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
Wednesday Podcast: Issued. Click link in upper left of page to subscribe to Daily_Weather_Synopsis.mp3
General Weather Summary:
Apologies for being a bit late today - lots going on behind the scenes today.
It seems the transition to spring has begun across most of New England, as today marks not only the final day of February, but also the final day of meteorological winter, which runs from December through February. Normal dailly average temperatures rise steadily over the next few weeks, with the next 5 days marking a milestone as the New England average high temperature surpasses the 40 degree mark. Therefore, milder weather like that experienced by New Englanders Wednesday is actually not far from normal. Of course, spring can still bring some impressive storms, and one of these creatures is in store Thursday night into Friday.
In the meantime, a large area of high pressure packing cold and dry air is flexing its muscle well to our north, across Hudson Bay, Canada. Though far away, this fair weather cell will play a major role in our forecast through the end of the week, and I'll be referencing it again later in this discussion. For now, the slight southeast expansion of the high pressure center means a somewhat increased wind from the northwest, carrying some of this cool and dry air southward across New England. The most immediate result has been to bring more widespread breaks of sunshine Wednesday morning, though patches of blossoming low altitude clouds were still causing a few areas of persistent instrumental flight rule conditions for pilots in Eastern New England (low-altitude cloud deck) and dropping a few light flurries for some, evident in the radar links to the right of this discussion. Even in the cloudier areas (specifically Cape Cod), more sunshine should break through over the course of the day, thanks to the influx of somewhat drier air from Canada. With only a light wind, colder temperatures will have nothing forceful to thrust them southward, and therefore temperatures should still rise into the 40s for most Central and Southern areas, and above freezing in all spots, with no wind chill factor to speak of. With an continued light wind from the northwest overnight Wednesday night, cool and dry air will continue to settle southward, and this will ensure mostly clear skies with temperatures cooling into the teens and 20s south and either side of 10 north. Black ice will be a concern in patches once again, as it was early Wednesday morning, but especially where melting snowbanks refreeze overnight Wednesday night.
To our west, an atmospheric show will prove to be quite a spectacle for weather enthusiasts and even the mildly interested over the next 48 hours. Already, blossoming areas of cold clouds (meaning they're built high into the sky) can be seen on national satellite imagery (linked to the left of this discussion, in the sidebar) and represent multiple areas of formidable energetic disturbances. One of these areas has been moving east out of New Mexico and across Northern Texas. Another disturbance is moving east across the Rocky Mountains and a third is diving southeast across the Northern Plains. These energetic disturbances will combine to form a strong, powerhouse of a storm over the nation's midsection today through Thursday. The first spectacle has already resulted in an extremely localized but intense nature. This morning, just southeast of Quincy, Illinois (southwestern Illinois), a narrow band of intense precipitation developed as warmth and moisture streamed rapidly north over a cold surface dome. The result was a moderate thunderstorm with a temperature of 32 degrees - that is, a thunderstorm of freezing rain! Lightning was reported all around the airport making the observation. Though there is certainly no direct relation to weather here at home from an event like this, it surely is impressive to see unfolding so early in the game, and is a true testament to the strength of both the cold air near the surface, and the warmth and moisture surging in aloft. Meanwhile, severe thunderstorms are a possibility later Wednesday in the Southern Plains, but a much more likely potential across the Southeastern United States on Thursday. These storms will come as the primary storm center wraps north toward the Western Great Lakes, but a new storm center develops in the copious amount of moisture and warmth over the Tennessee River Valley, breeding flooding rain and intense thunderstorms that will likely bring another Southeastern tornado outbreak during the day Thursday.
Closer to home, we'll watch the action from afar for most of Thursday, as cold air continues to slowly bleed southward on a light northwest wind. A sunny start with patches of black ice will yield to increasing clouds by afternoon - the first signs that moisture and warmth are streaming into New England. By late Thursday afternoon, skies will be mostly cloudy for many New England communities, and a very slow moving band of light snow and rain will be creeping northeast across Upstate New York and Pennsylvania, inching into western New England as flurries by evening. Farther southwest, however, a deeper and more meaningful thrust of Gulf of Mexico warmth and moisture will be streaming northward. This moisture is tropical in nature, and when it arrives to New England overnight Thursday night, it will clash violently with the cold air already in place. The result will be development of heavy bands of precipitation, breaking out in Western New England after 8 PM, Central New England around 10 PM, and Eastern New England by midnight - at least as an early estimate. This initial burst of precipitation will fall into cold and dry air, and therefore will fall as snow, heavy at times, Thursday night. With a developing southeast wind, it's likely that any snow along the south coast of New England would be extremely short-lived before a change to rain as ocean-modified (warmer) air is carried north on that southeasterly wind. On northern parts of Cape Cod, a brief period of snow is possible before the changeover. Elsewhere, however, snow will fall heavily enough to accumulate quickly Thursday night, dropping a few inches from Hartford to Providence before enough warm air could move in to mix and change snow over to sleet and then to rain. Farther north, a brief period of freezing rain would be possible in the valleys of southern Hampden, Worcester and Norfolk counties after the burst of snow and before a morning change to rain. Even farther north into the cold air, expect all snow Thursday night with accumulations of around half a foot near and north of the Massachusetts Turnpike just by Friday morning! Delays, closings and cancelations will be found regionwide, as even those areas that saw a few inches of snow before changing to rain will have very difficult travel in slush, slop and big puddles.
As Friday wears on, cold air will be quite stubborn to let go of interior New England, and will never let go of most of Northern and Central New England. This will mean a very gradual progression of the rain/snow line, making its way northwest as a southerly flow propels it northward, and an easterly surface flow of warm ocean air erodes it from the east. More importantly, air just about two thousand feet above our heads will be moving from south to north, meaning warmth will be streaming north just off of ground level. The result will be a change from snow to sleet, and perhaps then to freezing rain, as far north as Central New Hampshire and Vermont, and extreme Southern Maine, by midday. Along the coast of Maine, a coastal front will develop - the clash between warmer ocean-modified air, and cold air hanging tough through the interior - and this will result in an afternoon change to rain within about 10 miles of the coastline, while snow will continue to fall through interior Maine. Meanwhile, winds will gust to gale force over our coastal waters on Friday as the storm center moves over Southern New England and into the Gulf of Maine, to a position due east of Portsmouth and due south of Casco Bay by 7 PM Friday.
Of course, with so many types of precipitation, the effects will vary greatly across New England. Most of Northern New England will see almost all snow from this storm, and amounts will total up to and perhaps once again over two feet in the band of heaviest snowfall, so Wednesday and Thursday are most definitely the days to push back your snow banks. Farther south, snow will accumulate to between 6 and 10 inches before changing to a wintry mix of sleet and freezing rain. Farther south, still, snow will accumulate to around half a foot near and north of the Massachusetts Turnpike before warmer air changes precipitation to a mix or, closer to the coastline, rain. Of course, where we do change to rain we'll be raining heavily on top of snow, creating lots of heavy slush and also resulting in big puddles that will cause hydroplaning concerns. The farther south one is, the more heavy rain that will fall and therefore the greater the threat for urban, street, poor drainage and stream flooding to make a mess even late Friday morning into Friday afternoon. By Friday night and Saturday, some smaller rivers in Southern New England - especially Connecticut and Rhode Island - may exceed bankflow.
Colder air will set in Friday night and the combination of snow, slop, slush and puddles will all freeze over, but gradually rather than a flash freeze. This cooler air will moderate during the day Saturday, as deeper chill will wait in the wings to our north and west, allowing highs to jump into the 40s south and 30s north Saturday afternoon. Meanwhile, a cold front will be slowly settling across New England, prompting new areas of light rain and snow amidst building clouds, blotting out yielding breaks of sun from earlier in the day. Colder air will move in a bit more deeply on Sunday, bringing temperatures below normal across the area and serving as the start of a cooler streak that will last through the middle of next week, sure to continue great skiing and snowmobiling in the north.
Enjoy your Wednesday. Accumulations out tomorrow morning on NECN, and as soon as I can get a post out here, later in the morning.
Matt
Matt's Technical Meteorological Discussion: Updated Wednesday, February 28 at 1:20 PM
Hardly any time today due to lots going on behind the scenes but those of you who read often know I at least have to get some quick and succinct thoughts out on this upcoming storm - really wanted to post yesterday but had an appearance immediately following the midday show. So without further hesitation...
Quiet today, tonight and most of tomorrow with northwest wind gradually filtering colder and drier air southward from expansive high over Hudson Bay. The whole weather pattern graduallly moves E next 72 hours with that high shifting E across Canada and a primary low up into the Great Lakes while secondary shoots from TN river valley to coastline and then across NewEng. Good agreement on most facets of this storm among guidance and I think the biggest challenge is to present it in a clear, cohesive way for the public. That is, too much focus on the rain changeover shortchanges public on significance of snow burst Thu night. I've reviewed all model suites from 00Z and 12Z GFS/NMM and am astounded by amazing agreement on thermal fields. That's rare in a storm like this and - provided it works out correctly - is wonderful to see millions of dollars of technology paying off so nicely ahead of such a complex storm! Storm center should cut from interior Nrn NJ to position E of PSM and S of Casco Bay by 00Z Sat. This is a no-brainer for changeover near and S of path. Ahead of low center arrival, tho, deep and intense warm advection occurs with 70+ kt 925 mb llvl jet blasting up from the south, resulting in amazing speed convergence in the llvls directly over a tightly packed llvl baroclinic zone. This tremendous isentropic lift is going to result in some amazing precip rates Thu ngt into Fri AM for one and all in Central/Srn NewEng and is the reason I have no problem going for over half a foot Turnpike N and likely closer to 10 inches MA/NH border before changeover arrives. SE sfc wind - and E wind farther up the SNE coastline - will push ocean warmth inland. I can make an excuse to hold cold air at sfc from ORH hills westward thru most of the storm, but at 925 mb we don't hold that cold and therefore with such a warm layer so close to the ground, think change to freezing rain after brief sleet for these areas. Farther N into Lakes Region of NH, closer to a foot of snow is likely - perhaps even more - before a change to sleet. Farther N still, all snow and copious amounts of tropical Gulf of Mex moisture means another two foot storm. Last time we recorded 3 feet in Cambridge, VT (Valentine's Day), so can we do it again? Probably not given lower ratios thanks to less intense arctic air. That storm brought warmth and moisture into air that was barely above zero - this one will find air in the 20s and a very different lower atmospheric profile that should produce significantly lower ratios, so probably looking at 2 feet or perhaps a bit higher for the more impressive amounts. Have tried to indicate deformation band on the ptype overview map in the General Wx Summary. Farther S, change to rain doesn't come easily as this will mean lots of street flooding with big puddles courtesy of combo of clogged storm drains and melting snow. Major commute problems expected front end of Fri with wintry precip and back end with water - ice farther interior. Wraparound snow to stick in Whites and mountains of ME thru most of Fri ngt tho well pronounced dry slot moves into Srn NewEng by late afternoon, cutting off precip that is mostly warm advection driven in these areas that don't get into any wraparound. Watching for small river rises Fri Ngt into Sat, esp Housatonic, CT, Blackstone rivers, and smaller Central/Ern MA rivers may have to be watched, too.
Occluded air is mild air, at least as a general rule, so I've had to delay shot of cool until occluded airmass is out, and that means go mild on Sat. Normal highs would be around 40 and I've actually gone slightly above for most sites. Frontal boundary looked at for potential wave development on Sat or Sun now looks like it will be slower to drop S thru NewEng, and this decreases greatly the possibility of any meaningful wave S of us, and instead puts it overhead along the front, meaning enhanced regeneration of rain/snow showers Sat afternoon thru night is likely. Colder air for Sun marks leading edge of more significant chill for early and mid next week.
Enjoy the storm - will try to post something techie here tomorrow tho another public appearance so will have to crank in order to get it out. Will do my best.
See you on TV!
Matt
Monday's Discussion:
1:20 PM: A fun morning for snow lovers with the one to two inch per hour burst that came thru parts of Srn NewEng. Those of you who checked in here Friday and again for the special update yesterday may have wondered why I was holding onto accums the way I was for this burst and the bottom line was the combo of decent warm advection with an energetic vort. As for model performance, many will say the models blew it but the Canadian Ensembles were consistent and correct since last Thursday, and the ECMWF did very well with 700 mb RH field forecast from that far out as well, so let's be sure to give credit to the foreign guidance that has performed superiorly in most events this year. The NMM was certainly amazingly consistent, but amazingly consistently wrong, as it's been in other events this year.
Nonetheless, we turn to what lay ahead and that's another disturbance tonight. This time around the setup is different with a much more strung out, channeled vort that is weaker with far weaker isentropic lift. The result will be a far less impressive scenario. Omega is negative in the lowest layers of the atmosphere where boundary layer will be sufficiently but not strongly below freezing, and the corridor of max ascent is fairly low in altitude - 900 to 800 mb - meaning we're looking at a thermal profile only favorable for about 10 to 1 ratio most areas. For as unimpressive as this vort is comparitively speaking, it's doing a good job of regenerating the snow shield over the Finger Lakes today and that does represent a band of at least some isentropic lift that will fall more gently than last night but for longer duration. The result will be highest amounts where most orographic help is available, and that's in Western Central/Srn NewEng, esp west of the CT river valley. Good agreement on close to .25" here, and this is where I placed 3" average amounts. Decrease in amounts farther E is due both to lack of orographic influence and lack of PVA as vort becomes less distinguishable.
Similar setup for both Tue and Wed with no major forcing mechanism but low level baroclinic zone nearby for plenty of clouds and weak vorts riding overhead to enhance these from time to time. By Thu, key player is the confluent flow on south side of upper low over Quebec, as it will be responsible for holding the cold. Looks as tho it can do that for all of NewEng on Thu, but deeper moisture doesn't arrive until Thu eve/night when confluent flow begins to pull northeast and sfc high moves SE of NewEng. This is never a good position for Srn NewEng to get prolonged wintry precip, tho an initial burst is still a good possibility, and Central/Northern NewEng don't look all that bad for prolonged snow or snow to sleet in the case of some Central NewEng areas. At this point, it's a matter of fine details on placement of warm layer, but this should be encouraging for skiers and snowmobilers who are looking to extend a late-starting season.
Farther down the line I'm interested to see what happens with the cold front that this end-of-week system will pull down, as indications from Ensemble members are that it doesn't make it much farther south than NJ, which makes sense given a ridge battling back over the SE US. The curiosity here is that the combo of a front stalled there and an incoming shortwave raises eyebrows for a possible Sunday low pressure wave, but that is a low-probability event at this point given uncertainty in placement of the front and evolution of the shortwave. Either way, deeper cold to the tune of 8 C below normal at 850 mb streams south to begin next week, so no warmup to end February and begin March. By the second week of March, signals are for warmer and even above normal air at 850 mb, but a series of bubble highs moving E across Srn Canada may keep a classic late-winter NewEng chill in the air.
Enjoy your Monday!
Matt
