Evening Update: New site addition is the Winter Sports and Recreation page, linked here. Post introducing it is on the homepage. Enjoy! -Matt
One note: Please see main page if you haven't already for a truly awesome charity event to benefit military families, and children who've lost a parent in action, this Saturday.
Weatherwise, an upper level disturbance producing plenty of clouds has also been carrying rain and snow showers from west to east into and through New England Thursday afternoon. This disturbance is just another in the string of repeating jet stream disturbances high in the sky, prompting the development of weak surface low pressure centers and gradually tugging one slug of cold air after the next farther southeast. Though it's coming in marked installments, the cold air will settle over New England for much of the upcoming weekend. As the cold lets go, warmth and moisture come streaming in, producing a swath of snow and rain by late Sunday and Monday.
For now, the quick changes that have been occurring aloft
should be an indication that the weather pattern remains active. As
mentioned here earlier in the week, the jet stream winds high in the sky that
steer our storms and disturbances are racing across the country,
screaming across the Pacific Northwest before dipping into a broad and slowly deepening trough over the eastern two
thirds of the United States. The nature of this trough, and the fact
that has been slowly sinking southward, means cold air has only gradually been settling south,
as well, and each time an energetic disturbance drops into the trough
it holds the potential to strengthen on its trip across the Eastern
United States, and to deliver another shot of cool air in its wake. Each upper level disturbance carries a
reflection of at the surface, as well, either as a surface trough
(wind shift), a series of fronts, or a developed storm center. Today's system has come with a weak surface low pressure wave along a cold front, draped from north to south and pushing east through New England. Ahead of the front, southerly winds gusting to 35 mph have transported warmth northward all the way into the North Country, where deeper valleys will be too warm for anything more than a rain/snow mix and perhaps a solid coating of snow, but terrain above about 1500 feet will see all snow, and that snow line will work lower in elevation Thursday evening. In fact, behind the front winds will stay active but will shift direction to blow from the west. This cold windflow has already begun picking up moisture off of the Great Lakes and has been producing lake effect thunderstorms - later to be intense lake effect snow bands - off of Lakes Erie and Ontario. The band of snow off Lake Ontario will thrive as another follow-up disturbance aloft moves across Upstate New York and New England Thursday overnight, and that same disturbance along with lake moisture will keep snow squalls going on the west facing mountain slopes of Northern and Western New England, with amounts of 2"-5" likely in these spots. Elsewhere, Thursday night's west wind will add a chill factor to already dropping temperatures beneath partly cloudy skies, making it feel like it's only in the teens!
Though chilly air will be in place for Friday, the approach of yet another energetic disturbance will
prompt a west to perhaps even southwest wind in the lower few thousand
feet of the atmosphere on Friday, keeping deep cold just north and west of New
England and bringing the likelihood of more mountain snow squalls
Friday afternoon and night. Behind this disturbance, the floodgates to
deeper cold will open and a cold, windy Friday night will give way to
an intensely cold Saturday for some! The chunk of air heading for New
England this weekend originates where high temperatures have only been
in the single digits and teens over South-Central Canada, and today observed over the Upper Midwest, but the cold
will certainly moderate as it moves southeast. Nonetheless,
temperatures will struggle to get out of the 20s in many communities
of Northern, Western and Central New England Saturday afternoon, even with any early morning clouds giving way to
sun. While temperatures in Southern New England may be a touch warmer,
an active wind will drive the wind chill even lower!
Sunday will begin quiet after a very cold night Saturday night, but
problems will be afoot. One source of the problems coming for Sunday night and Monday is the active jet stream and the numerous northern stream disturbances those jet stream winds are steering across the northern tier of the United States, redirected farther south as the jet stream winds dip south into the Eastern United States trough. Another player in the forecast, however, is an intense upper level storm southwest of the Baja Peninsula, left behind several days ago by the jet stream winds and a source of substantial moisture pluming out of the Pacific. This Pacific tropical moisture will take aim on the Southwestern United States, delivering a few inches of rain to the Phoenix area Friday night - not necessarily a common occurrence for this time of the year - then feeding into a storm center developing near the Rockies as a result of northern stream energy. Obviously, when combined with the contrast of cold air spilling through the Northern United States and warmth over the Southeast, the players are involved for a strengthening storm to move across the nation, and that storm will move through the Great Lakes on Sunday after crossing the Central Plains and Midwest on Saturday. The expansive counter-clockwise flow of air around this storm will pull warmth and moisture northeast across the Ohio Valley and Mid-Atlantic on Sunday, prompting the development of a second storm center somewhere around the Delmarva Peninsula and Atlantic City, New Jersey, on Sunday afternoon and evening. Of course, such development along the coastline means the Atlantic Ocean will become involved as well. This developing storm, in conjunction with the primary storm wrapping through the Eastern Great Lakes,
will usher warmth and moisture into our cold dome resulting in thickening clouds on Sunday after morning sun, with highs stuck in the
lower to middle 30s south, and 20s north. As moisture increases, the threat for precipitation grows, and precipitation is expected to develop from southwest to northeast Sunday afternoon and evening. The air in place will be plenty cold enough to
support snow in most of New England and I still
expect widespread accumulating snow to develop from southwest to
northeast Sunday evening into Sunday night for many areas. The key to determining the
forecast from there is based on the track of the storm Sunday night
into Monday. With the original storm
center tracking to our west, the secondary storm developing along the Mid-Atlantic coast at this point is expected to track across Southeastern Massachusetts and into the Gulf of Maine on Monday. Such an evolution would still spread not only
moisture but also warmth into New England as the cold air gradually
lets go without a big Canadian high pressure cell to keep it in place, and is the reason I think we'd see our burst of accumulating
snow Sunday evening and early Sunday night turning to rain from south
to north, then falling primarily as rain into Monday. Nonetheless, this still may be sufficient to whiten the ground in Southern Connecticut IF the onshore flow doesn't scour out the cold first (a southeast wind this time of year with ocean water in the upper 40s means even if it does snow so far south, it would be unlikely to last much longer than a whitening), and to bring out the plows for a lot of New England as at least a couple of inches would be possible through interior Southern New England, with higher amounts the farther north one goes, primarily away from the warm ocean. In fact, if the forecasted track across Southeast MA and into the Gulf of Maine verifies, this would change snow to rain in most of Southern New England late Sunday night into early Monday, but would keep snow falling through interior Maine (away from the coastline), all of Northern New England, and perhaps North-Central New England as well (see map on New England Forecast page for definition of south/central/north)! This means the potential is there for a significant snowstorm through the interior of central and *especially* northern New England Sunday night through Monday.
Behind the storm, regardless of whether you see rain or snow or both
at your house, cold air will come streaming into New England, and I
expect next week to be a cold week before we see an easing of the the
cold for the latter half of December. Not necessarily a disappearance
of the cold thanks to a pool of remaining cool over the Northeast for
awhile, but certainly a dramatic lessening of the below normal cold as
we slowly be exhaust our supply of Canadian cold for now, leaving above
normal temperatures though most of North America for the second and
third weeks of December. In the short term, this will have no negative
impact on winter sports as temperatures will remain cold enough for
natural and manmade snow in the mountains. Admittedly, the longer
range consequences will depend on whether we reload Canadian cold by
the end of December, though with warmer than normal temperatures
expected from Siberia to the Arctic Circle in the middle of December,
that may be a tough task to accomplish. That's obviously a long way
out, but winter resorts should make hay while the sun shines, so to
speak, and blast snow as much as you can in the coming couple of weeks.
Have a great Thursday.
Matt
Matt's Technical Discussion - Updated Thursday, November 29 at 2:35 PM
I'll spare you from a re-write of all the details in yesterday's techie, which is below, and just expand on a few issues worth re-evaluating, esp the Sunday/Monday scenario.
Short term everything is working out about as planned, and lake effect band is impressive over Western NY off Lake Erie with thunder and lightning. Real fun comes when colder air streams in! Band of LES expected off LO (Lake Ontario) tonight and this will extend east quite a way thanks to steep low level lapse rates so I expect enhancement owing to topography when the convergence band reaches the Greens, with recurrent squalls on the western slopes where 4" of snow may fall in the Southern Greens, with a general 2"-4" in the higher terrain of the Greens and Whites between afternoon, evening and night squalls as a followup shortwave, channeled but moderate intensity, rides overhead tonight.
I've been watching Friday's shortwave all week so why take our eyes off of it now? It's the one to drive the most meaningful cold front thru Fri ngt and should drive some meaningful mountain squalls thru, too, tho probably not much action farther south where terrain won't provide such a helping hand outside of the Berkshires. These squalls should be fairly intense overnight when they come thru for Nrn NewEng and will drop several inches of snow in esp the Nrn Greens.
No change to Sat. Sunday questions are abound but the questions get more finite with time, and that's a good thing and how this is supposed to work! As the big issues resolve, the smaller details become the pivotal points. Let's start with the big issues and that's the respect for this system not only because of the baroclinicity assoc with cold north/warm south airmasses, and not only thanks to active jet stream loaded with Northern Pac vorticity, but also the deep tropical Pacific moisture input from the upper low by Baja, which will pump an amazing few inches of rain into Phoenix Fri Ngt before being ingested into developing Rocky Mtn low. This low will follow the mean flow across the Central Plains, Midwest and Great Lakes which of course is typically a warm track for NewEng. But there are a few other factors for NewEng to consider, including both antecedent cold air and secondary low development. Let's deal with the latter first - secondary development. I still think with the amount of energy at play and more importantly the cold wedge of air over the Northeast secondary low development is likely, but that's really not a question anymore anyway - one of the bigger issues that becomes self-evident. Now the focus is where does it develop, how quickly does it strengthen and where does it track. Though guidance solutions to these issues are varied, the Canadian Ensembles have done a phenomenal job of leading the way on the past several events and have been leading the way this time, too. They are in good agreement with the Operational Canadian and now the GFS Ensembles - making their third major shift in three days - are close, too. This would develop secondary low near Delmarva/Srn NJ 00Z Mon and carry it over Cape Cod 12Z Mon to position S of Washington County, ME, by 00Z Tue. I'm not sure I buy a track over Cape Cod - seems a little too far southeast - but the end game puts the storm where I'd expect it to be near Downeast coastal ME and ready to shift E toward Nova Scotia. The reason I think I'd favor a slightly farther northwest track over SE MA instead of the Cape (splitting hairs?) is the same reason I don't think there's much real chance of this being an all snow event for most of Southern New England. And that reason brings us to the former of the two points for discussion - the antecedent cold air. It is impressive, it is dense and it will provide for snow in many spots. But it lacks a good high to hold it in place over Eastern Canada as the high splits north and south with both centers weakening and retreating in their respective directions. You can't change the facts that without a strong Eastern Canada high, you cannot hold the cold. No matter how cold the models want to make it, reality almost always will prevail, and especially when your water temperatures are between 45 and 49 degrees and a southeast wind is forecasted. In fact, there's a real part of the forecaster that should be wondering how much of Srn CT/RI/SE MA would get into any snow at all, but that really comes down to precip timing. With a SE wind developing and strengthening ahead of the primary, then secondary low developing along the primary warm front, this all favors a strong marine influence warming the far Southern parts of NewEng. Therefore, to get snow you'll have to bring the precip in before the SE wind does its dirty work, which you have a much better chance of doing in Srn CT than you do on Cape Cod. Farther inland one is, the longer the cold will hold, but without that good high you really can't hope for more than a warm advection burst that could still not only drop a couple of inches but would bring the plows out Sunday night through interior Srn NewEng, at least (maybe to the coast in some spots - again, a fine detail that really can't be accurately worked out so far in advance) before the change to rain. At some point, however, the warm advection stops. This is apparent in the S-shaped thicknesses that carry northwest of the center and it's on the cold side of this baroclinic zone that the most snow will fall. There is actually rather surprising agreement among the guidance today on this baroclinic zone lining up from Srn VT/NW MA to SCentral NH to interior ME, away from the coast by several miles. If this pans out, areas north of that line would be in for a substantial snowstorm, and near that line a heavy wet snow would fall. David Majercik, our NECN weather observer from Westhampton, MA, would probably be south of the action, but points out the fruit trees still have 80% of their leaves on them...any of you reading this know the status of fruit trees farther north...add 'em in the comments or email me if you do, I'd appreciate it, as it'll be a concern for damage to those trees if they still have their foliage. Of course, wind would increase owing to pressure gradient, as well, on the S and E side of the storm but with inverted trof between primary and secondary low, and with absence of strong sfc high, wind probably wouldn't be a huge factor in the snow spots...at least that's my initial thought. Though remember, inverted troughs are important for enhanced convergence and enhanced precipitation amounts!
The longer range thoughts beyond that haven't changed.
For now, there are still questions to be worked out with the storm but I'm actually really impressed by the overall consensus of the guidance at this point - sure we could find differences in exact placement of a 0 C line, etc., but at this stage of the game, synoptics are key (our brains can take it from there) and the synoptics, at least right now, are in decent agreement. I'm also really happy to see the agreement is upon the solution I've been believing in...at least for now - we all know that can change!!!
Have a great Thursday. I have a public appearance tomorrow so have to guess I probably won't get a techie out unless I'm Speedy Gonzales.
-Matt
Wednesday's Discussion:
Last night's snow amounts a bit of a surprise for me in places like
the 5.5" of East Montpelier but conditions were favorable for windex
event so I suppose I should have been more cautious of this.
Nonetheless, dissipation of clouds for most areas with dry air today
and temps have been highly elevation and latitude dependent. Cold
draining north wind has pockets of lake effect clouds floating around
the shores of Lake Champlain while mountains hold some bands of
orographically enhanced clouds. Downwind, downsloping wind is stronger
that I'd have expected as high axis has been slower to move east. What
are the effects on this slower high progression on the forecast? Logic
says longer period of quiet wind tonight so valleys decouple and Tds in
the teens suggest even Ci clouds spilling in shouldn't stop a drop into
the 20s for many places with teens in valleys. Increasing clouds
expected Thu ahead of next shortwave, which does a decent job of
winding up en route to NewEng. Though there is limited moisture to
work with when sfc reflection weak low along cold front crosses NewEng
on Thu afternoon, there should be good low level isentropic lift with
positive theta-e advection in esp central and northern NewEng. The
northern focus of advection will also mean a northern focus of precip,
and Northern neweng is where I expect heaviest precip amounts to fall -
though guidance is backing off on QPF and now general good agreement on
either side of a quarter inch. Ratios won't be great given low level
warmth, and 925 mb temp fcst from GFS brings 0 C line all the way to
the Canadian border at 18Z Thu. NMM is typically colder, and a good
question to ask is which product to trust more. As of this writing, a
blend may have been the best way to go for today, a morning whose 00Z
runs predicted 0 C and -6 C for the same Southern NewEng locale on GFS
and NMM, respectively, and a difference between -6 C and -12 C at 925
mb in Northern NewEng. This is a ridiculous difference in only an 18
hour forecast and left me scratching my head this AM at exactly what's
going on between the guidance here, and diffs are evident for Thu when
ptype is a factor, though diffs are not as pronounced. Nonetheless,
using blend of thermo profiles yields mostly snow with dynamic cooling
near Canadian border and in far north, snow above 2000 feet for rest of
Northern NewEng and mountains of Southern Greens, and rain/snow combo
in Northern NewEng valleys that may coat grassy surfaces but should
melt on roads with warm BL temps.
Shot of cold tries to follow Thu ngt into Fri but is cut off by fast
flow with next shortwave already inducing weak WAA, so will go cooler
but not deep cold and keep chc mountain snow squalls with vort passage
later Fri into Fri night. Deep cold should arrive on active wind Fri
ngt and be in place on Sat, when MOS guidance begs for low to mid 30s
but progged 925 and 850 temps on GFS support widespread highs only in
the 20s even with ample sun after any morning clouds and ECMWF only
slightly warmer - a solution I've followed for now given downslope flow
and propensity for elevation/latitude based cold. Haven't gone highs
in the 20s for everyone yet, but felt free to go below MOS in all spots
and am willing to drop more if it looks like guidance falls in line
with coldest GFS.
Plenty of cold in place on Sunday as next storm approaches. HUGE
shift in the GFS Ensemble guidance over the last 24 hours from
secondary strong SE of NewEng to primary strong west of us and perhaps
weak secondary overhead. That fits the forecast I had going based on
Canadian Ensembles which really have led the way this season thus far.
This will mean swath of warm advection snow Sun PM into early Sun ngt
but unstoppable warmth with retreating Canadian high means over to rain
after a few inches of snow most spots and if a secondary cuts over
Southern NewEng, northern mountains could keep snowing and make out
quite well!
Thoughts on longer range are laid out in General Wx Summary but are
based on idea of Ern US trof keeping pool of cool aloft after intense
dish of cold behind Mon storm, and that cool pool likely lingers into
second week of Dec. This can occasionally result in coastal snow
storms, but once the cool pool is gone we're above normal across most
of the high latitudes and that means no deep cold likely second half of
December until we can reload Siberia or the arctic circle.
I'm excited to share with you my newest page on my website - the Winter Sports and Recreation page! Many of you who utilize my site daily are avid skiers, snowmobilers and winter sports enthusiasts, and you deserve this page! It can be accessed under the list of Mattnoyes.net pages in the left sidebar.
Snow squalls have been a recurring theme in the mountains of Vermont, New Hampshire and Maine this week and will continue into the weekend. Alex Kaufman grabbed a shot of the snow at Sunday River and writes:
AN EVENT SURE TO BE A TON OF FUN, FEATURING A NUMBER OF LOCAL CELEBRITIES, WITH A SINCERE MESSAGE OF CARE DURING THIS HOLIDAY SEASON - AND WE WANT YOU TO BE THERE THIS SATURDAY!
