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El Nino In The Driver Seat - More Mild Air Ahead

Lots of maps being circulated by weather purveyors these days (myself included) showing bright oranges and reds across the United States. Does it mean it's time to pop the top on a corona and head to Nauset Beach? Ah, no. Those 'warm' maps are warm by winter standards, but not by most measures of actually being warm. This was a point that the Capital Weather Gang recently addressed and bears repeating, considering our slightly warmer than average winter outlook. It's still December. And 'warmer than average' just means your nose hairs won't freeze, most of the time. Let's take a closer look at the setup ahead.

For starters, none of this is unexpected. It's a classic El Nino setup with strong ridging of the jet stream across Canada and the northern United States. The Arctic Oscillation is positive, bottling up the truly cold stuff. It's been part of the seasonal outlook for a long time, and is verifying nicely. El Nino is peaking around all-time record strength as we speak, and is expected to decline as we head deeper into winter. Before its decline, the impact will be pronounced for the Lower 48. After a very mild November (9th warmest on record in Boston), we're expecting an unusually mild December to follow suit.

ecm_eps_t850a_5d_conus_11

ECMWF EPF temperature anomalies at 850mb for next week. Just a ton of milder than average air everywhere you look, particularly for the far northern U.S and into Canada. Source: Weatherbell

You can pick any model guidance you like, but they're all screaming the same thing. Next week is particularly impressive with even the ensemble mean anomalies (which normally are more smoothed out and less dramatic than operational runs) showing incredible 'warmth' across almost all of the U.S. In particular, Canada and the Midwest will see a remarkably mild stretch. The Arctic Circle may even manage some above-freezing temps - no easy feat in December.

This is the way things look through at least the middle of the month. After that, there are a few signs that the pattern will become more volatile. But I don't have high confidence in that outcome at this time. Some of it may be climatology in the models, and we'll find out in due time. I'm skeptical that we'll get much prolonged cold at any point this month. Let's take a look at the dailies ->

 

End of This Week/Weekend:

Thursday is our transition day with gusty WNW winds (30-40mph) and drier air punching its way into southern New England. For the snow lovers - some solid 6-12" amounts are expected for interior Maine, and we may even luck out with a plowable snow in northern New Hampshire. Around these parts I wouldn't rule out a flurry or two across the higher terrain of southern New Hampshire or northern Massachusetts.

weekend

This weekend: Cancel weather. Giant area of high pressure firmly in control, with the only U.S. storminess along the Pacific Northwest coast. Source: Weatherbell

Another cold front swings through Friday, but is moisture starved. There should be a deck of broken clouds along in during the afternoon/evening, and we may squeeze out a sprinkle or higher-terrain flurry. Not much fanfare. Both Thursday and Friday will see highs in the upper 40s, which is on target for this time of year.

The weekend looks absolutely glorious with abundant sunshine and warming temperatures. There are a TON of holiday strolls and events planned across the region, and Hanukkah begins Sunday evening. Our weather will certainly cooperate. We'll jump well into the 40s on Saturday with blue skies and light winds. By Sunday afternoon we'll soar into the mid/upper 50s, and I wouldn't even rule out a few towns at 60F. That's 10-15º above average. Comfortable as it could possibly get at Gillette as the Patriots take on the Eagles.

pats

 

Next Week: Potential Coastal Storm:

We're still in the 50s on Monday with a dry start to the week, but onshore winds should hold us back in the mid/upper 40s on Tuesday (still above average). The time frame to watch is Wednesday into Thursday, as high pressure starts to shift offshore and an area of low pressure attempts to form near the Mid-Atlantic. With the high sliding east, there should be a long fetch of southeasterly or easterly winds leading up to this storm, which would likely keep us mild enough for all rain. The only chance for snow is if it can really intensify and then dynamically cool down the column, bringing perhaps some higher elevation snow. That's an outlier for now, but we'll keep an eye on it. The overall trend has been for a relatively weak storm center and a long onshore fetch, bringing rain and cooler temps for Wednesday and Thursday.

lows

ECMWF EPS low locations for next Wednesday. There's still a wide spread, and the question is whether high pressure shunts it off to the south out to sea, or it heads up along the coast. Either way, it should be mild enough for rain. Source: Weatherbell

After that another tall ridge slides east and pumps up the mild air again. I'm expecting well above average temps for Friday into the weekend, and more snowless weather. Once we get past the weekend there's a chance things will cool down and look a little more wintry, but as I mentioned above there's reason to believe the overall mild pattern will dominate December.

ridging

Colder air dives into the west next weekend, but very mild air surges up the East Coast. Source: WSI Energycast

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