US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
437 PM EDT Thu Sep 23 2021
 
Valid Sunday September 26 2021 - Thursday September 30 2021
 
Hazards:
- Heavy rain across portions of the coastal Pacific Northwest, Sun-Tue, Sep 26-Sep 28 and Thu, Sep 
30.
- Heavy rain across portions of the western slopes of the Cascades, Sun-Mon, Sep 26-Sep 27.
- Heavy rain along portions of the Texas coast, Tue-Wed, Sep 28-Sep 29.
- Heavy rain across portions of the central and southern Plains, Thu, Sep 30.
- Flooding possible across portions of the central Appalachians to the northern Mid-Atlantic, as 
well as
portions of the lower Great Lakes and northern Florida.
- Flooding occurring or imminent across portions of central Tennessee.
- Much above normal temperatures across much of the northern and central Plains, Sun-Tue, Sep 
26-Sep 28.
- Heavy precipitation across much of the Alaska Panhandle, Wed-Thu, Sep 29-Sep 30.
 
Detailed Summary:

The medium range forecast period (Sunday, Sep. 26 to Thursday, Sep. 30) will likely begin with a 
heavy rain threat departing Maine.  Nevertheless, models continue to show difficulties resolving 
the timing of the associated low pressure system forecast to develop quickly while departing Maine. 
 The slower model solutions still indicate a threat of heavy rain on Sunday.  This scenario is not 
indicated on the present hazards outlook, however.

Meanwhile, there continues to be model signals for additional moisture to reach portions of the 
Pacific Northwest this weekend. The moisture influx appears to be most significant from Sunday into 
Monday, lingering into early Tuesday. Thereafter, a notable break in the heavy rainfall Tuesday 
into 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 scenario that the ECMWF now agrees very well with the GFS.  A heavy rain 
area is now indicated along portions of the Texas coast Tuesday into Wednesday, and another heavy 
rain area is introduced over portions of the central and southern Plains for next Thursday.

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 few days of much above normal temperatures over 
much of the northern and central Plains during the medium range period.  The warmth should be most 
widespread from Sunday through Tuesday.  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 to 20 
degrees above normal 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 next Wednesday into Thursday.

Kong