Everything from tornadoes to paralyzing ice to blizzard conditions will be unfolding over the next several days as a massive storm system, dubbed Winter Storm Jonas by the Weather Channel, takes shape over the eastern half of the United States. Computer models have doggedly pointed to this scenario for the better part of a week, and the model consensus on the big picture continues to be unusually strong. The crosshairs for the heaviest urban snow appear to be on the Washington, D.C., area; more than two feet are possible there and nearby. Blizzard warnings were in effect Thursday afternoon in and near the Washington, D.C., area. The crystal ball is cloudier on where the storm’s north edge will end up--and that location is crucial, since it could be near New York City.
This sprawling storm is only now beginning to take shape across the South. Upper-level energy diving into the region will soon be cutting off from the main jet stream, leaving a powerful upper low in the Southeast that will move slowly northeast--in typical nor’easter fashion--along the East Coast. Along the way, a surface low located in northern Louisiana on Thursday afternoon will be succeeded by a new surface low predicted to develop just east of the Delmarva Peninsula by Saturday. That second surface low will team up with the upper-level low near the Gulf Stream and intensify rapidly over the weekend.
Below is a rundown of the key impacts expected from Jonas, followed by a closer look at potential snowfall amounts over the megapolitan area from D.C. to New York.Figure 1.
24-hour odds of at least 0.25” of freezing-rain accumulation during the 24 hours from 06Z (1 am EST) Friday, January 22, 2016, to 06Z Saturday. Image credit: NOAA/NWS Weather Prediction Center
.Freezing rain and ice across mid-South
A large swath of the mid-South from eastern Arkansas to southern Virginia is in line for accumulations of ice on Friday into Saturday, as freezing rain develops on the north side of the still-evolving winter storm. The bull’s-eye for highest icing risk appears to be Charlotte, NC, where the timing could hardly be worse: the city is playing host to the NFC championship game on Sunday between the Carolina Panthers and Arizona Cardinals. Odds are better than even for Charlotte to get at least a half-inch of ice, which could be a devastating amount for this large urban area. Major disruption to game-related activities over the weekend is a strong possibility, and thousands of people planning to travel to the area for the game may end up disappointed by massive air and road gridlock across the East, although the worst of the storm will be over in Charlotte by the scheduled game time.Figure 2.
At midday Thursday, NOAA’s Storm Prediction Center was calling for an enhanced risk of severe weather through Friday morning along the central Gulf Coast, with a slight risk in northern Florida and southern Georgia later on Friday. Severe weather along the Gulf Coast
Thunderstorms popped up on Wednesday night in Oklahoma atop low-level air close to freezing, a sign of the potent upper-level storm heading toward the East Coast. Storms were intensifying across northern Louisiana into north Mississippi on Thursday afternoon, and these should continue to work their way east across the lower Mississippi Delta through the evening. Low-level moisture is not quite as plentiful as it was during the holiday-week severe weather of late December, but very strong upper-level dynamics will largely compensate. High winds, large hail, and heavy rain are all possible, along with a few tornadoes. The risk of strong tornadoes appears relatively low. (Sharp-eyed scrutinizers of Figure 2 will notice the area of thunderstorms on Friday along the northern California coast, a region getting quenched this month by plentiful rain courtesy of Pacific storm systems.)Figure 3
. WunderMap depiction of surface winds at 8:00 am Sunday, January 24, 2016, based on the GFS model run from 12Z Thursday, January 21. Wind speeds are in knots; add 15% for miles per hour. Coastal flooding along the mid-Atlantic
A coastal flood watch is in effect for the period from late Friday night to Sunday morning along most of the New Jersey and Delaware coast. WIdespread moderate flooding is expected, with some localized areas of major flooding. High waves of up to 15-20 feet just offshore will pound the coast, along with winds gusting to 50-60 mph or more. Beach erosion is a near-certainty, and some road and property damage is possible. The threat is being compounded by the full moon on Saturday night, which is adding 1-2 feet to the regular tidal cycle. The highest astronomical tide is on Saturday night, with tides about a foot less on Saturday and Sunday morning. Due to the storm’s timing, all three of these cycles could produce storm tides (astronomical + lunar + storm-driven) of around 7-8 feet across southern New Jersey and northern Delaware.
Storm surge expert Hal Needham has more on the coastal flood threat in a Thursday morning blog post
. “I do not expect that this surge event will be one for the record books,” says Needham. “Although the winds will be howling from late morning until after dark on Saturday, the duration of this wind event will not be long enough to really get a big surge setup. So in places like coastal New Jersey, don't expect water levels to approach historical levels reached by Hurricane Sandy or even the 1962 Ash Wednesday Storm.”Last but not least: Big snow for the Northeast urban corridor
Below are probabilistic maps drawn from several NWS offices, showing the low-end, mid-range, and high-end expectations for snowfall from this storm. By going to the higher-res versions linked from each caption, you can view the individual totals shown on the map--but it’s important to focus on the large-scale expected patterns of snowfall rather than the point-source projections.Figure 4.
Low-, mid-, and high-end snowfall amounts (in inches--see legend at top) projected for the region around Washington, D.C. as of 2 pm EST Thursday, January 21, 2016 for the period from 1 pm Friday to 7 am Sunday. For higher-resolution images, see the NWS/Baltimore-Washington
may end up with a truly historic snowfall. The mid-range amount shown below would be the city’s second heaviest on record, topped only by the Knickerbocker storm of 1922. Expect mesoscale banding to generate the heaviest snow in strips oriented from southwest to northeast. These bands could be only about 30-50 miles wide, but snow on either side would still be significant. There is some chance of a brief changeover to sleet toward the Delmarva Peninsula, but any changeover in or west of D.C. should not greatly affect snow totals.
From the NWS maps above:Least to expect in D.C.:
Low-, mid-, and high-end snowfall amounts (in inches--see legend at top) projected for the region around Philadelphia as of 2 pm EST Thursday, January 21, 2016 for the period from 1 pm Friday to 7 am Sunday. For higher-resolution images, see the NWS/Philadelphia
should have more trouble getting its second-highest storm total of all time than D.C., as its two highest amounts are 31” (Jan. 6-8, 1998) and 28.5” (Feb. 5-6, 2010). Compared to Washington, there is also more low-end uncertainty in Philly, but the area is still at high risk of a high-impact storm.
From the NWS maps above:Least to expect in Philadelphia:
Low-, mid-, and high-end snowfall amounts (in inches--see legend at top) projected for the region around New York City as of 2 pm EST Thursday, January 21, 2016 for the period from 1 pm Friday to 7 am Sunday. For higher-resolution images, see the NWS/New York City
website.New York City
is perhaps the toughest forecast call of this event. The local NWS office issued a blizzard watch on Thursday, and it should be seen as just that: a watch, rather than a warning. Watches indicate where a particular event is possible, but not yet expected with confidence. As late as Thursday morning, there was huge model disparity in placing the north edge of the heavy snowfall, and that north edge will be a sharp one. As a result, New York City could get as little as a nuisance event or as much as a city-crippling storm. Subsequent model runs will be crucial in narrowing this range of uncertainty. Note that a blizzard is defined not by snow amounts but by at least three hours of high wind (frequent gusts or sustained winds of at least 35 mph) and poor visibility (no more than 1/4 mile). These conditions could be met in or near New York City even if snowfall amounts are relatively low.
From the NWS maps above:Least to expect in New York:
All the ingredients are coming together for a blockbuster winter storm over the highly populated urban corridor from Washington, D.C., toward New York. The 0Z Friday suite of computer models tonight will be bolstered by data from dropsondes being released this evening by a NOAA Gulfstream-IV hurricane-hunter jet. Once we get to Saturday, short-range models such as the HRRR will become increasingly useful in pinning down the location of mesoscale bands as they evolve, as well as the crucial north edge of the storm.
I’ll be back with a new post by 3 pm EST Friday afternoon. We’ll also be launching a live blog tonight (watch our main WU page
for a link) that will run through the duration of the storm. At 4 pm EST Thursday, WU meteorologists Shaun Tanner and Tim Roche will be joining me for a live-stream discussion of the storm on a special installment of “This Week in Weather”. You can watch the show and submit your questions through a link that’ll appear at show time on the This Week in Weather
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