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 cold front has swept across New England, leaving noticeably cooler air in its wake. The cool air spilling into New England is only the outer fringes of deep arctic cold that has swept across the Great Lakes, producing record snows for Buffalo, NY. In fact, check out some of these amazing pictures sent by Sarah Stanbury, a friend of mine from Cornell who lives and teaches in Buffalo. Sarah reports two feet of heavy, wet snow, numerous downed trees and powerlines, a State of Emergency in the city, and part of the New York State Thruway shut down!
Of course, seeing these winter scenes begs the question: what's in store for New England?! Rest assured, lake effect snow bands will NOT produce scenes anywhere close to what's been witnessed in the Niagara Frontier, though a few snow showers will fall in the mountains before the weekend is done.
In the meantime, cool air has gripped the six-state region and driven temperatures some 15-20 degrees cooler than they were on Thursday. This cool air, however, is dry, and will prohibit any significant precipitation from falling over the weekend in most spots, though a few showers of rain and snow will be possible for some of us. In the meantime, a classic fall mix of sunshine and cumulus clouds will prevail Friday afternoon, with an upper level disturbance passing over Northern New England resulting in a few rain showers for the mountainous terrain. This upper level disturbance was launched east by the same trouble-maker over the Upper Great Lakes that has been bringing the lake-effect snow to our west - a large spiraling low pressure center and its corresponding counter-clockwise wind flow. This storm has grown so large and powerful, that it wrapped cold air all the way around its belly and into New England - meaning our breezy southwest wind, which normally carries warmer air into the region, has been cooling us off!
This cold air will be well-entrenched Friday night, and with only a few clouds across the Green Mountains and clear skies for most of New England, temperatures will free-fall into the 20s north and west, and 30s for most other locales. This will promote a widespread frost for most communities Friday night, and a hard freeze through the interior. Keep in mind that a hard freeze requires temperatures below 32 for at least 3 hours, though a frost can develop when air temperatures are as warm as 37 or 38 degrees, as a thin layer of air called the "laminar layer" - only a few millimeters thick, and surrounding all objects - can cool much quicker. This laminar layer is a big reason why I expect widespread frost - even in the valleys of Cape Cod - even though not all temperatures on the coastal plain will dip below 32. It's important to note that folks in Boston or other Southern New England urban areas will not see a frost because the concrete and road surfaces hold heat, then re-radiate it at night. For those who are expected to see a frost, many folks in Southern New England who haven't seen a frost yet probably can get away with steady irrigation of plants - spraying them with water constantly throughout the night - to avoid laminar layer cooling and frost development, but in valleys (most of you have already seen a frost who live in deeper valleys of Southern New England) where temps may go below 32, this would obviously not help the problem much!
Our chilly start Saturday will give way to a rather quiet day, even though the weather setup is somewhat complicated. The complications come from two disturbances riding near New England - one passing just southeast of Cape Cod, and another racing east from the big Great Lakes storm again. The disturbance to our southeast was the one that I thought yesterday might bring Friday night showers to Cape Cod, but at this point it looks both slower and farther south, so those showers have been dropped from the forecast. Still, this upper level disturbance will move north after it passes New England, rising up toward Nova Scotia. At the same time, the new disturbance pushing east out of the Great Lakes will strengthen overhead. After a sunny and dry start, this new disturbance is likely to bubble up plenty of puffy "cumulus" clouds - the puffy white ones - that will grow heavy and dark-bellied as the day wears on, dropping rain and snow showers in the Northern Mountains, and an afternoon rain shower or quick downpour between 3 PM and 7 PM in Eastern Southern New England. The net effect on your day, however, should be rather limited, as none of these will last long - even a healthier downpour in Eastern MA and NH later in the day wouldn't be more than a quick interruption in the hours indicated, and the snowflakes in the Northern Mountains of Vermont, New Hampshire and Maine will likely be limited to elevations above 2000 feet.
While most areas will find clearing skies and another frost/freeze Saturday night, clouds will wrap into Northeastern Maine around a developing storm center. That developing storm will contain both the disturbance moving over New England, and the one that missed to the east over Nova Scotia, meaning a rather powerful creature will be brewing east of Maine. This powerful circulation may wrap enough moisture to the west side of the storm to bring at least some light rain - with snow in the higher terrain - to Eastern and Northern Maine on Saturday night into Sunday morning. Otherwise, drier and cool air continues to grip New England on Sunday. FYI - I'll be out at the American Diabetes Association walk at Merrimack College in Andover, MA, that kicks off at 10 AM, though if you'd like to come out, registration will be about 9:30.
It's important to understand that while there is plenty going on in the atmosphere this weekend that I described above, the weekend - overall - will be quiet and enjoyable, just cool for one and all. It's just important to me that when you come here you get a complete overview of how your weekend will shake out, even if that means explaining what will be only a 10 minute scattered shower or downpour Saturday afternoon!
Our next rainstorm is on the horizon for the middle of next week, when what is now Tropical Depression Norman - moving east across the Eastern Pacific - will have crossed Mexico, emerged over the Gulf of Mexico, and carried up the Appalachian Mountains and into New England.
Technical Discussion: I've been as descriptive as I can above, and previous discussions are below. Will pass for today and be back on Monday.
Matt
Matt's Technical Meteorological Discussion: Updated Thursday, October 12 at 1:25 PM
Our October gale certainly was plenty impressive, downing trees and lines in ME per KCAR LSR. Elsewhere, record daily rain in BDR and many areas picked up over 2" as system of tropical origin began looking quite tropical - dumping rain on NYC and SW CT before transitioning to baroclinic system and shifting heaviest precip east to NE side of well-defined circulation overnight Wed Ngt into Thu AM that came over Srn NewEng at 997 mb.
With this sys beyond us, we turn attention to cold front slicing into Wrn NewEng that is bringing convective downpours to Wrn NewEng as of this writing. The front will continue E and thanks to a combination of weaker cyclonic vorticity advection and downsloping flow in the lower levels, convection is not progged by guidance to fire up in Srn NewEng this eve. This may be a bit too simple, as limited insolation is indeed pushing temps into the upper 60s and 70s, and this will boost instability as mentioned in yesterday's discussion (below), so I think a slight chance of a shower or thunderstorm needs to remain in the fcst for Srn NewEng, tho the aforementioned negating factors will help to limit the coverage. Interesting to see SUNYSB MM5 actually developing activity over extreme Ern MA Thu eve with fropa - not over interior - which is an argument that certainly can be made given southwest sfc flow from relatively mild waters S of NewEng combined with effects of leftover tropical airmass that was quite literally left in the wake of this morning's low, evident in dewpoint observations.
Passage of front Thu eve leads to a breezy night as a relatively uniform airmass with respect to diurnal range and horizontal gradient moves into NewEng - that is, fairly straight-forward temp forecast on 30s many areas and 40s coastal plain tonight with very little frost given active wind, then temps holding squarely in 50s Fri tho cooler in higher terrain. Two areas of cyclonic vorticity advection to affect NewEng on Fri - one assoc with upper low cyclonic flow moves into NW NewEng while other will be with multiple shortwaves embedded in fast and channeled flow on northern edge of jet stream. The former will promote healthy Cu and resultant convective afternoon rain showers in Nrn NewEng and esp VT, where Fri eve and ngt temps are cold enuf to support snow showers above 2000 feet, tho lake input Fri Ngt will be minimal as it now appears given trajectory pointed too far north. Over Cape Cod, will hold chc shra with stream of vort maxes riding overhead Fri overnight, and will bring chc shra into Ern ME on Saturday AM. Elsewhere and otherwise, a rather quiet Fri. Another strong northern stream vort comes charging across Nrn NewEng on Sat and this one - stronger than its predecessor - will once again lead to convective development in Nrn NewEng. This time, rain and snow showers that develop ahead of the shortwave should easily carry farther east across most of Nrn NewEng. This is admitedly a complex and difficult period of the forecast, as the vorticity maximum is progged to amplify as it crosses NewEng. The NMM has responded to this by creating a very small bulls-eye of very meaningful precip in SCentral ME, in air that at all levels from 850 mb and up is cold enuf for snow. The placement of this precip is decent given that it's on the north side of a vort trying to close off, but my problems are that this vort is still quite progressive and though it is amplifying, it takes on its pronounced negative tilt and closes off as it moves out of ME. Therefore, while I think this is a great reason to keep the going fcst I have of rain and snow showers for Nrn NewEng, I don't think it's a reason to jump overboard yet, though it certainly bears watching. As for ptype, I still think we're going to need a couple of thousand feet in elevation to realize snow showers given that the vort max comes thru during the second half of the day into the eve, after some diurnal work has been done and valleys/lower elevations will be warm enuf for liquid. Farther west, Sat Ngt and Sun - esp Sat Ngt - will allow trajectory off Lake Ontario to input moisture into Greens and this will enjoy the help of upslope flow to keep snow showers in the forecast, tho deeper valleys will still have warm enuf temps for liquid after diurnal htg.
As mentioned yesterday, the storm formerly known as Norman should be a lot of meteorological fun for the middle of next week, so rest up and enjoy the weekend!
Matt
Wednesday's Discussion:
1:35 PM: Developing circulation evident in sfc analysis and in radar imagery off Mid-Atlantic coast with bands of tropically infused convection spreading north and west away from the center. This, as 70+ kt jet streak at 250 mb rides up the Eastern Seaboard with right rear quadrant ready to assist low development with diffluence aloft. Assoc with this jet streak are two moderate strength shortwaves riding over the SE US and creating parallel swaths of precip as they race to the coastline. These upper level dynamics will combine with low-level thermodynamics and tropically infused air leftover from the persistent circulation that had been off the Carolinas to create a strengthening low. Not sure it will officially qualify as a "gale center" as the center will not be gale, but the pressure gradient force between the storm and the departing sfc ridging will bring wind gusts to gale force Wed ngt into Thu AM from S to N. Looks as tho there may not be enuf PGF to get gusts much over 35-40 mph on Cape Cod overnight, but wind corridor forecasted to strengthen, blowing from the SE, as low level winds crank to over 60 kts late Wed Ngt and early Thu along the coast of ME. Have applied gusts of greater than 60 at the coastline on ME...dropping as one moves south. Please see map in General Wx Summary. As for rainfall totals, good agreement that amounts increase as one moves E, and it makes sense that greatest llvl jet should crank out greatest precip amounts in coastal ME where amounts will exceed 2"...again, reference map in General Wx Summary.
I doubt much of Nrn NewEng will break out on Thu - staying clouded over as baroclinic zone does not lift much north of Canadian border, but deep dry air wrapping ahead of main upper low will mov across Srn NewEng and likely will mix enuf in tropical and therefore well mixed atmosphere to bring sun out. Naturally, warm airmass will respond nicely to insolation and temps should climb quickly in Srn NewEng. In fact, enuf moisture and with insolation enuf warmth that LIs drop to 0 and SBCAPE rises to near 500 J/kg in some spots which will be enuf to warrant chc thunder in Srn NewEng Thu afternoon with passage of prefrontal trof.
Winds should increase with and behind passage of this trof, and stay active Thu Ngt ahead of approaching front, progged to cross NewEng from W to E during the overnight. Good news here is that the lack of pressure gradient with no strong sfc high has completely mitigated the threat for damaging wind along and behind the frontal boundary. The not-so-good news here is that this actually means wetter weather will be the result on Fri, as the surface front quite literally outruns the upper level support. It appeared all along as though the upper level flow certainly becomes more parallel to the front as it runs farther east, but now this should keep NewEng squarely on the cool side of the surface front Fri, but directly beneath the midlevel front that will interact with a number of upper level disturbances to keep precip going across NewEng on Fri. Kudos to the GFS if this evolves as such, as that model lead the way on this potential by picking up on it yesterday, and now is joined by the NMM, Operational Canadian, and some support from the GFS Ensembles. This also delays the timing for getting good trajectory developed off Lake Ontario to enhance snow shower potential in Green Mountains on Fri Ngt - esp when looking at sfc wind component - but winds at 850 come in line and have kept chc in given moisture input and upslope flow off the surface.
Another shortwave to swing thru NewEng on Sat in the nrn stream and this will likely promote convection in the mountains of the North where rain and snow showers will fall later Sat. Quiet weather sets in into Mon, while a huge rainmaker charges thru the SE quarter of the US, likely en route to NewEng on the backside of departing high to deliver a shot of heavy rain to NewEng. This system will be what is currently Tropical Depression Norman, who will cross Mexico, drag Tropical Pacific moisture across the Gulf of Mexico, then bring the consolidated slug north while NewEng would likely see low level Atlantic input, as well! Yikes! Could make tonight into tomorrow look easy, but let's keep an eye on the trends for now.
Have a great day.
Matt
Monday's Discussion:
1:35 PM: Nary a cloud in the sky today with deep dry air and split energy on the Eastern Seaboard as upper low stays south and westerlies ride north. WSW flow has advected both warmer and more moist airmass into NewEng and this will be reflected in overnight temps esp prior to cold fropa tho that fropa takes place by around midnight most areas...a bit later far Srn NewEng. This leaves a NE wind for most areas on Tue which will bring a dramatic airmass difference.
Strong cyclogenesis is set to take place Tue into Wed as potent Nrn and Srn stream shortwaves merge for deep upper low over Great Lakes. I think it's a bit early to try and get too specific and too fancy here in NewEng but a lot can be garnered from a synoptic thought process. First, the large storm surface and aloft S of Hudson Bay at the start of this week is yanking down a chunk of Canadian cool that will sit in waiting just over the border, north of the Grt Lakes, waiting to be tapped. Meanwhile, it will drag a cold front across the Plains and Srn stream wave will induce cyclogenesis along the frontal boundary. A combo of PG flow and ageostrophic flow will tug this well of cold air south, which will in turn greatly increase baroclinicity as it plows into well-established tropical feed from Pacific and Gulf. The result will be the intense cyclogenesis progged for several days now as the surface low pulls into the Great Lakes. Last week I discussed the likelihood of record cold through the Plains and early season snow in the Upper Midwest and that still appears to be the case even thru the Upper Great Lakes, with the potent cold penetrating far south into the TN valley where record cold is likely on Fri.
Of course, NewEng is ahead of the system which in this case doesn't start out quite as exciting but proves to be equally if not more challenging for a longer duration. That is, our first chore is determining when to bring precip in and to what intensity. The bottom line here is that if we maintain a SE sfc flow on Wed, which we should do with a nose of sfc ridging holding on over NewEng, the warm front gets squashed by NYC and we can forget about any warming. In fact, have gone rather significantly below statistical guidance for Wed given warm advection aloft but combo of sfc ridging and onshore flow holding cool dome at the sfc and this will create plenty of clouds along with sct showers in isentropic lift over shallow dome. Well ahead of the cyclonic vorticity advection and deep tropical warmth or moisture, it is unlikely we'll see any heavy precip, but the clouds and scattered showers we do see will hold temps down significantly, esp when coupled with the onshore component of the wind. Early Thu is when our greatest warm and moist advection arrives, and therefore should be when our heaviest precip arrives. Tho the guidance will continue to put out timing diffs, synoptic thought must prevail and that highlights late Wed Ngt thru the first half of Thu. There is likely to be a break after this initial slug of WAA precip, though expanding wind field from intense low pressure well to our west will develop, esp thanks to PGF between departing high and incoming low. Fropa timing looks to be Thu Ngt when intense winds are possible across the Northeast ahead of front with strong llvl and midlvl jet overhead - this certainly has the potential to be a damaging event for higher terrain. Fri has the potential for damage as well, tho what may save us is that there is no well-developed high building in, and the tightest gradient is found under the belly of the primary low, still over the Upper Great Lakes. Thus, while cold air spills in and the winds howl a plenty, we may avoid damage on Fri, tho there is a core of intense wind rotating around the belly of the primary low that meteorologists should continue to pay heed to. There is enuf cold air moving in on Fri that I have no problem putting Green Mountain snow showers in the forecast. The remainder of the mountains will probably see a brief period of flurries or snow showers as moisture departs late Thu Ngt or early Fri, then there will be lingering instability showers on Fri esp in Nrn NewEng when most of the mountains are likely to see at least rain/snow mix showers in convective clusters tho insolation between cumulus will mean not totally a winter scene. By Fri Night, however, lake effect streamer should be cranking off Lake Ontario and given instability and moderately fast wind flow this will carry into the Greens where upslope flow will enhance them and large area of snow showers should result, getting skiers awfully excited. This setup should continue thru Sat.
Enjoy your day!
Matt
