US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
504 PM EDT Tue Mar 16 2021
 
Valid Friday March 19 2021 - Tuesday March 23 2021
 
Hazards:
- Heavy rain across portions of the Central Plains, the Mississippi Valley,  and the Southern 
Plains,  Mon-Tue, Mar 22-Mar 23.
- Heavy snow across portions of California, the Great Basin, the Pacific Northwest, and the 
Northern Rockies,  Fri, Mar 19.
- Heavy snow across portions of the Central Rockies and the Central Plains, Sun, Mar 21.
- Flooding possible across portions of the Central Plains and the Middle Mississippi Valley.
- Flooding occurring or imminent across portions of the Central Plains, the Middle Mississippi 
Valley, and the Southern Plains.
- Flooding likely across portions of the Central Plains and the Middle Mississippi Valley.
- High winds across portions of the Mid-Atlantic and the Northeast, Fri, Mar 19.
- Heavy precipitation across portions of the Alaska Panhandle, Tue, Mar 23.
 
Detailed Summary:

The medium-range forecast period (Friday, March 19th to Tuesday, March 23rd) features an area of 
deep low pressure just off the Northeast Coast and an area of strong high pressure over Ontario and 
Quebec in Canada on Friday.  The pressure gradient between the two systems will produce strong wind 
along the Northeast and Mid-Atlantic Coast on Friday.  Meanwhile, an upper-level low over the 
Northwest Coast will weaken and open as some of the upper-level energy moves southeastward to 
Southern California by late Sunday afternoon.  The upper-level energy and weak onshore flow will 
help produce heavy snow over the Cascades southward into the northern Sierra Nevada Mountains on 
Friday.  Additionally, the energy will help produce heavy snow over parts of the Northern 
Intermountain Region and parts of the Northern Rockies on Friday as well.  The associated front 
extending from the Northern High Plains southwestward to Southern California will move eastward to 
the Northern Plains to the Central Rockies by Sunday and the Upper/Middle Mississippi Valley into 
the Southern Plains by Tuesday.  The front and an associated wave of low pressure will help produce 
an area of heavy snow over parts of the Central Rockies on Sunday. 

Ahead of the front, temperatures will be about 12 degrees above average over the Upper Midwest on 
Saturday into Tuesday.  The recent snow over the Upper Midwest will have melted by Friday.  The 
snow depth was shallow, about 2 to 3 inches.

Moisture will pool along the boundary over the Middle and Lower Mississippi Valley.  Heavy rain 
will develop over parts of the Middle Mississippi Valley and Central Plains on Monday.  As the 
front moves southeastward, heavy rain will develop over parts of the Lower Mississippi Valley and 
Southern Plains.  Along with this system, rain will move northward over the Upper Midwest.   Since 
the aforementioned snow over the Upper Midwest will have melted the snow by Friday, the addition of 
rain is unlikely to produce any flooding over the area.

For Alaska, low pressure over the Bering Sea will move eastward across the Alaska Peninsula and 
into the Gulf of Alaska by Sunday.  The low will move into the Alaska Panhandle and dissipate by 
Monday.  The system will have light precipitation associated with the storm.  A second area of low 
pressure will develop over the North Pacific on Sunday.  The area of low pressure will strengthen 
on Monday and move into the Gulf of Alaska later on Monday.  By Tuesday, a plume of moisture will 
stream into the Alaska Panhandle, producing an area of heavy precipitation to the panhandle. 

Ziegenfelder