Milder and mostly dry today into Monday; then stormy through next weekend with rain except wintry mix in northern areas Tuesday into Tuesday night; potential big storm Thursday into Friday with snow changing to rain; milder with rain next weekend; then more typical April weather with occasional rain, lack of real cold, and little or no snow

Plain-language summary:

 

After being dry and unseasonably cold Friday and Saturday, it will turn milder but not particularly warm later today into Monday, with it remaining dry except light scattered snow showers mainly in northern areas. It will then be rather stormy through next weekend. Tuesday into Tuesday night will be rainy except a little snow to wintry mix possible in northern areas from central Quebec to northern Maine. It will turn cooler and drier on Wednesday before a widespread potentially big storm bringing snow to wintry mix to rain occurs late Thursday into Friday, with the best chance of a big snowstorm from central Quebec to northern Maine. It then turns warmer with rain next weekend before it turns cooler, but without much if any arctic air to the north to tap into, leading to a more typical April weather pattern with occasional rain chances but likely little if any snow especially at lower elevations.

 

Meteorological discussion:

 

Milder but not particularly warm later today into Monday but staying mainly dry; rain to south and wintry mix to north on Tuesday

 

March has been characterized by a huge temperature contrast between persistent arctic air over central and northern Canada and record-breaking heat in the western and central U.S. This persistent temperature contrast is characterized by a -PNA, +AO, and +NAO, virtually the opposite of most of the past winter. This battle will continue for the next week and play a key role in the weather in our region. The largely dry arctic air mass of Friday and Saturday is moving out with little or no precipitation except light scattered snow showers in northern areas with little or no accumulation. This fits the theme of the winter of it being difficult to ram rich Gulf of Mexico or Atlantic moisture into the cold air masses in our region. Dry southwesterly flow will bring milder air later today into Monday, with a weak surface low-pressure system passing to the north on Monday carrying its precipitation mainly north of our region. The warmer air will fall well short of the incredibly warm temperatures to our southwest. A cold front will pass Monday night, and arctic air will try to push in again, but like most of this month, the upper-level ridge to the south will be too strong for the cold front to advance much, with the ridge actually centered over the southeast U.S. instead of farther west like last week. Therefore, the front will stall over our region as another somewhat stronger but elongated, more moisture-rich low-pressure system advances from the west. With an arctic surface high-pressure to the north over northern Quebec and the surface low-pressure system passing through our region, widespread precipitation will occur on Tuesday and Tuesday night, mainly as rain for most of the region given that the cold air is not really able to advance southward much before the precipitation arrives. However, northern areas deeper into the cold air, from central Quebec to northern Maine, could receive a bit of snow changing to a wintry mix of ice pellets, freezing rain, and rain. Low-level cold air channeled southwestward through the St. Lawrence Valley could lead to freezing rain there especially near Quebec City. Southern areas from southern Vermont to southern Maine will get into the warm sector, with temperatures surging above 60F (16C) for a brief time.

 

Source: TropicalTidbits

 

 

Source: Climate Prediction Center

 

 

Cool, dry Wednesday, then potential big storm with snow to wintry mix to rain late Thursday into Friday, perhaps last widespread snow of season 

 

The low-pressure system will move out by Wednesday, with another arctic surface high-pressure system pushing in with colder and drier air. But once again, the upper-level ridge to the south will remain strong, while some upper-level troughs and storminess finally reaches the western U.S. after being baked in dryness and record warmth for the past few weeks. One disturbance will be moving eastward through the Plains and U.S. Midwest on Thursday, and eventually reaching our region Thursday night into Friday. With the arctic air able to push a bit farther south this time and still being relatively fresh ahead of the storm, precipitation will likely at least start as snow for most of the region, perhaps except for far southern areas, though this will depend on the exact storm track which has been trending northward lately, perhaps a testament to the strength of the upper-level ridge to the south. This might be one of the few times this cold season in which rich Gulf of Mexico moisture is rammed straight into a fresh cold air mass cold enough for snow, with the surface high-pressure to the north and northeast providing low-level cold air (albeit not as strong as in winter given that it will be April) for the warm, moist Gulf of Mexico air to overrun aloft. There is remarkable agreement (for 4-5 days out) on a scenario like this occurring. As a result, precipitation could be rather heavy, and someone could receive a lot of snow, perhaps one of the biggest of the season. That said, the relatively warm temperatures (warmer than -8C) through a deep layer of the lower-troposphere will not favor ideal dendrite formation and favors riming that leads to lower snow-to-liquid ratios and wetter snow, limiting snow depth. Areas south of a line from Ottawa to Montreal to Bangor, Maine will likely change to ice pellets and then a cold rain by Friday, unless the storm track goes farther south than currently shown. For now, the best chance of a big snowstorm is from central Quebec to northern Maine. This could be the last widespread snowfall of the season for our region.

 

Source: TropicalTidbits

 

 

Warmer with rain next weekend, then cooler but likely lack of arctic cold and more typical April weather pattern with occasional rain chances

 

Another stronger storm will follow closely behind with an almost closed off upper-level low approaching the region next weekend. By this time, the cold air will have become stale, and the strength of the storm combined with is track well north of our region into northern Quebec will likely ensure precipitation will fall as rain for everywhere in our region with warmer air arriving. Cooler and drier air comes in behind the storm, but by this time, the supply of arctic air to the north appears to finally weaken in earnest, and yet the upper-level ridge to the southwest of our region will have weakened. This will reduce the temperature contrast and yield a more typical early-mid spring weather pattern, with mostly mild days and occasional temperature swings and storminess but without the big temperature contrasts, and any snowfall likely being at most sporadic and mostly at higher elevations. 

 

Source: TropicalTidbits

 

First real taste of spring through Tuesday; major storm brings wintry mix, rain, and warmth Wednesday and early Thursday; back to winter with unseasonable cold late Thursday into next week with snow likely Friday-Friday night and following Monday

Plain-language summary:

 

It will be very mild through Tuesday, marking the first true taste of spring for our region. Then, it will turn colder in northern areas as a major storm bring ice pellets and freezing rain to northern areas Wednesday into early Thursday, while southern areas stay very warm with some rain. A brief period of heavy showers or even a thunderstorm is possible early Thursday before turning much colder, possibly accompanied by a little snow. Winter weather will likely then dominate for at least a week, albeit the March sun angle will make the cold less intense but could also make any storms stronger with stronger dynamics and more moisture. Snow is likely, especially in northern areas, late Friday into Friday night, with a bigger storm possible the following Monday. It remains very cold for March afterward but perhaps drier before possibly turning milder later the following week.

 

Meteorological discussion: 

 

Very mild and mostly dry through Tuesday

 

Right after the calendar flipped to March, the weather pattern has flipped completely from the cold, suppressive wintertime weather pattern, sort of like last year. A +EPO, +NAO, and +AO has scoured the arctic air out of the contiguous U.S. and southern Canada with an active storm track to the north leading to persistent mild westerly to southwesterly flow of Pacific or even Gulf of Mexico air. The upper-level trough in western North America (-PNA, rare this winter even if relatively modest) has also boosted the eastern North American upper-level ridge, with rain falling deep into Quebec yesterday with a storm tracking way to the north. Even the cold front behind it will only briefly turn the winds to northerly, and the air mass will still be warmer than average for this time of year. Southeast of the Appalachians, sunshine and downsloping westerly winds will actually make it warmer than yesterday, when that area was stuck in low-level cold air damming. Another clipper tracking well to the north on Monday will back the flow to southwesterly again, leading to Monday being even warmer with many lower elevation locations, especially in southern areas, reaching 60F (16C) or higher in lower elevations given the higher March sun angle, melting and degrading snow cover, and unseasonably warm air mass and upper-level ridging, and it will be dry as well.

 

Source: TropicalTidbits

 

Source: Climate Prediction Center

 

Low-level arctic air bleeds into northern areas with major storm Wednesday and early Thursday leading to ice pellets and freezing rain in northern areas, continued warmth and some rain in southern areas, possibly ending as a little snow everywhere

 

At the same time, a very cold arctic air mass will be pushing across central and eastern Canada on Tuesday and Wednesday behind the clipper's cold front, but like last week's arctic air mass, it will not be able to push south much due to resistance from the strong upper-level ridge. The front will be almost stationary as another elongated disturbance entering the northwestern U.S. will ride along the front. After a mild Tuesday, the front will slowly push through Northern Maine and areas north of the U.S./Canada border, allowing the low-level cold air to bleed in starting later Tuesday with northerly to northeasterly flow. The low-level cold air will be enhanced by terrain-induced channeling along the St. Lawrence Valley and even the Champlain Valley initially. However, areas to the south will get even warmer, possibly even breaking some daily records, and it will remain warm aloft everywhere due to the upper-level ridge. 

 

The disturbance from the west will strengthen into a formidable storm in the Great Lakes on Wednesday, especially as it at least partially phases with and picks up a cut-off upper-level low in the southwestern U.S. This interaction has been a difficulty for models to predict, with models initially showing this phase creating a very strong storm cutting northwest of our region, then a couple of days ago showing a much flatter northwestern U.S. disturbance that does not phase with the cut-off low, leading to a weaker, farther south, and colder storm, and now the models have reverted back to at least a partial phase. Given the low-level cold air in northern areas, precipitation will likely at least start as ice pellets and/or freezing rain, possibly heavy at times, while southern areas will stay just rain, possibly south of the main precipitation shield. Some areas could see a real ice storm, most likely in eastern Ontario and southern Quebec and possibly parts of Maine, if the storm is more elongated, which would allow for the heavy precipitation and precipitation types to train over the same area as opposed to a stronger storm that would push everything north with time with stronger warm advection. If the storm is farther north and stronger, the unseasonable warmth will push into all of our region at least briefly, possibly with a dry slot, followed by a sharp cold front with a brief period of heavy showers or even a thunderstorm early on Thursday before turning much colder, perhaps with a brief period of light snow depending on how much energy is left dangling to the southwest of the main storm. Usually, such scenarios with a strong storm tracking to the north do not favor backside snow, especially in recent years. If the storm is farther south and weaker, wintry precipitation will continue for a full day in northern areas with a constant supply of low-level cold air from the northeast until the storm exits on Thursday. As I wrote in my blog post a week ago, it is ironic that the region was struggling to get good moisture with all the suppression, but now the suppression suddenly breaks and now the upper-level ridge is too strong for snow in most or all of our region.

 

Source: TropicalTidbits

 

Old model runs showing alternative scenarios. Source: TropicalTidbits

 

Winter returns late Thursday, snow likely Friday into Friday night especially in northern areas and major storm possible Monday

 

The flip back to winter weather is powered by the return of the western North American ridge (+PNA) and a weakening of the Pacific jet, though interestingly, the AO and NAO are expected to remain positive, so there will not be any appreciable blocking or push of arctic air deep into the southern U.S. This will maintain a stronger than the already typically strong temperature gradient at this time of year, acting as fuel for storms especially with the lower springtime stability. As such, the active weather pattern will continue afterward, with another clipper already approaching our region from the west-northwest on Friday. This clipper appears stronger than most from mid-winter, perhaps powered by the March sun angle making the air masses less stable and strengthening the warm air masses to the south clashing with the arctic air to the north. Given the cold air, albeit modified by the March sun angle, precipitation will fall as snow throughout the region at least initially later Friday, possibly mixing with and changing to scattered showers south of the storm track Friday night as warm advection occurs again. Given the dynamics, the favored locations north of the storm track could get rather heavy snow for several hours. The trajectory and strength are still in question this far out, but right now, it appears that the heaviest snow will likely target northern areas. 

 

Another arctic air mass follows behind it before another disturbance riding along the temperature gradient has the potential to become a big storm, colder than this upcoming week's storm, depending on how amplified the weather pattern is. The position of the broad upper-level trough axis to our west puts our region in a favorable spot for cyclogenesis and moisture transport from the south straight into the arctic air, something not seen often this winter. It has the potential to finally be a widespread big snowstorm, especially given the strengthening warm and humid air masses in March pushing into the storm, but it could very well be too weak and suppressed like most of this winter, or even too amplified and going too far north, leading to a change to rain.  

 

Source: TropicalTidbits

 

Staying unseasonably cold for March through most of following week, possibly drier mid-late week and then milder

 

After that, the upper-level ridge/trough pattern appears to shift east, with the upper-level trough axis pushing east of our region later the following week, likely leading to drier weather but perhaps still unseasonably cold for March. Throughout much of this period, highs could be at or below freezing on most days, with the occasional night at or below 5F (-15C), more typical of January or February. However, the lack of -AO or -NAO high-latitude blocking suggests we could see a warmup as well with dry west-southwesterly flow from the Rockies, which will likely be unseasonably warm by then, but it remains to be seen how much resistance the arctic air will provide in our region, especially given the abundant arctic air projected to remain across Canada.

 

Source: TropicalTidbits

 

Very cold through Monday, then turning milder through Thursday with a little snow in southern areas Tuesday night into Wednesday; potential wintry mix Thursday night into Friday before warm next weekend into following week; then turning stormier and then colder

Plain-language summary:

 

After being very cold through Monday, it will turn milder, yet for most, the transition period will fail to produce much snow like such periods often do. Instead, it will be mostly dry through Thursday except a little snow from southern Vermont to southern Maine Tuesday night into Wednesday. Shallow cold air will lead to one last chance of wintry precipitation Thursday night into Friday, though it is more likely to be freezing rain than snow. It then turns warm through following week with frequent rain chances, though any day that does turn sunny could be exceptionally warm for March. Northern areas may still have the risk for wintry mix or freezing rain depending on the exact configuration of the weather pattern. It will likely turn stormier and than colder for mid-March, possibly with snow returning. 

 

Meteorological discussion:

 

Very cold Arctic air through Monday, then milder with light snow in southern Vermont to southern Maine Tuesday night into Wednesday while it stays dry to the north 

 

After a brief thaw yesterday, a very cold Arctic air mass directly from the north with no modification will likely bring the last sub-0F (-18C) night of the winter tonight as surface high-pressure crests overhead leading to an ideal radiational cooling setup of light wind, clear sky, dry air, and deep snow cover. Afterward, the arctic surface high-pressure will move offshore the U.S. East Coast, and a series of elongated clippers will pass to the north next week. Both of these combined will lead to a warming southwesterly flow aided by a stronger March sun. An almost closed-off upper-level low will enter the western U.S. on Monday, with weak pieces running out ahead of the main upper-level low that will produce light warm advection snow in southern Vermont to southern Maine later Tuesday into Tuesday night. This southern jet disturbance has a decent amount of moisture, and if the prevailing jet pattern had been more amplified, especially with the polar jet upper-level trough being stronger and phasing with and picking up the southern jet disturbance, this could have been a much bigger snowstorm like models had shown a few days ago. However, this will be yet another potential bigger storm that mostly fails to materialize. The northern upper-level trough is very flat and is not digging far enough south nor in the right position to pick up the juicier southern disturbance, leading to a very stretched out and suppressed disturbance with relatively weak forcing and precipitation at any one location yet again. Central Maine could get the jackpot with locally up to 4" (10 cm). Areas from the U.S./Canada border on northwestward will stay dry in between the clipper passing to the north and the stretched out southern disturbance to the south Tuesday night into Wednesday, though everyone will turn milder and see increasing clouds.

 

Source: TropicalTidbits

 

Transition period to warmer weather mostly fails to produce wintry precipitation except one last iffy chance Thursday night into Friday

 

Afterward, the weather pattern will change dramatically, powered by a much stronger Pacific jet (+EPO), +NAO, +AO, and -PNA. This change will not only scour the arctic air from the contiguous U.S., but also force upper-level troughing in western North America that further promotes a ridge in eastern North America and western Atlantic and a storm track way to the north. It is ironic that we had so much potential for storminess and snowiness from a temperature battleground over the past month, yet the weather pattern ended up being repeatedly too suppressive, and now, it will simply flip 180 degrees to having way too strong of a ridge for snow in our region, especially in southern areas, after next Friday. It has been an incredible waste of potential for big snowstorms; it just needed to be in between the suppressive and ridge-dominated patterns. Even the transition period from cold to warm pattern, which usually produces a decent snowfall, appears to mostly fail to produce much if any snow for most. 

 

Source: Climate Prediction Center

 

However, there is still one last slight chance for snow for northern and eastern parts of the region next Friday. On Thursday, an arctic surface high-pressure will press southward just slightly, barely penetrating south of the U.S./Canada border, behind a stalling cold front from the previous weakening clipper passing to our north on Wednesday. Meanwhile, the main upper-level low, though weakening, will finally push northeastward into our region as another upper-level trough into the western U.S., pumping the eastern U.S. ridge and leading to southwesterly flow aloft. This flow of warm, moist air from the Gulf of Mexico will ram into the shallow arctic air in northern and eastern parts of our region, leading to possibly heavy precipitation Thursday night into Friday. Most models indicate that the arctic air, although is very cold, will mostly stay just north of our region and is so tenuous and shallow with above freezing temperatures persisting aloft for most of the region except Maine, where cold air damming will help block the surge of warmer air. But if the cold air can press in more, and the upper-level low is timed perfectly to arrive just as the cold air is coming in (not too early, before the cold moves in, and not too late, after the cold is about to leave), it could be just cold enough for a more widespread wet snow. Most likely, the cold air will be shallow and dammed against the Appalachians and channeled southwestward through the St. Lawrence Valley, leading to freezing rain, and icing could be substantial for some given the strength of the shallow arctic air. The system could also be weaker, resulting in little precipitation, especially if more of the energy gets pulled out Tuesday night into Wednesday ahead of the main upper-level low.

 

Source: TropicalTidbits

 

Warm next weekend through following week with frequent rain chances, maybe still wintry precipitation chances in northern areas

  

Despite the low-level arctic air that will be initially difficult to scour out, eventually, the next upper-level trough will promote a storm track well to our north next weekend, leading to the arctic air retreating well to the north, warming temperatures, and some rain. A blowtorch for most of our region is likely at some point between next weekend and the following week given the strength of the upper-level ridge, with several storms tracking well to our north and warm southerly flow blasting into our region. Temperatures could exceed 70F (21C) in lower elevations if there is enough sunshine! Occasional cool downs behind storms could occur, but the air masses will not be very cold. Even the feedbacks of frozen Great Lakes and deep snow cover will be no match for the strength of this ridge, and the warmth will obliterate the snowpack. Even if the ridge is weaker than modeled like has been the case for the past month, it will likely not be enough to change this general narrative. Unless it turns very cold again in mid-late March, it will be the 6th warmer than average March in a row. Given the warm, moist Gulf of Mexico air involved, there could be heavy rain at times depending on the storm track, especially along cold warm fronts, but the storm track could be so far north that the best dynamics and heaviest rain stays to our northwest, especially next weekend. Still, it will likely not be a "clean" warm-up with dry weather and sunshine, perhaps except next Sunday and following Monday, which is rare this early in the spring anyway, especially in northern areas. Such warm air masses traversing over snow cover and cold ground usually lead to a lot of low clouds and fog especially initially with the warm advection, and this could be amplified with the progression of storms and repeated fronts. If the overall upper-level trough/ridge pattern in western/eastern North America is a little weaker, there could be sneaky surface arctic high-pressure systems well to the north that lead to much cooler surface temperatures, especially in northern areas, while it stays warm aloft, a recipe for low clouds and even a wintry mix or freezing rain if the storm track is close enough.

 

Source: TropicalTidbits

 

Source: TropicalTidbits

 

Cold air likely to return at end of following week, possibly with storminess and even return of snow

 

Models are also in good agreement that the upper-level ridge will gradually weaken towards the end of the following week, and with the Pacific jet weakening, arctic air is likely to make a comeback across southern Canada and northern U.S., initially to our west but eventually spreading eastward for mid-March. In the transition period, it could be quite stormy, with warmth and heavy rain and possibly even thunderstorms. But it is possible that as the cold air and baroclinic zone slowly pushes southeastward that there is one or two storms that spin up along it in which our region is on the cold side, leading to snow. It is almost always difficult to get a big snowstorm from rain changing to snow, as usually the cold air needs to be established first, but in such an amplified weather pattern, it is plausible even if not very likely. It will be mid-March with an obliteration of the snowpack, so any cold air will not be nearly as strong as we have seen over the past month, but it could still be cold enough for snowfall, and if the weather pattern is less suppressive as it usually is later in March as the jet stream climatologically moves northward, and it becomes easier to tap into the strengthening warm, moist air masses in the southern U.S., the potential for bigger storms still exists. Of course, with averages rapidly climbing, it will be more difficult to keep precipitation as snow, but it is certainly still possible through early April.

 

Source: TropicalTidbits