US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
420 PM EDT Fri Oct 01 2021
 
Valid Monday October 04 2021 - Friday October 08 2021
 
Hazards:
- Heavy rain across portions of the Northeast, Mon, Oct 4.
- Heavy rain across portions of the Southeast and Southern Appalachians Mon-Tue, Oct 4-Oct 5.
- Heavy rain across portions of the Southern and Central Appalachians and the Mid-Atlantic, 
Wed-Thu, Oct 6-Oct 7.
- Flooding occurring or imminent across portions of the Great Lakes.
- Heavy precipitation across portions of mainland Alaska, Wed, Oct 6.
- Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Wed-Fri, Oct 
6-Oct 8.
- High winds across portions of mainland Alaska, Mon-Wed, Oct 4-Oct 6.
- High winds across portions of mainland Alaska and the Aleutians, Mon-Fri, Oct 4-Oct 8.
 
Detailed Summary:

The main concern during the medium-range forecast period (Monday, Oct 4th to Friday, Oct 8th) will 
be the threat for widespread and potentially significant heavy rain with a slow moving storm system 
across the eastern half of the country. At the beginning of the period, a low pressure center will 
be located over the Great Lakes with a stationary front draped eastward across the Northeast and a 
trailing cold front extending southwestward through the Mississippi Valley. An upper-level low will 
also be developing over the area. Widespread showers and storms are expected to continue along and 
north of the stationary front for portions of the Northeast, mainly southern New England, on Monday 
(Oct 4th), bringing the threat for heavy rain. This region has seen several instances of 
significant rainfall recently, exacerbating flooding concerns with any additional heavy rainfall. 

The focus then turns southward, where several days of widespread and potentially significant heavy 
rainfall are forecast from the Southeast/Southern Appalachians north to the Mid-Atlantic. The 
upper-level low is forecast to become cut-off from the mean flow and stall over the Southeast, 
providing continued support for the development of showers and storms on the east side of the low. 
Heavy rain is initially most likely from central Georgia north to the southern Appalachians on 
Monday (Oct 4th) and Tuesday (Oct 5th) ahead of a developing occluded surface low as the cold front 
passes east through the area and becomes stationary along the Atlantic Coast. This low is forecast 
to slowly progress northeast, with the heavy rain threat spreading northward into the central 
Appalachians, Piedmont, and Mid-Atlantic on Wednesday (Oct 6th) and Thursday (Oct 7th).  
Significant rainfall totals look possible (widespread 3"+), with storm development and heavy 
rainfall potential aided by broad low-level easterly flow and orographic forcing along the higher 
terrain of the Appalachians. Additional heavy rainfall is possible on Friday (Oct 8) for portions 
of the northern Mid-Atlantic and southern New England as a secondary low develops off the coast, 
but opted to focus on highlighting the more certain heavy rain areas earlier in the period given 
the potential for significant rainfall. 

For Alaska, a strong low pressure system crossing the Bering Sea, the remnants of Typhoon Mindulle, 
is expected to bring high winds to the Aleutians and western coast of the mainland on Monday and 
Tuesday. A second system will following immediately in its wake will continue the threat for high 
winds into Wednesday. Some heavy precipitation is also possible across the western Mainland as the 
initial storm system passes through. Increasing moisture ahead of both systems, as well as the 
development of low pressure in the Gulf of Alaska, is forecast to lead to both heavy snow in the 
mountains as well as heavy rain for lower elevations and coastal areas from the western Alaskan 
Range southeast to the Kenai Peninsula and into the Panhandle. The heavy precipitation is most 
likely for areas surrounding the western Alaskan Range on Wednesday, and will continue ahead of the 
system in the Gulf from the Kenai Peninsula southeast through the Panhandle Wednesday into Friday. 
Finally, another storm system is forecast to deepen over the Bering Sea late in the period. There 
is some spread in the guidance on both the progression of the system and degree of deepening, but 
most models are trending towards a deeper system bringing a continued threat for high winds to the 
Aleutians for Thursday and Friday. 

Putnam