US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
324 PM EST Wed Nov 10 2021
 
Valid Saturday November 13 2021 - Wednesday November 17 2021
 
Hazards:
- Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, 
Sun-Mon, Nov 14-Nov 15.
- Heavy rain across portions of the Pacific Northwest, Sun-Mon, Nov 14-Nov 15.
- Flooding possible across portions of the Pacific Northwest.
- Flooding occurring or imminent across portions of the Southeast.
- Flooding occurring or imminent across portions of the Southeast.
- Flooding occurring or imminent across portions of the Southeast.
- Flooding likely across portions of the Pacific Northwest.
 
Detailed Summary:

The upcoming medium range forecast period (Saturday, November 12th - Tuesday, November 16th) 
features continued wet weather over the Pacific Northwest, while fairly tranquil conditions persist 
over the rest of the CONUS and Alaska. Over the Pacific Northwest, guidance maintains general 
agreement regarding the arrival of Eastern Pacific troughing off the British Columbia coast days 
3-4. The accompanying west-southwesterly flow pattern will tap into a fetch of Pacific moisture and 
steer it toward the Pacific Northwest to focus heavy rain and elevation mixed precipitation chances 
beginning Sunday. North-south uncertainty remains with the placement of the incoming moisture 
plume, as model disagreement grows with the amplification and timing of the pattern in the West 
beyond day 4. However, favorable terrain along the northern Coastal and Cascade Ranges will support 
enhanced precipitation rates even if the main axis of moisture return ends up further north over 
British Columbia. Rising snow levels will keep mixed precipitation in the forecast for most of the 
Coastal and Cascade Ranges, with the best snow chances relegated to the peaks of the Cascades. 
Otherwise, a pronounced ridge off the California coast will maintain above average temperatures 
west of the Rockies for much of the medium range, where a few overnight low records could be 
threatened over the West Coast and Intermountain West. Toward days 6-7, the advertised arrival of 
the British Columbia trough will facilitate a gradual cooling trend west of the Rockies to about 
normal, while the migratory ridge should spread above average warmth into the Plains.

East of the Rockies, High Plains shortwave trough activity is forecast to slide southeast and 
reinforce a deep Midwest trough Sunday-Monday. An associated cold front will sweep across the 
eastern half of the CONUS and inject cool continental air southward, which translates to high 
temperatures 10 degrees below normal. No hazardous precipitation is anticipated with this activity, 
although cool north-northwesterly flow atop the uncovered Great Lakes will favor periods of lake 
enhanced precipitation through early next week. Moreover, the arrival of the front in New England 
early next week may support mountain snows in the peaks of the Adirondack, Green, and White 
Mountains, but hazardous weather is not expected.

The relatively quiet weather also extends into Alaska. Some of the moisture associated with the 
aforementioned British Columbia trough may spill into the southern Alaska Panhandle later this 
weekend, but overall the highest precipitation totals are expected to stay south of the area. 
Afterwards, guidance advertises the general return of a wet pattern the over Panhandle toward the 
end of the medium range, with low confidence in specifics beyond that. Cold temperatures will 
migrate north into Central Alaska from the Alaska Peninsula through early next week, as ensembles 
support cool high pressure building overhead on the back side of an upper trough. High temperatures 
over West-Central Alaska will be well below normal through much of the medium range, although 
hazardous conditions are not anticipated.

Asherman