The odds are increasing for a large and powerful storm to take shape and deliver a wide variety of adverse weather conditions in the days following the Thanksgiving holiday. The dynamic storm will begin bringing impacts this weekend in the Deep South and, as it develops, will expand northward over the Midwest and Northeast states on Monday and into Tuesday.
As of Wednesday afternoon, the backbone of the potential storm was a mass of showers and thunderstorms far out over the northern Pacific Ocean, hundreds of miles west of the U.S.-Canada coastline. This atmospheric feature is not expected to reach the West Coast of the U.S. until the end of the week.
Should the storm unfold the way AccuWeather meteorologists believe it will, a host of bad weather conditions has the potential to cause significant travel disruptions over the eastern third of the nation. Heavy rain, gusty winds and snow will all be on the post-Thanksgiving menu. Along with that, the risk of dangerous thunderstorms in parts of the Southern and Eastern states will erupt early next week.
At some point early next week, the storm is likely to adversely affect the timely departure and arrival of flights in the major hubs of Chicago, Atlanta, New York City, Philadelphia, Detroit, Pittsburgh, Boston, Baltimore, Washington, D.C., and Charlotte, North Carolina.
The early roots of the storm are forecast to produce drenching rain and gusty thunderstorms along the upper and western part of the Gulf coast from Friday through Saturday.
"A general 1-3 inches of rain is forecast with local amounts to 8 inches likely in parts of southeastern Texas and southern Louisiana from Friday through Sunday," AccuWeather Senior Meteorologist Dan Kottlowski said.
Where the rain is most persistent, flooding in urban and low-lying areas can occur.
This will be just the start of what is likely to result in a number of problems due to increasing winds and a zone of drenching rain that will expand in a northeast direction from Sunday to Monday.
As the storm strengthens early next week, winds in absence of severe thunderstorms can become strong enough to break tree limbs and cause power outages. Winds frequenting 20-40 mph with gusts near 60 mph over a broad area from near the Mississippi River to the mid-Atlantic and New England coasts are likely at the height of the storm from Monday and Tuesday.
A general 1-2 inches of rain is forecast to fall with locally higher amounts to 3 inches as the storm moves northeastward early next week. Where the rain falls on saturated ground, rapid runoff may cause small streams to rise to reach their banks. Street flooding can be made worse where leaves have fallen and blocked storm drains.
Rain and wind are not likely to be the only troublesome aspects of the storm as colder air will invade the system and lead to a transition to snow from parts of the Midwest and then to portions of the Appalachians.
"While it is too early to give precise amounts of snowfall, since the actual track and intensity of the storm is still in question, there is the potential for a moderate to heavy amount of snow to fall from portions of Tennessee and Kentucky to parts of Ohio, Indiana, Michigan, Illinois and Ontario," AccuWeather Senior Storm Warning Meteorologist Brian Wimer said.
"These areas would likely receive rain or a wintry mix at the onset of the storm from Sunday to Monday, but then a transition to snow or snow showers from Monday to Tuesday," Wimer said.
This transition can also extend farther to the east over the Appalachians during the latter part of the storm. Should the storm travel farther to the west, the area of heavy snow may shift farther to the west as well, and snow may be delayed in the Appalachians.
Since temperatures may be within a few degrees of 32 degrees Fahrenheit, or perhaps even the middle 30s, the snow is likely to be wet and clingy in nature, which can weigh down tree limbs and potentially lead to power outages. Gusty winds may increase the danger for limbs to break and take power lines with them. Road surfaces in the snow area may range from just wet to slushy and snow-covered where the heaviest snow persists.
Another key factor in the storm will be the warm and moist air that is likely to be drawn northward from the Gulf of Mexico and the Gulf Stream over the western Atlantic Ocean.
"Atmospheric conditions may unfold to the point where an outbreak of severe thunderstorms is possible from Florida, southern Alabama and southern Mississippi to the Carolinas and eastern Virginia from Sunday to early Monday," AccuWeather Lead Storm Warning Meteorologist Eddie Walker said.
The risk of severe thunderstorms could even extend as far north as southern New England on Monday.
At this early juncture, strong wind gusts will likely be the main threat from the storms, but occasionally dynamic storm systems of this nature can lead to a few isolated tornadoes as well.
The temperature pattern may become so convoluted that areas in northern New England could be 30 degrees warmer than areas in the Midwest and the interior South for a time. New England may be the last zone to feel the effects of the colder air in the storm's wake as a result and could be delayed until Tuesday or Wednesday, while colder air is likely to sweep quickly through the Southern states.
With such a large and slow-moving storm now more likely to unfold, the aftereffects of cold air, blustery conditions and snow showers with locally heavy lake-effect snow are likely to persist during the middle and latter parts of the week in the Central and Eastern states.
The details on the extent of heavy snow and locations at greatest risk of severe thunderstorms will unfold in the coming days as the exact track, strength and timing of the storm become more clear.