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Tuesday, January 20, 2015

Watching two more potential storms over the next week but both are far from guaranteed

2 days and 15 inches of snow since the last update and once again there are some new forecast ideas that will require an introduction while other ones might need to be scrapped. The changes today are not quite so drastic compared to last week but it is nonetheless remarkable how inconsistent medium range forecast ideas have been. Even the normally reliable European model has generally failed to lock on and stick to an idea for more than a day or 2. The American GFS model ? Well, this numerical weather prediction package just underwent a major upgrade where the resolution was increased in the long range, product fields were added and model components were changed amongst other things. The results on a strictly empirical level certainly leave something to be desired. Typical GFS model biases remain and these biases seem to result more from problems with the model physics than any resolution related shortcoming. I digress however. Numerical Weather Prediction are the fruits of some hard labor by many others and it has made amazing strides over the last quarter century and should continue to do so over the next quarter century.

Still nothing doing from Wednesday clipper and the overall forecast appears free of accumulating snow for the duration of the week. Temperatures will remain within few degrees of seasonable levels and visibility should stay pretty good given the season. Not one, but two updates ago we had discussed  a potential southern branch feature becoming our next significant weather feature. In the last update I squashed this storm as it looked "squashed" by several different computer models yielding hardly a dent anywhere on the East Coast. As of Tuesday afternoon, this system looks far less "squashed" again. It is rising to prevalence out of the ashes and is expected to leave a mark on coastal areas. For most the storm will bring rain which might change to snow as the storm exits. If the storm continues to appear stronger and farter north and west with an expected storm track, I will get very excited for Sunday. As of now it is still a whiff. It is also killing the potential clipper I had advertised as the cause for some light snow Saturday. Lets just hope for one or the other.

The overall long wave pattern will become extremely amplified as this storm departs Sunday. It will become this way without the overwhelming weight of the Polar Jet which means the East Cost will be a "powder keg" of sorts. Indeed, the next clipper which is expected to begin its approach late Monday could very well explode into something of great significance Tuesday in this set up and will warrant a close watch over the next few days. We could see ideas  with the Sunday storm and this potential Tuesday storm shift as models refine the forecast and digest the various ingredients associated with all these players. It will turn chilly later Tuesday into the middle of the week and we should see more polar jet energy by late in the week bring a reinforcing blast of potentially even colder temperatures.

The polar jet is then expected to recede just slightly into early February as we lose some support from the NAO but not enough I think to completely eliminate the cold or pose a significant risk for a thaw. The biggest upper air feature in the Northern Hemisphere by early February will be a large blocking ridge which is expected to settle in the Bering Sea. This means the Polar Jet moves south but should focus the arctic air on the western US. Jet energy undercutting this ridge in the Pacific should provide some energy for 1 or 2 well organized storm systems in early February. No reason to think that something big can't happen in this period but we will just have to wait for anything concrete to show its face.

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