Very cold today, then major snowstorm through Monday; then cold gradually moderates with mostly dry weather except a little snow Tuesday and later next week along and northwest of Appalachians; more arctic air with storminess possibly resuming early February

Plain-language summary: 

 

Our region is experiencing the coldest air of the season just as the enormous and widespread winter storm affecting the southern and eastern U.S. is turning northeastward into our region as a major snowstorm, especially in southern areas where 8-14" (20-35 cm) will fall with locally higher amounts, a surprise compared to expectations several days ago. It will be a long-duration snowstorm with dry, fluffy snow. It will then continue to be cold, though slowly moderating, with mostly dry weather except a little snow Tuesday and later next week along and northwest of the Appalachians. Renewed arctic air with resumed storminess could occur some time in early February.

 

Meteorological discussion: 

 

Major and long-duration snowstorm through Monday with generally light to moderate snowfall rates and dry, fluffy snow

 

Our region is experiencing the coldest air of the season, with an arctic surface high pressure parked over our region. The northwesterly flow straight out of the arctic with little modification on Saturday, courtesy of the very negative AO, combined with mostly clear skies and light winds, led to some rural and cold hollows falling below -22F (-30C) this morning. Just as this is happening, the enormous and widespread winter storm affecting the southern and eastern U.S. is turning northeastward into our region as a major snowstorm. This is quite different from model solutions several days ago showing the storm staying well to our south. Even multi-model ensembles generally did not show any real possibility of the storm reaching our region. However, an upper-level trough in western Canada digging farther south and west, allowing it to interact with and pick up (even if not entirely phase with) the much more moisture-laden subtropical jet disturbance over the southwest U.S. Combined with the suppressive upper-level low over Atlantic Canada that moved eastward out of our region faster than modeled, the upper-level flow is now southwesterly instead of westerly, allowing the storm to pick up Gulf of Mexico moisture and ram it northeastward into an extremely cold air mass deposited behind Friday night's cold front. It is this clashing of rich moisture into arctic air that is producing such a huge area of snow and ice.

 

Source: TropicalTidbits

 

 

Source: TropicalTidbits

 

 

For our region, it will be just snow, and it will last longer than most snowstorms, around 24 hours or even a bit more for many. The warm advection snow will initially push into Vermont through Maine this afternoon and evening, accompanied by warm frontogenesis. Precipitation rates will be heavier to the south where the moisture will be wrung out before reaching the very cold air in our region, but light to moderate snow will encompass almost the entire region. Then, the slowly-strengthening upper-level trough still hanging back to the west will provide additional forcing for ascent late tonight into Monday, targeting an area slightly north of the warm advection this evening, with a pronounced dry slot in between to the south but staying south of our region, ensuring a continuous snowfall for our region. The long duration will make up for missing the heavier precipitation rates to the south. In addition, temperature profiles support a very deep dendritic growth zone (between -10C and -20C where the big, fluffy dendrites develop), and with relatively weak winds, the dendrites will not shred apart easily. Due to this, high snow-to-liquid ratios of 15-20:1 are expected for most of the region, producing a large fluffy accumulation of 8-14" (20-35 cm) south of the U.S./Canada border from Ontario/New York to Quebec/New Hampshire and extending into central Maine, with locally higher amounts where heavy bands form. In far northern regions, the moisture and ascent will be less, and the atmosphere might actually be too cold for ideal dendrite formation, and the ascent might not be strong enough to generate enough supersaturation in the clouds for ideal dendrite formation, which could lead to lower snow-to-liquid ratios.

 

Source: TropicalTidbits

 

 

Source: Weather Prediction Center

 

 

Cold continues for rest of the week though slowly modifying with a little snow Tuesday and later in the week, mostly in areas along and northwest of Appalachians 

 

After the storm leaves Monday evening, it will likely be much drier for the foreseeable future, with arctic air continuing to dominate though slowly modifying as the cold air mass gets cut off from any additional reinforcements from the arctic due to strong Greenland blocking (-NAO). At the same time, the Pacific jet will become a little more active, which will promote arctic air to retreat from most of the U.S. and western Canada at least. However, with the upper-level ridge in western North America continuing to dominate (+PNA), upper-level troughs with cold air from the north will still push into our region and prevent any thaw. But this upper-level trough (actually cutting off into a very broad upper-level low) position over New England into Atlantic Canada promotes a northwesterly flow cutting off our region from any Gulf of Mexico or Atlantic moisture again. A weak clipper will move into our region later Tuesday but will be weakening and produce very little snow. Interestingly, the weather pattern could be so blocked that the broad upper-level low over Atlantic Canada could wrap a little Atlantic moisture counterclockwise into Labrador and then southward into region later next week, and these situations lead to warm advection from the north, which could lead to light snows. Given the brisk northwesterly flow, the snow will likely be limited to areas along and northwest of the Appalachians.

 

Source: TropicalTidbits

 

 

Slight chance of an East Coast storm around next weekend or a bit after, but most likely missing our region, then potential for renewed arctic air and increased storminess some time in early February 

 

Next weekend, another storm in the subtropical jet will be moving eastward across the southern U.S., possibly producing snow there, but given the broad upper-level low in our region through Atlantic Canada, this storm will likely scoot out to sea well to the south of our region, unless a clipper in central Canada can be more amplified and dig much farther south than currently shown on the models and phase into the southern storm to produce a big East Coast snowstorm, a scenario that a few rogue model runs and ensemble members have shown occasionally. After that, a brief mild spell is possible as the western North American upper-level ridge tries to nose eastward into our region as arctic air continues to gradually retreat, though the -NAO and western Atlantic upper-level trough could thwart any thaw, and a clipper or two in the northwesterly flow could bring light snows. It is possible that beyond that, the upper-level ridge in western North America amplifies, retrogrades to the West Coast, and noses into Alaska again, allowing for another amplified upper-level trough with renewed arctic air to push into the central and eastern U.S. some time in early February. Given the +PNA, -NAO, and -AO continuing, and the upper-level trough position farther west, that could be more favorable for storminess and snowiness to resume in our region, though the upper-level trough could still be too far east as well.

 

Source: TropicalTidbits

Source: TropicalTidbits

  

 

Source: Climate Prediction Center

 

Widespread snow showers through tonight, heavier and steadier in southeastern areas tonight and Sunday night; light snows in northern areas Monday, Wednesday, and Friday; extreme cold but likely drier after, possible moderation end of January

Plain-language summary:

 

It is relatively mild today with snow showers throughout the region, though with steadier and heavier but still modest snow from southern Vermont to eastern Maine through tonight. Another modest snow will fall from southern Vermont to southeastern Maine Sunday night. Light snows will fall in northern areas on Monday, Wednesday, and possibly Friday, with heaviest in the Laurentians. It then turns extremely cold but likely drier for several days or more, in contrast to stormier expectations a few days ago, with moderation possible toward the end of January.

 

Meteorological discussion:

 

Snow showers and relatively mild throughout the region today, heavier and steadier from southern Vermont to eastern Maine, with another modest snow for southern Vermont to southeastern Maine Sunday into Sunday night

 

A broad upper-level trough is dominating eastern North America downstream of an upper-level ridge in western North America that has returned (+PNA). It briefly turned very cold after a storm that brought heavy snow to southern and eastern Ontario (much farther northwest than model projections in days prior) on Thursday, but now, several disturbances picked up relative warmth and moisture from the Great Lakes and have pulled the arctic air out of our region temporarily. One disturbance is centered on the northern shore of Lake Huron but is very broad, with snow showers extending from Minnesota to Maine, but nothing very heavy or organized. This is the disturbance that is bringing southwesterly flow that routed out the arctic air. With the low stability of the air modified by the Great Lakes, some of the snow showers will be convective and briefly heavy through tonight from Ontario to Vermont and Quebec, though total accumulations will be light. Another disturbance is just getting going to the south and will bring somewhat heavier and steadier snow to southern Vermont to eastern Maine through tonight, though few if any will get more than a few inches or 10 cm. Yet another system will round the base of the upper-level trough Sunday and try to come up the East Coast at the last second Sunday night, but the overall weather pattern is too broad with too many disturbances for the East Coast storm to really develop into a full-fledged Nor'easter, a classic scenario of recent winters. However, the storm will still clip southern Vermont to southeastern Maine with modest snow. 

 

Source: TropicalTidbits

 

 

Clippers brings light snow mostly in northern areas Monday and Wednesday, then arctic cold returns 

 

Right after the late-forming East Coast storm, another clipper will move into western Quebec, to the northwest of our region again, on Monday, bringing southwesterly flow that is still modestly cold but not arctic cold. This will lead to light snow mostly along and northwest of the Appalachians, with the most and steadiest in the Laurentians except lake-enhanced snow off Lake Ontario streaming northeastward along the St. Lawrence Valley into southern Quebec. Arctic air will come in from the northwest behind the cold front until yet another clipper tracks into the Great Lakes on Wednesday and brings southwesterly flow with light snow mostly north of the U.S./Canada border again, though northern Maine could also experience snow. All these clippers are basically disturbances in the polar jet rotating around the polar vortex over Hudson Bay that is displaced southward by all the high-latitude blocking (-AO), and that is also allowing for the arctic air to descend into the mid-latitudes. Interestingly, the NAO is positive, which could be why systems are still moving rather quickly with a strong north-to-south temperature gradient. The really cold air will get more and more entrenched into the weather pattern with the passing of each clipper.

 

Source: TropicalTidbits

 

 

Possibly one more clipper on Friday, then extreme cold but drier, contrary to prior expectations

 

Details become murky after Thursday, but there could be one more clipper on Friday before the most extremely cold arctic air that will have covered almost all of Canada descends into our region directly from the north, instead of from the west being modified by the Great Lakes. A few days ago, models showed the upper-level trough axis shifting to the Rockies with a southeast U.S. ridge developing, allowing storms to finally eject out of the Rockies and into our region, but now, most models agree on a very broad upper-level trough and arctic air mass extending from the Rockies eastward, which would suppress all of the moisture southward. It has been difficult to get a storm track from the central or southern Plains northeastward this winter and also last winter except for February. It is somewhat surprising during a La Niña winter, but it seems like there just is never a trough digging sharply into the Plains without other disturbances interfering to enable such a storm track. The NAO turning negative for a time will also help suppress storminess to the south, and barring some major shifts in the synoptic-scale weather pattern, it looks like a very dry and extremely cold several days starting next weekend into the following week for almost all of eastern North America. Some parts of our region could drop below -22F (-30C)! In fact, all of North America could be dry with almost no storminess coming in from the Pacific Ocean and a massive upper-level ridge connecting from Alaska to Greenland. It is amazing that the vast majority of the U.S., including southeastern parts of our region, will likely still have below average snowfall after all the arctic air, similar to last winter. Perhaps it is still too early to completely rule out a shift back to a more amplified upper-level trough over the Rockies that would allow a system with Gulf of Mexico moisture to push northeastward into our region, as shown by a few rogue outlier models and ensemble members.

 

Source: TropicalTidbits

 

 

Possible moderation for end of January 

 

There are some signs that toward the end of January, the Pacific jet will strengthen, breaking down the Alaskan upper-level ridging and allowing more Pacific air to move into North America, leading to a milder early February that could be less suppressive, but how this evolves is still quite uncertain. Though the way this winter is going, I would still bet on some amount of southwest U.S. upper-level ridging preventing the juicy southern storms to reach our region, with either cold high-pressure still dominating our region or clippers tracking to our north. It has been the warmest winter on record in the western U.S., a testament to how difficult it has been to get upper-level troughs in that region.

 

Source: TropicalTidbits

 

 

 

Source: Climate Prediction Center

 

Heavy snow in northern areas through Sunday night, with wintry mix farther south; briefly colder Monday, then milder Tuesday and Wednesday though more snow in Laurentians; two snowstorm chances late week into weekend for southern and eastern areas, though neither appears very likely; wintry weather continues following week, then possibly turning stormier

Plain-language summary: 

 

After a brief thaw with widespread rain yesterday, a winter storm will bring heavy snow, locally >10" (25 cm), from southern and central Quebec to northern Maine tonight through Sunday night, with a mix of snow, ice pellets, and rain farther south with much less accumulation. It will briefly turn colder Monday before a little snow Monday evening along and northwest of the Applachians and then milder temperatures later Tuesday into Wednesday, with intermittent light rain in the St. Lawrence Valley and more substantial snows in the Laurentians. There are then two chances for East Coast Nor'easters (one Thursday into Friday, one next weekend) that could bring moderate to heavy snow to southern and eastern areas, though neither appears particularly likely for now, but it is also too far out to have much confidence in any scenario. Arctic air returns afterward, perhaps with light snow the following Monday, with the wintry weather pattern continuing and possibly turning stormier, even with the possibility of brief thaws.

 

Meteorological discussion: 

 

Heavy snow tonight followed by lighter snow through Sunday night in northern areas, mix of snow, ice pellets, and rain farther south

 

After a brief thaw yesterday with rain well into central Quebec, the storm's cold front brought colder air directly from the north today, just in time for the next storm coming from the southwest and strengthening. The cold air mass is not at all arctic and is actually still considerably warmer than average for January, but it is just cold enough for snow tonight north of the U.S./Canada border and in northern Maine, with temperatures in the entire lowest few kilometers being between 23F (-5C) and 32F (0C). This is quite a departure from models several days ago which almost unanimously showed this storm being the second part of a several-day thaw with almost all rain. Since the storm is strengthening and coming from the southern U.S., it is actually bringing Gulf of Mexico moisture into the marginally cold air, a rarity this season. The storm will not become particularly strong with a lack of true polar jet energy, being well to the north, to give a boost to the storm, but in this case, that will prevent the storm from over-amplifying and flooding the entire region with warm air as models had shown days ago. It will first peak in Lake Huron late tonight before occluding and re-forming and re-strengthening along the Maine coast Sunday night, just in time to cut off the surge of warm air north of the U.S./Canada border. The eastward elongation/occlusion of the storm will promote warm frontogenesis from eastern Ontario to northern Maine, and combined with a moisture-rich and marginally cold air mass with instability aloft, will lead to heavy snow for several hours tonight, perhaps heaviest in the St. Lawrence Valley between Montreal and Quebec City where terrain-enhanced convergence could boost snowfall slightly. The Laurentians to northern Maine will continue to see lighter snow through Sunday night as the occlusion and re-formation occurs. The strengthening upper-level low will also promote instability and upward motion for a time across eastern Ontario and northern New York through southern Quebec and New Hampshire Sunday afternoon and evening, leading to scattered but possibly briefly intense snow showers.

 

Source: TropicalTidbits

 

 

Source: TropicalTidbits

 

 

Source: TropicalTidbits

 

 

Some areas could see >10" (25 cm) of snow total. South of the U.S./Canada border, a messy mixture of snow, ice pellets, and rain is expected, becoming more rain farther south, though it could change to snow during the heaviest precipitation, and slight cold air damming east of the Green Mountains could lead to some more snow and ice pellets in the favored areas there, though without much of a cold air mass to begin with, this is not the ideal setup for cold air damming. In these areas, snow accumulations will be much less though more dense. There will also be less precipitation south of the U.S./Canada border, as that region is farther from the best dynamics given the storm track.

 

Source: Weather Prediction Center

 

 

Briefly colder Monday, then a bit of snow northern areas Monday evening before milder again late Tuesday into Wednesday, though significant snow still possible in Laurentians 

 

Colder, though still not arctic air briefly returns behind the storm, but another Alberta clipper already approaches our region later Monday. A much weaker initial wave will produce light snows along and northwest of the Appalachians Monday evening, followed by the much stronger Alberta clipper Tuesday night into Wednesday night that although will not truly tap into Gulf of Mexico moisture, is strong enough to pull in considerably milder air from the southwest. Most of the region south of the U.S./Canada will simply stay dry and relatively mild during this period. The St. Lawrence Valley could see a little snow initially followed by intermittent light rain, while only the Laurentians is likely to see significant snowfall with both upslope enhancement and cooler temperatures, given the storm track well to the north.

 

Source: TropicalTidbits

 

 

Two chances of Nor'easter snowstorms mostly for southern and eastern areas late week into weekend, though neither appears very likely

 

Such a clipper track normally just brings a cold front with brief snow showers after it passes, but in this case, additional pieces of energy will dive into a deepening upper-level trough in the eastern U.S., aided by an upper-level ridge building in western North America (+PNA) after a brief pause earlier this week. Some, though not overly strong high-latitude blocking (-AO, though the NAO is surprisingly slightly positive) will also help. This could lead to a coastal Nor'easter low-pressure system forming Thursday into Friday that slows down as the polar jet retreats and leaves the storm behind, and this position would be better to tap into Atlantic moisture and produce significant snows, though for now, most indications are that this will only be from southern Vermont to southern Maine, and perhaps not even that, given that the Alberta clipper leaves behind a slightly positively tilted upper-level trough (trough axis oriented southwest to northeast) that would steer a storm more to the east than to the north. It is also being kicked out by more pieces of energy entering the Midwest U.S. 

 

Source: TropicalTidbits

 

 

Source: Climate Prediction Center

 

 

Those additional pieces of energy themselves constitute another Nor'easter storm threat for next Saturday into Sunday. However, most indications are again that they will likely fail to interact favorably to phase into a big storm, staying separate or not timed right, the southern disturbance being too weak or too slow lagging behind the northern disturbance, and/or perhaps with another Alberta clipper approaching for the following Monday helping to kick everything to the south and out to sea. To get a big storm, the southern disturbance has to be strong enough and run just ahead of the northern disturbance that would guide the moisture-rich southern disturbance northward up the East Coast and also cause it to strengthen, which also requires the upper-level trough to be strong and sharp enough. The most likely area to get hit would be eastern New England, though there would still be lighter snow elsewhere from the northern disturbance. Another miss for a Nor'easter would fit a common theme in recent years with many pieces of energy but never phasing to create a big storm even with a favorable upper-level trough position in the eastern U.S. However, it is too far out to rule out any scenario, including a big storm scenario, as relatively small differences in the disturbances will determine the outcome, and there is large corresponding model disagreement.

 

Source: TropicalTidbits

 

 

Arctic air returns afterward, possibly with light snow for following Monday and then potential stormier weather pattern starting later in the week with continued wintry pattern 

 

After another possible Alberta clipper bringing light snow for following Monday, a true arctic air mass will likely push into the region, leading to the coldest temperatures since the beginning of January if not mid-December. The overall weather pattern likely will retrograde later in the week, with the coldest air retreating to western Canada (classic -PNA La Niña weather pattern), with a southeast U.S. ridge appearing but not being particularly strong. This could promote a classic Colorado low track from southwest to northeast that picks up Gulf of Mexico moisture and runs it into the arctic air mass dominating Canada, leading to frequent snow and ice events, though we have seen this pattern in long-range model forecasts earlier this winter, and they mostly have not happened. There could also be more low-pressure systems coming out of the Pacific Northwest or Canadian Rockies instead of from the southern and central Rockies, which would promote more Alberta clipper tracks with less moisture. In either case, with the arctic air mass remaining strong in Canada and some high-latitude blocking persisting (at least AO being negative) will keep things wintry in our region (though brief thaws are possible if the southeast U.S. ridge is stronger than modeled) and possibly stormy also.

 

Source: TropicalTidbits

 

Cold but mostly dry weekend; light snow in southern areas early Sunday and late Monday; gradual warmup next week with snow and/or mixed precipitation likely Wednesday, then rain Friday into next weekend possibly ends as snow; only modestly colder for following week before possible return of arctic air mid-January

Plain-language summary: 

 

It will be cold but dry this weekend except a little snow in southern areas late tonight into Sunday morning. A substantial but relatively gradual warmup will occur next week, contrary to expectations a few days ago. Light snow for southern areas is likely late on Monday. More widespread snow and/or mixed precipitation is likely on Wednesday, though precipitation amount and type is uncertain. Rain and a thaw is very likely Friday into next weekend before turning modestly colder but not colder than usual for January for following week, with possible snow or mixed precipitation in between. Arctic air may return in mid-January, perhaps with a long-awaited return of stormier weather, though the long-range forecast has been incredibly uncertain recently.

 

Meteorological discussion: 

 

Cold weekend, then gradual warmup, with light snow in southern areas early Sunday and late Monday; likely snow and/or mixed precipitation on Wednesday but precipitation intensity and type are uncertain

 

While models have shown signals of stormy and snowy weather patterns in the long-range this winter, they have mostly not materialized other than the big rainstorm a week before Christmas and the post-Christmas icing event. The big snowstorm is still elusive for most of the region despite having the coldest December since 2017 or even 2000 for most. This weekend will be cold, but fittingly mostly dry now that it is cold, except for intermittent light snow in southern areas tonight into Sunday morning from a weak elongated disturbance. Then, the upper-level ridging in the western U.S. breaks down, with upper-level troughing coming into the West Coast from the eastern Pacific, extending all the way to the Northwest Territories (-PNA). Combined with high-latitude blocking collapsing sooner than earlier expected (NAO and AO trending toward neutral), this will lead to mild Pacific air to flood most of North America by later next week, in contrast to all model expectations several days ago, though it will be a rather gradual process. Before that though, the warm advection combined with a weak disturbance will lead to a weakening area of light snow moving eastward from the Great Lakes Sunday night into Monday, though there may be little if any snow from Lake Champlain on northeastward. Weak warm advection will continue through Wednesday, with another disturbance likely to bring some snow or possibly mixed precipitation (given the milder air) into the region, though the strength of the disturbance, which is rather uncertain, will determine the intensity and type of precipitation. A stronger disturbance will produce heavier precipitation but will also advect more warm air into the region, leading to a farther north rain/snow line. Given the antecedent low-level cold air, a narrow zone of freezing rain is also possible, though it is unlikely to be nearly of as the same magnitude as last Monday's icing event.

 

Source: TropicalTidbits

 

Source: Climate Prediction Center

 

 

Mild with rain and a thaw likely Friday into next weekend, possibly ending as snow

 

After Wednesday, the weather pattern further amplifies, with a stout upper-level trough and ridge in western and eastern North America respectively. With the cold air in our region already stale and getting scoured out, the next storm that finally ejects out of the southern Rockies next Thursday and likely reaches our region around next Friday or possibly Saturday will likely be rain area-wide. It's ironic, since it has been hard to get any moisture-rich disturbances from the southern jet to move northeastward into our region this winter, and now that there is one, the cold air is routed out so thoroughly that even a relatively favorable track will yield rain. For now, it appears unlikely to get warm enough to melt the snow cover away like the mid-December thaw. The upper-level ridge could be strong enough that the storm's cold front stalls and allow another storm from the southwest to reach our region, perhaps with just enough cold air for snow for at least some. Arctic air is not required to get snow in January. 

 

Source: TropicalTidbits

 

 

Modestly colder but not arctic cold for following week, perhaps drier

 

It appears to get modestly colder afterward, but unlike in December, Canada does not look nearly as cold this time, and temperatures could still be slightly above average. Nonetheless, given that it is January, this will be cold enough to snow, provided that there are not additional amplified storms ejecting out of the Rockies. The models have had a really hard time figuring out the long-range weather pattern, so anything beyond this point has a very high uncertainty. It could just quickly dry out with an upper-level ridge over western and central Canada providing suppressive and dry but not particularly cold northwest flow as the real cold air staying well to the north. The majority of model guidance shows this scenario, which would only allow for moisture-starved Alberta clippers to reach our region, and given the inability for any moisture-rich southern jet disturbance to reach our region with any decent cold air, this would not be surprising.

 

Source: TropicalTidbits

 

 

Source: TropicalTidbits

 

 

Perhaps arctic air returns with more potential storminess starting mid-January, but very uncertain 

 

There are some signs of Alaskan upper-level ridging allowing for more arctic air and central North American upper-level troughing starting in mid-January, as well as a more amplified synoptic configuration being slightly more favorable for the more classic storm track from the southwest bringing more substantial snows to our region, but this is very uncertain given the chaotic run-to-run changes in model guidance.

 

Source: TropicalTidbits