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 linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net. This blog is for you, so I hope you enjoy it! -Matt Noyes
General Weather Summary:
Tuesday night and Wednesday morning snow was quite limited in scope across the Northern reaches of New England, falling only in the highest terrain of Vermont, New Hampshire and Maine as moisture found only limited focus ahead of our early Wednesday disturbance, largely due to a uni-directional wind - that is, not much of a wind shift to crank out the moisture. Nonetheless, our active weather pattern will continue for the next several days into the weekend, and will bring another strong storm by Friday night. Meanwhile, the same large storm in the upper levels continues to park a pool of cool air over New England, favoring development of puffy cumulus clouds and a few showers of rain and snow.
While the passage of the upper level disturbance and an associated wind shift at the surface brought anywhere from a trace to 3" of snow to the higher terrain - and FAR less snow than I anticipated to high terrain at the Canadian border of northeastern Vermont (valleys remained warmer and saw rain, as expected) - it should still succeed in carrying increased wind gusts and continued chilly air to most of New England, and a follow-up disturbance will move into the North Country tonight, adding to storm totals in areas that thus far have fallen short. Though some snow and rain showers will linger into early afternoon around the Champlain Valley, the higher terrain of the White Mountains and Maine Mountains, and in Eastern Maine, most areas will find a blend of sun and large, puffy cumulus clouds that will drop only a few sprinkles or light rain showers from time to time, with the balance of the day staying dry for most of New England. Winds will blow out of the west-northwest, gusting to over 30 mph at times under the belly of the mature storm east of New England.
By Wednesday night, yet another weak disturbance will move through Northern New England aloft, and snow showers will find new life across the high terrain of the north. With slightly colder air in place, the rain/snow line will likely drop lower in elevation than it was Tuesday night - perhaps to around 900 feet in Vermont and 1300 feet in New Hampshire and Maine, though accumulations would be rather light in most areas. Elsewhere, expect a chilly night Wednesday night with winds subsiding a bit, though still breezy especially early. Thursday will bring another cool blend of sunshine and billowing clouds - a break in the action before our weather turns stormy once again.
This end-of-week storm comes with a history, as two key weather systems will come together in its formation. The first is what was once Hurricane Paul, crossing Mexico as a large mass of moisture, heat and energy heading for Texas en route to the southeastern United States, carried by the subtropical jet stream. To the north, a strong energetic disturbance is moving southeast down the Western Canada coastline, caught in the polar jet stream that carries energy centers and cold air from the north. This storm, too, will dive toward the Southeastern U.S., where it will meet with the remnants of Paul late in the week. In the early stages of the merger, snows will develop in the Rockies where Winter Storm Warnings are in effect, and heavy rains will likely jeopardize the World Series game Wednesday night in St. Louis.
The strengthening storm to the southwest of New England on Thursday will launch a slug of meaningful warmth and moisture toward New England late Friday. Ahead of this slug of moisture, most of Friday should remain dry with increasing clouds late in the day as a split area of high pressure defines warmer air to the south and cool air to the north in Canada, but holds the moisture at bay. The Canadian fair weather cell packed with cool air will be settling north of New England later Friday, and this will provide a weak supply of cold air to New England. The result will be a stubborness of the cold air to let go from Northern New England as moisture comes streaming in, and this likely will crank out at least some snow across Northern New England when precipitation moves into New England Friday night into Saturday, and perhaps into Sunday as well. Though this will be a concern in the mountains of the North - where a mix of many types of precipitation are likely this weekend with an elevation dependency - most of New England will find a windswept rain Friday night into Saturday, as the storm center moving out of the Southeastern United States passes over the waters southeast of New England, holding a northeast wind and therefore very cool air in place.
As this storm wraps northeast of New England later Saturday and Sunday, cold air will wrap around the back of the circulation, and this will result in a changeover to wintry precipitation in the north, though there are questions just how much moisture will still be available once the lower elevations of the north (where most of us live) change to snow. Nonetheless, the potential is there for significant snow in some areas, so this continues to bear watching. By Sunday, skies will be partly sunny in Central and Southern New England, while snow showers and bursts of snow will linger in the north, with breezy conditions for one and all.
Enjoy your Wednesday.
Matt
Matt's Technical Meteorological Discussion: Updated Wednesday, October 25 at 2:20 PM
Winds kicking up on cue across NewEng this afternoon and with gusts to over 30 mph at times, this is especially raw across Nrn VT where rain showers have been lingering beneath cold pool and with assistance of upslope flow. Remainder of north seeing sct rain and snow showers with multiple weak vorts and localized upslope flow, along with lingering instability thanks to cold air aloft. Conditions stay similar overnight but without diurnal disruption due to thermally induced mixing, and this will allow revitalization of upslope areas of snow showers, where some light accumulation is possible on the order of 1-3" for higher terrain - esp above 1200-1400 feet from VT to NH/ME as profile is colder over VT. In fact, below freezing profile reaches 900-1000 feet in Nrn Greens by predawn Thu.
Overall trend for slower progression of weather pattern offsets a few parts of the forecast for us, starting with Thu when more clouds will linger below sluggish cold pool, then for Fri when we can extend dry weather thru the day with increasing clouds late.
Yesterday's thoughts on the weekend storm focused upon Dr. Colucci's "always beware the col" and the belief that this upcoming storm would take a track southeast of NewEng toward the well-defined col. 00Z GFS and Canadian Ensembles have both come back with eastward leaning solutions, but there are plenty of factors that need to be considered in this forecast for NewEng. First of all, let's understand what's going on in the longwave pattern, and that is the combination of two big factors: 1) The continued and, in fact, accelerated breakdown of the Greenland block that has been in place, and 2) a large amount of Alaskan energy ejecting from the Aleutian low (which has shifted N recently in response to Siberian input) and diving into the mean trof position which begins W of NewEng but comes directly overhead given these two major factors at play. What's to be truly amazing come Friday is the interaction of systems that take part in this longwave redefinition, which includes 1) Pacific energy sliding into the Pac NW currently that will carry a primary low well to our west, 2) the remnants of what was Hurricane Paul, coming across TX and tapping the Gulf for copious amounts of moisture and a storm center chock full of latent heat expenditure, and 3) the aforementioned Siberian/Alaskan energy combo that slides quickly SE in the fast Westerlies and is the final addition to prompt a negative tilt of a wildly amplifying trough. Diffluence ahead of this system will be quite impressive aloft on Saturday over the waters south of NewEng, and this, coupled with tight baroclinic zone and aforementioned col will aid in steering quickly strengthening storm over the waters S and SE of NewEng on Sat, to a position N of NewEng where the low will become vertically stacked and bomb over Ern Canada, ensuring very windy conditions across the Northeast on Sun/Mon, though without much available deep cold (we've expended a large chunk of it already and there is currently no well of deep cold available in the Northern Hemisphere) it's unlikely we'll find more than a shallow surface dome of cold moving in, which will mix enough diurnally to warm on Sun and Mon, esp in Srn NewEng where strong wind is also downsloping wind.
We'll pick that thought up again in a moment, but before we get too far ahead of ourselves it's important to cover more details on the events that will transpire with the weekend storm itself. We left off with storm track, likely to be S and SE of NewEng before hooking N as the surface center is pulled beneath the upper low and bombs as a result. The question of the last few days has been just how much cold air holds on with the approach of the storm, and what ptype we're looking at for whom. There remains little doubt that this event will be a liquid event for Central and Southern New England, where 850 temp anomalies of +2 to +6 C move in ahead of storm thanks to tropical input from remnants of Paul. This is where it's important to keep in mind the origins of a storm, which I often will refer to in these technical discussions, as airmass origin can and does make a difference later down the line. With so much tropical air available, it's quite likely there will be a slug of midlvl warmth that will be nearly impossible to stop without deep cold, of which we'll be out of when the moisture arrives. The warm advection will be so intense that it's likely to overtake most of NewEng with warm air as the storm pushes N on Sat. That's not the end of the story, however, as warm and moist advection means the influx of higher potential temperature air, which will create isentropic lift. Strong enough isentropic lift will aid in dynamic (adiabatic) cooling, which will in turn hold a colder atmospheric profile. Yesterday I noted the presence of a surface anticyclone in Eastern Canada that would serve to hold the low level cold into Nrn NewEng for me to consider significant snows in the mountains of the North, though the slowing of the pattern has allowed this high to weaken as upper level diffluence lifts north Fri night into Sat, which means we've lost the mechanism originally in place to hold the cold, and all we can count on for wintry precip is old, diminishing low level cold and dynamic cooling. The end result of this should be a burst of snow in the mountains of Maine, especially, and perhaps in Northern Maine to begin the storm. With a northeast surface wind ahead of the storm center thru most of Sat, until the passage of the occluded front connecting the primary low over Ontario with the secondary low swinging northward, east of NewEng, we are likely to hold the surface cold into esp mountain valleys in Maine, but the warm surge aloft in the midlvls (750-600 mb) assoc with the tropical moisture should be too strong to hold off, and ptype will swing to rain even thru most of ME later Sat, tho perhaps could hold as sleet for a time in the mountain valleys.
Elsewhere, heavy rain and strong wind will be the features of the strengthening low, with a well-established tropical moisture tap loading the system and intense dynamics assisting in wringing this moisture out, esp along low and midlvl baroclinic zone that lifts across interior NewEng where banded heavy precip is most likely. Given high precipitable water values, should be able to exceed current guidance and crank out 2"-3" liquid QPF for these interior locales - even though most of the QPF comes with the slug of warm advection, this still lasts a good 12 hours during Sat. Potent low level jet will crank ahead of this storm and this will translate to strong sfc winds near the storm center along Eastern Coastlines from the E on Sat...perhaps beginning NE but then will have to come E or even SE as this low pressure center is developing as secondary/triple point along occluded front.
As the storm pulls away Sat Ngt/Sun, mentioned above that storm deepens rapidly and winds kick, but lack of deep cold thanks to lack of strong anticyclone means no rapid surge of cold for all of NewEng, though low level cold will be intense enuf in Nrn NewEng to turn ptype to snow and snow may come down hard in Nrn ME during this period as wraparound comma head will come all the way under belly of circulation...biggest question here is whether it misses just north of ME or delivers a windswept snow to Nrn Aroostook County, which is possible on Sun. Farther southwest, upslope flow will be maximized in mountains of ME on Sun, but lots of instability Cu will layer the skies of NewEng with snow showers in most of the mountainous terrain. As the upper low churns over Ern Canada, it essentially creates its own pool of cold air courtesy of dynamic cooling, and this cool pool settles over NewEng middle to end of next week, and though it is progged to be at least 8 C anomalously cold at 850, the shallow nature of the cold is likely to allow mixing and therefore modify the impact somewhat, though clearly below to much below normal temp regime will continue.
Matt
Tuesday Discussion:
1:10 PM: No techie update yesterday thanks to server failure at provider - apologies, especially considering I'm off to a public appearance today so limited time to share my thoughts. Let me get them out as quickly as possible:
Well defined vort max to swing southeast across VT/NH/ME overnight and into early Wed AM. The cyclonic vorticity advection (CVA) ahead of this vort is fairly well distributed - largely normal to the flow - and that will provide extra impetus to generate convective precip overnight. Couple this with cold air aloft providing instability and upslope flow in Nrn mountains and you have a fairly favorable setup for accumulating snow even though sfc winds may not be the ideal NW direction I'd like to see. Nonetheless, 925 mb temps fall steadily late this afternoon thru Tue Ngt and this shud ensure elevated areas are cold enuf for snow. To take thermal fcst profiles literally, no snow will fall below 1500 feet, but I'd expect the convective nature of the precip in the CVA ahead of the vort max to overcome this inhibiting factor and lower the snow level considerably. Elevated terrain will benefit from the combo of cold profile, abundant moisture, good snow crystal growth and upslope flow to crank out amounts as high as 6"-8" in favored locales like Jay Peak and perhaps Sugarloaf, as well. Enuf warm air in the valleys that locales below 500-600 feet will probably have trouble getting snow to stick well as sfc temps stay above freezing. Still, vort max passage doesn't occur until Wed AM in Srn NH and near coastal plain of ME where some snowflakes certainly may mix in, and wouldn't want this to be a shock to the awakening public in the AM so have adlibbed this possibility accordingly. Have carried D-1" rather far south, as well, but am stressing elevation dependence - bottom line here is that I'm untrusting of the pattern with the combo of instability and vorticity, I'm untrusting of the low-level wind flow that is not only non-ideal upslope north, but more importantly to this point is non-ideal downslope south, and I'm untrusting of moist low levels. Nonetheless, anything that does survive the trip would die or ship out quickly Wed as a final mix of mostly raindrops and some snowflakes, tho upslope flow will strengthen on Wed in the Nrn mountains where snow showers will continue. Let's also not forget the connection from Lake Ontario, which has dropped light rain showers in SW CT earlier today and tho it has broken up with diurnal htg and assoc mixing, should redevelop overnight tho will be warm enuf for rain in these areas.
Moisture mixes out a bit better on Wed but cold pool is slow to decay and while I expect more sunshine, more mixing, greater wind speeds than Tue, clouds will still bubble aplenty during the afternoon beneath the cool pool. Thu is a decent break in the action, and the trend has been for slower progression of Fri system which makes sense for at least a little while as Pacific energy and Tropical Storm Paul merge in the trof over the SE US. This significant amplification will slow the progression, but once Paul's remnants are absorbed into the circulation, this will enhance the thrust of warm and moist advection ahead of the storm, and precip should develop later Fri from SW to NE. 1020 mb bubble of high pressure over Ern Canada bridges to high pressure over MidAtl while col (area of light wind) sets up between these two anticyclones and the cyclones to the southwest and northeast of NewEng. At Cornell University, one of my meteorology professors, Dr. Colucci always would say "always beware the col". As the low level flow becomes weakly convergent in this coll, it serves as a magnet for secondary storm development and/or track, and the GFS is close to this line of thinking. A track from the MidAtl coast to the col for a secondary low would allow cool air to hold into Nrn NewEng enuf for a significant accumulating snow event Fri Ngt into Sat and am carrying that in fcst for now, with liquid much more likely ptype in Srn NewEng.
Enjoy your day.
Matt
