Friday, January 13, 2012

How Sustained Will Cold Shot Be

Much was made ado about more sustained cold about a week ago and that this upcoming shove of winter would last a bit longer.  Well, it will last a couple of days longer than the shot of winter we had about ten days ago but it won't last on the order of ten days like we discussed in our post last week.  The next ten days will feature more of the yo-yo January weather that's been "the norm" this year, only this time featuring cold for three more days, warm for a day (as a storm system moves through and warms us up ahead of the front), and then cold for two to three more in the wake of the frontal boundary.   The upcoming cold won't be anything that we're not used to...and very "typical" January weather as temperatures will hang in the 30's on the cold days, potentially warming into the 50's on the day(s) where the front is around next week.

Getting this cold pattern to sustain itself is potentially an impossible task, however.  While there was a shift in the pattern in the Pacific, the lack of a sustained blocking pattern in the Atlantic will prevent any sort of sustained cold pattern from setting up for us on the East Coast.  The longer range modeling is suggesting a milder look will begin to take hold after eight/nine days, with the week of January 22nd potentially quite mild for the Eastern US.  The country sets up in a bit of a zonal/gradient pattern, with the Atlantic featuring a bit of a ridge of high pressure with the Pacific featuring a bit of a trough farther out.  Given the broader nature of the trough/ridge relationship, it results in a cold setup in Alaska and Northwest Canada but returns much of the US to above average temperatures...with cold fronts sliding along on the border and putting a dent into the chill occasionally to our north.

The week of January 23rd might be one of the warmer to average weeks we've seen in a while.  Not going to say it's quite the warmest week of winter but it's possible we get a full blown January "thaw".   My tongue is firmly implanted in cheek when I say that given how little winter we've really had but if this look in the computer models from the GFS and Euro holds -- we could get a sustained period of at least 50 degree weather for the week after next...with 60's a distinct possibility and the chance it could approach 70 late in the month.    We aren't saying it necessarily will hit 70 but that the possibility is there if everything breaks right.

The pendulum swings back in a warm direction after a week generally on the cold side.

For ultimate fun, I have the complete list of January 70 degree days (all 13).   The list is a rare accomplishment to make but we have done this...but in 1906, 1932, and even 1950 I could imagine the snow starved's reaction to the utter lack of winter weather when the thermometer cracked 70 on multiple days within January.   This winter, for us at least, is shaping up a bit like 2001-2002 or 2007-2008...occasional shots of cold sandwiched around those warm shots that last a lot longer.   Whether that pattern persists into February remains to be seen but the latter portions of January, at least, are looking pretty warm at this point.