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:
A sprawling area of Canadian high pressure, packed with dry and cool Canadian air, will soon take hold of New England and provide pleasant but cool autumn days through the upcoming weekend. In the meantime, however, New England enjoys one more day of summer warmth's return.
A chunk of very warm summer air, with a history of producing high temperatures in the 80s and 90s from the Ohio Valley to New York City points southward on Tuesday, will stream into New England. This summer air is being transported northeast in the strengthening southwest flow sandwiched between an area of high pressure southeast of New England, and the strengthening wave of low pressure ejecting east out of the Great Lakes and poised to move across Northern New England. This increasing southwest wind will end up gusting to over 30 mph at South Coastal locales by the end of Wednesday, and will gust over 20 mph by the end of the day for most of the remainder of New England. With the passage of the aforementioned wave of low pressure, a frontal boundary situated over Southern Ontario and Quebec will begin dropping south, as the counter-clockwise flow of air around the low pressure center turns winds from the north and pushes cooler air southward out of Canada. The transition between summer wamth and returning autumn cool will be a rather bumpy one, with thunderstorms developing along the cold front - the leading edge to our new fall airmass - and these storms will move into the North Country from 2 PM onward, though a few showers will likely arrive sooner there. As the line of thunder and downpours drops south, reaching Concord, NH, to North Adams, MA, by around 5 or 6 PM, and Northern MA but around 7 or 8 PM, a few of the storms in this line will be capable of producing damaging winds for a few communities. Later in the evening, the band of rain and thunder will settle across Southern New England, no longer capable of producing damage but still dropping heavy rain.
Lingering rain showers in Southeastern New England early Thursday morning will quickly push south of the region as drier air spills southward just a few thousand feet off the ground. In the lowest few thousand feet of the atmosphere, however, enough moisture will linger that clouds will be somewhat more stubborn to break up, though enough dry air aloft will allow for continued breaks of sunshine through the day. A brisk wind from the north will gust to 20 mph behind the departing storm center moving well northeast of New England, and ahead of the expansive high pressure center - a fair weather cell - dropping in from Canada.
This fair weather cell looks as though it will remain situated over the northeast this weekend, and although it comes with a slug of chilly autumn air that will bring at least valley frost to New England Thursday and Friday night - though perhaps not to all of Southern New England and once again perhaps not to elevated terrain. This dome of cool and dry air should keep New England protected, by holding a storm at bay that will developing off the Mid-Atlantic coastline. Given high astronomical tides, beach erosion and coastal flooding may result for parts of the Mid-Atlantic coastline, but as long as this storm behaves and remains south - as it currently appears it will - here in New England we shouldn't see more than an increase in high altitude clouds from the system. I'll keep you posted, for sure.
Enjoy your day!
Matt
Matt's Technical Meteorological Discussion: Updated Wednesday, October 4 at 4:25 PM
Very late today, I know - a busy week behind the scenes that will continue through the remainder of the week with systems upgrades underway.
That said, let's get right to it. Shortwave to cross NewEng tonight is losing moisture support after enhanced convection by Great Lakes moisture input that resulted in severe convection into the early AM hours in the Central Great Lakes and an impressive 28 kt gust at KBUF. Nonetheless, tho wind field aloft is quite impressive, extensive Ci shield rode out ahead of the system and instability is limited tho 500-1000 J/kg CAPE will be capitalized upon to bring downpours and embedded thunder. Winds at 850 mb do not appear to be verifying at present, which limits severe threat significantly, tho a damaging burst will still be possible in a few cells this eve as the activity enters Western NewEng.
Shortwave is very well defined on radar, as is warm and cold frontal boundaries emanating from the vortex. Cold front brought a sharp drop in AM min temps Wed morning and cool air will not wait long behind the front. This will send Nrn NewEng temps tumbling late, but an active wind and too little too late will keep most Nrn locales from dropping belo the 40s, while Srn NewEng will find little diurnal spread from AM min to PM max on Thu, wtih cool enough air to support upper 50s to around 60 even when taking downsloping flow into account. Some question regarding how much low level moisture will linger - certainly low level lapse rates are steep enough to breed at least sct Sc but with the sfc front slowing overnight Wed Ngt into Thu, the concern is there for a BKN deck by afternoon and is likely to develop in esp Srn/Wrn NewEng.
Large anticyclone still expected to take hold into the weekend tho storm brewing off Mid-Atlantic coast is certainly problematic on operational GFS...tho this model is the far northern outlier. I think the bottom line here is that the Ensembles are in good agreement on cutting the upper low off well south of us - far enough to keep us out of low level warm advection but close enough for mid and upper level moist advection for at least a Ci shield on Sat, before that too is forced southward - or perhaps more accurately disintegrates as warm advection weakens aloft. Thereafter, the next well defined northern stream wave in the westerlies approaches on Monday, and as the flow around the closed low opens up with the approach of the wave, some moisture entrainment northward is likely, which may enhance a shower threat with passage of the shortwave on Monday.
Matt
Monday's Discussion:
1:55 PM: Clouds waited for diurnal effects to fill in but the process has begun as of this writing and will continue to rapidly fill the sky as convective temp has been reached in most spots thanks to cool air aloft and abundant low level moisture available for convective growth. Brightest locales will be far Srn/SW NewEng. Have included gusts to 20 mph given mixing to 925 mb and winds to 25 kts progged at that level.
Cu should diminish after sunset and winds slacken which will allow cooling, tempered by moderate warm advection in the mid and lower levels. This warm advection comes in advance of an approaching shortwave currently moving across the Midwestern US that will move steadily E in the westerlies. Decent agreement on a morning passage of assoc midlevel moisture in Nrn NewEng, and afternoon passage in Srn NewEng. Shouldn't disregard the amount of moist advection occurring in advance of the shortwave, either, which brings 850 mb Tds of +11 C on Tue and is sufficient to boost SBCAPE to over 1000 J/kg. Initial concern for me was that the NMM in particular may be exercising its occasional bias of bringing llvl moisture in too quickly, but analysis of llvl theta-e progs from current data show this is a rather impressive moist tongue to be reckoned with, so felt comfortable in adding chance thunder to my shower chance for Tue.
The trick heading into Wed is how the atmosphere behaves behind Tue shortwave. That is, at first it seems self-evident that warmth returns until late Wed shortwave comes swinging thru, and my morning fcst reflected the return of this warmth. I fear, however, that I failed to give proper respect to the density of a fall airmass, as the rules are changing now that we've transitioned from summer. In summer, an airmass rebound of warmth like this would be easy to believe, but this time of the year, even a slight southward tug of cool fall air behind the lead shortwave means we have more work to erode the cool surface dome. I don't think this is going to have major implications on my forecast for NewEng from this AM, but I do think there are some important subtle details that can be garnered from properly understanding this interaction, namely that there should be at least a band of BKN midlevel clouds - probably altocumulus - that will start over Srn NewEng Wed AM then shift across the north and thicken with the approach of the next shortwave. It certainly appears as though this warm front will be able to surge north thru most of Srn/Central NewEng, but Nrn NewEng is likely to find the thickening clouds leading directly into showers assoc with approaching wave. Farther south, where warm air does rebuild well, instability rises again to over 1000 J/kg, and with better dynamic forcing I would expect more widespread rain and thunder certainly than what I'm expecting on Tue. With 850 mb llvl jet cranking from the SW to 60 kts across Central/Nrn NewEng by later Wed, severe weather is a decent potential. Let's be sure not to grow lax to this potential for thunderstorm damage and remember that this time of the year is often a potent severe weather producer given the combination of baroclinicity and dynamics. This was evidenced in Friday's tornado in Berwick, ME, and given backing flow along and ahead of warm front pushing into Ern NH/Wrn ME on Wed afternoon/evening, the atmosphere will be primed to pull a similar stunt.
The forecast becomes more straight-forward thereafter as longwave trof migrates E thru NewEng with SE US ridging extending N this weekend and anomalous cold the end of this week transitioning to anomalous warmth later in the weekend - and likely strongly anomalous given the combination of a high pressure cell shifting S of NewEng, the heat building in the nation's Southern, Central and Northern Plains, where sfc max temps were near 100, in the 90s, and 80s respectively, combined with a downsloping flow Sun.
That's all for today.
Matt
