(Click on all images below to enlarge) A major change to the weather pattern this coming weekend will send the jet stream winds - the fast river of air aloft that steers our storm systems and separates cold air from warm - careening south, meaning cold air takes charge of the Northeast. As mentioned in the 8-14 Day Forecast Monday, what holds interest in such a pattern is the potential for a strong shot of atmospheric energy to round the base of the jet stream trough, or dip, during the middle of next week, prompting storm development that will run from the Central United States to the Northeast.
The first signs of storm development will come Sunday into Monday, with lowering pressures from the Central Plains to the Mississippi River in response to the arrival of the upper level energy that will drive storm development. Gulf of Mexico moisture will be available, and a swath of rain will develop. This Gulf moisture will continue to feed the developing storm, ensuring plenty of precipitation will accompany the storm center.
As warmth and moisture rushes northeast ahead of the storm, an area of "overrunning" snow and rain will develop in the battlezone where mositure meets cold air, and by Tuesday, this will likely mean some snow showers moving into New York and New England, though given daily high temperatures in the lower 40s, on average, some areas will find rain showers instead. At this point, a classic Northeast snowstorm needs something we just aren't expected to have - strong high pressure that holds firm and forces the storm center to relocate along the Mid-Atlantic coast. Because that's not expected to happen, chances are good any wintry precipitation in Southern and probably even Central New England would change to rain by Wednesday.
In fact, with a storm center heading into the Eastern Great Lakes, New England can almost always bank on mostly rain, because of the south wind ahead of the storm that takes over. In this case, however, enough cold air will probably be in place to force the storm center to shift east around the southern base of the cold air - in other words, right over Central or Southern New England. This would put warm air into these regions, but leave Northern New York State, and Northern New England, in sufficient cold air for snow, possibly mixing with sleet as warm air moves in aloft. Add to this the potential for "cold air damming" around the mountains of Northern New England - particularly New Hampshire and Maine - and the chances for considerable North Country snow rise even more.
There's no question we have plenty to watch! And, as mentioned in the 8-14 Day Forecast on Monday, more energetic disturbances may come in the days to follow.