US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
511 PM EDT Fri Sep 24 2021
 
Valid Monday September 27 2021 - Friday October 01 2021
 
Hazards:
- Heavy rain across portions of the coastal Pacific Northwest, Mon-Thu, Sep 27-Sep 30.
- Heavy rain across portions of the western slopes of the Cascades, Mon-Tue, Sep 27-Sep 28.
- Heavy rain across portions of the central Plains, Thu, Sep 30.
- Heavy rain across portions of the southern High Plains, Thu-Fri, Sep 30-Oct 1.
- Flooding occurring or imminent across portions of the lower Great Lakes and central Appalachians.
- Much above normal temperatures across much of the northern and central Plains, Mon-Tue, Sep 
27-Sep 28.
- Heavy precipitation across much of the Alaska Panhandle, Wed-Fri, Sep 29-Oct 1.
- Heavy precipitation along the southern coastal section and higher terrain of Mainland Alaska, 
Thu-Fri, Sep 30-Oct 1.
 
Detailed Summary:

The medium range forecast period (Monday, Sep. 27 to Friday, Oct. 1) will likely begin with a low 
pressure system departing Maine into the Canadian Maritimes.  The major of the guidance indicates 
the threat of heavy rain should end by Monday morning although the slower guidance shows the 
possibility of heavy rain lingering into Monday morning.

Meanwhile, there continues to be model signals for additional moisture to reach portions of the 
Pacific Northwest early next week. The moisture influx appears to be most significant from Monday 
lingering into early Tuesday. Thereafter, a notable break in the heavy rainfall later Tuesday into 
early Wednesday appears to be in the offing before the next wave of moisture arrives.  This second 
wave appears to impact areas closer to the Olympic Peninsula whereas the first wave is forecast to 
bring the threat of heavy rain farther inland along the western slopes of the Cascades.  Details in 
the coverage and duration of these heavy rain threat areas are reflected in the hazards map.

Over the southern Plains, there continues to be emerging model support for tropical moisture 
pushing northward from the western Gulf of Mexico into the region by early next week.  A key 
component is for an upper-level trough/low to exit the southwestern U.S. into the central/southern 
Plains early next week.  A heavy rain area is now indicated for portions of the central Plains for 
next Thursday, with another heavy rain area generally encompassing the southern High Plains for 
next Wednesday and Thursday ahead of an approaching cold front.

Meanwhile, between the two areas of upper troughs in the Pacific Northwest and New England, a warm 
ridge of high pressure aloft will ensure at least a couple more days of much above normal 
temperatures over much of the northern and central Plains early next week.  High temperatures well 
into the 80s to the lower 90s are forecast to continue daily across the Plains down into Oklahoma.  
These temperatures are 10-15 degrees above normal over the central Plains to nearly 30 degrees 
above normal near the Canadian border for this time of year.

In Alaska, latest model ensembles continue to indicate a sizable and deep cyclone to approach the 
Alaska Peninsula by the middle of next week.  There continues to be good model support for heavy 
rain to affect much of the Alaska Panhandle from Wednesday onward.  The heavy rain and 
high-elevation snow is forecast to stream further up the coast and impact the southern coastal 
sections by next Thursday.

Kong