Arctic air returns to the Lower 48 tomorrow and will increase in coverage over the next 7 days. As this arctic air sweeps south and east bringing a sharp drop in temperatures following the abnormal mild of today and tomorrow, many ask, who where and how much snow will fall.

Over the next 36 hours, as a storm system skirting the Canadian border slides east which will open the door for arctic air to drop south into eastern Montana and the Dakotas, I expect to see a 2-4 inch swath of snow tomorrow night into Friday. Later Friday after Chicago warms into the 60s Thanksgiving, snow showers are possible Friday night but the real action will be areas located downwind of the Great Lakes. Expect anywhere from 1-3 to as much as 8-14 inches of snow Friday night into Saturday following the passage of the cold front. Highs Saturday surrounding the Lakes will be stuck in the 30s but factor in a 10-20 mph wind with gusts beyond 30 mph and it feels cold. Chicago could fail to hit freezing Saturday. As per usual, the highest snow amounts will be where the narrow but most intense bands of snow form in the classic downwind snow belt areas.

[s2If current_user_can(access_s2member_level1)]

As the cold air advances east, shivering the interior Northeast Saturday and coastal Northeast Sunday with Philadelphia, New York and Boston all potentially struggling to hit freezing Sunday with wind chills in the 20s all day, snow showers are possible too.

However, a storm system is expected to form over the heartland and on the southern edge of the cold pool early next week with a second lobe of arctic air diving south. The models show this system moving along the underside of the trough and it may push the 540 height line (rain-snow line) north or may pull it south, this will keep Chicago close to the boundary but the question remains, where does this system track, north or south of the Big Cities later next week? To the west and it’s a rain event and to the south, it’s snow. Today’s runs show it running west, therefore bringing all rain. However, the NAO is tanking and so this would suggest otherwise. With the NAO tanking, I suspect the cold air is further south and therefore not only does Chicago see several inches of snow mid next week but the system could track SOUTH of Philadelphia, meaning a few inches or more from Philadelphia up to Boston later next week.

Below is the chart out at 132 hours or next Tuesday. See how the GFS shows a system formed along the southern boundary of the cold air and the precip area building.

Here’s by next Wednesday, notice the northward jog lifts the rain snow line up into New England.

And by Thursday, the low deepens to 988 but still is shown to track NW opf the major cities, keeping them in the rain. As stated already, the fact the NAO is tanking, should suggest a deeper Eastern trough and therefore a further south and east track. This is still a way out and lots can change, somehow I think the GFS is raising heights too much in the east and the trough is deeper, along with the air being colder.

While there is a lot of uncertainly at the moment regarding next week and the possibility of a snowstorm from DC to Boston, the next few weeks will be very interesting, especially once we get into December as the cold shots will continue to come down thanks to the -NAO/AO. Each shot appears to be colder than the last.

Hey speaking of the NAO/AO, check out this.. wow!

Finally, here’s the latest NAO.

and AO.

[/s2If][s2If !current_user_can(access_s2member_level1)]

Sign in to read the full forecast…

Not yet a member? Start your 7 day free trial

Create your free markvoganweather.com account today to get unlimited access to Mark Vogan’s premium articles, video forecasts and expert analysis for 7 days.
[/s2If]