US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
324 PM EDT Mon Jun 28 2021
 
Valid Thursday July 01 2021 - Monday July 05 2021
 
Hazards:
- Heavy rain across portions of the Southeast, the Lower Mississippi Valley, the Southern Plains, 
and the Tennessee Valley, Sat-Mon, Jul 3-Jul 5.
- Heavy rain across portions of the Mid-Atlantic, the Lower Mississippi Valley, the Central 
Appalachians, the Tennessee Valley, the Middle Mississippi Valley, the Northeast, the Southern 
Appalachians, the Southeast, and the Ohio Valley, Thu-Fri, Jul 1-Jul 2.
- Flooding possible across portions of the Central Plains, the Middle Mississippi Valley, the Great 
Lakes, and the Ohio Valley.
- Flooding occurring or imminent across portions of the Central Plains, the Great Lakes, the Middle 
Mississippi Valley, and the Southern Plains.
- Flooding likely across portions of the Southern Plains.
- Excessive heat across portions of the Central Great Basin, the Northern Plains, the Northern 
Rockies, California, the Northern Great Basin, and the Pacific Northwest, Thu-Mon, Jul 1-Jul 5.
- Excessive heat across portions of the Upper Mississippi Valley and the Northern Plains, Fri-Sat, 
Jul 2-Jul 3.
- High winds across portions of mainland Alaska and the Aleutians, Thu, Jul 1.
 
Detailed Summary:

This upcoming medium range forecast period (Thursday, July 1 through Monday July, 5) will feature 
continued upper ridging over the western U.S. and the development of a closed-off low over the 
Midwest and Ohio Valley. There are signs that the overall pattern deamplifies and becomes more 
progressive toward the end of next weekend. Starting in the West, the heat wave will persist across 
much of the northern Intermountain region and Rockies through the period. Record or near 
record-breaking temperatures are expected through the weekend across eastern Washington across 
Idaho and into western Montana with highs around 15-20 degrees above normal (generally ranging from 
the upper 90s to mid 100s). Above normal temperatures will continue across the Pacific Northwest, 
but with the western part of the ridge gradually eroding, temperatures are not expected to approach 
any of the extremes currently being experienced over this region.

We did maintain the excessive heat area across central and eastern sections of Montana through next 
Monday, but the brunt of the heat will be Thursday-Friday, then lessening a few degrees over the 
weekend. This is partly in response to the weakening ridge, but also due to an increase in moisture 
and weak upper level disturbances that should allow for a little more cloud cover and the potential 
for isolated/scattered showers and thundershowers during the afternoon. Marginally excessive heat 
will also extend across sections of North Dakota and northern/central Minnesota Friday-Saturday 
before weak short wave troughing sliding across southern Canada results in a very slight cooling 
during the latter part of the weekend.

Farther to the south and east, a slow-moving frontal system associated with the developing cut-off 
low will provide a focus for deep Gulf of Mexico moisture and bring widespread showers and 
thundershowers from southern New England and the mid-Atlantic states southwestward into the 
Tennessee Valley during the latter part of this week. Much of this area has been relatively dry 
over the past couple of weeks, so the rainfall will mostly be welcome; however, the potential for 
isolated flooding exists in areas that experience repeat bouts of rainfall. The front is expected 
to settle southward toward the Gulf coast and stall out over the weekend. This will set the stage 
for potentially significant rainfall this upcoming weekend from southern Alabama and Florida 
Panhandle westward into southeastern Texas. This may be of particular concern from around New 
Orleans east to Tallahassee where rainfall has been upwards of 200-400% of normal during the past 
couple of weeks.

In Alaska, a strong low pressure system moving through the Aleutians will draw deep Pacific 
moisture northward and bring heavy rainfall (1-3 inches and locally higher) to the Alaska 
Peninsula/Aleutian Range and Kodiak Island Thursday. This will be accompanied by strong 
southeasterly winds along and in advance of the associated surface frontal boundary. This system 
will remain relatively strong as it rotates into and across interior Alaska later Friday through 
the weekend, with model guidance indicating the potential for areas of heavy rainfall. It's a 
little hard to pinpoint with confidence where the heaviest rain will focus, but in general, the 
models suggest that the western part of the mainland is favored Saturday, with a possible shift to 
the east during Sunday.

Klein