US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
539 PM EST Mon Jan 18 2021
 
Valid Thursday January 21 2021 - Monday January 25 2021
 
Hazards:
- Heavy rain across portions of the Middle/Lower Mississippi Valley, the Central/Southern 
Appalachians, the Tennessee Valley, the Southern Plains, and the Ohio Valley, Mon, Jan 25.
- Heavy rain across portions of the Southeast, the Lower Mississippi Valley, and the Tennessee 
Valley, Thu-Fri, Jan 21-Jan 22.
- Heavy snow across portions of California, the Pacific Northwest, and the Northern Great Basin, 
Sun, Jan 24.
- Heavy snow across portions of the Southern Rockies, the Central Rockies, the Great Basin, and the 
Southwest, Fri-Sat, Jan 22-Jan 23.
- Heavy snow across portions of the Northern/Central Plains, the Great Lakes, and the Upper 
Mississippi Valley, Sat-Sun, Jan 23-Jan 24.
- Flooding occurring or imminent across portions of the Southeast.
 
Detailed Summary:

A front extending across the Western Gulf Coast westward across Northern Mexico will have moisture 
from the Western Gulf of Mexico overrunning the boundary, producing Heavy Rain across parts of the 
Lower Mississippi Valley eastward into parts of the Tennessee Valley Thursday into Friday.  The 
area of Heavy Rain depicted on the Hazards Chart may become larger or smaller over the next few 
days since there has been some uncertainty in how much rain will fall, with some models suggesting 
a large area and others a smaller area.  The problem here is that the uncertainty is not during one 
model cycle run, but it is instead across several days of model cycle runs.

On Friday into Saturday, upper-level energy and an associated surface feature moving into the 
Southwest will help produce Heavy Snow over the Unita Mountains, Wasatch Mountains, Mogollon Rim, 
San Juan Mountains, and other mountain ranges in the Central Rockies.

A Wave of low pressure over the Central Rockies on Friday will move eastward to the Middle 
Mississippi Valley/Western Ohio Valley by Monday.   The storm will pull moisture northward from the 
Gulf of Mexico over the Plains and Mississippi Valley into the Upper Midwest.  The moisture and 
energy will help produce an area of Heavy Snow over parts of the Northern Plains into parts of the 
Upper Great Lakes on Sunday into Monday. 

Meanwhile on Sunday, a front will approach the West Coast along with a plume of moisture.  The 
moisture and the boundary will help produce Heavy Snow over the Cascades Mountains into the 
Siskiyou Mountains on Sunday.   

Additionally, a front along the Central Gulf Coast and moisture moving northward out of the Gulf of 
Mexico around an area of high pressure just off the Carolina Coast will help produce an area of 
Heavy Rain from the Lower Mississippi Valley to the Central Appalachians on Monday.  There is a 
problem here that is similar to the issue dealing with the area of Heavy Rain over parts of the 
Lower Mississippi Valley into the Tennessee Valley from Thursday and Friday.  There is uncertainty 
with the size and exact location of the Heavy Rain.  Some models have the rain farther north and 
over a narrower region, while others have the rain over a much larger area.  At this point, NWS are 
depicting an area that might change in shape, size, and location as Monday the 25th draws near.  

Over Alaska, an area of deep low pressure over the Bering Sea on Thursday will have a plume of 
moisture streaming into the Southwest and South-Central portion of the mainland.  There is a 
possibility of Heavy Precipitation developing along the coast and inland from parts of the eastern 
Alaska Peninsula, Kuskakwin Mountains, Kodiak Island, and the Kenal Peninsula on Thursday and 
Friday.  At this point, there is uncertainty in how much moisture will stream into the mainland.  
On Monday the 18th, NWS chose not to depict an area of Heavy Precipitation, but if the models come 
into a better agreement, this may change over the next several days.  The weather will become a 
little calmer on Saturday and Sunday.  On Monday, another deep low will move into the Bering Sea, 
bringing more precipitation to the state. 

Ziegenfelder