Plain-language summary:
Today will be quite cold even with sunny skies, and tonight will easily be the coldest night until next winter. It will quickly warm up and thaw through the middle of next week, with a little snow possible north of the U.S./Canada border on Tuesday changing to a widespread soaking rain Tuesday night into Wednesday night, though rainfall amounts will not be exceptionally heavy, which should prevent a total meltdown of the still deep snowpack and major river flooding. There could be light snow accumulations along and northwest of the Appalachians at the end of the storm Thursday evening. It will turn colder afterward but not as cold, with perhaps frequent chances of light snow but likely no major storms for at least a week. It will likely turn much warmer the week after next week, though it is not clear yet if it will be persistent warmth, or it will be more of a roller coaster with still occasional chances of snow with any well-timed storms meeting with transient cold shots. Either way, the currently deep snow cover will be melting away rather quickly in the next few weeks.
Meteorological discussion:
Very cold today, tonight will be coldest night until next winter
Behind yesterday's stronger than previously-modeled clipper, an Arctic air mass has advected into the region directly out of the north-northwest with little modification. Even with sunshine, temperatures for areas along and northwest of the Appalachians will stay below 14F (-10C) all day today. With the surface Arctic high pressure promoting clear skies and calm winds, and with deep snow cover still throughout the region even after the thawing over the past week, ideal radiational cooling will occur tonight, with widespread below 0F (-18C) temperatures throughout the region away from the Atlantic coast, almost certainly the last time it will get that cold until next winter.
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| Source: TropicalTidbits |
Quick warmup and rain Tuesday through Thursday, with brief snow at onset possible north of U.S./Canada border and possible light snow at end of storm Thursday evening
However, the cold will be short-lived, as the cold surface high pressure will quickly move off the U.S. East Coast and promote southerly flow on the back side, leading to quickly warming temperatures on Monday and Tuesday. A strong storm will be coming out of the Rockies and enhancing the southerly flow, with no high-latitude blocking (+NAO and +AO) to keep the cold air in our region and storm track to the south. A lead wave ahead of the main storm could bring a little wet snow to areas north of the U.S./Canada border on Tuesday, but eventually, the warm advection will win, and everybody will change to a soaking rain Tuesday night into Wednesday night, though the Laurentians could have a period of briefly moderate to heavy snow before the changeover. The already strong and mature storm will stop intensifying by Wednesday night, leading to the precipitation lightening, and our region will also get into a large dry slot. As the main storm moves into the eastern Great Lakes on Thursday, the dry slot will promote some sunshine in parts of the region, and with warm southwesterly winds, many lower-elevation locations south of the U.S./Canada border, especially east of the Adirondacks with the help of downsloping, will likely exceed 50F (10C) for the first time this year, leading to a quick snow melt, though the relatively modest amount of rain should prevent a total meltdown and major river flooding. However, unlike most storms taking such a northern track, there is the possibility of light to briefly moderate snow along and northwest of the Appalachians on the back side of the storm Thursday evening due to the upper-level trough digging rather far to the south in the eastern U.S., perhaps even closing off, and triggering secondary cyclogenesis in eastern New England. In such a setup, the higher terrain would get the most snow, and rain changing to snow rarely leads to heavy snow accumulations, and this is probably not an exception.
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| Source: Climate Prediction Center |
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| Source: TropicalTidbits |
Colder later next week with chances of light snows, but major storms are unlikely
Colder air follows behind the storm, but it does not appear as cold as today. Also, it is March, and if it is sunny, it is hard for daytime temperatures to be super cold given the higher March sun angle. Still, it will be cold enough for any weak disturbances coming in from the northwest to bring us snow, though given the deep northwesterly flow, they will be rather moisture starved, limiting snow accumulations even with the relatively high snow to liquid ratios usually associated with these systems. A bigger, more moisture-laden storm associated with the subtropical jet will be ejecting out of the Rockies next Friday or so, though the timing is still a bit uncertain. However, the broad, suppressive nature of the jet stream and trough to the northeast of the storm means that the storm will likely be suppressed to our south, perhaps weakening, in the deep west-northwesterly flow, unless there is an unexpected disturbance that is placed in a more favorable location, like directly north of the storm, that digs southward and helps favorably interact with the storm and push it northeastward toward our region. As is currently expected, this would make for two storms coming out of the Rockies that would otherwise have the potential to become big Nor'easters or winter storms in our region, but likely fail to do so for almost opposite reasons, continuing the amazing lack of classic East Coast Nor'easters in recent years. Still, we could see several light snow events anyway from weak disturbances coming in from the northwest.
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| Source: TropicalTidbits |
Spring likely really sets in after March 10, though not clear if persistent warmth or back-and-forth pattern with occasional snows still possible
Starting around March 10, the ridge in the northeastern Pacific and/or Alaska that has been so prevalent this winter, allowing frequent and persistent shots of cold air into most of the contiguous U.S. this winter, will mostly collapse, being replaced by troughing instead, with a strong Pacific jet stream extending into North America and flooding North America with storminess (-EPO and -PNA) but also Pacific air, and also supporting a storm track generally to our north. Combined with a still +NAO and +AO, this will lead to spring weather really taking over in most or all of central and eastern North America, likely including our region, which would mean that March would likely end up being warmer and less snowy than average for most of our region. Record highs could be broken if there is enough southwesterly flow and sunshine, especially in southern areas where the snow cover is currently thinner and will melt the fastest. However, it is not certain yet if we will fully get into the persistent warmth, or if it will be more back-and-forth with one storm going to our north pushing warm air in, but then cold air coming in behind the storm and possibly still leading to occasional snow chances if any well-timed storm can meet up with the cold air. The NAO is expected to be closer to zero in mid-March, which could help squash the persistent warmth to the south, even with the -PNA. There could also be snow in the transition period when the cold retreats and warmth tries to push in. Climatologically, our region does not completely stop seeing snow in most years until early April at lower elevations and even later at higher elevations, though with this milder pattern, most or all of the previously deep snow in February will be mostly gone by late March, at least in lower elevations, perhaps a little sooner than we earlier expected. Also, it is possible that the warmup is accompanied by a major storm with heavy rain, but it is also possible that the deep-layer flow stays mostly westerly and dry, leading to more sunshine and little precipitation in the warm sector and with most of the dynamics and precipitation staying to our north.
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| Source: TropicalTidbits |
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