A Snow-Gone Conclusion

Monday 1/28 7PM: That was certainly a nice taste of winter - near blizzard conditions for about 6 hours Sunday night and all told about ten inches of snow on average across the Cape. (Final totals are available here.) The wind did not get quite as high as I thought it might, but still, frequent gusts to 50 mph will do and buoys offshore reported wind gusts to 70 mph - which was what I feared we might deal with at times Sunday night and Monday morning. In terms of impact, the big saving grace was a much colder storm than expected. Temperatures actually fell through the life of the event, eventually ending up in the mid to upper 20s late Sunday night. The north wind kept readings from rising into the 30s. That made for a far drier snow, which saved us from widespread tree damage and numerous power outages.

Anyway, it's time to look ahead and see what's coming up over the next 5 days or so...a hint: look at the title.

It's not unusual for big snowstorms on the East Coast (does this qualify considering we here on the Cape were the sole beneficiaries?) to signal pattern changes. Plenty of research illustrates the changes that follow a large cyclone as it lifts into Atlantic Canada. Sometimes these storms are followed by a long-term switch to colder weather as troughs develop in eastern North America, while other times, they signal a return of milder air as the cold air lifts out behind the storm. It's all relative to the jet stream. While our blizzard didn't necessarily fit the mold of a traditional Mid-Atlantic / New England nor'easter pattern-changer, it still wants to signal the start of an overall pattern change.

If we look back at what we've seen so far in January, we notice three distinct temperature regimes and a correlation to storms. Let's look at Hyannis' temperatures so far this month: The first week of the month saw a quick but strong cold snap, with highs on the 3rd failing to reach 20°F and overnight lows dropping to 6°F on the 4th. Daily means were nearly 20 degrees below average. This was pattern 1. However, after the 6th, and straight through to the 14th, we saw a prolonged stretch of mild weather as pattern 2 gradually took hold (this one sans storm systems), with daily readings reaching into the 50s four times - resulting in daily means some 20 degrees above normal for several days in a row.

But, on the 14th and 15th a strong coastal low developed southeast of the Cape and deepened into a big storm over Nova Scotia. That storm dumped 7" of snow in Boston and 10.5" on Portland, ME. That big coastal low also got rid of the warmth and brought on a 2 week stretch of near normal temperatures - or pattern 3 of the month. If we say the average temperature during that 2 week span is supposed to be about 28°F (roughly 36 by day, 20 by night), we see that the period from the 15th to the 27th averaged out at .3 degrees below normal - so essentially a zero departure given the rough initial estimate. And what happened on the 27th? A big coastal storm. And what are the simple computer outputted numbers for the next 7 days?? About +8°F when compared to average. Welcome to Pattern 4.

So a mild spell is on the way, beginning Tuesday and likely holding through at least next Monday. While this spell of mild weather won't rival the mid-January warmth we saw, we can expect several days with readings unto the 40s, with perhaps a 50°F reading on Friday depending upon the exact track of low pressure. Speaking of which...

We have a couple storm systems to track this week and both look like rain producers here on the Cape (snow-gone conclusion). The first arrives on Tuesday night and is essentially a cold front attached to a major low pressure center that will track from Texas to the Great Lakes Tuesday and Wednesday. Out ahead of this front, mild southerly winds will tug warmth and moisture northward into New England and send a wave of rain across the region. Given the fast movement, rainfall totals should average under a half inch - but a few quick downpours are possible and some strong southerly winds are likely. Behind the front, gusty westerly winds will develop and colder air will head into the region. Now, if you look at the current temperatures across the nation today and you see all the bitterly cold air over the Northern Plains you might think that the air coming in behind the front would be extremely cold. However, the strong low pressure center heading into Canada will actually help pull the coldest air into Ontario and Quebec - leaving us with near normal temperatures on Thursday. But that cooler air won't last too long...

Our next storm is another inland runner on Friday with a low track similar to its mid-week predecessor. This one will have a stronger surge of warmth with it and should send a solid slug of moisture into the region - with one inch rains possible. In addition, the system has the potential to bring another round of strong winds. The big trick to the Friday forecast will be high temperatures as those numbers will hinge upon if and where a secondary storm tries to form. Should a coastal low take hold, cooler air will hold tough and readings would be capped in the upper 30s and low 40s. Should the primary storm remain dominant, temperatures in the low 50s will be possible.

Things will dry out and cool down over the weekend - but readings will still be slightly above normal both days as the coldest air remains locked up to our north and west.