A significant storm is on the cusp of developing over the Gulf Coast this afternoon. Over the next day, the storm will rocket towards the Great Lakes and grow into a major wind, rain, and snow producer that promises to snarl holiday travel.
What's going on?
An existing low pressure system over Wisconsin is dragging a cold front across the southern United States at this hour, firing off some severe thunderstorms in Mississippi and Alabama. Spotters and weather radar have already confirmed one damaging tornado near Hattiesburg, Mississippi this afternoon, and more severe weather is possible through the nighttime hours.
Along the southern end of the existing cold front is a newly-formed center of low pressure that will cause all of the problems as we go into Christmas Eve and Christmas Day. The Weather Prediction Center analyzed the center of the low over southern Louisiana at noon local time, and the system will rapidly strengthen and dart towards the Ohio Valley and Great Lakes over the next 24 hours.
What will happen tomorrow?
By 12:00 PM Central/11:00 AM Eastern tomorrow (pictured above), the storm will be producing heavy rain across the entire East Coast from southern Florida through Maine, with thunderstorms possible in the warm, unstable air mass ahead of the cold front. On the back side of the low, snow and an icy mix are possible from Missouri through Michigan.
How much snow will fall?
The exact track of the low will determine who sees the most snow. Above is a map of forecast snowfall totals from the National Weather Service. Chicago looks like it's positioned to see the most white doom from this storm—if the band of heavy snow manages to set up right over the Windy City, some spots could see more than six inches of heavy, wet snow by Christmas morning.
We would normally see more snow from a system that forms around Christmas (because of that whole winter thing), but this storm is going to be so potent and so far to the west that it's dragging very warm, moist air up the length of the East Coast. High temperatures tomorrow will top out in the 60s as far north as Washington D.C. and Philadelphia, with upper 50s likely in Boston on Christmas morning.
What about rain?
Elsewhere, wind and rain will be the big stories of the day. Most areas east of the Mississippi River will see a nice soaking, with one to three inches of rain expected by the end of the day on Friday. The most rain will occur closer to the Gulf Coast where thunderstorms are able to tap into a deeper supply of atmospheric moisture.
How strong will the wind get?
Wind is going to be a big issue on Christmas Eve, especially in areas closest to the track of the low. Locations from the Ohio Valley through the Great Lakes will see the worst winds, with gusts up to and over 50 MPH likely at times. The gusts will cause issues in areas that have saturated ground or heavy snow on trees and power lines. It's not a stretch to say that some people will wake up without power on Thursday morning.
High wind watches and warnings are in effect for eastern Michigan and the shores of Lakes Erie and Ontario, and these will likely be expanded west tonight or tomorrow. A wind advisory is in effect for much of the Ohio Valley as well, for wind gusts that could exceed 50 MPH at times.
Will my flight get cancelled?
That's always a tricky question to answer during a situation like this. The storm will very likely affect air travel tomorrow, especially around Chicago, Detroit, and Cincinnati, all of which are hubs for various airlines. Weather at your departing, connecting, and arrival airports could all have an impact on whether your flight is delayed or cancelled, but it doesn't end there. Many planes can go through five or six segments in a day, and any delays or cancellations down the line could affect your flight. One airplane getting stuck in Chicago, for instance, could trigger six cancellations down the line for all of the flights it was supposed to complete later in the day. It's the domino effect from hell.
Heavy rain and low clouds are enough of a wrench to throw into flight plans to begin with, but when you add the potential for thunderstorms, gusty winds, and even snow into the mix, it will definitely have an impact on air travel. Expect the worst delays out of ORD, MDW, DTW, and CVG on Wednesday, with congestion and residual delays and cancellations at the big East Coast hubs like ATL, IAD, DCA, and the NYC-area airports, especially once the rain and poor visibility sets in.
Will Santa crash?
Santa will not crash. They recently upgraded Rudolph's bright nose so he has the most advanced reindeer technology, complete with on-board radar and a wind shear detection system. He will be able to find you and deliver your lump of coal right on time. Heathen.
[Images: NASA, WPC, NWS, WPC]