Nor’easter chance this week will bust, but still chilly for the end of March; another storm brings rain and perhaps mixed precipitation Friday and the weekend; another cold shot afterward before possible more springlike, changeable temperatures

Plain-language summary:

The Nor’easter potential early this week is gone, sealing a relatively snowless second half of March except for northern Maine and along and north of the St. Lawrence River. After some showers and snow squalls along and northwest of the Appalachians Wednesday night, it turns quite cold for late March on Thursday and possibly Friday. A possibly elongated storm will bring widespread rain late on Friday through next weekend, with possible snow at the start and end, especially in northern areas. It turns quite chilly again afterward, but it appears to not last as long as models earlier, with more springlike back-and-forth temperatures perhaps dominating after the beginning of April.

Meteorological discussion:

The Nor’easter potential early this week that looked promising a week ago has all but vanished. There are two main pieces of energy in the southern branch, both of which will be too stretched out and not consolidated together to produce a major storm on their own, and neither of them will phase with the potent northern stream trough to produce a bigger storm either. This bust, combined with last weekend’s storm tracking well to the north, means that the second half of March will end up being mostly a bust for snow across our area, except northern Maine and along and north of the St. Lawrence River. Either the troughs in the western U.S. have been too strong, allowing for a storm track well to the north, or a storm that would be in the right location is too weak. Nonetheless, models have trended stronger again with the first piece of energy, leading to light snow over the southern Adirondacks through southern New Hampshire tomorrow evening.

Source: TropicalTidbits

Source: TropicalTidbits

However, it will still be chilly for late March, especially later this week, with the potent northern stream trough digging into Quebec and then Atlantic Canada by Thursday. A weak surface low will track northeastward just ahead of the trough from the Great Lakes into Quebec, with a line of showers or snow squalls (especially in higher elevations) likely Wednesday night, especially along and northwest of the Appalachians. The greatest snow accumulations will likely be in the Laurentians just north of the St. Lawrence River, where a few hours of heavy snow are possible. Behind that, temperatures will struggle to get above freezing for most on Thursday and possibly Friday, though Friday will likely be slightly milder especially farther west. 

Source: TropicalTidbits

 Meanwhile, another potent trough in the western U.S. will lead to a storm forming in the Plains and moving northeastward into the Great Lakes (again!) by Friday. The antedecent air mass might be cold enough for snow initially from the Adirondacks on northeastward, again especially in higher elevations given the time of year. The storm track itself is still somewhat uncertain, and the storm could be stretched out or come in two parts. Last night’s ECMWF model had the extreme scenario of an arctic air mass coming in fast enough for a snowstorm in a narrow swath of Northern New England next weekend, but this looks rather unlikely at this time, with mostly rain after a bit of possible snow initially on Friday being the most likely scenario south of the U.S./Canada border. However, the arctic air is close enough by, and with the trough over Atlantic Canada, negative NAO, and Greenland blocking, it is too early to rule out a little snow at the end as well. Northern Maine and areas north of the St. Lawrence River, where snow has been the most abundant all winter long, are the most likely areas to receive substantial snow, since even a storm cutting into the Great Lakes could redevelop along the Maine coast at the last minute, keeping the cold air in there. 

Source: TropicalTidbits

It will also turn sharply colder for a couple of days behind that storm. However, most indications are that systems will be moving surprisingly fast given the negative NAO and Greenland blocking, perhaps due to the tenuous Gulf of Mexico and southeast U.S. ridge enhanced by the unusually warm Gulf of Mexico and western Atlantic waters, combined with the tenuous western U.S. trough enhanced by the cooler than average waters off the U.S. West Coast. This pattern seems to make it difficult to sustain cold and troughiness in our area, despite long-range ensembles repeatedly try to indicate it. Now, the long-range models have reversed somewhat, showing another storm cutting into the Great Lakes bringing warmer air and rain shortly after the cold shot, with the cold air retreating and allowing a much milder pattern to envelop most of the eastern U.S. However, northern New England on north appears to be in the battlezone. If correct, that would mean more changeable temperatures, more typical of spring than the unusually constant temperatures so far this March.

Source: TropicalTidbits

 

Source: Climate Prediction Center

 

Source: NOAA