White Christmas out east could mess up holiday travel
AccuWeather reports a storm bearing strong winds, heavy snow, torrential rain, thunderstorms and fog will converge on the Northeast and Midwest on Christmas Eve and will likely create major travel delays, both on the roads and at airports.
The early stages of travel problems from patchy rain and fog will develop on Tuesday, AccuWeather said. But the most widespread travel disruptions and the worst weather conditions in terms of windswept rain and travel-impairing snow will be centered on Christmas Eve, it said.
Problems due to snow and wind will continue in the Upper Midwest and central Appalachians into Christmas Day, it said.
Fog could be another problem. As warmer air surges north with the rain, the risk of travel delays due to fog will increase, AccuWeather said.
"Areas and episodes of fog can be a problem for travelers in the Midwest and Northeast spanning Tuesday into Wednesday night," AccuWeather Chief meteorologist Elliot Abrams said in a statement.
The fog could create flight delays particularly in eastern cities.
Winter's beginning
Winter will officially begin at 5:03 p.m. Chicago time on Dec. 21.
That marks the point at which the least amount of sun falls across the northern half of the globe, and dark means cold.
"Obviously with daylight pretty much absent in the northern latitudes, the days are getting very short and that is the nursery for our polar and arctic air masses," said Michael Schlacter, a meteorologist with Weather 2000 Inc. in New York.
In New York City, Dec. 21 will have 9 hours, 15 minutes and 16 seconds of daylight, according to Timeanddate.com. When the new workweek begins, things will already be looking up because daylight will have increased by a second.
In Boston, the daylight on the 21st will be about 10 minutes shorter than in New York, while Chicago will have about seven minutes less. As depressing is that sounds to people who like sunshine, Toronto's daylight only lasts 8 hours, 55 minutes and 43 seconds, which is still more than an hour of what will fall on London.
We'll refrain from using the colloquial "shortest day of the year" because even Dec. 21 will have 24 hours.
The cold will wax and wane through the course of the winter for a variety of reasons. One is that after truly frigid air drops out of the Arctic into the more temperate latitudes of North America, it takes time to rebuild the supply.
Recharging freezer
Schlacter said for the U.S. to have a winter that lasts, cold snaps have to be interspersed with milder periods.
"You don't want every week to be freezing cold if you want to have a long winter," he said. "You have to recharge that Canadian freezer."
Snow on the ground can also influence temperatures. The sun's energy is used up melting the frozen crust rather than heating the air.
As of Dec. 18, 37.9 percent of the contiguous U.S. was covered by snow, down from a high of 50.2 percent in November, according to the National Operational Hydrologic Remote Sensing Center in Chanhassen, Minnesota.
Drought can also make the air cooler than it would be otherwise.
Then there are larger weather patterns - El Nino in the Pacific and the Arctic and North Atlantic oscillations.
El Nino can push the jet stream around to alter storm patterns across North America and bring milder readings to regions near the U.S.-Canadian border.
Cold air
The Arctic Oscillation can determine if the coldest air will stay bottled up at the North Pole or will come spilling down into North America, Asia and Europe.
The North Atlantic Oscillation determines whether any cold air that swings into North America will stay there or pass on through to Western Europe.
Schlacter said the current thinking is that the North Atlantic Oscillation is going to shift negative by next week, which will mean North America gets cold.
So while temperatures in New York are forecast to reach 55 on Dec. 24, the bottom will fall out shortly afterward.
Cold is coming. It's just a matter of when.
• Bloomberg contributed to this report.