US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
306 PM EDT Mon Jul 27 2020
 
Valid Thursday July 30 2020 - Monday August 03 2020
 
Hazards:
- Heavy rain across portions of the Central/Southern Plains, the Middle/Lower Mississippi Valley, 
the Tennessee Valley, and the Ohio Valley, Thu-Sat, Jul 30-Aug 1.
- Heavy rain across portions of the Central Plains, Thu, Jul 30.
- Heavy rain across portions of the Middle Mississippi Valley, the Great Lakes, and the Ohio 
Valley, Sat-Sun, Aug 1-Aug 2.
- Heavy rain across portions of the Central/Southern Appalachians, the Tennessee Valley, the 
Mid-Atlantic, the Southeast, and the Ohio Valley, Thu-Fri, Jul 30-Jul 31.
- Flooding possible across portions of the Central Plains and the Middle Mississippi Valley.
- Flooding occurring or imminent across portions of the Northern Plains.
- Flooding likely across portions of the Central Plains.
- Excessive heat across portions of the Central Great Basin, California, and the Southwest, 
Thu-Mon, Jul 30-Aug 3.
- Much above normal temperatures across portions of the Northern Rockies and the Northern Great 
Basin, Thu-Fri, Jul 30-Jul 31.
- Heavy rain across portions of mainland Alaska, Thu, Jul 30.
- Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Sat-Sun, Aug 1-Aug 2.
 
Detailed Summary:

In the medium range period (Thursday, July 30 - Monday, August 3), heavy rain is expected along a 
frontal system. This wavy east-west oriented front should help focus rainfall and the potential for 
flooding and flash flooding from the Central Plains through the Middle Mississippi, Tennessee, and 
Lower Ohio Valleys toward the Appalachians through late in the week. Then, a surface low along the 
front is forecast to lift northeastward, bringing heavy rainfall to much of the Ohio Valley. After 
that time, uncertainty increases with the axis of the heaviest rainfall, with model guidance 
indicating heavy rain could next approach the Lower Great Lakes, Northeast, and/or Mid-Atlantic. 
Will continue to monitor forecast trends before outlining any area farther north or east. 
Temperatures are forecast to be several degrees below normal in parts of the Plains and Mississippi 
Valley due to the cloudiness and rain.

Meanwhile, an upper-level high will take hold over the Southwest U.S. after a respite with last 
week's monsoon. Temperatures are expected to be above 110 degrees in the Desert Southwest through 
early next week as the high barely moves. An upper-level ridge should extend from the high into the 
Northern Great Basin and Northern Rockies, causing temperatures that are above normal by several 
degrees, and some temperatures could top 100 in lower elevations Thursday and Friday. These areas 
should moderate back to normal as upper-level troughing moves in due to an upper low in the 
northeastern Pacific.

Another area to watch in the medium range is the potential for a tropical low to move across the 
Atlantic and possibly approach the Southeast coast early next week. It is too soon to nail down 
specifics, but regardless of tropical development, the system could cause rainy conditions. Did not 
include an area for heavy rain on today's hazards graphic considering the uncertainty in 
development potential as well as strength and track if a tropical cyclone does develop, but an area 
may be needed in future days. Tropical moisture could stream in even ahead of a potential system.

Over Alaska, a slow-moving low pressure system in the Bering Sea could cause locally heavy rainfall 
over far southwestern Alaska and parts of the Alaska peninsula on Thursday. Then, moisture could 
increase in the Panhandle around Friday and cause some rain. Currently, the better chances for 
heavy rain are over the southeastern and east-central portions of the mainland over the weekend as 
the moist air moves westward. Uncertainty remains with the positioning of the heavier rainfall, 
with some model guidance highlighting the terrain with higher amounts, while some take heavy rain 
more into the Yukon Flats. Then by early next week, somewhere around the south-central to 
southeastern Gulf of Alaska coast could see heavy rain, but once again the placement is in question 
and will need to be nailed down in later forecasts. Temperatures could be warmer than average over 
the lower elevations of interior Alaska, with highs in the 70s or near 80 especially through the 
end of this week, while the North Slope remains cooler than normal. The Panhandle should also 
become cooler by the weekend.

Tate