US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
253 PM EST Fri Dec 13 2019
 
Valid Monday December 16 2019 - Friday December 20 2019
 
Hazards:
- Heavy precipitation across portions of California, and the Pacific Northwest, Thu-Fri, Dec 19-Dec 
20.
- Heavy precipitation across Ohio Valley, the Mid-Atlantic, and the Northeast, Mon-Tue, Dec 16-Dec 
17.
- Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Fri, Dec 20.
- Heavy rain across portions of the Lower Mississippi Valley, the Southeast, and Central 
Appalachians, Mon-Tue, Dec 16-Dec 17.
- Heavy snow across portions of the Mid-Atlantic and Northeast, Mon-Tue, Dec 16-Dec 17.
- Severe weather across portions of the Lower Mississippi Valley and the Southeast, Mon, Dec 16.
- Flooding occurring or imminent across portions of the Northern Plains.
- Flooding likely across portions of the Northern Plains.
- Heavy precipitation across portions of the Alaska Panhandle, Mon-Tue, Dec 16-Dec 17.
 
Detailed Summary:

An Arctic airmass will migrate from the Northern Plains and Great Lakes region into the parts of 
the Ohio Valley and the the Northeast this weekend. Meanwhile a mid/upper-level trough will track 
across the central U.S. allowing a surface low pressure system to lift from the Southern 
Plains/Gulf Coast to the Mid-Atlantic region by Tuesday, and off the Northeast coast by early 
Wednesday. A deep layer of warm, moist air will be streaming northward ahead of this advancing 
front. A corridor of moderate to heavy rainfall is expected along this boundary extending from the 
Deep South to the Central Appalachians. As the precipitation encounters the cold airmass over the 
Ohio Valley and northern Mid-Atlantic region, it will transition into mixed precipitation before 
changing over to snow over northern Pennsylvania and portions of southern New England. There 
continues to be some uncertainty in regards to how much falls in the form of snow... or for areas 
across the northern Mid-Atlantic, the precipitation could start out as a wintry mix then change to 
rain as warmer air moves in. Therefore, maintained a broad area denoted as heavy precipitation to 
account for the mixed phase.

A series of low pressure systems tracking through the Gulf of Alaska will spread precipitation all 
across the southern coast and into the panhandle. There may be periods where the precipitation 
becomes locally moderate to heavy, particularly over the Southeast.

Campbell