Plain-language summary:
It will be cool, but not particularly cold, and dry today and tomorrow. A major, slow-moving, and long-duration snowstorm will move in Tuesday night and likely lasting into at least Thursday night. Lower elevation areas may start as rain, but everyone will eventually see snow, potentially a lot of it. Snowfall amounts will be sensitive to elevation, and higher elevations areas could see feet of snow. It gradually clears out and warms next weekend, with the large-scale pattern favoring dry weather and relatively clear skies on eclipse day, April 8. It likely continues to warm up afterward, with potential rain later in the week.
Meteorological discussion:
Broad surface high pressure in central Canada will be ushering in cool (but not terribly cold) and dry air into our region today and tomorrow, with near to slightly below average temperatures. Meanwhile, a pronounced Greenland blocking high pressure system is developing, while at the same time, a trough is ejecting eastward from the Rocky Mountains.
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| Source: Climate Prediction Center |
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
By Tuesday, the storm will have moved into the Ohio Valley, bringing with it a lot of Gulf of Mexico moisture, while another northern disturbance dives into the far northern parts of the Midwest U.S. and starts to interact with the main storm. How strong the northern disturbance is and how far its associated trough deepens and interacts with the main storm will determine the exact evolution of the whole system, and we won't know the details for another couple of days. However, we have a reasonably confident broad picture of the evolution of the storm, which will move rather slowly due to the pronounced blocking pattern. The primary storm will initially strengthen and turn north into the Great Lakes Tuesday into Tuesday night, but with the blocking surface high pressure to the north and an upper-level trough over Atlantic Canada, the path northward will be blocked. Instead, the primary storm will stall out and weaken while a secondary storm will develop along the U.S. East Coast, likely along the mid-Atlantic U.S. coast, and strengthen and take over as the dominant storm later Wednesday into Wednesday night. All this happens while the northern upper-level trough cuts off and strengthens into a strong upper-level low slowly tracking across the Great Lakes, upstate New York, and then into Atlantic Canada.
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| Source: TropicalTidbits |
Initially, precipitation will be likely limited to from eastern Ontario to southern Maine on south Tuesday night into Wednesday morning as the primary storm stalls and weakens. Precipitation will then blossom across all of northern New England and likely southern Quebec, depending on the exact storm track, Wednesday evening, as the secondary coastal storm takes over. Precipitation may start as rain in lower elevations, but both the northern disturbance and the upper-level trough over Atlantic Canada will also inject somewhat colder air into the storm. Combined with dynamic cooling from ascent and precipitation with the strengthening coastal storm and upper-level low, any rain initially will change to snow, even at lower elevations. The secondary storm will slowly move north or northeastward and occlude on Thursday, with heavy precipitation fading but widespread wraparound moisture and light snow continuing through Friday in many areas, and possibly even Friday night in the favored upslope areas. Although everyone will see snow, near to just above freezing temperatures will lead to melting and less accumulations at lower elevations. The high sun angle could also lead to snow showers changing to rain showers in the afternoon at lower elevations when precipitation is light. With the storm's long duration, some higher elevations spots could see feet of snow, while lower elevations end up with a pasty wet snowstorm impressive by April standards.
The storm will slowly move away next weekend, with a broad and slow-moving area of high pressure both at the surface and aloft leading to gradually clearing and warming conditions, though deep northwesterly flow will block true warm air from the southern U.S. This is aided by a trough entering western North America, pumping the central U.S. ridge and causing the ridge to meet up with and join the Greenland or high-latitude block. This means a favorable synoptic-scale setup for dry weather and clear skies on the solar eclipse day, Monday, April 8th, though it remains to be seen if smaller-scale features cause clouds in some areas. Tomer
Burg’s website has an excellent resource for eclipse cloud cover model
forecasts.
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| Source: TropicalTidbits |
Afterward, it continues to warm up, as the ridge persists over the eastern U.S. and a storm moves slowly northeastward from the Plains into northern Ontario or northern Quebec, leading to warm southerly winds, before the storm possibly brings rain to our region late in the week. It
might cool down briefly that, but it is unlikely to be particularly cold for
April given the lack of true cold air over most of Canada. With the lack of
cold air and the blocking pattern easing, allowing for warm surges from the
southern U.S. into our region, a generally warm pattern is expected for
mid-April. As such, this week’s snowstorm is likely to be the last of the
season for most of the region, especially at lower elevations.
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| Source: TropicalTidbits |
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