US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
500 PM EDT Wed Jul 29 2020
 
Valid Saturday August 01 2020 - Wednesday August 05 2020
 
Hazards:
- Heavy rain across portions of the Southeast as well as the lower Great Lakes, Sat-Sun, Aug 1-Aug 
2.
- Heavy rain possible along much of the Eastern Seaboard up into New England, Mon-Wed, Aug 3-Aug 5.
- Flooding possible across portions of the central and northern Plains.
- Flooding occurring or imminent across portions of the central and northern Plains.
- Excessive heat across portions of the Desert Southwest, Sat-Sun, Aug 1-Aug 2.
- High winds across portions of Florida, Sat-Mon, Aug 1-Aug 3.
- Heavy rain possible across portions of eastern Alaska, Sun, Aug 2.
- Heavy rain possible across portions of coastal southern Alaska, Sat-Mon, Aug 1-Aug 3.
- Heavy rain possible across portions of the Alaskan Panhandle, Tue-Wed, Aug 4-Aug 5.

Detailed Summary:

For the medium range period (Saturday, August 1 - Wednesday, August 5), the eastern U.S. should 
become the main area of concern as a potential tropical cyclone could track across the region.  The 
initial setup over the eastern U.S. will be an omega blocking pattern over Canada with a positively 
longwave trough lingering across the eastern-central U.S.  A wave of low pressure forming along the 
associated frontal boundary should lead to heavy rain across the lower Great Lakes during the 
weekend as Potential Tropical Cyclone Nine (PTC 9) is forecast to track up the vicinity of Florida 
Peninsula at tropical storm intensity.  Forecast uncertainty increases further for early next week 
as PTC 9 could track further up the East Coast or moving more slowly farther south.  The heavy rain 
area assumes some form of interaction between PTC 9 and a slow-moving frontal boundary that extends 
into New England.  Please consult the National Hurricane Center for the latest updates on PTC 9.

Meanwhile, an upper-level ridge will remain over the western North America. Temperatures are 
expected to be above 110 degrees in the Desert Southwest through early next week as the center of 
the ridge stations itself over the region. Abnormally hot conditions should extend north through 
the Great Basin and into the Intermountain West, but current forecasts indicate temperatures 
falling just short of excessive heat criteria. The regions with the odds of perhaps contending with 
the most anomalously hot conditions could be in the rain shadow areas of eastern Washington and the 
northern High Plains. Elsewhere, the Southeast and Mid-Atlantic will continue to deal with heat 
indices ranging from 100-105 with some 110 degree heat indices also possible.

Over Alaska, an occluded storm system associated with a remarkably deep upper trough for late 
July/early August in the Gulf of Alaska is forecast to advect copious amounts of moisture northward 
into the Panhandle and southeast mainland this weekend. While rainfall totals likely fall just 
short of heavy rain criteria in the Panhandle, it is the southeast mainland that could pick up 
anywhere from one to three inches of rainfall with locally heavier amounts possible. The pattern 
remain active into early next week as guidance hints at yet another potent upper trough and 
resulting frontal system near the Aleutians and Bering Sea making its way across the southern tier 
of the state early next week. There is likely to be plenty of moisture with this system as well, 
but details on amounts are still murky due to uncertainty in forecast track, speed, and intensity 
of the upper level system.

Kong