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: Quick Note: I'll be out of town this weekend, so the normal Monday through Friday schedule for updates holds here - we'll pick up on Monday where we leave off today.
After areas of black ice and a very cold start to our Friday, ample sunshine Friday morning will continue to help us rebound. Localized areas of freezing fog in some deeper valleys will continue to burn off quickly during the morning. While the winds at ground level will remain from a cool northwest direction, a shift to warmer winds will be underway aloft and by afternoon, this will mean a rapid increase in high and middle altitude clouds. These clouds will be a sure sign that warmer air is returning to New Englan, and they are likely to block out the sun for the second half of the day and halt temperature rises for most areas. By Friday night, this increase in warm and moist air will begin to reach lower altitudes, and a few light showers of rain and snow will be possible in the mountains of Northern New England.
For most communities, this increasing warmth will be felt on Saturday afternoon. Though the leading edge to cool and dense air in Eastern Canada - a cold front - will be settling southward toward New England, many locales will find a southwest wind continuing to feed mild air northward through Saturday afternoon, and temperatures will rise into the 40's. In fact, the potential would be there - given enough sunshine - to rise to around 50 degrees in parts of Southern New England Saturday afternoon, but tempering this warmup a bit will be cloud cover sliding southward ahead of the Canadian cold front, and limiting the amount of available sunshine. In Northern New England, this southward sliding cold front will keep more clouds than sun locked in through most of the day with scattered showers of rain and snow a possibility throughout the day.
This cold front will dig southward through the remainder of New England Saturday night, leaving cooler air in its wake on Sunday. Meanwhile, a small piece of the same storm that brought rain to portions of the Southwestern U.S. on Wednesday...then snows to the Rocky Mountains on Thursday...was left behind in the Western United States and will trudge east across the nation, approaching the Northeast later Sunday. The counterclockwise flow around this storm center will tap warmth and moisture from the Gulf of Mexico, and the collision of warmth from the south, and this new cool air from the north, will spell plenty of clouds for all of New England on Sunday. By Sunday afternoon, it's likely that these clouds will grow heavy enough with moisture to begin producing light rain and snow from west to east across at least part of the six state region. This precipitation will fill in and become steadier and heavier Sunday night. There will be enough of a contrast between these two airmasses to allow for a rain/snow line Sunday night, and while these can be difficult to determine even just prior to a storm, at this early juncture it appears likely that most of Northern New England will receive an accumulating snowstorm, while most of Southern New England will find a mainly rain event - but likely beginning with a burst of snow that may accumulate a few inches through the interior.
But even if this assessment is correct, snow lovers in Southern New England should not fret, because another bundle of significant Pacific energy will be moving in on the heels of the leading storm. In the wake of Sunday night's storm, it's entirely likely that northwest winds will have dragged cold air southward across most of New England in time for the approach of the follow-up Monday night storm. As a result, there is a much better chance of a colder, snowier storm Monday night into Tuesday. This storm is likely to bring windswept precipitation, heavy at times, to New England later Monday through Tuesday. While ocean waters are around and just over 40 degrees, the southern edge to a cold Canadian area of high pressure will be building southward across New England and sending cold air southward. As the storm approaches Monday night and Tuesday, winds will come out of the northeast, tapping this nearby well of cold air, and even coastal locales excepting perhaps the South Coast would turn cold enough for significant accumulating snow. At this point, it's still early to lay out the precise details, but a plowable snow looks like a real possibility for especially Central and Southern New England Monday night into Tuesday with a nor'easter underway.
As for the remainder of February, remember what we've reviewed together in these discussions in the past - the abnormal warmth of January and the end of December has resulted in a large amount of available atmospheric energy across the United States. And this warmth hasn't been confined only to New England - most of the nation has been abnormally warm, and therefore most of the nation houses a higher amount of available energy than would normally be present this time of the year. Strong indications are that by the second weekend of February, a significant pattern shift will have occurred across the nation, allowing much colder air that's been locked on the opposite side of the globe and near the North Pole to spill southward into the United States. In this transition, the available atmospheric energy will have to be expended, and large storms are likely to be the result. The question for these will of course be storm timing and track - though with warmth bubbling up from the southeastern U.S., this does favor a track that would put New England on the snowy northern side of storms over the next couple of weeks. Time periods that look to feature potential big bangs to usher in this new weather pattern include this coming Tuesday, then again approximately one week later, on the following Tuesday which may be a larger storm that really marks the change to a new cold and wintry pattern. There are no guarantees and the world of the atmosphere, of course, but certainly the atmospheric signs are that February may begin with a bang, before significant cold may move in for the middle of the month. Time will tell...
Enjoy your weekend - see you back here and on NECN on Monday!
Matt
Matt's Technical Meteorological Discussion: Updated Friday, January 27 at 8:15 AM
Below is a refreshed version of yesterday's discussion in case you missed it. I'm off today but the Weather Summary above has been updated and I wanted to freshen this up for today...will be back at it on Monday.
Fri dawns with plenty of sunshine, valleys that decoupled with freezing fog see it burn quickly with diurnal heating. Mid-level frontogenesis to occur directly over NewEng Fri afternoon as rapidly rising heights associated with sharp ridge building in from the west will be associated with rapid increase in mid-level temps and as cold air is slower to depart, elevated baroclinic zone to develop. Sfc warmth will still lag significantly behind thanks to slower movement of sfc ridge, but warmth rushing in aloft will be responsible for rapid generation of mid and upper level cloud deck over NewEng Fri afternoon, so skies should become overcast thru the day. This will help to temper any temperature rise as diurnal heating will be limited for the latter half of the day. Clouds lower and thicken enuf across the Canadian border by Fri ngt with warm advection reaching lower levels of the atmosphere along with a strung out vort that whips thru aloft that it makes sense to hold chance of light snow/rain shower we've had for several days running for the North Country. Farther south, low level baroclinic zone is more diffuse as it rolls thru and this brings little chance of precip and in fact, skies likely to be only scattered cover. This strung out vorticity maximum really marks the beginning of faster flow - snapping through NewEng and clearing the way for a racing west to east flow. It's this fast flow that's the reason the guidance is quicker to bring precip in on Sunday...more on that in a moment, first we have to get thru Saturday.
Saturday looks to be a fairly benign day with regard to sensible weather, though there are a few subtle details that not only are important for Saturday's forecast, but that setup the weather for the remainder of the weekend and into early next week. The frontal boundary slides thru Northern NewEng on Sat propelled by a vort skirting across the North Country and an 850 low-level jet humming along at about 50 kts, so what seems like a benign frontal passing will likely bring strong wind-swept showers of rain and then snow squalls to follow to the mountains of Northern NewEng Sat afternoon thru eve. Farther south into Southern and Central NewEng, front stalls as it encounters stubborn ridge off the SE US coast. But critical to the end of weekend forecast is exactly where this front stalls, as this in conjunction with speed and amplification of approaching shortwave will determine all-important rain/snow delineation on Sunday when precip moves in.
ECMWF had been a loner with its forecast of cranking this storm up well to our west and bringing enough warm air in for a warm advection precip slug on Sunday then warm sectored into early next week but is coming around to the idea of a colder coastal scenario, which eases minds as we're now coming into an increasing agreement among the guidance on the scenario we looked at yesterday. Developing confluent flow in Eastern Canada just north of NewEng that sets up thru the period suggests flow should be fast enough initially to pull leading vort in and probably allow it to shear a bit as it races across NewEng Sun Ngt with a slug of warm advection precip. GFS keeps colder air in place farther S than the NAM and at this point I favor this solution, both due to the building ridge over Hudson Bay mentioned a couple of days ago, and due to the strongly confluent flow that establishes just north of NewEng and should force this front farther south. Additionally, anticyclone building southeast through Canada is strengthening while warm anticyclone off SE US coast is retreating out to sea and weakening, also suggesting the northern high - full of cold dense air - should be able to win the battle in the lower levels, esp with the help of that confluent upper flow. This means Sun afternoon and night precip is mainly snow in Northern NewEng and mainly rain farther South than South-Central VT to Lakes Region to Maine coast.
How this system plays out is critical to the following system for Mon Ngt and Tue. If I was incorrect in my assessment of the Sunday shortwave, the following scenario will be incorrect, but increasing agreement on this solution has me thinking it was the right way to go. But, the logical followup to my above thinking is that this first system races by and we're left with a break in the action before the next much stronger shortwave which will be digging and amplifying over the MS River Valley. This next vorticity maximum and is associated area of low pressure should be significantly juicier than its predecessor, but ahead of it, the southeast migrating and still-strengthening anticyclone will be eager to throw cold air southward onto NewEng. And why shouldn't it be able to with a northerly wind direction behind the departing dampening shortwave? This would guarantee a farther south storm track with the Mon Ngt/Tue storm, putting most of NewEng on the cold side of the system and resulting in only coastal rain/snow issues that would have to be dealt with, though even those may be a moot point given what would be strong ageostsrophic northeast component to the wind, filtering air from a cold and strong Canadian high. At this point, therefore, I favor a mostly snow scenario with the potential for significant windswept accumulating snow Mon Ngt/Tue with a full-fledged cranking nor'easter, but please keep in mind that this depends heavily on my idea of handling the first Sun Ngt system being correct.
As for the longer term, lots of inquiries from folks about how February is looking. Those of you who read regularly know my thoughts on this: The entire nation has seen above to much above normal temperatures for several weeks now, with very few exceptions. Cold air has been situated on the opposite side of the globe, and locked at the north pole with a failure for the polar jet stream to tap this arctic supply. In one sense, this gives the impression that winter will be a lackluster. But in a much more important sense, this sets up a scenario where the ground, the air, the water all are filled with heat they wouldn't normally be filled with. We know in the world of meteorology that heat is a form of energy, and furthermore, we've just watched a dazzling upper level low and associated cold pool move directly overhead with some remarkable dynamics given mild air at the surface. It shouldn't be too much of a leap in our thinking to apply this to the bigger picture - once the jet stream pattern shifts and allows cold air to spill into the lower 48, the only way to find atmospheric equilibrium will be to reshuffle this energy, and that will have to happen in the form of storms. Now, if this were an extended warm and DRY period, we'd be talking about a different story...but there's been no lack of moisture lately and indeed this has been a warm and moist extended period which has effectively loaded the cannon.
But the next important question is, does the jet stream ever really change? Guidance has been wrong in the past and will be wrong in the future, but when I see every Ensemble member carving out a gargantuan trough in the US by the middle of February, that should be a first tip-off to a major change that may be in the works. But to look at this as an ingredients-based thinking, the first step is to notice changes on the hemispheric scale. The first shift that stands out is the breakdown of the strong upper low over Northern Russia as releases its grip and migrates east across the Eastern Asian continent. This does a few things - first, it allows the Rex Block in place over Western Europe to release, and second, it sends a significant chunk of energy pinwheeling across the pacific during the first weekend in February. This energy eventually hooks up with the Aleutian low, strengthening the below normal height deviations there. This amplification of the pattern over the Aleutian Islands will force a restructuring of the longwave pattern, with a downstream amplification response in the Western US/Western Canada ridge. In essence, this is the first step to a "build-your-own-cold-trof" recipe. The reason I say this is because this amplification of the Western ridge will be so pronounced, that deep northerly flow will set up from the North Pole into Central Canada. Finally, you've tapped the cold air that has been sitting across the far north, untouched for so long on this side of the Northern Hemisphere. Of course, it doesn't all come at once, but what happens is that you bleed this cold air southward over the next two weeks in the low levels and thereby lower the heights gradually. By somewhere around Feb 8 you've lowered heights enough that aside from the Aleutian low and associated polar vortex that's been tugged southward in response, the lowest heights in the Northern Hemisphere will be associated with the northern half of this trof...across Central and Northern Canada. This is when we remember that the atmosphere works like a sink, and that colder air will rush to the lowest point - in this case the lowest heights. That position will first be the polar vortex/Aleutian low, but thanks to the amplified western Canada ridge that will persist long enough for a very strong anticyclone to dominate western Canada at the surface, we'll see an additional pumping mechanism in the clockwise flow around this high pressure center to help usher not only North Pole cold, but also some Aleutian cold into our newly developing trough as well.
There should be two primary results to this: 1) Significant displacement of energy in the transition and 2) plenty of cold for the middle of February and likely beyond. In the process of this transition, there are two time periods that are keyed in on for strong shortwaves driving in the changes to this new regime - the first shot across the bow comes Mon Ngt/Tue, and the second major shot appears to be slated for one week later. There is enough energy present in the lower atmosphere for either of these to be very powerful storms, though if our thinking is to build our own trough the second week of February, it makes sense that the second of these storms would be the powerhouse. And with cold air spilling in gradually and a southeast US ridge unwilling to fold, this should place the strong low level baroclinic zone south of NewEng with ample moisture available, which means substantial snow events will be of concern during this two week transition period.
Have a great weekend!
Matt
