To anyone living east of the Mississippi River, the Christmas travel rush feels as if it is occurring in the spring. The weather that will grind travel to a halt at times on Wednesday and Thursday are typical spring hazards: severe thunderstorms, including the possibility of intense tornadoes, not to mention periods of dense fog in the Northeast.
On Wednesday morning, New York City's three major airports were accepting a just a handful of flights per hour as visibility struggled to rise above one-quarter mile in dense fog. The city is expected to have its warmest Christmas Eve on record Thursday, when the high temperature could approach the all-time December record for that location of 75 degrees Fahrenheit -- about 35 degrees Fahrenheit above average for this time of year.
Dozens of cities are likely to see their warmest Christmas Eve and Christmas Day on record this year, boosting the number of warm temperature records that have already been broken or tied in the U.S. this month alone to well above 6,000.
Some of the largest temperature anomalies are projected to occur across eastern Canada, including Ontario, Quebec and the Canadian Maritimes, where temperatures may be as much as 40 to 45 degrees Fahrenheit above average on Christmas Eve and Christmas Day.
With the warmth, though also comes the threat of intense thunderstorms, including a potentially significant tornado outbreak across the South on Wednesday. Thunderstorms could complicate air and road travel from Louisiana north to Illinois as a storm system slides eastward on Wednesday, with storms targeting the nation's busiest airport of Atlanta on Thursday.
In an unusual move for this time of year, the Storm Prediction Center in Norman, Oklahoma, has issued a "moderate risk" severe weather outlook for parts of Arkansas, Tennessee, Missouri and Mississippi. The biggest city that is in the middle of the moderate risk area is Memphis, Tennessee, the home of FedEx's air fleet, which is responsible for delivering packages ahead of Christmas morning.
While tornado outbreaks do occur in December in this part of the country, it's relatively unusual to have one that garners such an elevated risk outlook, along with such a large geographic footprint.
Shades of March 2012
The exceptional warmth in the East will ensure that many cities -- from Boston to Portland, Maine and Burlington Vermont, south to New York City -- clinch records for the warmest December on record. Not only that, but the records themselves will set milestones as many locations will blow away their previous December benchmarks by large margins.
Christmas Eve in the Mid-Atlantic will be dominated by air from the deep tropical Atlantic- record warm! #weather pic.twitter.com/hNcYQ1WaCT— Eric Blake (@EricBlake12) December 23, 2015
Take Philadelphia, for example. It's likely that December 2015 will be several degrees milder than the second-mildest such month, which would be only the second time since records began there, in the late 19th century, to have a monthly record that exceeds the old record by such a large margin. A similar situation is expected to occur in Boston and New York, as well, among other locations.
At New York's Central Park, the monthly average temperature through Dec. 22 was a staggering 11.8 degrees Fahrenheit above average.
Average temperatures for the month-to-date have been running at least 8 degrees Fahrenheit above average across parts of the Midwest and East Coast, which is off the chart that the Climate Prediction Center uses to keep track of such statistics.
This statistic from @NWS_MountHolly's forecast discussion yesterday is astounding to me. #pawx pic.twitter.com/ISz0BA24ZQ— Matt Lanza (@mattlanza) December 22, 2015
Many parts of the East have not seen such large monthly average temperature anomalies since an exceptional heat wave vaulted temperatures into the 80s to near 90 degrees Fahrenheit in March of 2012. That month also featured a cool and stormy West Coast, with storms failing to pull down cooler air from Canada and sweep such air masses southeastward.
The warmth in the East will be contrasted with colder, snowier conditions out West. In fact, a blizzard is likely to develop in North Texas, southeastern Colorado, and parts of Oklahoma and Nebraska this weekend, as a new storm system moves eastward.
Based on computer model forecasts, though, the blizzard is unlikely to mark a pattern change, with more milder than average air ready to surge up the eastern seaboard for the first week of the new year.