An active and relatively chilly pattern will continue through the end of December for much of the nation. Blocking over the North Pole will help shunt COLD Arctic air southward into the Plains and further eastward. A shot of this will be felt late this weekend into next week. In addition, the upper level weather pattern will be active with a southwest flow with several storm systems dropping out of western Canada into the SW US and then northeastward into the central and eastern US. This pattern will deliver several chances for wintry precipitation for the Plains, MS Valley, OH Valley and Northeast. A true battle ground will set up for the zone between I-40 and I-70.
A surge of Arctic cold will drop into the Pacific NW on tonight into Saturday. With it will be a wide swath of snow for much of WA/OR/MT/ID. Snow will even make it to the Pacific coast and affect cities such as Seattle and Portland this weekend. These cities will likely see between 1” and 3” through Sunday. The Cascades will see the heaviest snowfall where 1 to 2 feet of snow is likely. Winter Storm Warnings are already issued for most of WA/OR/ID with Winter Storm Watches issued for most of MT/UT/WY/CO.
The Arctic Cold that will accompany the snow will be the coldest so far this winter season. Temperatures will drop to around -30F in MT Sunday night and high temperatures on both Sunday and Monday will be well below zero (-15F to -20F). The brunt of the cold will shift into ND Sunday through Tuesday.
Widespread snow/wind will cover most of the northern Plains beginning Saturday night and continuing eastward through the Upper Midwest through Tuesday. The punch of cold will also sink southward early next week and the front edge of the Arctic air mass will make it as far south as Amarillo-Oklahoma City-Little Rock-Nashville-Lexington-Pittsburgh-Rochester by Monday evening. In addition, a large amount of moisture will be confined near the frontal edge of this air mass. This will set up for the potential of a significant icing event on Monday in the Mid-MS Valley. This potential should be monitored closely.
Another piece of energy will eject out of the SW US middle of next week. It will likely deliver another round of significant snowfall to many in the Plains and Upper Midwest. The battle ground area in between I-40 and I-70 through OK/MO/KS/IL will have the potential for more icing but that will strongly depend on the amount of Arctic air that remains at the surface. Again this event should be monitored closely by those who live in this region.