The SI Weather
18Dec/12Tue

1:30 PM | It’s not the end of the world, but a significant pattern change begins on Friday – the 1st day of winter

Discussion

Winter is now hitting on all cylinders across much of the world and it is about to arrive in the Mid-Atlantic region - both on the calendar and in the atmosphere.

In the US, snow has piled up over the last couple of days across northern New England and also in many higher elevation locations in the western US. Widespread heavy snow will pile up later tonight through Thursday night from the southern Rockies to the central Plains and Upper Midwest where more than a foot is possible. Meanwhile, Alaska has continued to be very cold with Fairbanks bottoming out at -48°F yesterday morning – their coldest reading since 1999. Around the world, hundreds of cars are trapped in 10 feet of snow in Ukraine (one source region for our cold air), China is suffering through one of their coldest Decembers ever, Russia has their coldest winter in 70 years, and western Canada and Europe have also had some serious cold and snow.

What about here in the Mid-Atlantic? The overall pattern changes significantly on Friday (happens to be the 1st day of winter) when a strong cold front ushers in colder air to the Mid-Atlantic region. While this air mass will not be bitter cold, it’ll be quite a change from what we’ve experienced during much of this month so far. Rain will fall heavily at times Thursday night as the front moves through and there might even be a rumble or two of thunder. The rain could end briefly as snow early Friday as temperatures drop, and the winds will pick up in intensity as the day wears on. In fact, winds will stay quite strong right through Saturday night with 40+ mph gusts possible at times. This pattern will result in a significant “lake-effect” snow event later Friday through the weekend in those locations downwind of the eastern Great Lakes such as western and northern PA. There can also be some snow shower activity here along the I-95 corridor later Friday and Saturday as the storm hangs around the Northeast US.

Looking ahead to next week, the cold air tends to stick around and overall temperatures will likely average below normal for the last week of the month. Another strong storm is likely to cross the country in the Tuesday/Wednesday/Thursday time frame and it will be loaded with moisture and there will be lots of cold air around. Some computer forecast models have the storm heading towards the Great Lakes by the middle of next week which would produce rain around here, but there are reasons to believe that it could take more of a “southern route” to the Mid-Atlantic coastline due to expected upper atmospheric blocking pattern setting up in southeastern Canada. A “southern route” for this next storm would certainly increase the odds for snow around here by about the middle of next week. Very cold air is likely to follow this storm at the end of next week.

Stay tuned as the weather gets quite interesting beginning with the vigorous frontal passage on Thursday night and early Friday.

Filed under: DEN, LA, NYC, PHL, WMA Comments Off
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