US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
351 PM EST Thu Dec 12 2019
 
Valid Sunday December 15 2019 - Thursday December 19 2019
 
Hazards:
- Heavy precipitation across portions of the Northeast, the Central Appalachians, the Mid-Atlantic, 
and the Ohio Valley, Mon-Tue, Dec 16-Dec 17.
- Heavy precipitation across portions of western Washington, Thu, Dec 19.
- Heavy precipitation across portions of northern California and western Oregon, Thu, Dec 19.
- Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the Southern 
Appalachians, and the Southeast, Mon-Tue, Dec 16-Dec 17.
- Severe thunderstorms across portions of the Middle and Lower Mississippi River Valley, Mon, Dec 
16.
- Heavy snow across portions of the Central Rockies, Sun, Dec 15.
- Heavy snow across portions of the Central Plains, Sun, Dec 15.
- Heavy snow across portions of the Northeast, Mon-Tue, Dec 16-17.
- Flooding occurring or imminent across portions of the Northern Plains.
- Flooding likely across portions of the Northern Plains.
- High winds across portions of the Northeast, Sun, Dec 15.
- Much below normal temperatures across portions of the Upper Mississippi Valley and the Northern 
Plains, Sun, Dec 15.
 
Detailed Summary:

An intensifying surface low exiting the Northeast U.S. on Sunday will likely generate high winds 
across eastern New England, particularly near the coast and across the higher elevations. As this 
low lifts northward across eastern Canada, a very cold Canadian airmass will drop southward across 
the Upper Midwest and northern Plains, bringing a period of much below normal temperatures 
(anomalies 15 to 20+ below normal) to portions of the eastern Dakotas and Minnesota on Sunday. 
Temperatures should moderate by early next week as the arctic airmass settles eastward.

An upper-level trough is forecast to take shape over the Western U.S. this weekend, increasing the 
potential for heavy snow across portions of the Colorado Rockies on Sunday. With this storm system 
emerging across the central Plains on Monday, a surface low should lift from the southern 
Plains/Gulf of Mexico to the Mid-Atlantic region by Tuesday, and off the Northeast coast by early 
Wednesday. The surge of moisture northward ahead of the cold front will likely result in a corridor 
of moderate to heavy rainfall extending from the Deep South to the central Appalachians, and wintry 
precipitation from the Ohio Valley to the Northeast states. Uncertainty remains at this point on 
how much of this may be 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. At this 
point, a broad heavy precipitation area including portions of the Ohio Valley, Central 
Appalachians, Mid-Atlantic, and Northeast was drawn for the hazards outlook graphic. The potential 
for wintry weather will need to be monitored as the event gets closer.

For Alaska, a series of low pressure systems should pass west to east across the Aleutians and 
southern Alaska coast, bringing precipitation to those areas, which could be locally heavy through 
Monday. Then the possibility exists for another low to track northward across the Panhandle by 
Monday and Tuesday, which could also cause locally heavy precipitation.  Two separate heavy 
precipitation areas were added to account for this.

Hamrick