An unseasonably warm and impressively waterlogged storm system is set to bloom across the Eastern United States late this week, bringing the chance of severe weather — including a few tornadoes — and widespread heavy rains.
Low pressure will form over the Texas-Oklahoma border Friday, scuttling northeast over the weekend and unleashing a slew of impactful weather.
Ahead of the storm, which will develop from a burst of energy now centered over the Gulf of Alaska, mild temperatures will feel springlike at times. Highs this weekend may approach 25 or 30 degrees above average in the East, nestled within an extended period of atypical warmth. Some temperature records may be tied or broken.
Behind the storm system, colder air will make a run east, moderating temperatures into early next week. It could flip rain to snow for places like Chicago over the weekend though, possibly piling up moderate accumulations.
The most ominous weather looms in the Friday-through-Sunday time frame, but signs point to yet another storm potentially on the way afterward, on Tuesday of next week. That secondary storm would probably have more of an impact in the Southeast, sparing most of the Midwest.
Severe thunderstorms and potential tornadoes in the South
The storm system’s first menacing act will brew on Friday, when scattered to perhaps numerous thunderstorms, a number of which could be severe, are forecast to erupt from eastern Texas and Oklahoma into portions of northwest Louisiana and southern Arkansas.
As a zone of low pressure begins to take shape near or north of the Red River on Friday, a strong low level jet stream from the south will carry a warm, humid, and unstable air mass over areas to the east. The ingredients will fall into place to fuel severe thunderstorms, and the developing low’s encroaching cold front could serve as an ideal trigger.
Meanwhile, the roaring low-level jet, akin to a river of swiftly moving air less than a mile up in the atmosphere, will also impart plentiful wind shear to the environment beneath it. Wind shear describes a change in wind speed/direction with height. Storms that span multiple layers of the atmosphere could exhibit rotation.
These ingredients will favor a tornado risk, along with scattered bouts of damaging straight-line winds and perhaps urban flooding from heavy downpours.
The threat will then shift east into Dixie Alley and the Gulf Coast states on Saturday, bringing the corridor of greatest severe risk to parts of Mississippi and Alabama.
This severe weather episode may be similar to the recent Deep South severe weather events that have occurred in the past few weeks. However, signs point to the low pressure center tracking a little farther northward, expanding the “warm sector” of unstable air as far north as perhaps southern Tennessee. This could make the severe risk more widespread.
Thunderstorms may still rumble across portions of the Southeast on Sunday but with a lesser severe risk.
Heavy rain and possible flooding from the southern Plains to the Great Lakes
Meanwhile, just east of the low pressure system’s center, heavy rains fueled by anomalously warm and moist air will set the stage for potential flooding. A slow-moving cold front will focus the heavy precipitation, as if wringing out a soaked atmospheric washcloth. Some locations may see as much as half a foot of rain.
The heaviest rains will fall over the weekend in a swath from East Texas into Arkansas and the Ozark Plateau, eventually reaching the Midwest and eastern Great Lakes on Saturday. By Sunday, heavy rain will be falling in Upstate New York and western New England, with some question about precipitation type in parts of New Hampshire, Vermont and Maine.
Across this broad strip, a general 2 to 4 inches of rain is expected. From the central Mississippi Valley north toward Illinois and Indiana, localized 5- to 6-inch amounts are possible.
The key timing for this is late Friday through Saturday, possibly lingering into Sunday in eastern areas. For the Northeast, this is mainly a Sunday event.
Snow behind the front
As temperatures plummet behind the front, a few areas may switch from rain to snow.
In Kansas City, a brief burst of snow is possible on Friday night. Lows will fall into the lower 20s.
There are indications a band of moderate snow could develop on the backside of the front, as arriving cold air flips precipitation from rain to snow. This looks to be a narrow but hefty event from Missouri and Illinois into northern Indiana and Michigan. The key time frame for this would be on Saturday.
There is considerable uncertainty with this feature, however, so expect shifts in the prognosticated totals during the coming days. Chicago could see itself missed altogether or wind up with a plowable snowfall.
Eventually, the snowy side of the system will move into northern New England to start next week. Accumulating snows are likely there.
Toasty in the East
The meteorological seesaw may feature snow in the West, but at the same time a “torch” weather pattern will be toasting the East — by January standards, anyway.
Saturday could be downright balmy in a few areas, with temperatures near 70 in Atlanta, Raleigh and Charlotte. Washington could wind up in the upper 60s to near 70 degrees. There’s even a shot that Boston — where the average high this time of year is 36 degrees — could make a run at 60 on Saturday.
Temperatures for much of the Eastern Seaboard will run 20 to 25 degrees above average before the cold front moves through late in the weekend and early next week.