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A very powerful storm is crossing the country: Five things to know

The storm could be historic in some areas for its March intensity, while unleashing heavy snow, tornadoes and flooding, and drawing record warmth northward

The American GFS model simulates a strong storm system moving through the Tennessee Valley. (Pivotal Weather)
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March 1 marks the start of meteorological spring, but the atmospheric transition is far from graceful. A pronounced battle of the seasons that is unfolding across the Lower 48 is marked by a strong cross-country storm system that will bring hazardous weather to millions.

Blizzard warnings were issued Monday for California’s Sierra Nevada, where 6 feet of snow and hurricane-force winds combined into a freezing whiteout that the National Weather Service called “life-threatening.” A pronounced dip in the jet stream is swooping over the West, allowing frigid Canadian air at high altitudes to spill into the Rockies and along the Pacific Coast. Some of the cold will bleed eastward through the Upper Midwest into the Northeast, setting the stage for snow.

Significant severe weather episode possible late in the week in Southern U.S.

In stark contrast comes the unusual warmth over the South and Southeast, where temperatures swelling some 15 to 25 degrees above average will fuel an outbreak of dangerous thunderstorms. The Storm Prediction Center is warning that a few “strong” tornadoes may be possible in parts of the South, where severe thunderstorms are expected Wednesday, Thursday and Friday.

Where the atmosphere wages war, heavy rainfall and flooding are probable, too. Flood watches have already been issued for parts of Arkansas and Tennessee, and may be expanded.

Here are five things to know about the ongoing system.

1) A multiday severe thunderstorm outbreak is imminent

The temperature contrasts associated with this powerful storm system will trigger severe thunderstorms over the next several days. Thursday has the potential to produce the most widespread storms capable of dangerous impacts that include damaging straight-line winds, tornadoes and large hail.


Storms — some that will rotate, becoming supercells — will erupt near and just northeast of the Dallas-Fort Worth area Wednesday afternoon. They will work east along Interstate 30, slipping into southern Arkansas and eventually northern Mississippi and Alabama during the evening into the overnight. Initial storms may contain hail larger than pool balls. A low-end tornado risk will be present, and strong to damaging winds also could accompany storms.


A level 4 out of 5 risk of severe weather has been assigned by the National Weather Service Storm Prediction Center to the zone northeast of Dallas and southwest of Little Rock. It also encompasses stretches of Interstates 20 and 30.

Dallas, Little Rock, Memphis and Jackson, Miss., are under a level 3 “enhanced risk” of severe weather, while a lesser level 2 risk covers Houston, Austin, Jackson, Tenn., and western Alabama west of Tuscaloosa.

“A regional severe-thunderstorm outbreak appears possible across parts of the southern Plains into the ArkLaTex and ArkLaMiss regions Thursday into Thursday night,” wrote the Storm Prediction Center, “with a few strong tornadoes, widespread damaging wind, and hail all possible.”

It is likely that a line of thunderstorms will form along a cold front near I-35 in Texas during the afternoon, progressing east with time. Those storms probably will contain damaging winds and a few tornadoes and blast east through much of the overnight. What is less certain is whether supercell thunderstorms containing a greater tornado risk will develop ahead of the main line.

Regardless, the atmosphere has considerable pent-up unrest, and in some way, shape or form, it is going to be unleashed Thursday.


The storm threat will shift more into the Southeast on Friday, with a level 2 risk of severe weather from Alabama and eastern Tennessee to South Carolina and western North Carolina — including Nashville, Atlanta and Charlotte.

“Severe thunderstorms capable of damaging wind gusts and a few tornadoes will be possible,” the Storm Prediction Center wrote.

2) Snow to expand northeast as California blizzard subsides

Across the Golden State, blizzard conditions will ease during the daylight hours Wednesday, but prolific amounts of snow already fell after a tongue of moisture lapped at the coastline. Much of that moisture was forced up the mountains, where it cooled, condensed and fell as feet of pasty snow. The Central Sierra Snow Laboratory in Soda Springs, just west of Truckee on I-80, measured 52.2 inches in 36 hours; the total is up to 41.27 feet of snow for the season to date.

Blizzards push California snowpack to nearly twice normal levels

Kirkwood Meadows got 43 inches, Donner Peak logged 3 feet, and the Northstar ski summit had 27 inches.

Some places above 7,000 feet elevation have received 15 feet or more within the past 2½ weeks.

The entire Sierra Nevada is running far ahead of average for season-to-date snowfall; the southern Sierra Nevada is at 224 percent of what’s “normal” at this point in the season, whereas the central and northern Sierra are between 150 and 200 percent of climatological norms.

The snow, while relentless, is a precious resource for California’s scant water supply.

Meanwhile, the storm will encounter cold air in the southern Rockies, Upper Midwest, Great Lakes and interior Northeast. It is probable that a swath of snow, perhaps heavy, will affect the region, mainly through Thursday in the Rockies and Friday into Saturday farther east.

3) Flooding is possible from the Southern Plains to the Ohio Valley

Flooding will be of significant concern north of a stalled frontal boundary draped west to east from near the Oklahoma Red River to Nashville. Moisture wafting in from the south will ride up and over a lip of cooler air. That will lead to a round of showers and downpours in the days ahead. Combined with the leftovers of severe thunderstorms coming up from the South, it is likely the heavy rainfall will lead to flooding.

At greatest risk will be Arkansas, where the Weather Prediction Center has drawn a level 3 out of 4 risk of flash flooding Thursday. That said, an enormous patch of the southern United States as well as the Mississippi, Tennessee and Ohio valleys could see a broad 2 to 4 inches of rain through Friday. Localized totals may top 6 inches.

4) Record warmth is likely in the South ahead of the storm

Southerly winds ahead of the surface low will allow a very mild air mass to overspread the South and Southeast, as well as parts of the Ohio Valley.

On Tuesday, dozen of locations across the South had their warmest winter days on record, according to climate analyst Maxilimiano Herrera, who tracks temperature extremes. Among them: Baton Rouge; Mobile, Ala.; Columbia, Miss.; West Palm Beach, Fla.; and Macon, Ga. These locations recorded highs in the mid-80s to near 90 degrees. That was just the beginning.

On Wednesday, highs are forecast to reach 79 degrees in Frankfurt, Ky.; 73 in Columbus, Ohio; 71 in Indianapolis; and 85 in Jackson, Tenn. In Frankfurt, that could break the March 1 record of 77 degrees set in 1997; for Columbus, Wednesday’s reading should obliterate the current record of 65, also set in 1997. Indianapolis may tie its record of 71 set in 1976, and Jackson, Miss., is expected to eclipse its record of 83 degrees set in 2012.

By Thursday, a few more records are likely across southern Mississippi, Louisiana and Alabama, as well as in Florida. The Sunshine State’s spate of exceptional warmth should continue into Saturday.

This very warm, humid air will help fuel the thunderstorms expected across the region.

5) The storm could set records for low pressure over the Mid-South

Air pressure may sound like an abstract concept, but it’s quite simple — it is basically the weight of the air on top of you. High pressure systems bring sinking air, which squashes cloud cover. Lows, on the other hand, feature rising air that helps build clouds and generate precipitation. Generally, the lower the pressure, the stronger the storm.

Average sea-level air pressure is 1,015 millibars, but the developing surface low pressure may fall to about 980 millibars as it passes through northern Arkansas on Friday morning. That discrepancy induces a vacuum-like effect, which is why the low will pull so much warm air northward across the Mid-South and Southeast.

The intensity of the low pressure could set records for March. In fact, most places across the Mid-South have not recorded a mean sea-level air pressure lower than 982 to 983 millibars.

Jason Samenow contributed to this report.