To be notified of news about this storm and others through the season:

For computer model forecasts, visit our charts page.

Nor'Easter threat early next week

There is a growing threat of a pair of systems striking the Northeast early next week, as is evident in the computer models. The first storm should pass just south of New England on Sunday, spreading very light accumulations of snow (generally 1-3 inches) across much of the area. In the model chart note the transition between the red and blue dashed contours roughly depicts the rain - snow line and the green shaded area represents precipitation.

By running the models several times and slightly tweaking the initial conditions we can get a measure of how confident we are in the forecast by seeing how much the model output changed. The GFS is maintaining above normal confidence (represented by the green area in the chart) in its temperature forecasts. Wind confidence can be used a proxy for confidence is the track of the storm, as the two fields are very dependent on each other. The wind confidence drops dramatically below normal (represented by the red area) as the low passes by New England.

However, there is a much bigger question looming for Tuesday. A much larger storm is expected to again move south of New England and the impact of this storm still remain very much up for debate. The GFS (the main American model) is calling for a direct hit on southern New England. This forecast is showing a class December Nor'Easter bringing moderate snowfalls across the region, especially southeast Massachusetts. Southern New England could see widespread accumulations of 4-8" of snow. Of course these accumulations are still very rough and it is far to early to be talking seriously about this number.

The UK model is calling for the second low to track much closer to the coast and change over the snow to rain in southeastern New England. In the UK chart, the red contour passing down the back of the L (the 540 decameter thickness line) is roughly the rain - snow line.

The Canadian model is tracking the low much further out to sea, but it is still spreading snow back into the Northeast. In this forecast all of the precipitation over the Northeast, which is represented by the shading, is falling in the form of snow.

0:Model forecast of Sunday's storm
1:GFS forecast of the 2nd storm
2:UK model forecast of the 2nd storm
3:Canadian model forecast of the 2nd storm
4:GFS temperature confidence
5:GFS wind confidence

Posted by Bryan Woods | Permalink