US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
446 PM EDT Wed Sep 23 2020
 
Valid Saturday September 26 2020 - Wednesday September 30 2020
 
Hazards:
- Heavy rain across portions of the Pacific Northwest and the Northern Great Basin, Fri-Sat, Sep 
25-Sep 26.
- Heavy rain across portions of the Southeast, the Mid-Atlantic, and the Southern Appalachians, 
Fri, Sep 25.
- Heavy rain across portions of the Lower Great Lakes, the Mid-Atlantic, and the Northeast, 
Sun-Mon, Sep 27-Sep 28.
- Flooding possible across portions of the Lower Mississippi Valley and the Southern Plains.
- Flooding occurring or imminent across portions of the Southeast.
- Much above normal temperatures across portions of California, the Central Great Basin, the 
Pacific Northwest, and the Northern Great Basin, Sun-Tue, Sep 27-Sep 29.
- Much above normal temperatures across portions of the Central Plains, the Northern Plains, the 
Central Rockies, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Southern 
Plains, Fri, Sep 25.
- Much above normal temperatures across portions of the Southern Plains, Sat, Sep 26.
- Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Tue, Sep 29.
 
Detailed Summary:

Low pressure moves into the Pacific Northwest on Friday and Saturday.  Moisture associated with the 
low will aid in producing an area of heavy rain over parts of the Pacific Northwest on Friday and 
Saturday.  The rain on Friday will be lighter than on Saturday but will meet the criteria for 
depicting an area of heavy rain on Friday.  The heaviest rain will occur on Saturday. There will be 
some rain on Sunday but it will be lighter than what will fall on Friday so there is no area of 
heavy rain depicted on Sunday.   Meanwhile, on Friday a quickly moving upper-level ridge will be 
over parts of the Upper Midwest will aid in producing temperatures that will be 12 degrees above 
average over parts of the Upper/Middle Mississippi Valley into parts of the Central Plains/High 
Plains into parts of the Southern High Plains on Friday.  This meets the criteria for an area of 
much above normal temperatures over the region on Friday.  On Saturday, upper-level troughing will 
move over the region on Saturday so the much above average temperatures will not be there.  
Upper-level ridging pokes eastward over parts of the Southern High Plains allowing the temperatures 
to remain above normal for one more day on Saturday. 
 
Rain associated with Post-Tropical Cyclone Beta will produce an area of heavy rain over parts of 
the Southeast/Southern Appalachians on Friday.  Furthermore, a front moving from the Lower Great 
Lakes to the Northeast Coast on Sunday into Monday will produce an area of heavy rain.  The 
boundary will produce enough rain to meet the heavy rain criteria of one inch per 24 hours on 
Sunday into Monday.  There is too much model uncertainty to put an area
of heavy rain over the Northeast on Tuesday.  Overnight Saturday an upper-level high will develop 
over parts of the West Coast. The high will allow temperatures to become much above normal over 
parts of the Pacific Northwest into parts of Northern/Central California from Sunday into Tuesday.  
In addition, strengthening high pressure over the Great Basin and Intermountain West may lead to 
increased wildfire risk due to dry conditions, low humidity levels, and the potential for high wind 
gusts.  Southern California could contend with a Santa Ana wind event late this weekend into early 
next week should recent trends in model guidance persist.

For Alaska to start the medium range period as another potent storm system crosses the Gulf of 
Alaska and weakens. Moisture will moderate to low over the Gulf of Alaska and model uncertainty has 
made yesterdays are of heavy precipitation look too uncertain to include today.   Another low over 
the North Pacific will move into the Gulf of Alaska on Tuesday.  The moisture associated with this 
storm is much higher than the previous storm with the moisture streaming into the Alaska Panhandle. 
 An area of heavy precipitation will extend from east of Valdez into the panhandle on Tuesday.  

Ziegenfelder