US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
456 PM EDT Thu Apr 29 2021
 
Valid Sunday May 02 2021 - Thursday May 06 2021
 
Hazards:
- Heavy rain across portions of the Southeast, the Lower Mississippi Valley, and the Southern 
Plains, Sun-Mon, May 2-May 3.
- Heavy rain across portions of the Central Plains, the Lower Mississippi Valley, the Tennessee 
Valley, the Great Lakes, the Central Rockies, the Southern Appalachians, the Southeast, the 
Southern Plains, and the Ohio Valley, Mon-Tue, May 3-May 4.
- Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle 
Mississippi Valley, the Southern Appalachians, the Southeast, the Southern Plains, and the Ohio 
Valley, Wed-Thu, May 5-May 6.
- Heavy snow across portions of the Central Rockies and the Central Plains, Mon-Tue, May 3-May 4.
- Severe weather across portions of the Lower Mississippi Valley and the Southern Plains, Mon, May 
3.
- Severe weather across portions of the Southeast, the Lower Mississippi Valley, and the Tennessee 
Valley, Sun, May 2.
- Flooding possible across portions of the Central Plains, the Lower Mississippi Valley, the 
Tennessee Valley, the Middle Mississippi Valley, the Southern Plains, and the Ohio Valley.
- Flooding possible across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, 
the Southern Plains, and the Ohio Valley.
- Flooding occurring or imminent across portions of the Southeast, the Lower Mississippi Valley, 
and the Southern Plains.
- Flooding occurring or imminent across portions of the Lower Mississippi Valley.
- Flooding likely across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, 
and the Southern Plains.
- Flooding likely across portions of the Lower Mississippi Valley.
- Enhanced wildfire risk across portions of the Southern Rockies, the Southern Plains, and the 
Southwest, Sun, May 2.
 
Detailed Summary:

At the beginning of the hazards forecast period on Sunday (5/2), ensemble and deterministic 
guidance is in good agreement regarding the synoptic pattern over the CONUS: a digging West Coast 
trough, with a downstream wave over the Southern Plains. In the Northern half of the U.S., largely 
zonal flow will persist on the heels of a departing upper low north of Maine. At the surface, a 
frontal complex is forecast to egress the Plains southeastward, ahead of a maritime tropical 
airmass surging north through the Deep South into the Midwest. This pattern will set the stage for 
what will be an active week of hazards for the aforementioned areas. An initial bout of 
convective-driven heavy rain is likely in southeast Texas and Mississippi Valley Sunday, as the 
lead disturbance over the region exits over the Southeast. Global models are in general agreement 
as to the timing of the disturbance corresponding to favorable diurnal heating atop a 
moisture-laden airmass, characterized by precipitable water anomalies one standard deviation above 
normal. Above average soil moisture anomalies for the region support the idea of some problematic 
areas for heavy rain. In addition to the heavy rain threat, the Storm Prediction Center has 
highlighted the possibility of severe weather over eastern Louisiana and Mississippi, owing to the 
combination of vertical wind shear and instability. The activity is expected to expand into the 
Ohio/Tennessee Valleys Monday and Tuesday (5/3-5/4) as the lead disturbance exits, while the main 
frontal system continues to push southeast. A moist airmass ahead of the front, coupled with 
favorable jet streak dynamics per global ensemble means support the idea of heavy rain potential 
across the area. Meanwhile, the progression of the western trough over the Southern Plains atop 
unstable air has led the Storm Prediction Center to highlight Northeast Texas, Eastern Oklahoma, 
and Arkansas for severe weather potential Monday. Yet another chance of heavy rain is possible 
across the Deep South Wednesday and Thursday (5/5-5/6) as the main trough ejects eastward and the 
front surges south. By day 7 (5/7), the frontal passage begins to scour out the deeper moisture in 
the region.   

Over the north-central High Plains, a combination of convergence along and upslope flow behind the 
front will help to enhance the precipitation Sunday into Monday. The actual precipitation amounts 
are only marginally heavy, but the hazard area has experienced above normal precipitation recently, 
so the rainfall may have greater impact here in terms of isolated flood risks. Moreover, a shot of 
wet heavy snow appears likely in elevation along the Front Range. High probabilities of exceeding 
.25 inches liquid equivalent in the area prompted the addition of a heavy snow area Monday through 
Tuesday.Further west in New Mexico, Arizona, and Texas, a fire weather threat will exist Sunday 
(5/2) as a developing lee cyclone facilitates dry, windy conditions in the area. Accordingly, the 
Storm Prediction Center has highlighted the area as a risk in the Fire Weather Outlook. 

Across Alaska, the pattern does not favor major storm systems impacting the state. While conditions 
will be unsettled over the Panhandle and much of the southern part of the mainland, nothing at this 
time is expected to have major impacts.

Asherman/Klein