US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
324 PM EST Tue Nov 30 2021
 
Valid Friday December 03 2021 - Tuesday December 07 2021
 
Hazards:
- Heavy precipitation across portions of northwestern California, the Pacific Northwest including 
the Cascades, as well as parts of the northern Rockies, Sun-Mon, Dec 5-Dec 6.
- Flooding occurring or imminent across portions of northwestern Washington state.
- Flooding likely across portions of northwestern Washington state.
- Much below normal temperatures across portions of southwestern Alaska, Fri, Dec 3.
- Much below normal temperatures across portions of southwestern and interior Alaska, Fri-Sat, Dec 
3-Dec 4.
 
Detailed Summary:

Latest model guidance continues to feature broad troughing across the northern tier states through 
the medium range period while a broad ridge will tend to maintain itself over the western U.S.  The 
fast upper-level flow within the broad upper trough will tend to send clipper systems eastward 
across the northern tier states with relatively modest precipitation amounts associated with them.  
The fast flow pattern also introduces timing issues with these clipper systems.  There is some 
model/ensemble support for further development of one of the clipper systems across the Great Lakes 
to the Northeast early next week.  But due to the timing uncertainty and relatively modest 
precipitation amounts in the forecasts, no areas of precipitation hazards are indicated there.  
Nevertheless, a general area of wintry precipitation can be expected to spread across the Great 
Lakes followed by interior New England Sunday into Monday.

With a broad ridge prevailing across the western U.S., the medium-range period will start out dry 
throughout the region.  However, a gradual lowering of heights will progressively erode the ridge 
by the weekend.  By Sunday night into Monday, moisture ahead of the next Pacific cyclone is 
forecast to reach into the Pacific Northwest region.  It appears that areas from the Cascades 
westward to the coast will be impacted by moderate to heavy precipitation during this time frame, 
with some inherent timing and amount uncertainties.  The higher elevations of the Washington 
Cascades will likely see snow while other areas will see rain.  Some of the heavier precipitation 
should also spread into parts of the higher elevation of northern Rockies.  A general decrease of 
precipitation amounts are expected thereafter as the system dips further inland through the central 
Rockies and the Great Basin.

Temperature-wise, widespread milder than normal conditions are likely across much of the Nation 
before returning to near average conditions over the eastern half of the country by Sunday.  Below 
average and winter-like temperatures are expected to be confined to New England, where lows could 
dip into the teens and single digits beginning on Saturday.  Colder weather will attempt to filter 
across the northern Plains and upper Midwest by the weekend, but lows will remain close to average 
for this time of year.

Alaska will likely enter a period of increasingly active weather as a series of fronts and cyclones 
are forecast to track across the Bering Sea toward western Alaska by Friday.  The bitterly cold 
airmass initially engulfing the southwestern and interior portions of the state will give away to 
moderating temperatures along with the likelihood of snowy and windy weather.  The greatest threat 
of snow appears to be next Monday across interior southwestern Alaska where areas of enhanced 
snowfall are possible as the center of a cyclone is forecast to push onshore.  While a general area 
of moderate snow is expected across western and southwestern Alaska, snowfall amounts are forecast 
to be mostly a foot or less, and therefore, heavy snow is not indicated on the chart for these 
areas.  Nevertheless, this area will continued to be monitored for the potential of heavy snow.

Kong