A big nor’easter is heading for the Eastern Seaboard early next week, but it’s still too soon to tell whether the urban corridor from Washington to Boston will be doing more digging versus more wading. The timing and location of rain/snow transition is a perennial forecast challenge with Northeast snowstorms, especially in late-winter and early-spring storms like this one. What we do know is that this storm at least has the potential
to be a prodigious snow-maker.
The thermal foundation for next week’s big storm is a sharply frigid air mass for early March that’s now descending on the eastern two-thirds of the U.S. This air mass can be traced back to Canada’s Northwest Territories, and it feels that way. Readings were a few degrees below zero Fahrenheit on Friday morning across North Dakota and northern Minnesota. This is far from record cold for the region—Grand Forks, ND, has dipped below –30°F in mid-Marches past—but it’s a distinct change from the record warmth that’s enveloped much of the eastern U.S. in recent weeks. Temperatures will be 20°F to 30°F below average in many places east of the Mississippi by Sunday, with a light freeze possible as far south as Columbia, SC. Some daily record lows are possible across the Northeast as temperatures drop into the single digits in Boston, teens in New York City, and low 20s in Washington.
Another lobe of the polar jet stream will push down a second dose of chilly air across the East early next week. That lobe will also dig more sharply, pulling in subtropical energy and moisture and cutting off as a strong upper low around New York and New England by Wednesday. Energy will be transferred from a surface low in the Ohio Valley to another surface low predicted to strengthen rapidly near the mid-Atlantic coast on Tuesday. Meteorology buffs will recognize this as a classic Miller Type B
set-up. Because Type B lows are usually located closer to shore than their more straightforward Type A counterparts, they typically bring more warm, moist air inland and produce a messy, hard-to-predict array of precipitation types. Whether the low tracks well offshore, near the coast, or just inland will largely determine who gets snow or sleet as opposed to rain. Model trends have leaned in the direction of snow for the urban corridor, and I’m leaning that way as well, given the intense dynamics associated with this storm and the cold air masses that will both precede and follow it.Figure 1.
Locations of the nor’easter surface low predicted by the 06Z Friday run of the 20-member GFS model ensemble (GEFS) for 7:00 am EST Tuesday, March 14, 2017. Numbers show the last two digits of the surface pressure in millibars (e.g., “91” = 991 millibars). The map shows how much uncertainty remains in the forecast. The ensemble members agree that a surface low will be intensifying along or off the mid-Atlantic coast, but the locations differ by hundreds of miles—enough to produce vastly different outcomes along the East Coast. The European model ensemble is trending a bit further offshore, which would result in higher odds for a major snowfall from Washington to New York. Image credit: tropicaltidbits.com
Whatever form it takes, the precipitation from this storm could be quite heavy across the Northeast’s urban core. The 12Z Friday run of the GFS model, consistent with runs from late Thursday, is dumping more than 2” of liquid equivalent from just east of Washington, D.C., across the New York metro area, with another two-inch-plus stripe over eastern Massachusetts. The heaviest snows are projected to be just northwest of these corridors. The 12Z GFS run shows snow amounts of more than a foot possible close to the D.C.–New York corridor, with potential totals approaching two feet over eastern Pennsylvania and the Hudson Valley of New York. Again, everything will hinge on the exact placement of warmer vs. colder air and the precise configuration of the upper and surface lows, and it’s far too soon to know these with confidence.
Late Friday morning, Capital Weather Gang’s Jason Samenow gave 55% odds
that central D.C. would get at least an inch of snow, with a 30% chance of at least eight inches. The latter would be among the heaviest March snows on record
for the city, he noted.
“While we want folks to be aware of this possibility, for it to materialize in the immediate area would require all of the storm ingredients coming together just right — which has a low likelihood — maybe one-in-three,” wrote Samenow
.Mid-March can produce memorable Northeast snowstorms
Some of the most epic nor’easters on record have occurred at the tail end of the winter snow season, even as far south as Washington, D.C. On March 12-15, 1993, the “Storm of the Century”
dropped incredible snows all the way from the Florida Panhandle (4”) and Birmingham, AL (13”) to Pittsburgh, PA (25.2”) and Syracuse, NY (43”). Along the urban corridor, where sleet mixed with the snow in some areas, Dulles International Airport notched 14.1” and LaGuardia International Airport racked up 12.3”, with winds gusting to 71 mph. This was the first weather event to trigger the closure of every major East Coast airport
. Some 270 deaths were attributed to the storm.Figure 2.
Meteosat-3 infrared image of the 1993 Storm of the Century at 1200Z (7:00 am EST) Saturday, March 13, 1993. Along with huge amounts of snow, the storm pushed a major storm surge into Florida’s west coast and a destructive squall line across the peninsula. Image credit: CIMMS Satellite Blog
Another famed mid-March storm is the Great Blizzard of 1888
(March 11-14), which focused its snowy wrath on eastern New York and New England. The Smithsonian Institution called it
“a weather event so fierce that it's still a storm by which other East Coast storms are measured.” Mildness gave way to brutal cold as this ferocious system moved in, dumping snow so heavy and wind-drifted that we still don’t know exactly how much fell in some places. Measured totals included 22” in New York City; 45” in New Haven, CT; 48” in Albany, NY; and 58” in Saratoga Springs, NY. New York’s Central Park recorded a low of 6°F and a high of 9°F on March 13; these remain the coldest values ever recorded at Central Park so late in the season.
More than 400 people are believed to have perished in the Blizzard of 1888, including some 200 in New York City. The storm’s impact on elevated train lines prompted the city
to begin planning its now-iconic subway system.
We’ll be back with a new post by Monday. Have a great weekend, everyone!
Bob HensonFigure 3.
A scene from Northampton, MA, on March 13, 1888. Image credit: Forbes Library, Northampton,
via Smithsonian Institution