Wednesday, January 22, 2020

Weekend storm much more likely to deliver for the high country without the help any arctic cold

Though the polar jet continues to show no signs of providing any help for the rest of January, the forecast has improved led mainly by a much better outlook regarding our weekend storm. The week will finish as expected with sunshine on Thursday boosting temperatures on the mountain to near 30 with the same being said for Friday except with the addition of some high clouds. The pattern for the rest of January will allow Vermont to enjoy a bit of "southern Rocky Mountains" winter weather. Cold nights, comfortable afternoons, some elevation sensitive snowfall and only a minimal amount of wind. Very atypical for Vermont in January but I am delighted for this outcome as opposed to a 2nd bad January thaw.

The weekend storm is anchored by a vigorous upper level jet stream feature that is expected to spin east-northeastward, just north of the Ohio River valley Friday. The initial surface storm will never successfully attain a significant amount of moisture before it occludes over Illinois and Indiana, but an influx of Atlantic Ocean moisture into the storm on Saturday will give this system a 2nd life over the northeast. Most importantly, the track of this regenerated storm has shifted inland which represents a massive improvement for us. We had two asks with this storm 1) The above-mentioned coastal regeneration capable of providing the moisture 2) An optimal "inland" but not too far inland track allowing Vermont to ascertain this moisture without accompanying warm air. These were tough asks, especially given the lack of available cold, but we are asking and it looks a lot better that we shall be receiving beginning Saturday afternoon. Ultimately this will evolve and become a "vertically stacked" storm meaning that the upper low will move directly over the surface storm. These situations create a very elevation sensitive dynamic. Snowfall accumulations, snow consistency, perhaps for a small period - precipitation type and certainly temperature will all be dependent on elevation. We should receive a decent burst of snow Saturday evening and then a lot of elevation sensitive snow Sunday, Sunday night and into early Monday. If the outlook for the storm can settle on the current consensus, snowfall totals will likely be less than 6 inches total for the low lying valley areas but over a foot across the high country. The snow consistency will also be pretty gloppy in these low lying areas but drier and more powdery above 2000 feet. This outlook is also likely to change somewhat so stay tuned.

As mentioned, we aren't expecting either a lot of wind or a lot of cold in the wake of this storm Monday. Temperatures will stay in the sub-freezing category but only by a few degrees on both Monday and Tuesday afternoons. Models have been flirting with the notion of a one day thaw in the mid-week period and this is in association with a storm system that has threatened to track well into Canada after originating in the southern plains. Fortunately, models have backed off this idea and this would leave Vermont with more of the same - above normal temperatures but not above normal enough to create problems for us. Midweek precipitation is still certainly possible (in some form) but this remains a wait and see situation given model volatility.

There have been hints of a more substantial jet amplification over eastern North America, Superbowl weekend. The polar jet is still glaringly absent and this leaves the door open for some adverse scenarios; that said, there are fruitful possibilities that are also in play.  There are no improvements on the horizon regarding any blocking in the Arctic or weakening of the jet in the Pacific but some cold air is expected to invade in the wake of our hypothetical Superbowl storm. This would ensure at least seasonable temperatures during most of the first full week of February.