Major storm to bring severe weather, possible blizzard, fire concerns in Central U.S.

WEATHER NEWS: Major storm to bring severe weather, possible blizzard, fire concerns in Central U.S.

A sprawling, significant springtime storm system will bring an onslaught of dangerous weather across the Lower 48 over several days, as well as dangerous wildfire conditions and a probable blizzard across the Northern Plains. Much of the Plains and the Mississippi Valley could be facing a risk of strong tornadoes, while North Dakota, on the system’s cold side, could be looking at a foot of snow.

Scientists predict seventh straight above-average hurricane season

The National Weather Service Storm Prediction Center has issued a level 3 out of 5 “enhanced risk” for severe weather Monday, Tuesday and Wednesday, citing the potential for a few strong tornadoes. Uncertainty is through the roof for the outbreak, with a “boom or bust” possible for many Tuesday with equal chances of blue skies and destructive thunderstorms. Seventy million people could be at risk of severe thunderstorms through Wednesday.

Behind the thunderstorms, a bone-dry air mass is surfing gusty winds into the High Plains, leading to “extremely critical” fire weather concerns. Ignition will occur easily, amplifying the risk of human-sparked wildfires growing uncontrollably.

On the system’s northwest side, wraparound moisture will overlap with frigid Canadian air tugged south in the sprawling storm’s wake. That’ll drop a foot or more of snow across portions of the High Plains, which will combine with winds gusting over 40 mph to produce blizzard conditions.

Setup: An approaching upper-air disturbance will lead to cooling temperatures aloft. That will help destabilize the lower atmosphere, since the much milder surface air will be able to rise into the high-altitude bone-chilling cold. Those pockets of rising air will become strong-to-severe thunderstorms that will pose the risk for damaging straight-line winds, large to very large hail, and tornadoes, which could be strong.

A major impetus at the surface is a dryline, or the boundary between parched air from the Desert Southwest and moisture-rich air streaming north from the Gulf of Mexico. The resulting clash of tropical humidity and desert aridity will foster severe thunderstorm development. Other boundaries such as the warm and cold fronts will also act as storm formation zones.

Monday: Today’s risk of severe weather will be maximized over Arkansas along the Interstate 40 corridor. Cities such as Fort Smith, Jonesboro and Russellville, Ark., are included in a level 3 out of 5 enhanced risk for severe weather, while a level 2 out of 5 slight risk encompasses a broader stretch from Waco, Tex., and Dallas to Jackson, Tenn., and southern Illinois.

Thunderstorms will form during the afternoon, along a surging and weakening cold front, but those storms will be linear, meaning mainly damaging winds are expected. Ahead of the front, however, particularly in eastern Oklahoma, northeast Texas along Interstate 30, and west-central Arkansas, a few lone, discrete rotating thunderstorms known as a supercells are possible. Those, assuming they form, won’t have to compete with neighboring cells, allowing them to tap into the atmosphere’s full fury. In addition to straight-line winds, that will lead to the chance of large hail and tornadoes.

Tuesday: Tuesday is looking increasingly disconcerting. An enormous area from Iowa to Central Texas is under a level 3 out of 5 enhanced risk, including major cities such as Dallas, Oklahoma City, Kansas City, Omaha and Des Moines. Tornadoes are likely to occur with the most severe storms, and the Storm Prediction Center is warning that “some of the tornadoes could be strong.”

It’s unclear how many storms will form and when. A stout “cap,” or lid of warm air a mile or so above the ground, will inhibit the ability of surface air to rise most of the day, precluding severe thunderstorm formation. That will be the case until very late. However, it’s not clear if the cap will fully break. If it does, pent-up instability, or “juice,” will be explosively released in the form of dangerous thunderstorms and tornadoes. Otherwise, blue skies may prevail during the day, before a squall line develops at night and sweeps eastward.

The greatest chance of the cap breaking during the day and storms erupting may be along the northern reaches of the dryline in Iowa and eastern Nebraska along the Missouri River. The forecast will be refined with time and may be changed depending on how strong the cap is modeled to be.

Wednesday: Wednesday could feature nasty storms across a widespread area, with an enhanced risk that swallows most of the lower and middle Mississippi Valley. Areas between Chicago and northern Louisiana are included, along with cities such as Indianapolis, Memphis, Little Rock, St. Louis and Shreveport, La.

The large-scale storm system will have a giant warm sector, or slice of warmth, riding north ahead of an approaching cold front. That means a corresponding sprawling swath of severe weather risk.

A dip in the jet stream will be approaching from the west, with upper-level winds screaming northward. That will impart a change of wind speed or direction with height, known as wind shear, which will cause thunderstorms to rotate.

That will present a threat of tornadoes to a broad area if discrete cells form ahead of the cold front. A couple of the tornadoes could be strong. Otherwise, hail, wind and a few brief spin-up tornadoes will accompany a QLCS, or squall line with embedded tornadic circulations, that will march east along the front.

Potentially historic blizzard

The parent low-pressure system spawning all the chaotic weather will eject out of the Colorado Front Range and slip over the Sandhills of Nebraska on Tuesday morning before moving into Minnesota by early Wednesday. On the backside, moisture entrained northwest around the counterclockwise-spinning low will fall into subfreezing air crashing south. The result will be heavy snow.

In Bismarck, N.D., a foot and a half of snow could fall through Wednesday morning, which would approach or eclipse the 17.8 inches that fell in mid-April 2013 to become the city’s biggest April snowstorm on record.

Snow will break out in patches of Wyoming and Montana on Tuesday morning, becoming moderate to heavy at times and expanding in coverage. It will shift into North Dakota and northern South Dakota during the afternoon before pivoting into northwest Minnesota and ending as snow showers pinwheeling from the north Wednesday.

The National Weather Service in Bismarck is warning that “travel should be restricted to emergencies only.” Strong gusty winds in the system’s wake could continue lofting fallen snow long after precipitation ends, prolonging the risk of blizzard conditions and low visibilities.

‘Extremely critical’ fire weather

Red-flag warnings, which represent fire danger, stretch from the Texas Trans-Pecos to southern Nebraska. In Texas, relative humidity behind the dryline will fall to about 6 percent Tuesday, with blustery winds picking up and gusting over 30 mph. Across the High Plains, a few gusts may top 60 mph Tuesday afternoon.

The Storm Prediction Center has outlined the Texas and Oklahoma panhandles and adjacent southwest Kansas as having an “extremely critical” fire threat.

“A significant fire weather outbreak is possible across the southern and central High Plains [on] Tuesday,” they write.

Source link