Wednesday, January 21, 2009

Pattern change = discontinuity

With regards to the potential I have spoken about for next week, there is a lot of model disagreement with the evolution of the energy in the southwest US. This is common for the breakdown of a +PNA ridge.

A cut off H5 low develops somewhere out west, but with a -EPO, we are back to the split flow pattern that we had back in December. Again, with converging jets in the east, this is an excellent set up for overrunning snows.

The timing for this is progged between Sunday and Wednesday, with multiple waves moving along a stationary boundary.

The issue is that with the time of year, and a very well established snowpack and antecedent cold, the axis of the snowfall will be shifted much further south, and in fact New England will likely remain dry. The focus should be over the Mid Atlantic region, where notable accumulations will be possible.

The energy festering out west is the next problem. These situations are historic for timing issues - when does the energy finally eject eastward? At this point, it looks like it should happen toward the end of the week. A lot of different solutions exist for this storm, and so there is huge uncertainty for this period. But a signficant winter storm looks likely for a portion of the eastern US Thursday into Saturday next week.

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