US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
347 PM EDT Wed May 12 2021
 
Valid Saturday May 15 2021 - Wednesday May 19 2021
 
Hazards:
- Heavy rain across portions of the Central Plains, the Great Lakes, the Middle Mississippi Valley, 
the Southern Plains, and the Ohio Valley, Sat-Mon, May 15-May 17.
- Heavy rain across portions of the Southern Plains, Sat-Sun, May 15-May 16 and Tue-Wed, May 18-May 
19.
- Heavy rain across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, and 
the Southern Plains, Mon-Wed, May 17-May 19.
- Flooding possible across portions of the Northern Great Basin.
- Flooding occurring or imminent across portions of the Lower Mississippi Valley and the Southern 
Plains.
 
Detailed Summary:

Much of the medium-range forecast period (Saturday, May 15th through Wednesday, May 19th) should be 
relatively hazards free across the Lower 48, with the threat of heavy rain confined to central and 
south-central sections of the country. At the surface, a large high pressure system is forecast to 
be found across the Ohio Valley and eastern U.S. through the weekend and remain over the Southeast 
into the middle of next week. Meanwhile, a warm front situated over the Central Plains should 
slowly extend eastward through the Midwest and Ohio Valley by Monday. This warm front could be the 
focus of showers and thunderstorms that eventually grow upscale into multiple mesoscale convective 
complexes between central Kansas and northern Missouri. Thus, the threat of heavy rain from these 
thunderstorms extends from the Central Plains to the western Ohio Valley between Saturday and 
Monday. A few severe thunderstorms are not out of the question as well, but the overall magnitude 
of the severe threat appears low at this time. It is also important to note that forecast 
confidence is below average for this area and heavy rain could potentially shift southward into the 
Middle Mississippi and Lower Ohio valleys. By Monday, a weakening upper-level low ejecting out of 
the Southwest is also expected to spark thunderstorms across the Southern Plains and Lower 
Mississippi Valley. Moisture return from the western Gulf of Mexico should be sufficient and aid in 
scattered to widespread instances of heavy rain through at least Wednesday across the region. 
Confidence is particularly high on Tuesday regarding 1+ inches of rain across southern Oklahoma, as 
well as north-central and eastern portions of Texas. Additionally, an isolated severe threat is a 
possibility across much of the Southern Plains during this time period. Thunderstorms with heavy 
rainfall rates could also impact southern/southeast Texas this weekend as a shortwave crosses the 
far northwestern Gulf of Mexico. Additional rain is then expected to enter by Tuesday and Wednesday 
as convection moves eastward from central Texas. 

Temperatures across CONUS will start below average across the Southeast on Saturday before warming 
to near normal by the beginning of next week. Meanwhile, high temperatures will reach upwards of 10 
to 20 degrees above average throughout the Intermountain West and Northwest through Monday until a 
cold front sweeps in from the Pacific on Tuesday. Little to no precipitation is expected across the 
West outside of the Cascade and Olympic Mountains.

For Alaska, much of the area should remain relatively quiet through the weekend and into next week. 
A potent storm system may impact the Aleutians on Tuesday and Wednesday, but wind gusts at the 
moment appear to remain below hazardous threshold. There is also a signal for heavy precipitation 
to enter coastal sections of the Gulf of Alaska on Wednesday, but confidence is too low at the 
moment to add a highlighted area.  

Snell