I hope you enjoyed the relatively nice weather we've seen for the past few days, because things are going to change in a hurry. A major storm is trekking across Texas this afternoon on its way to the eastern seaboard, and it will culminate in what could be a decent snow event in the Northeast and Mid-Atlantic this weekend.
This week's dominating weather feature was a zonal (roughly east-west oriented) jet stream that prevented active weather from breaking out across most of the country. The biggest stories of the week were a series of Alberta Clippers that raced southeast across the Midwest and Mid-Atlantic regions, leaving behind several inches of snow in their wake.
A sharp, deep trough in the jet stream over the Plains, combined with the lifting effects of a jet streak (enhanced winds within the jet stream) over the Mid-South, will work together to strengthen a low pressure system moving into the Gulf of Mexico from Texas this afternoon.
The low will reach the North Carolina coast by early Saturday morning, and that's when things start to get tricky.
Track, Track, Track
One of the biggest rules about nor'easters during the winter is that track is everything. A few miles too close to land, and the storm is all rain for the major cities. A few miles too far out to sea and precipitation is relegated to the coast. Coastal storms need to take just the right track up the East Coast in order to produce heavy precipitation in the storm's cold sector, resulting in major snowfall along the I-95 corridor between Washington D.C. and Portland, Maine.
The ECMWF (Euro) model, widely regarded as the world's best weather model, has the storm tracking close enough to the coast that it produces accumulating snow over the Appalachians and foothills of the mountains, with snow swinging towards the coast and producing single-digit accumulations along the coast from Maryland through Connecticut. The model shows snowfall totals approaching double-digits in southeast New England around Rhode Island and Maine.
For the past couple of days, the forecast has been uncertain due to the GFS model diverging from the Euro and kicking the storm far enough out to sea to prevent people from seeing much snow. That changed as of this morning's run. The 7:00 AM EST run of the GFS shows the storm tracking too close to the coast, now, resulting in snow for inland areas near higher elevations, as well as southeast New England (think Rhode Island, Connecticut, eastern Mass.).
The models are coming into agreement that the storm will track close enough to the coast that it will produce snow, but the big question is "where?"
Where Will It Snow?
Snow will begin early Saturday morning close to the Mason-Dixon line, and the shield of precipitation will climb north through the afternoon hours. The heaviest rain and snow should reach coastal New England by Saturday evening.
There are two spots that have the best chances of seeing snow this weekend. The first is the Appalachians, of course. The mountains and other higher elevations in the foothills from North Carolina through Pennsylvania will likely see a modest blanket of snow on the ground by daybreak on Saturday.
The other spot is in coastal New England across eastern Connecticut, Rhode Island, and eastern Massachusetts. Models are starting to agree that, regardless of whether or not areas south of New England see snow, the low pressure system should come close enough to give some parts of coastal New England accumulating snow.
Coastal New England from eastern Connecticut, Rhode Island, and eastern Massachusetts could see a pretty hefty snowfall from this storm, with the worst case scenario producing double-digit totals in cities like Providence and Boston.
Whether it's in Boston or Charlottesville, Virginia, snow amounts wholly depend on the track of the system. The distance between the center of the low and the coast will determine where the rain/snow line sets up, and where the heaviest precipitation will coincide with the cold air. The major cities along I-95 are often right on that rain/snow line, and a similar situation could play out this time.
Let's take a look at what the National Weather Service and The Weather Channel are saying about this storm. There are at least fourteen different National Weather Service offices whose area of responsibility could see snow from this system, and since forecasters aren't a monolithic group who think in lockstep, forecasts will vary depending on where you live. Right now, the only winter weather alerts in effect for this particular storm are in the parts of southeastern New England models indicate will likely take the brunt of this system.
NWS Boston has a winter storm watch in place from Hartford, Connecticut to Lawrence, Massachusetts in anticipation of a disruptive snowfall. The office's current snowfall forecast shows a bullseye of six to eight inches falling mostly east of Worcester, but their forecast will change as models continue to refine and pinpoint exactly who will see what.
The Weather Channel—whose name for this storm is "Iola," which is a beautiful name that means "dumb public giving us free advertising"—is just using a slightly modified version of the GFS model's snowfall output as their forecast on weather dot com this afternoon.
If you're one of the lucky (or unlucky) folks who is too close to the coast to expect snow, you're not out of the precipitation at all. What doesn't fall as snow will come down as rain, and it'll be pretty heavy in some spots. The heaviest rain will fall in the southeast where thunderstorms will develop and tap into tropical moisture; many locations can expect one to two inches of rain on average, with higher rainfall totals likely in stronger thunderstorms.
If you live anywhere from the southern Appalachians through New England and into Atlantic Canada, keep an eye on the forecasts this weekend. Snowfall coverage and totals will inevitably change as we get closer to the event, and remember that a few miles either way on the track of the low could be the difference between a non-event and a disruptive storm.