US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
515 PM EDT Tue Oct 05 2021
 
Valid Friday October 08 2021 - Tuesday October 12 2021
 
Hazards:
- Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, 
Sat-Mon, Oct 9-Oct 11.
- Heavy rain across portions of the Southeast, the Mid-Atlantic, the Upper Mississippi Valley, and 
the Northern Plains, Sat, Oct 9.
- Heavy rain across portions of the Southeast, the Southern Appalachians, the Mid-Atlantic, and the 
Central Appalachians, Fri-Sat, Oct 8-Oct 9.
- Heavy precipitation across portions of mainland Alaska, Fri, Oct 8.
- Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Fri-Sat, Oct 
8-Oct 9.
- High winds across portions of mainland Alaska and the Aleutians, Fri-Sat, Oct 8-Oct 9.
 
Detailed Summary:

The general pattern over the medium range period (Friday, October 8th - Tuesday, October 12th) 
features a series of upper-troughs progressing northeastward through the eastern half of the CONUS 
atop a gradually building ridge, ahead of a strong upper-trough in the Intermountain West early 
next week. Accordingly, expect the bulk of the hazardous weather activity to gradually transition 
from the Mid-Atlantic and Upper-Midwest this weekend to west of the Continental Divide. Meanwhile, 
active weather remains in Alaska this weekend with wintry precipitation and high winds anticipated 
along the Alaska Panhandle and Peninsula, respectively.      

This Friday, a heavy rain threat from the short range period will continue over the Appalachians as 
a shortwave trough over the Midwest lifts to the northeast. Anticipated rainfall over the region 
prior to Friday will act to saturate the soils over the region, in turn increasing vulnerability to 
excess runoff rainfall. The antecedent rainfall combined with the upper-trough and orographic 
ascent along the Appalachians should promote a more focused area for heavy rain going into the 
weekend, before the heavy rainfall threat shifts to the Coastal Carolinas/Outer Banks Saturday as a 
frontal wave and coastal trough focus rainfall there. Over the Upper Midwest on Saturday, shortwave 
trough activity should propagate a strengthening frontal system and associated 
showers/thunderstorms across the Northern Tier. A feed of Pacific moisture into the deepening low 
may facilitate efficient rainfall production ahead of the front aside from any convection that 
forms, although the progressive nature of the system and lower-than-average streamflows limit the 
spatial and temporal extent of the heavy rain threat over North Dakota. Wintry weather is also 
expected to make an appearance in the West beginning this Saturday over the Cascades as more moist 
Pacific air tied to an atmospheric river ascends the terrain. The arrival of a strong upper-trough 
and associated cold front beginning Sunday will invigorate additional wintry precipitation chances 
along the Cascades. As cold air tied to the trough spreads eastward through early next week, 
snow-levels will lower over the Intermountain West and Great Basin. The potential increases on 
Monday for appreciable snow accumulations across the Northern Rockies, although the best snow 
should be tied to the highest terrain locations. Precipitation aside, anomalously cool temperatures 
will persist across the western U.S. through the medium range. The most noteworthy cool weather 
will arrive west of the Rockies by Tuesday as the aforementioned strong trough digs south, with 
high temperature anomalies 20-25 degrees below normal possible. This will translate to chilly 
weather, but highs will remain far above freezing in most locations. East of the Rockies, the 
gradually building mean ridge will support above average warmth throughout the medium range period, 
but is not anticipated to be hazardous.    

Over Alaska, a potent low pressure system will produce high winds and mixed precipitation for most 
of southern Alaska early in the medium range period. High winds will impact the Aleutians, Alaska 
Peninsula, and Kodiak Island through Saturday as the system makes its way toward the Gulf of 
Alaska. As moist southwesterly flow ascends the terrain, wintry precipitation will occur over an 
area extending from Kenai into the northern Panhandle on Friday. A separate Heavy Precipitation 
area was added for Saturday along the terrain roughly from Yakutat to Ketchikan as lingering mixed 
precipitation occurs with the low taking a southeast turn Sunday. Afterwards, the next round of 
active weather begins early next week as another strong system arrives from the west. More heavy 
rain/precipitation and high winds are possible with the arrival of this storm system, although 
uncertainty regarding the evolution of the system precludes any Hazards areas for now.   

Asherman