US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
253 PM EDT Wed Aug 19 2020
 
Valid Saturday August 22 2020 - Wednesday August 26 2020
 
Hazards:
- Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Mon-Tue, Aug 
24-Aug 25.
- Heavy rain across portions of the Southeast and the Lower Mississippi Valley, Sat-Wed, Aug 22-Aug 
26.
- Heavy rain across portions of the Southeast, Mon-Wed, Aug 24-Aug 26.
- Excessive heat across portions of the Central Great Basin, California, and the Southwest, 
Sat-Wed, Aug 22-Aug 26.
- Excessive heat across portions of California and the Southwest, Mon-Wed, Aug 24-Aug 26.
- Excessive heat across portions of the Central Rockies, the Central Great Basin, the Northern 
Rockies, the Northern Great Basin, and the Southwest, Sat-Mon, Aug 22-Aug 24.
- Heavy rain across portions of mainland Alaska, Mon, Aug 24.
 
Detailed Summary:

The primary hazards over the lower 48 for the August 22-26 period remain the same as yesterday; 
excessive heat across many of the western states and the potential for heavy rain with tropical 
cyclone activity in the Gulf Coast states and Florida.

Starting in the West, the persistent and strong upper level ridge will maintain above normal 
temperatures across much of the Great Basin, California and the Desert Southwest through the 
period. However, with the exception of much of Central California the Mojave Desert region, the 
heat will abate somewhat. Over the Southwest, monsoonal moisture, some associated with Hurricane 
Genevieve, will stream northward across southern Arizona and southern California. This will bring 
cloudier conditions with the threat for afternoon and evening thunderstorms during this weekend. 
Drier conditions are possible next week, so the heat is likely to return, though given the ridge is 
somewhat weaker, temperatures may not return to levels experienced recently. Across the Great 
Basin, short wave energy moving in from the Pacific will weaken and flatten out the ridge during 
the early-mid part of next week. As a result, temperatures will lower, especially across Oregon, 
Idaho, and northern sections of Nevada and Utah. In addition, there are indications that some 
monsoonal moisture will push into the Four Corners region, increasing the threat for scattered 
thundershowers.

Across the Gulf Coast states and Florida,the weather will be unsettled for much of the period. Over 
the weekend, the focus for potentially heavy rain will likely be along the coast from the central 
Florida panhandle westward to extreme southeastern parts of Louisiana. This is in response to short 
wave troughing between the Bermuda ridge and the ridge across the Four Corners region, plenty of 
Gulf of Mexico moisture and the presence of a dying frontal boundary. Beyond the weekend, attention 
turns to the tropics. Two systems, one currently in the central Carribean and the second in the mid 
tropical Atlantic, have the potential to impact the U.S. during the early to middle part of next 
week. Please see the latest outlooks from the National Hurricane Center for more information about 
these features. Right now, guidance suggests that the central Carribean system will affect the 
Texas Gulf Coast, while the system in the central Atlantic impacts Florida and the eastern Gulf 
Coast region. Confidence at this point is low, but the entire Gulf Coast region will need to 
monitor the tropics over the coming days.

Elsewhere, a weak upper level disturbance will likely trigger scattered showers and thundershowers 
in the vicinity of a dying front in the mid-Atlantic states Saturday. While amounts are currently 
not expected to be particularly heavy, parts of this region have had much above normal rainfall 
this month, so rain on top of saturated soils could lead to isolated runoff problems.

In Alaska, the pattern will be changing as a rather strong low moving across northeastern Russia 
pushes a pretty well-defined cold front across much of the mainland this weekend. The models 
continue to highlight a marginal potential for heavy rainfall (locally around 1-1.5 inches) across 
the western and central Alaska range on Sunday with the front. Low pressure traversing the Gulf of 
Alaska will support widespread rainfall over coastal sections of south-central Alaska on Monday, 
but at this time, amounts don't look high enough to support a threat area. The other impact of this 
system will be to knock down temperatures to near or even below normal levels.

Klein