently expected but the warmest anomalies are forecast to stay over the Southwest. After a warm 
Thursday along the East Coast, a cold front ushers in a shot of colder than normal conditions into 
the East for Friday and Saturday. 

A brief warm-up in the Midwest on Saturday is quickly squashed by another intrusion of cold 
Canadian air on Sunday and into Monday. This air-mass is linked to a potent upper level trough 
diving south from the Yukon that at the same time, a ridge is building along the West Coast and a 
blocking ridge is building over the Davis Strait. This setup is showing up in teleconnections that 
indicate a -NAO/AO and +PNA by early next week, which suggests colder and stormier conditions in 
the East are likely in the days leading up to Thanksgiving. However, deterministic model guidance 
and individual ensemble members continue to show a great deal of spread in both precipitation 
totals, timing, and track. There are no hazards currently on the maps for the potential threat of a 
winter storm in the East for early next week at this time due to low confidence in where these 
hazards confidently line up. That said, this potential winter storm will be revisited tomorrow and 
in the days to come and as guidance comes into better agreement, weather hazards may be introduced 
if deemed necessary.

In Alaska, the state will remain under the influence of a strong ridge to the northwest, injecting 
much of the state with below normal temperatures. The coldest conditions will be centered over 
southwest Alaska where daily anomalies will range between 20-25 degrees below normal for much of 
the medium range. Farther south, unsettled weather returns to the Panhandle as a storm system 
tracking south of the Aleutians brings heavy precipitation to the region on Sunday and lingering 
into Monday. The storm system is tapping into rich subtropical moisture that may bring several 
inches of rain to the Panhandle and heavy snow totals to the higher elevations.

Mullinax