US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
343 PM EDT Wed Oct 21 2020
 
Valid Saturday October 24 2020 - Wednesday October 28 2020
 
Hazards:
- Heavy precipitation across portions of the Northeast, Mon, Oct 26.
- Heavy rain across portions of the Central Plains, the Mid-Atlantic, the Lower Mississippi Valley, 
the Central Appalachians, the Tennessee Valley, the Great Lakes, the Middle Mississippi Valley, the 
Northeast, the Southern Plains, and the Ohio Valley, Sun-Mon, Oct 25-Oct 26.
- Heavy snow across portions of the Central Plains, the Central Rockies, the Central Great Basin, 
the Southern Rockies, the Southern Plains, and the Southwest, Sun-Mon, Oct 25-Oct 26.
- Heavy snow across portions of the Central Plains, the Northern Plains, and the Northern Rockies, 
Sat, Oct 24.
- Flooding occurring or imminent across portions of the Southeast and the Lower Mississippi Valley.
- Much below normal temperatures across portions of the Central Plains, the Great Lakes, the 
Central Great Basin, the Northern Plains, the Southern Plains, the Northern Rockies, the Central 
Rockies, the Middle Mississippi Valley, California, the Northern Great Basin, the Upper Mississippi 
Valley, and the Pacific Northwest, Sat-Wed, Oct 24-Oct 28.
- Much below normal temperatures across portions of the Central Plains, the Central Rockies, the 
Lower Mississippi Valley, the Central Great Basin, the Southern Rockies, the Middle Mississippi 
Valley, California, the Upper Mississippi Valley, the Southern Plains, and the Southwest, Mon-Wed, 
Oct 26-Oct 28.
- Enhanced wildfire risk across portions of California, Sun, Oct 25.
- Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sun-Mon, Oct 
25-Oct 26.
 
Detailed Summary:

Early season arctic air is expected to bring record to near record breaking cold temperatures to 
much of the western and central U.S late this weekend through early next week.  The core of the 
coldest air over the weekend will extend eastward from the Pacific Northwest through the northern 
Rockies and northern and central Plains states.  Temperatures will range from 20-40 degrees below 
normal, resulting in lows below zero and highs in the teens for parts of the northern high Plains 
and northern Rockies.  The cold weather will not spare the Pacific Northwest, where eastern 
Washington and Oregon will experience single digit lows in the coldest locations.  Needless to say, 
this will equal or break multiple low temperature records this weekend.  Along with the cold 
temperatures, an upper level disturbance will bring the potential for heavy snowfall to the higher 
elevations in Montana and Wyoming, with marginally heavy amounts extending eastward into North and 
South Dakota on Saturday. The heaviest snow potential then drops into the central Rockies on Sunday 
as the trough deepens and cold air progresses southward.

Much below normal temperatures will continue to advance south and eastward early next week, 
essentially affecting all of western two-thirds of the country.  The air mass will only slowly 
moderate; widespread temperatures 15-30 degrees normal across much of the western and central U.S. 
This will likely bring the first freeze of the season to many locations of the south/central 
Plains.  Thereā€s some uncertainty regarding the upper troughing in the Rockies during this 
period, but the potential exists for heavy snowfall across central and southern Colorado into 
northern New Mexico on Monday.  Another concern, though not specifically depicted on the chart, 
will be the potential for strong gusty winds late this weekend and early next week, particularly 
over northern and central California; this could exacerbate the spread of ongoing wildfires.  

Deep moisture will pool along the boundary separating the arctic air mass from relatively balmy 
conditions over the eastern states. Low pressure riding along the front will support a broad area 
of moderate to heavy rainfall Sunday into Tuesday from the central Plains northeastward through the 
upper Ohio Valley and northern mid-Atlantic states.  Rainfall amounts over this region may range 
upwards of 1-3 inches and locally higher.  As precipitation spreads into New England, there may be 
enough cold air remaining to support a period of snow over northern/central Maine, but this should 
change to rain as warm air from the south overspreads the region.

Across Alaska, an area of low pressure lifting into western sections of the mainland will be 
preceded by a southwesterly flow of very moist Pacific air.  Expect heavy precipitation from  
southeastern portions of the mainland (Prince William Sound eastward) through Yakutat beginning 
late in the weekend and continuing through Monday.  The heaviest precipitation will then spread 
southward across nearly the entire Panhandle during Monday into Tuesday. Heaviest rainfall will 
generally be along the coast, with snow over higher elevations.

Klein