Just in time for Christmas, a developing storm will create headaches for anyone planning to travel east of the Mississippi River later this week. The storm will drop heavy snow on the Great Lakes and bring thunderstorms, heavy rain, and gusty winds to almost the entire East Coast. Merry Christmas!
The bulk of the storm occurring on Christmas Eve is reminiscent of what happened the day before Thanksgiving, when a storm dropped heavy snow on the megalopolis and snarled air traffic on the busiest travel day of the year. Thankfully for travelers, the storm will form further inland this year, providing heavy snow to parts of the Great Lakes (mostly Michigan and Ontario) and heavy rain for almost everyone to the storm's east.
Let's take a look at the storm's impacts, beginning with the most hated and loved four-letter-word in the country.
If you're dreaming of a white Christmas and you live in western Michigan, you're in luck, my friend. The most likely area to see snow from this system is along the shores of Lakes Michigan and Superior. The location of the low pressure system will drag large amounts of warm, moist air north from the Gulf of Mexico, so the storm will be a rainmaker for almost everyone except for that narrow corridor near Lake Michigan.
The exact location of the heaviest snow is a little uncertain right now, as the exact track of the cyclone will determine where the heavier bands of snow set up. Runs of both the European and GFS models this morning show that a coating of snow will fall from the northern half of Illinois and across the lake into western Michigan and the U.P. The parallel GFS is painting the heaviest snow across eastern Wisconsin right now, as it takes the low farther to the west than the other two models.
Exact totals vary, but a few inches of snow are a good bet, especially in western Michigan. This part of the country sees this kind of snow on any given day in January, so it's nothing residents will freak out about. The snow and wind will make driving hazardous in any case, and depending on conditions, some flights into and out of Chicago and other regional airports could be delayed or cancelled.
Thanks to the placement of the low, winds across the East Coast will shift around to the north and pump warm, moist air straight up from the Gulf and Caribbean. This not-entirely-unwelcome influx of warmth will help to produce heavy rain and thunderstorms across much of the East Coast on Wednesday and into the night on Thursday.
As we typically see when a strong storm develops like this, a hefty cold front will accompany the storm to the south, while a warm front forms to its east. The strongest storms and heaviest rainfall will occur along and ahead of these two fronts—the cold front will trigger severe thunderstorms across the southeast, while the warm front will serve as a focus for heavy rainfall in New England.
The three areas that will experience the heaviest rainfall are along the track of the low near the Great Lakes, along the warm front in New England, and along the cold front's thunderstorms in the southeast near the Gulf. The thunderstorms in the south will produce the most rainfall, with five-day totals (including today's convection in Florida) clocking in near five inches in some spots.
As the low begins to develop in the Ohio River valley during the day tomorrow, the influx of unstable air from the south will prime the atmosphere for the development of strong thunderstorms along the Gulf Coast from Houston across to northern Florida. The Storm Prediction Center has already issued a slight risk for severe weather from Louisiana to Florida in anticipation of some of the storms becoming severe, with the main threats being damaging winds and even a few tornadoes.
The above model image is from this morning's run of the 4km NAM showing simulated radar reflectivity for noon on Tuesday. Damaging winds are most likely in line segments, while tornadoes are most likely in discrete (individual) storms that are able to tap into winds that enable rotation.
The second round of storms will come through after dark on Tuesday as the cold front gets its act together (above) and begins moving into the area. The line of convection will stretch from the Gulf north through the Tennessee Valley, eventually moving east into the Carolinas during the day on Wednesday.
Don't be surprised if a few of these storms wind up severe-warned—strong winds could mix down to the surface in some of these storms, producing the threat for wind damage in some spots.
Wind gusts of 30 to 40 MPH are possible behind both the cold and warm fronts, as well as near the center of the low pressure system. Again, the strongest winds will likely occur in any thunderstorms that develop.
The above image shows wind gusts (in knots) for 1:00 PM on Wednesday, as predicted by local NWS offices.
The greatest chance for delays and cancellations will be at Detroit Metro (DTW), as low clouds and a heavy, wind-driven rain will cause airlines and controllers to cancel and delay flights to keep up with traffic in poor weather conditions. Issues are also possible at O'Hare (ORD) and Midway (MDW) in Chicago, especially on Wednesday night if the snow threat comes to fruition.
Along the East Coast, airport delays and cancellations should be relatively low, but the best chance for delays on the coast are at the New York City airports, where rainy conditions and gusty winds will likely cause some issues for airlines that serve the area. Issues are also possible at smaller regional airports from the Gulf through eastern Canada where flights are dependent on connecting through a hub affected by bad weather.
The models have shown a surprising amount of agreement and confidence in this scenario playing out, so only little details are up for grabs right now. If you plan on flying somewhere on Wednesday or Thursday, make sure you're prepared for delays or cancellations. If you're driving, give yourself extra time and watch out for the people around you who can handle rain or snow on the road.
[Images, in order: AP, WeatherBELL, WPC , WeatherBELL x2, NWS]