US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
335 PM EDT Tue Aug 20 2019
 
Valid Friday August 23 2019 - Tuesday August 27 2019
 
Hazards:
- Heavy rain across the central Gulf Coast and much of the Mid-Atlantic, as well as portions of 
North and South Dakota, Fri-Sat, Aug 23-Aug 24.
- Heavy rain from across the central Gulf Coast to the interior portions of the Southeast, Sun-Mon, 
Aug 25-Aug 26.
- Heavy rain across portions of the Southern Appalachians, Fri-Mon, Aug 23-Aug 26.
- Heavy rain from across much of the Upper Midwest, Sun-Tue, Aug 25-Aug 27.
- Flooding possible across portions of the Central Plains and the Middle Mississippi Valley.
- Flooding occurring or imminent across portions of the Central Plains, the Southeast, and the 
Northern Plains.
- Excessive heat across portions of interior Oregon, Tue, Aug 27.
- Excessive heat across portions of the interior valleys of California, Fri-Tue, Aug 23-Aug 27.
- Excessive heat across portions of southern Texas, Fri-Sun, Aug 23-Aug 25.
- Heavy rain across much of the Alaska Panhandle, Fri-Sun, Aug 23-Aug 25.
 
Detailed Summary:

A more-or-less zonal upper-level flow pattern is forecast to persist into the medium range period 
(Friday-Tuesday) across the U.S. mainland.  Summer heat is expected to continue across the southern 
tier while occasional intrusions of cool air is anticipated from the northern Plains eastward 
toward the northeastern U.S.  A frontal boundary between the cool and hot air will be the focus for 
showers and thunderstorms.  Latest model guidance shows an increasing signal for heavy rain to 
impact portions of the Dakotas Friday into Saturday ahead of a warm front.  Another piece of energy 
arriving from the Pacific Northwest will provide a better chance of heavy rain across a larger area 
of the upper Midwest from Sunday into Tuesday of next week, as a low pressure system is forecast to 
develop near the Canadian border.  There are some uncertainties regarding the strength of this low 
pressure system, which will influence the chance of heavy rain in this region.

Farther south, as the zonal flow weakens considerably, lingering tropical moisture will keep a good 
chance of showers and thunderstorms from the central Gulf Coast across the interior Southeast 
toward the Mid-Atlantic during the medium-range period.  Additional moisture associated with a 
tropical wave from the Caribbean is forecast by some global models to reach the central Gulf Coast 
during the weekend.  This would result in a better chance of heavy rain to spread into the central 
Gulf Coast on Sunday, followed by the southeastern U.S. on Monday.

By early next week, global models indicate that an upper-level ridge/high pressure cell will begin 
to build from the eastern Pacific into the West Coast.  This will lead to a warming trend spreading 
into the West Coast, especially across the interior valleys where excessive heat is possible.  
Excessive heat is also forecast for southern Texas from Friday through Sunday as afternoon heat 
indices are expected to reach 115 degrees.

Across southeastern Alaska, heavy rain is possible by Friday and into the weekend as an occluded 
cyclone, which is partially originated from Tropical Storm Krosa from the western Pacific last 
week, pushes onshore.  Daily rainfall amounts could reach 2 inches in locations across parts of the 
Alaska Peninsula.  This will be welcome rainfall for the drought-stricken region.  However, the dry 
lands over the complex terrain could make it more susceptible to flash flooding.

Finally, global models are beginning to indicate the possibility of a tropical cyclone approaching 
Hawaii from the southeast by early to middle of next week.  This will be monitored more closely as 
the week progresses.

Kong