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:
While New England enjoys a relatively mild day on Thursday, big changes are on the way, as a storm Friday will mark the start of a transition in the weather pattern to a decidedly more winter-like appearance by next week. Intense energy dropping south from the North Pole will deepen both the cold air and increase the potential for storm growth in the Eastern United States by the beginning of next week.
Thursday undoubtedly began with more clouds than I'd anticipated - thanks at first to low level moisture trapped after yesterday's rains that bubbled into clouds during the overnight - clouds that I expected to be near ground level as fog, but instead formed above our heads. These clouds developed beneath what's called and "inversion" in the world of meteorology. Normally, temperatures get colder the higher up one goes in the sky in the layer of atmosphere where weather is made, but an inversion is a warm layer of air aloft - that is, a setup where the air gets warmer as one rises in altitude, and that was the case early Thursday morning. With a weakening sun angle, and cool air trapped beneath a consistently warming atmosphere aloft, it becomes difficult to entirely erode this inversion, and the result is stubborn clouds. Nonetheless, downsloping flow allowed for some mixing in the Connecticut River Valley Thursday morning, and that area of drier air has slowly been moving east across New England, followed in turn by more clouds that you can follow with the visible satellite imagery linked at left (during the day - infrared imagery after dark). With breaks of sun amidst the clouds, temperatures will once again respond fairly well, especially when aided by a southwest breeze.
Meanwhile, the next round of clouds is already on the move toward New England, well ahead of the next developing storm over the Mississippi River Valley, where lines of showers and intense thunderstorms are raging Thursday. This developing storm is the result of one chunk of substantial energy carving out a trough in the jet stream over the Central United States. Remember that the jet stream is the fast river of air aloft that steers our storm systems and acts as a thermostat for the atmosphere, separating cold air to the north from warmer air to the south. With a storm developing at the dip in these jet stream winds - the trough over the Mississippi Valley - it will be able to feed off of the difference between warmth and cool air, and will be driven by the strong, energetic jet stream winds aloft toward New England. As clouds thicken from north to south during the day Thursday, showers will follow suit, with showers developing Thursday afternoon in the north, then expanding over Central New England during the evening. By Thursday night, showers will expand into Southern New England witih most areas seeing showers by midnight.
All the while, the developing storm to our southwest will be strengthening and charging toward New England. This should deliver a swath of rain, heavy at times, to New England on Friday, with gusty winds as the storm strengthens directly overhead. I continue to favor a track over Eastern New England on Friday, and this will likely dump heavy rains in most of New England, falling fastest between mid-morning and late afternoon. This will limit warm winds to areas east of the storm track - especially Cape Cod and the Islands - where thunder would be possible in some of the rain bands. Additionally, this track will bring a strengthening storm over Eastern New England, cranking winds up quickly enough for gale force gusts from the southeast ahead of the storm in the Mid and Downeast coasts of Maine late Friday afternoon and Friday evening, and perhaps strengthening the storm quickly enough to even deliver gale force winds from the southwest to Cape Cod and adjacent waters Friday evening under the belly of the storm. All the while, the counter-clockwise circulation will continue to tap cold air from Southern Canada, tugging it closer to New England, and is likely to create a period of snow showers for the mountains of Vermont, New Hampshire and Maine Friday night (into Saturday morning in northeastern Maine) before tapering as drier air takes hold of New England.
The drier and cool air moving in will bring a decent Saturday after any lingering snow showers in Northeastern Maine, with a blend of sun and clouds elsewhere. After a chilly Saturday night, expect dry conditions to begin Sunday - so...all in all...most of New England does enjoy a decent fall weekend. That said, the next blast of energy - two strong disturbances merging from the Pacific and from near the North Pole - will be gathering strength and moisture across the nation's midsection. Clouds will increase Sunday and showers will likely develop by evening from west to east. This will set the stage for what will likely be a powerful storm for New England Monday into Tuesday. With cold air prior to the storm, and more cold air on the backside of the circulation, the threat for more widespread snow is present across Northern New England at the beginning of next week. This is a potential that needs to be monitored carefully for a possible early-season snow on especially the Northern Mountains. The most likely scenario would be for precipitation to begin late Sunday as a mixture of rain and snow or perhaps all snow but light in intensity across Northern Maine later Sunday night. For a time, most areas will see rain on Monday, but with substantially colder air available immediately west and north of the storm, rain should transition to snow later Monday or Monday night across the North Country. With moisture present, a northwest wind pushing up against the mountain faces, and cold air streaming in, "upslope" snows are likely to be generated Monday night through Tuesday in the Greens, parts of the Whites and the mountains of Maine.
While this surge of cold air will bring the potential for an early-season accumulating snow to Northern New England early next week, we'll all feel the result, as next week should be marked by much-below normal temperatures - perhaps producing record cold around midweek from the Northeast to the Mid-Atlantic, though admitedly, our records are already quite cold for the middle of next week - some dating back to the late 1800's, and the Mid-Atlantic may see a better chance of realizing record values. None the less, it'll be plenty cold!
Have a wonderful Thursday.
Technical Discussion: Another public appearance today will keep me from a techie discussion, but will have on tomorrow to take us into an exciting weekend.
Matt
Matt's Technical Meteorological Discussion: Updated Wednesday, October 16 at 3:05 PM
'Tis the season for surges of winter amidst lingering tropical warmth and moisture, and NewEng shud see both in the coming week. Tropical airmass in place as of this writing thanks to delivery by former TS Norman who chugged over NewEng last night dropping rainfall amounts over an inch to some, and under a quarter inch to others. Nonetheless, the storm has left behind an appreciable chunk of tropical warmth directly from the Gulf of Mexico and areas with sun have seen corresponding quick temp rises.
Shortwave embedded in the flow to cross between 18Z and 00Z this afternoon and have adlibbed isolated shra/tsra with warmth and low level moisture in Srn NewEng, tho cov'g should be limited. Enuf dry air aloft for breaks to remain in clouds overnight tho fog will be dense in many areas with relatively light wind and high dewpoints.
Fog and sun starts Thu before clouds advance along midlvl baroclinic zone stretched across Nrn NewEng. Approach of shortwave energy to interact with this zone in generation of showers for Nrn NewEng by early afternoon, expanding S as cool front approaches from NW and baroclinic zone tightens. Leading s/w ejects NE from base of Central US trof on Thu and fills showers and period of rain in across Srn NewEng Thu eve into the ngt. Thereafter, attention turns to strong shortwave migrating rapidly E in Westerlies. Tho this s/w will be strong, it will also be progressive until it reaches NE NewEng later Fri, where it interacts with colder air aloft and deepens/closes off NE of ME. There has been some issue as to the path of assoc sfc low pressure center(s) with this vort max, more so with the secondary low than the primary, which will cut north of NewEng. The secondary has been progged from NYS to offshore NewEng as a nor'easter (ECMWF) but consensus likely to be best, not to mention the solution of the GFS Ensemble mean - which places triple point low over Ern NewEng - inland - perhaps getting Cape Cod into warm air as it swings thru but bringing gale SE gusts to the mid and downeast ME coast and perhaps gale force SW gusts under the belly of the strengthening sfc low to SE NewEng.
As this storm wraps up while moving NE Fri Ngt into Sat, still feel there is enuf basis to include potential of snow in the fcst for Nrn/NE ME with wraparound precip early Sat. While operational models have varied greatly for this time period, GFS Ensemble mean has stuck to its guns of keeping high chc pops in NE ME at the same time cold air in Srn Canada is ingested into storm center. Additionally, with upper level low closing off, moisture wraps around back of circulation and will maintain chc snow showers in Nrn ME for Sat AM. Precip also may end as a few flakes in Nrn mountains of NE VT/NH where upslope flow can generate enuf lift, but dry air quickly moving in behind storm by that point. Ridging is quick to move back in aloft and this will mean cool but dry most of NewEng Sat into Sun. Next s/w in line is one that recently ejected from the Aleutian low and will drop into Central US trof, ejecting NE into NewEng like its predecessor, but with enuf airmass modification for rain in all locales except perhaps in Nrn ME where warm and moist advection will ride overhead before llvl flow can swing out of the N and this means a brief pd of light WAA snow would be possible in Nrn ME later Sun ahead of the s/w. Warm advection should win out Sun Ngt, however, with all areas going to liquid.
The real meteorological fun only grows more intense early next week, as a strong shortwave dropping south from the polar vortex near the North Pole will merge with a Pacific counterpart and amplify handily at the base of the trof to our west on Monday. The trick here is that the storm Sun into Mon will have already yanked down a hearty chunk of cold air from Canada, and the motherload of cold will be heading east across the Midwest. This will be another chunk of record cold in Iowa, and will end up spelling record cold for the Mid-Atlantic and at least some of the Northeast by the middle of next week. But the transition to this cold will likely come with an intense cyclone as the upper low deepens and generates its own cold air through continued dynamic cooling over Southeastern Canada, and drives sfc cyclone development over or very near to NewEng on Monday. This storm will already have picked up plenty of Gulf moisture during its amplification, and with the cold air to the north and west of the storm, sufficient baroclinicity will meet sufficient vorticity to generate a powerful storm whose circulation will tap the cold to our west and northwest. The result should be enuf cold air meeting up with a wound up storm that will wrap significant mositure around its west side to generate snows from Nrn ME thru the North Country where upslope flow will play a significant role. In fact, the situation looks quite favorable for accumulating upslope flow snows in esp the Green Mountains as cold advection meets with moisture on a strong NW flow. While this will not spell snow for Srn NewEng, it will spell a great pattern for cold air - a prolonged NW flow at the sfc meeting up with an airmass to the tune of 12 C below normal, creating record low temperatures, especially by midweek when winds will weaken but WAA will not have begun yet, and overnight lows should plummet.
What could change this outlook? Obviously storm track and timing of cyclogenesis is crucial. Slightly farther east...or west...upsets how the cold air and the storm can interact and the wind direction. This won't change the cold - that's coming - what it would effect is the potential for accumulating snow. But at this point, I'd say it's certainly the best chance of snow the North Country has had since spring.
We'll keep an eye on it together.
Matt
Monday's Discussion:
1:40 PM: Slow moving wx pattern has been northern stream dominated of late but that will change in the coming days as trof continues to dig in Wrn US and sends subtropical jet springing northward. This subtropical jet is active with the remnant of Norman, a former tropical storm who churned across the Eastern Pacific before crossing Mexico, then regaining an impressive satellite signature over the Western Gulf of Mexico this weekend before making landfall early Monday into the Eastern TX coastline, where winds gusted in excess of 40 mph. Torrential rain has been lifting north and will turn NE as it encounters the fast flow of the westerlies across the Midwest, and the vort max assoc with the remnant of Norman will charge NE and directly over Srn NewEng late Tue Ngt and Wed AM, bringing a shot of heavy rain with it.
In the meantime, high altitude Ci clouds will spill overhead in waves Mon Ngt as thicker moisture puts on the brakes crossing OH Valley, but dry air and light wind shud still allow for temps to fall quickly after sundown. If enuf Ci spill overhead, my fcstd low temps will be a bit too warm, tho with Tds in the upper 20s to around 30, I'd imagine most locales will see frost, and concern is for perhaps pockets of black ice where freezing fog may result in Pioneer Valley through Monadnock Region and Central NH. Any sun early Tue will quickly help to mix the atmosphere, tho Ci clouds will thicken and lower as midlvl moisture spreads NE across NewEng thru Tue.
Slug of moisture slated for Tue Ngt shud come in with progged vort max as referred to in first paragraph. 12Z GFS a bit drier than its preceding run, 12Z NAM not much more moist and still noticeably drier than GFS. Canadian Ensembles and GFS Ensembles both lean toward wetter solution, while most guidance insists on quick solution. Wet and quick both make the most sense with slug of isentropic lift intense thanks to tropical slug but quick moving embedded in the subtropical jet. The net result shud be a shot of 1" QPF for most of Srn NewEng with locally higher amounts, then lesser amounts Nrn half of NewEng. As warm and moist advection wanes Wed AM, rain will taper, tho quick progression of warmth and moisture aloft leaves behind the corridor of warm advection in the llvls, and this means plenty of moisture is left behind at 850 mb and below. Hence, clouds linger thru most of day Wed tho a few breaks not impossible Wrn areas as sfc inverted trof/weak warm front moves E and brings westerly flow, while drizzle immediately behind rain assoc with shift of winds to the N and llvl cool advection shud be found in ME coastline.
Still will have sfc low assoc with llvl remnant of Norman that will eject off MidAtl coastline and pass SE of NewEng, while new shortwave induces sfc low development in the Great Lakes and drags cold front with multiple waves across OH and TN valley. This front with waves will enter the I-95 corridor Thu Ngt and strengthening wave with tropical moisture will be rippling thru MidAtl Thu Ngt en route to NewEng for Fri. This happens at the same time Nrn stream wave moves E, carrying cool air behind it, and this is enuf to at least peak interest in how the incoming cold air will interact with northward rippling moisture-loaded wave. I say this because, at some point, these two features really should link up, but the question is how quickly does that happen? The 12Z GFS is one of the quickest to merge, and while I do think the GFS tends to handle waves of fronts better than most of the guidance, the key here is more in the handling of the Nrn stream shortwave, which takes on a neutral/negative tilt at the end of this week but does so just a bit too far west on Thu to let the cold come flooding in as quickly as the new GFS would paint. I think the end result is that the merger of cold and tropical occurs E of ME later Fri, and this means Nrn ME will be on-guard for wrap-around precip...and yes, perhaps snow...late Fri into early Sat. Certainly something to watch carefully.
Another watcher will be the beginning of next week, which the GFS Operational has not been nearly as bullish on as its Ensemble member counterparts, but bullish may be the way to go for next Mon/Tue as polar vortex deepens over SCentral Canada before nudging east and quite literally helps to create its own cold air that should be quite eager to move into NewEng, with strong energy aloft and sfc baroclinicity ready to encourage sfc low development over or near Ern NewEng, and once again raising eyebrows for those interested in snow prospects for the North.
We'll see...plenty to work out between now and then.
Matt
