This is a time of year in which normal climatology brings us lots of ups and downs in weather. We’ve recently had a few Novembers in which temperatures averaged a fair amount above average. This November often been Windier and occasionally Stormier than in those recent years.
This week of November 18th starts out seasonably cold and shifts over to seasonably mild temperatures before another transition to wintry temperatures occurs this weekend. This weekend: “Aye, there’s the rub.” Lots of uncertainty abounds, with large difference between the models, and their ensemble means. Sunday night, there were signs in the European model of a storm system which would have headed toward eastern New England and which might have given us a chance at some widespread snow. The Euro’s subsequent run took that storm farther north and east, with something of a cold blast moving in by Saturday night and Sunday. The GFS never showed that first Euro storm being close enough to us to give us widespread snow, nor did the Canadian. However, there is good agreement the coldest airmass of the season will be on its way this weekend with gusty winds and snow showers, along with some lake effect snow potential on a NW flow, which would focus the heavier LES on the hills again, well south. The GFS is considerably faster, bringing that arctic airmass in Saturday afternoon. I won’t dismiss that speed, since last week’s late week GFS wasn’t bad on the speed of Sunday night’s cold front. As of this Monday evening (bottom line) there are no good signs of a widespread heavier synoptic snowfall in WNY this weekend–though I’m not ruling out such signs recurring in future runs. But there’ll be no questioning the wintry atmosphere, with temps probably staying in the mid-upper 20s on a cold, windy Sunday, with a little moderation early next week. The GFS is chillier for Thanksgiving Day than the Euro, which has kept us consistently seasonable for that day. I won’t touch precipitation this far out.
For the bigger picture, the Climate Prediction Ctr (for newcomers…we just call it CPC) expresses high confidence for below average temperatures in the 6-10 day outlook, and average confidence for the 8-14 day outlook. That major 6-10 day cold anomaly may imply much below average temperatures for that whole stretch. However, I’m still expecting some ups within those downs. Here’s why. The indices don’t match up with a western ridge/eastern trough all that well. While I would expect the 2nd half, or even the last 2/3 of the weekend to be much colder than average, the pattern remains too progressive for a stable wrn ridge/ern trough to take up residence for too long a time. Plus, the positive heights which are showing up so frequently over the far SE also may be related to the lack of a persistently -NAO/-AO, and help to flatten the trough in the Grt Lks and NE. There continue to be no signs of a fundamental change in the PNA to cold/+ phase, so a western ridge which could force a cross polar flow simply won’t be there in the next 2 weeks. This doesn’t mean I’m expecting big Ups with any major above average temp periods…just not steady arctic air.
The MJO remains “incoherent”, weakly active, and is not expected to have a measurable impact on global weather in the next 2 weeks, at least not at our latitude. The ENSO forecast remains unchanged…neutral through next spring.