It has been a strange few months in the weather department. A record snowy October, statewide, followed by respectable snowfall in early November, only to fall off a cliff and enter a prolonged "snow drought" from the latter half of November into December. It's strange to be staring out at green(ish) lawns on the 22nd day of December and open water on many Minnesota lakes.
The serene weather honeymoon is about to come to a close, with a sudden, flaky fury. The arrival of arctic air will trigger a period of accumulating snow Wednesday, mainly PM hours as northwest winds gust over 30 mph, creating blow and drifting challenges, especially outside the Twin Cities metro area. Winter Storm Watches have been issued by the National Weather Service, and based on model trends I suspect those watches (and possible warnings) may be extended into the Twin Cities and much of Wisconsin.
Peak Wednesday Wind Gusts. Models predict winds gusting as high as 36 mph in the Twin Cities tomorrow, with 40-60 mph gusts possible closer to the Red River Valley. The criteria for blizzard conditions is sustained 35 mph winds and visibilities falling under 1/4 mile. I think we'll have blizzard conditions across much of Minnesota Wednesday afternoon and Wednesday night, when travel conditions will rapidly go from bad to worse.
3KM NAM Model. NOAA's high-resolution NAM model prints out 4-5" of snow across the metro (which I think is realistic based on everything I'm seeing) with higher snow totals north of the Twin Cities. The more I look at the data and model simulations the more convinced I am that this will be, in fact, a "plowable" snowfall for most of Minnesota and western Wisconsin.
3KM NAM Model. Snow will spread across the state during the day Wednesday, with plowable amounts likely across much of Minnesota. One of NOAA's models (above) shows 2-4" amounts, which may be on the low side.
European Model. Do I buy the predicted amounts at face value. No. But the trend for ECMWF is more snow with each passing model run. Meteorologists like it when models agree (which is fairly rare) and we look for trends over time: are models becoming snowier or less snowy with every passing run? Although we may not pick up a foot of snow in the metro area, my weather-spidey-senses hint at plowable amounts as high as 4-8", possibly more.
Important note: whatever falls will be whipped around by high winds, creating significant drifting, so measuring the snow may be tricky late in the day tomorrow. But I sense it's going to be a big pile by Christmas Eve.
A Nippy Christmas Eve. Although snowfall totals are still up in the air (always) there is no doubt that Christmas 2020 will feature a whiff of arctic air. Subzero wake-up temperatures Christmas Eve are likely from the northern suburbs of the Twin Cities to the Canadian border, with daytime "highs" holding below zero over the Red River Valley; only single digits for St. Cloud, the Twin Cities, Mankato and Rochester. Factor in a stiff wind and it will feel like -15 to -20F on Thursday. Ouch.
Bottom line: significant snow, wind and near-blizzard conditions are increasingly likely during the PM hours Wednesday, and travel will probably become treacherous after lunchtime tomorrow. That, and it sure appears that the pattern is shifting: we are heading into a colder, snowier weather regime as we end 2020 and enter 2021. It would be premature to write a real winter off just yet.