US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
225 PM EST Wed Dec 11 2019
 
Valid Saturday December 14 2019 - Wednesday December 18 2019
 
Hazards:
- Heavy precipitation across portions of the Ohio Valley, Central Appalachians, and the Northeast, 
Mon-Tue, Dec 16-Dec 17.
- Heavy rain from portions of the Lower Mississippi Valley to the Northeast, Dec 16-Dec 17.
- Heavy rain across portions of the Northeast, Sat, Dec 14.
- Heavy snow across portions of the Central Rockies, Sat-Sun, Dec 14-Dec 15.
- 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, Sat-Sun, Dec 14-Dec 15.
 
Detailed Summary:

A developing surface low moving into the Northeast to begin the medium range period (Saturday) will 
bring a threat for heavy rainfall on Saturday to eastern portions of New England. High winds are 
possible along the coast as well into Sunday as the low deepens as it quickly departs into the 
Canadian Maritimes. Behind this, a cold Canadian airmass will drop into the north-central U.S. 
bringing a period of much below normal temperatures (anomalies 15 to 20+ below normal) to portions 
of the eastern Dakotas and Minnesota Saturday and Sunday. Temperatures should quickly moderate by 
early next week as the high pressure slides eastward.

An upper-level trough is forecast to take shape over the Western U.S. this weekend, bringing a 
threat for heavy mountain snows to higher elevations, though the best chance for significant 
accumulations are expected over parts of the Colorado Rockies as the medium range period begins. As 
this system ejects into the Central U.S. on Monday, a surface low should lift from the Southern 
Plains/Gulf of Mexico into the Mid-Atlantic by Tuesday, and off the Northeast coast by early 
Wednesday. This will spread heavy rainfall from the Lower Mississippi Valley into the Tennessee 
Valley on Monday, spreading northward into the Mid-Atlantic and Northeast through Tuesday. From 
portions of the Ohio Valley to the Northeast, there is enough uncertainty remaining at this point 
on how much of this may be in the form of snow, or for areas across the Mid-Atlantic, the 
precipitation could start out as snow 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 could 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. Uncertainty in the 
placement and extent of the heavy rain and snow threat precluded drawing hazard areas on the 
Hazards chart for today.

Santorelli