Welcome to the weather blog - a regular Monday through Friday discussion of the weather! While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants. I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible. You'll find a quick weather synopsis and a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. My email is contact@mattnoyes.net. This blog is for you, so I hope you enjoy it! -Matt Noyes
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Matt's Quick Weather Synopsis (New!): Weak upper level disturbances moving over New England will bring more clouds than sun to Northern New England today with a few mountain snow showers, while the rest of us enjoy a blend of sun and clouds. While temperatures will rise above freezing through most of New England, an active southwest wind will bring breezy and therefore brisk day. Overnight Tuesday night, expect a nearby weak storm system moving through Southern Canada to bring a period of light snow with a couple of inches of accumulation in the Northern third of Maine. Southwest winds continue to blow on Wednesday, ushering in mild air for one and all, with temperatures climbing into the 40's under a pleasant blend of sun and clouds. Look for a repeat on Thursday before a stronger storm sweeps wind-driven rains and embedded thunder through New England Friday afternoon. This storm will yank a chunk of bitter arctic air into New England for the weekend - with high temperatures only in the teens in Southern New England, and in the single digits across the North Country! -Matt
General Weather Summary: A tremendous difference in temperature can be found in the morning surface analysis from the Northern Tier of the United States where temperatures are starting some 20-25 degrees, to the Southern Tier of Canada where Tuesday has dawned with temperatures some 20-25 degrees BELOW ZERO! Yikes! This well of arctic air will remain locked in Canada for the time-being, as the jet stream winds aloft - the fast river of air that steers our storms and acts as a thermostat for the atmosphere, separating northern cold from southern warmth - will lift to the Canadian border. This pattern change and sharp temperature difference along the Canadian border means two things for New England: 1) Warmer air will move in as we transition closer to that southern side of the thermostatic jet stream, and 2) Frequent disturbances will move across the far reaches of Northern New England, bringing periodic showers of snow and rain to the Canadian border.
As the warmer air takes aim on New England and is on the move northward, southwest winds will continue to increase in intensity on Tuesday - gradually ushering in this new airmass. While multiple weak upper level disturbances caught in the jet stream winds aloft will keep more clouds than sun - and even a few mountain flurries - in place across Northern New England, the remainder of our six-state region will enjoy a brisk blend of sun and clouds for most of the day Tuesday, with dry air in place through most of the atmosphere and a few high altitude cirrus clouds streaming overhead from time to time. The active southwest wind, though gradually bringing in a milder airmass, will add a bit of a chill to the air and those with outdoor plans may want to bring the hat and gloves along.
Yet another disturbance will move across the Canadian border Tuesday night, bringing a period of light snow to Northern Maine, where a couple of fresh inches of snow will fall by Wednesday morning. The rest of New England will remain quiet with passing clouds and low temperatures once again dropping just far enough below freezing for areas of black ice where daytime melted snow refreezes, especially on walkways and secondary roadways.
Those of you who read regularly will probably remember that over a week ago you and I began eyeing this brief pattern change together - really more of a weather pattern "reshuffling," whereby mild air returns for a few days before we jump right back into a cold and likely stormy pattern. We've arrived upon that pattern change, and beginning Wednesday this important shift in the weather pattern will make itself evident. The jet stream winds aloft flow in a wave-pattern across the globe, with ridges (bumps) and troughs (dips). The Eastern U.S. has been in a trough of late, which means New England has fallen on the cold side of these atmospheric winds - and we've felt the results! As the jet stream shifts northward and rises directly over New England for the middle and end of the week, we shift to the milder side of life. With very few strong disturbances for the jet stream to steer our way, the weather will be fairly tranquil for midweek.
Thursday, a stronger storm system will begin taking shape along the clash between cold and warm air along the Northern Tier of the Central and Western United States, and moving through the Central Rockies and Midwestern U.S. Ahead of this storm, a reinforcing shot of warmth and moisture will stream northward, at the same time cold air oozes southward from Eastern Canada. The result will be precipitation developing along the Canadian border again Thursday evening into Thursday night, and if enough cold air is in place, some limited accumulating snow would be possible. By Friday, the approaching storm center will bring periods of rain for all of New England, especially during the afternoon, along with gusty winds and one last mild day before a cold front sweeps through. This front is likely to bring a few Friday afternoon thunderstorms with it as it pushes through New England, and bitterly cold arctic air will come rushing in behind this front. In addition to the possibility of rapid freezing of standing water Friday night (dependent upon how much rain falls on Friday), this will set up a truly frigid weekend for the Northeast, with highs only in the teens for Southern New England Saturday and Sunday, and in the single digits across the north!
Remember that the mild air this week is truly just a reshuffling of the atmospheric pattern, which means that this bitter blast of arctic air - in my estimation - is a return to reality, and a return to a cold, wintry and at times stormy pattern that will persist until the end of the month, when another brief turn toward mild weather may surface again. In the meantime, there will be a couple of chances for storm - strong indications have been persistent for a storm sometime around next Tuesday, though with a storm track to our south, a snowstorm looks to be in the cards for the Mid-Atlantic, while here in New England we'll be watching this storm carefully, as the northern shield of snow may bring accumulating snow our way, and in addition, the storm will strengthen and turn north parallel to the coast at some point, and how close it hugs the coast will be another factor we'll watch carefully. Chances for snow will continue later next week, as well, so there will be plenty to watch.
Enjoy your Valentine's Day!
Matt
Matt's Technical Meteorological Discussion: Updated Tuesday, February 14 at 1:35 PM
Short term forecast is fairly straight-forward. It's a baroclinically charged atmosphere in place along the Canadian border with a 50 degree temp difference over about 350 miles centered along and just north of the US/Canadian border. This will become important in the forecast for Northern Maine, and will be worth paying attention to for the remainder of Northern NewEng in the short range, and for the rest of NewEng by the upcoming weekend.
Multiple weak shortwaves are prompting snow showers and continuous light snow from the northern Greens east through the Mountains of ME and Northern ME. This ribbon of clouds and broken precip extends westward thousands of miles, just south of the baroclinic zone, then curling SW across the Rockies and tapping moisture from the SW US upper low, which is in turn feeding off a Pacific flow. Overall, a rather remarkable train of moisture and energy not phasing with the Northern Stream, but instead trickling into it. In fact, the lack of phasing is what keeps the next few days dry, though a strong vorticity maximum dropping into the Pacific Northwest this afternoon has plans to change that by the end of the week.
But before we become too deeply entrenched in talk of the pattern and its repercussions in the medium and long range, let's briefly address the short-term first. Snow showers and heavier squalls in Northern and Central ME are the most intense snow in NewEng today - convective creatures working off the aforementioned baroclinicity and shortwaves rippling through the fast flow. I expect another shortwave to interact with this baroclinic zone overnight, and as it moves east the area of snow associated with it moving thru MI will propogate east into Northern ME with a couple of fresh inches of snow. Elsewhere, passing clouds will be the rule overnight with lows similar to or perhaps just slightly above last night's.
Mild flow continues Wed and wtih rising heights and SW surface flow, warming is evident thru all levels. Even with fresh snowpack, this warmth should boost temps into middle/upper 40's wtih good mixing and sunshine thru cirrus. Xpct areas of fog and more widespread black ice where we drop below freezing Wed Ngt. Continued mild flow Thu with a bit more in the way of clouds for most of NewEng as a couple of vorticity lobes race thru - the first to our north associated with the active northern stream will nudge a cold front southward from Canada and bring into to the Canadian border, while the second lobe of energy moves east well in advance of the Intermountain trof and moves thru Thu eve and night under modest warm and moist advection and associated isentropic lift. Now comes the part where folks along the Canadian border, and especially those of you reading from Northern Maine, will want to pay especially close attention, though let's go through the scenario for all.
Remember how intense the baroclinic zone sitting over the Canadian border is, and will continue to be this week. As the trof over the Rockies ejects east, dynamic forcing increases Thu Ngt into Fri along and near this baroclinic zone. After the passage of the Thu Ngt vorticity lobe, the frontal boundary will be draped along the Canadian border and then across Central Maine. Due to the very tight thermal zone, air should be cold enough along and immediately north of the boundary for snow, and lots of it given the isentropic lift that will result as warm advection lifts north ahead of the main upper level vorticity maximum. The result will be a period of extended accumulating snow Thursday night thru Fri for Central and Northern ME, with very heavy snow likely to fall during the day Fri. Great agreement on at least an inch of melted QPF in most of Northern ME - esp north of Dexter, ME, so a major snowstorm seems to be in the making for the Northern half of the state.
Elsewhere, let's review the facts of the Friday event: Strong vorticity maximum produces rapidly deepening surface low pressure center as it interacts with tremendously strong baroclinicity and strengthens from 1002 mb at 12z Fri to 991 mb by 00Z Sat. Well defined low-level wind shift to occur along cold front, extremely tight baroclinic zone to get wrapped into storm, strong lift ahead of front and strong subsidence behind it likely brings strong pressure fall/rise couplet, and winds are as follows: 500 mb 80-100 kts, 700 mb 60-80 kts, 850 mb 60-80 kts. All of these factors add up for what should be a widespread synoptic damaging wind event, brief shot of heavy downpours for Central and Southern NewEng while the North Country sees aforementioned snow far north, and rain changing to snow elsewhere across Northern New Eng. Southern NewEng will be vulnerable to elevated convection, as well, and while there are signals of a shallow surface inversion through parts of NewEng, some areas may erode inversion enough for damaging convection ahead of the synoptic wind event.
Behind this front cold air streams in Fri Ngt for what may be a flash freeze event, tho I'm not sold on this yet given the limited QPF that - at least right now - seems to be in the cards for Central and Southern NewEng. In other words, I want to make sure the rainfall won't simply dry up in the fast and drying winds before enuf cold air streams in. Arctic air builds in Fri Ngt and good agreement on cold being in place both Sat and Sun. While Sat high temps will only be in the teens south and singles north, I think Sun probably is even colder! Even tho the core of 850 cold is departing, there's no mechanism for surface warm advection and Sat night will be below zero almost all locales (perhaps singles Southern NewEng thanks to active downsloping wind...TBD) so you're not going to have much to build from on Sat.
Beyond this, I've been eyeing a potential major storm for Tue Feb 21 timeframe for quite some time now, but have had no opportunity to set it in writing in this discussion due to time crunches each day. Even today I'm running thin on time for in-depth discussion, but the short version is: with strong upper low that pushes thru this weekend ready to retreat back toward the north pole, new energy ejects from the polar vortex and is caught in fast northerly flow aloft over West-Central Canada Saturday into Sunday. With a ridge in place over Mexico and extending into the SW US, and a broad Eastern Pacific trough, this will prohibit troffing over the Rockies and the result will instead be a relatively flat W to E flow over the Intermountain Region as this next strong vort max arrives. With the strong and cold surface high moving off the ECoast during this period, this allows broadscale warm advection to return ahead of the incoming shortwave, allowing it to intensify as it moves E. This has long appeared to have its sights set on the Northern Mid-Atlantic for a sizeable snow event in the Ensemble Guidance, but there are two reasons to watch it here: 1) The potential for the northern part of the snow shield, but more importantly, 2) A tremendous block building just E of Greenland. This will mean the storm HAS to turn northward after moving off the coast - the key and the challenge will be determining how close to the coast it makes that turn.
I'm out of time for today - make it a great Valentine's Day.
Matt
