Welcome to the weather blog - a regular Monday through Friday discussion of the weather! You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is contact@mattnoyes.net. While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants. This blog is for you, so I hope you enjoy it! -Matt Noyes
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Matt's Weather Summary: Our pattern continues - fast-moving, energetic, but moisture-starved disturbances racing across New England, caught in the jet stream winds aloft. Without much moisture in the atmosphere, the result is for most of the snow showers associated with each disturbance to fall in the mountains of New England, with clearing skies between each fast moving energy center.
New Englanders once again find ourselves between systems and enjoying sunshine this Thursday morning - though still very chilly sunshine. With another energy center racing eastward, high altitude "cirrus" clouds will once again increase Thursday afternoon, then thicken during the evening with an increasing breeze through the day. Showers of snow will develop with the passage of this energetic disturbance across the mountains of Northern and Western New England again Thursday night, but shouldn't amount to much in most areas. This pattern of rapid-fire disturbances certainly drives home the point that there's plenty of energy flowing through the atmosphere. But in order to develop a strong storm system, this energy from the north must link with moisture from a southern stream disturbance moving across the Southern U.S., and without that interaction, these energy centers have not grown into larger storms.
By Friday, however, a stronger disturbance will be racing across the Upper Midwest. A piece of this disturbance will break off and sail due east toward New England - bringing lots of clouds through the day on Friday. With a slow feed of milder and more moist air moving into New England at the same time this piece of energy moves through aloft, a few rain and snow showers are likely here and there on Friday, and a round of snow...mixed with rain south...is likely Friday night, when areas from Springfield, VT, to Laconia, NH, to Portland, ME, points northward may pick up 2"-4" of snow. While this northern piece of the stronger disturbance moves overhead, however, the primary energy center farther west will be strong enough that it's likely to buckle the jet stream winds over the Ohio Valley. This will allow a new storm center to develop at the surface, dipping southward far enough to interact with plentiful moisture from the Gulf of Mexico. By Christmas Eve Day, the Gulf moisture and northern stream energy will be coming together for a developing surface low pressure center over the Tennessee River Valley. It's likely that the Christmas weekend will feature this storm center repositioning to the coastline, then moving northward toward New England on Christmas Day itself. Getting a storm to New England is an obvious first step for a fresh round of snow for a White Christmas and Hanukkah, but the second ingredient that's equally important is cold air. While there will be plenty of cold air around this week, an expansive area of high pressure over the Southeastern U.S. feeds milder air slowly northward, and by the weekend, our cold air begins to release its firm grasp on New England. The result will be a clash of airmasses, an approaching storm, and plentiful moisture all moving toward New England for Christmas Day.
But before these weather factors converge on New England, milder air will push northward Saturday, in advace of the developing storm that will still be found well to our south and southwest. There's likely to be some lingering clouds early Saturday...leftover from Friday night's snow showers mentioned above...but at least some sun will break through the clouds at times on Saturday, and this...combined with a southwest flow of air...will help to bring temperatures well above freezing in most of New England. Christmas morning may bring some dim sunshine, though clouds will be on the increase and will thicken through the first half of the day. With the jet stream winds - the fast river of air aloft that steers our storms and acts as a thermostat for the atmosphere, separating cold air to the north from warm to the south - shifting to a south-north orientation, moisture and warmth will be allowed to stream northward up the Eastern Seaboard with a developing area of low pressure on Christmas Day. The result will be enough warm air and moisture in place for rain to develop in Southern and Eastern New England Christmas afternoon, with snow developing in the northern mountains. Southern rains and Northern snows will continue Sunday night, with a sizeable storm in the offing for ski and snowmobile country. By Monday, enough cold air will wrap around teh back of this storm...and another bundle of energy may come racing up the coastline...to bring at least the threat for some snow to all of New England for the first full day of Hanukkah.
Only a couple of quiet days will follow before the same storm system that wreaked havoc in Japan last weekend makes its way to our corner of the globe after traveling the Pacific, rising up into Northwestern Canada, then dropping south and east again. How this potent system will play out for us - sometime likely either side of the 28th - is of course, still up in the air. The most likely result of it, though, would be storm development either near the East Coast, or more likely off the coast to our east, but close enough to pull down a blast of deep cold air for the end of December.
Stay safe while running those errands today.
Matt
Matt's Technical Meteorological Discussion: Updated Thursday, December 21 at 1:10 PM
Anybody else still have a lot of Christmas shopping to do? Me too. Is that a good enough excuse for a briefer than normal discussion today? :) You can always feel free to reference yesterday's lengthy post for more details if the following doesn't whet your appetite!
Short term is looking pretty much on track...interesting to see the high altitude clouds bubbling up so dramatically this morning in Western NewEng...now the broader shield of cirrus is moving in. That first burst of cirrus was so interesting because it really marked the beginning of a change in the weather pattern - at least in what the weather pattern has been bringing. By this I mean that each northern stream disturbance that's been racing overhead has brought a reinforcing shot of chill. Meanwhile, remember a few days ago in the techie discussion we examined warm air building across the Western US, and stretching up the Rockies all the way into Canada. In fact, I'd included a skew-t plot to show the significant inversion thanks to anomalous warmth aloft. We considered that with a continued northwest flow aloft, eventually the shortwaves would begin carrying this warmth far enough south and east into NewEng, and this morning's cirrus clouds marked the beginning of that process, as today's shortwave has begun the process of dragging down the warmer air aloft, and this sudden surge into our cold dome aloft resulted in the blossoming cirrus. A good indicator from nature that our thoughts on the pattern are...thus far...on track.
The actual shortwave responsible for this showcase of nature will move through tonight without much more fanfare than lots of clouds with mountain flurries that will be weaker than the last few nights. But as the shortwave passes early Friday, it leaves behind a mid-level frontal boundary that will serve as the focal point for mid-level cloud generation and Friday should be mostly cloudy as a result. Still, the lower levels will be relatively dry excepting Vermont and the Mountains of NH and ME, so most of the day will be dry for a lot of folks though some snow showers are likley to develop in the mountains during the afternoon and will become more widespread by evening.
We look to be on-track for a Northern NewEng snow with a sharp cutoff in precip on the southern edge Friday night, as axis of greatest QPF will be centered on axis of greatest low level warm advection. At this point, would expect a general 2-4" snowfall from roughly Springfield, VT, to Laconia, NH, to Portland, ME points north with slightly lighter amounts possible along that southern periphery.
Saturday became a frustrating forecast early this morning. Those of you who read yesterday know I was concerned about low level moisture trapped beneath an inversion and therefore held temperatures in the upper 30's under cloudy skies. The 00Z runs were dry at all levels and made it very difficult for me to hold that line, so I added sunshine, though I still refused to raise average highs above the lower 40's out of anxiety about my initial concerns. Now, the 12Z NAM clearly holds in lots of boundary layer high RH, which will mean a low gray deck on Saturday. Surprise, surprise. The good news is that with a 925 temp of 0 to +1 C in Southern NH/Nrn MA with a dispersed gradient, even under cloudy skies average max temps should still fall near 40, so the conservative move will help with verification.
By Sunday it's very interesting to see the NAM coming around to the solution discussed here yesterday. At that point, I found no operational models for support of my idea that we'd have one vort with an associated coastal wave on the slowing cold front Sunday, then this wave would yank down cold air, and the next wave would ride up Sunday night into Monday with more snow for more of NewEng. The NAM...as best I can tell of a cursory view of the 12Z models...is the first and only model to key in on these waves, but as mentioned yesterday, with the upper flow going nearly (though not totally) parallel to the surface flow, this does favor a slowing of the cold front, a seeping of cold air south, and another coastal wave on the front as the next vort max rounds the trough and heads northeast. So, I think the best forecast for now is to not jump whole-hog on the GFS and its compadres, and therefore just put a chance of showers in the forecast for later Christmas Day with snow expected in the mountains. I am quite confident that whatever falls in the mountains will fall as snow, because we'll have a cold 1018 high located over Western Hudson Bay Saturday afternoon that will move to James Bay and strengthen to 1022 mb as it continues sliding SE overnight Christmas Eve. This should be more than sufficient to lock/build in cold air for the north, then supply it for wave #2 for more of interior NewEng on Monday.
And...surprise, surprise...energy creating a juicy storm that may or may not miss us to the south around midweek next week, but either way a blast of serious arctic air comes surging in. This is associated with last weekend's Japanese storm, and should deliver some brutal arctic air - colder than the models would expect - as this storm continues to do its dirty work a whole half-world away.
Time to brave the crowds. Good luck to you and me both!
Until tomorrow,
Matt
