Tuesday, December 13, 2011

Perhaps a Cold Christmas

For fans of White Christmases in the Delaware Valley, this post may not be for you. However, if you like snow you generally need at least some cold air around or nearby (although Snowtober proves that dynamics can win in the right environment!) and it does look like we have a shot of having a cold blast of some sort on or near Christmas.

The uber long ranges of the GFS computer model -- not always able to verify but can give hints about what's coming down the pike -- suggest a continuation of the rinse-and-repeat pattern we've had for the better part of the last week or so.  Cool for a few days, warm up for a cold front, then cool back down.   Another storm system for the early portions of next week (Tuesday and Wednesday) may bring some additional rain (with perhaps some ice at the onset to our north) before we cool down in the wake of that second storm.   A third storm may be timing itself for Christmas Eve or Christmas Day with a relatively similar outcome.  However, this one could tap into a colder surge of air that may work south from the Arctic and allow for a colder shot of air for a few days just after Christmas.    The upper level pattern that one run of the GFS suggests shows a bit of a ridge building into Alaska, with a trough over the Northeast and into Eastern Canada (where the core of cold will reside).  It wouldn't result in a pure arctic outbreak in this scenario as the core of cold passes to the north through New England and Eastern Canada but it would result in probably our coldest days so far this winter if it were to verify.

The storm that triggers this on the models would bring rain to the region on Christmas Eve night -- it would certainly not be a White Christmas if the GFS was right!   However, it would help usher in a shot of cold that will certainly reinforce the thought that it was winter around here.