Weekend near 50 then winter arrives

Skies will be mostly cloudy tonight with some patchy fog still left over. There is a slight chance of a shower or even a snow shower after midnight tonight as a weak disturbance and associated frontal boundary cross the region. High pressure will move in from the west tomorrow allowing skies to clear up. Highs will top out in the 40s to near 50 in Keene (~10C above average). The same goes for Sunday as well, with a renewed southerly flow developing as high pressure moves east of the region.

A storm system currently in the western US will enter the region Monday spreading a chance of rain through the evening hours. A strong cold front will cut through the area Monday Night, changing rain to snow north of the Mass Pike. Temperatures will fall into the 20s behind the front Tuesday morning and struggle into the 30s Tuesday afternoon. A chance of snow showers will continue through the day Tuesday and some light accumulation cannot be ruled out.

This storm will set the stage for FINALLY a possible TRUE pattern change as we near Christmas week. As the countdown reaches 10 days, the question that is on the tongue of most people is "Are we going to have a white Christmas?" The question has been answered by many weather organizations and professionals in the past few days. While many would think after a horrendous November and start to December, of course no snow for Christmas, that thought could be quite a ways off.

The storm system Monday will pull out to sea Tuesday Night. The low is currently expected to propagate northeastward possibly setting up what has been missing so far this winter: A Greenland Block. Currently projected is a block setting up a little further east than what would be prefered for solid winter weather, however it should be enough to get the ball rolling on what has been so far, a very dismal winter.

Below shows the GFS model forecast for blocking:





The new blocking will let us transition into a -NAO/+PNA pattern. This is also what is prefered for significant winter weather, however memorable snow events have occurred with a +NAO in place.

A more seasonable, and possibly below normal air mass will hold strong over New England for what appears will be a good while. Highs in the 30s and lows around 20 will be the forecast at least into Christmas week.

Two significant snow events are possible during this time period. The first one (Friday 22nd) had a strong signal earlier but now the GFS is wavering. The second one (25-27) continues to receive support from the GFS.

With the first potential just entering the 7-day forecast and the second outside ten days, it will be a while before confidence in these storms can be expressed. As has been the case so far this season, the GFS has a tendency to put the carrot in your face at day 10, wave it around day 5 and then pull it back day 2. In other words, dont count on anything yet.