US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
422 PM EDT Mon May 03 2021
 
Valid Thursday May 06 2021 - Monday May 10 2021
 
Hazards:
- Heavy rain across portions of the Central/Southern Plains, the Middle/Lower Mississippi Valley, 
the Tennessee Valley, the Ohio Valley, the Great Lakes, and the Central/Southern Appalachians, 
Sat-Mon, May 8-May 10.
- Flooding occurring or imminent across portions of the Southern Plains.
- Much above normal temperatures across portions of the Northern/Central Great Basin and the 
Northern/Central Rockies, Thu, May 6.
 
Detailed Summary:

During the medium range period (Thursday, May 6th - Monday, May 10th), an upper-level low/trough 
will move from the eastern Pacific late week southeastward into the Northwest U.S. by the weekend. 
Ahead of this trough, upper ridging is forecast to be in place across the western U.S. on Thursday, 
causing temperatures to rise to 15 to 25 degrees above average in the Intermountain West. As the 
upper pattern shifts eastward Friday, above normal temperatures should shift east with it into the 
Central High Plains, but anomalies will not be quite as warm there. A suppressed upper-level ridge 
by the weekend could lead to somewhat above normal temperatures from the south-central to 
southeastern U.S. early next week, but likely not to hazardous levels.

The aforementioned upper trough/low is forecast to push a surface low pressure/frontal system 
across the western to central U.S. through the period. Temperatures are expected to cool down 
significantly (particularly in terms of highs) for the Northwest and especially into 
northern/central parts of the Rockies and High Plains by the weekend into early next week. These 
chilly temperatures will likely be in conjunction with precipitation. Higher elevations of the West 
are likely to see late-season snow; snow amounts remain in question at this point and thus no 
hazard areas were drawn, but some reasonably high totals are possible across the Northern 
Rockies/Wind River Mountains/Tetons/Bighorns. Additionally, postfrontal gusty winds are possible in 
the West, but at this point do not seem significantly strong.

The upper-level pattern is expected to stall somewhat by early next week, with the upper low/trough 
centered over the Northern Rockies, quasi-zonal flow across the East, and sloping southwesterly 
flow in between. This pattern will direct moisture from both the Pacific and the Gulf of Mexico 
into parts of the central and eastern U.S., and a meandering front should serve to focus this 
moisture and create the potential for heavy rainfall and flooding/flash flooding. Multiple days of 
rain are possible from portions of the Central/Southern Plains into the Mississippi, Ohio, and 
Tennessee Valleys and toward the Central/Southern Appalachians. Much of this area is receiving 
rainfall early this week and have been generally wetter than normal over the past few weeks, so 
soils may already be prone to flooding and flash flooding. Furthermore, chances of precipitation 
are likely to increase in the Central High Plains by early next week, but model guidance varies on 
amounts, so this should continue to be monitored.

Over Alaska, no hazards are delineated. The main concern in the state is ice breakup along some 
rivers as it melts and thins. This could cause ice jam flooding in some areas, but areas of highest 
concern are not able to be pinpointed this far in advance. A couple of rounds of precipitation are 
likely from the Alaska Peninsula to Southcentral Alaska during the period, but amounts vary among 
model guidance and overall do not seem particularly heavy.

Tate