Fire and severe weather threat in Plains before storm shifts into South

WEATHER NEWS: Fire and severe weather threat in Plains before storm shifts into South

The same parent storm system also will induce “extremely critical” fire weather concerns over the western Plains on Tuesday. Red flag warnings, signaling tinderbox conditions that can quickly kindle and fuel any ignition, are blanketing areas from western Texas to southern Nebraska. High wind warnings are in effect for parts of western Texas as well, where gusts could approach 60 mph.

Once the storm exits the Plains, the disruptive and potentially dangerous weather will shift east. The National Weather Service Storm Prediction Center has hoisted a level 4 out of 5 for severe thunderstorms in the South on Wednesday. The zone includes much of northeast Louisiana, Mississippi and Alabama.

“All severe hazards are possible, including significant gusts over 75 mph and strong (EF2+) tornadoes,” the center warned in its outlook for Wednesday.

By Thursday, storms with damaging winds could affect parts of the Southeast and Mid-Atlantic before moving off the coast.

The month has featured a barrage of tornadoes that tore through the Interstate 35 corridor in Texas on March 21; New Orleans’s strongest tornado on record the next day; and an EF4 tornado just south of Des Moines on March 5 that claimed a half-dozen lives. There are signs that April and May — usually the two busiest months for significant tornadoes — may prove anomalously active. It looks like a long road lies ahead.

Dry air is bringing dangerous fire weather

A dramatic clash between dry air to the west and a mild, Gulf of Mexico-moistened air mass to the east is instigating the storminess. The juxtaposition of air masses will occur along a boundary known as a dryline, which will sharpen over the High Plains on Tuesday afternoon. That will mark the leading edge of arid air from the Desert Southwest as it encroaches into an increasingly humid and unstable air mass — or one that’s supportive of pockets of surface air rising into strong/severe thunderstorms.

Plummeting dew points or atmospheric moisture content and increasing wind gusts to 45 mph or more behind the dryline will make for “critical” to “extremely critical” fire danger Tuesday. Areas in the Texas and Oklahoma Panhandles and adjacent southwest Kansas are at the greatest risk for what the National Weather Service is warning could be “a significant wildfire outbreak . . . across the southern High Plains.”

Behind the dryline, a cold front will move through during the evening and overnight, switching winds 90 degrees from the southwest to the northwest. That could prove logistically problematic for crews combating any ongoing wildfire.

“Numerous fires have occurred in the past 48 hours, indicating fuels are sufficiently dry for large fire spread,” wrote the National Weather Service.

Red flag and high wind warnings cover the map, the former denoting the potential for “rapid fire growth.”

Isolated severe storms over the Plains on Tuesday night

Southerly winds over the Plains will increase in response to strengthening surface low pressure passing through Nebraska and the Corn Belt. Meanwhile, temperatures aloft will be cooling ahead of a “shortwave” or lobe of high altitude cold air, low pressure and spin. The result will be thunderstorms that develop during the evening hours or around nightfall.

The Storm Prediction Center has drawn a slight risk from Central Texas through Oklahoma along the I-35 corridor and into eastern Kansas, western Missouri and southern parts of the Corn Belt. The risk area includes Dallas, Abilene, Tex., Waco, Tex., Oklahoma City, Wichita, the Kansas City area, Omaha and Des Moines.

In the northern half of the risk area, thunderstorms may be “outflow dominant,” exhaling more air than they ingest. That will reduce the tornado risk and cut back on the longevity of updrafts. Straight-line winds will be the main concern.

Farther south, thunderstorms in Oklahoma and perhaps northern Texas will probably congeal into a line around midnight, with damaging straight-line winds and isolated tornadoes the main hazard.

Widespread damaging winds over the Deep South on Wednesday

The line that organizes Tuesday night will become energized as day breaks Wednesday. By then, it’ll be at the doorsteps of Mississippi and northeast Louisiana. Alabama will see storms later in the day.

That’s where a level 4 out of 5 risk of severe weather has been drawn by the Storm Prediction Center. The bull’s eye encompasses Baton Rouge and Monroe in Louisiana; Jackson, Meridian, Tupelo, Starkville and Hattiesburg in Mississippi; and Tuscaloosa and parts of Birmingham in Alabama.

Storms are most likely to organize into a quasi-linear convective system (QLCS) or a squall line with embedded tornadic circulations. While shear or a change of wind speed/direction with height will be very high, cloud debris left by Tuesday’s storms will limit daytime heating. That means comparatively less “juice” will be available to fuel storms until the actual front arrives, so spinning storms in advance of the mainline are unlikely.

It’s atypical for a QLCS to pose a risk of “strong tornadoes,” but meteorologists at the National Weather Service are betting this one will. Issuing warnings for QLCS tornadoes is notoriously challenging; they form abruptly and can be quick-hitting, touching down between radar scans and lifting in the blink of an eye.

The Deep South is among the most vulnerable in the world to tornadoes because of meteorological factors and socioeconomic challenges such as housing type/prevalence of manufactured homes and an insufficiency of community storm shelters.

Storms will plow east into Alabama during the evening and overnight before gradually weakening on approach to Georgia.

A few strong storms in the East on Thursday

There are two areas to watch for isolated severe thunderstorms Thursday. The first will be in the Southeast, specifically from the Florida Panhandle into east-central Georgia, including Dothan, Ala., and Tallahassee. That’s where a few leftover storms along the segmenting squall line may come back to life because of daytime heating.

The other is in the Mid-Atlantic along Interstate 95 from just south of Philadelphia to near Raleigh, N.C., including Baltimore, Washington and Richmond.

Storms on Thursday probably will be low-topped, meaning they may not even grow tall enough to spit out much thunder or lightning. That said, with a swift jet stream screaming overhead, they’ll efficiently mix momentum down to the surface in the form of strong to locally damaging wind gusts.

Temperatures will fall behind the front into Friday and the weekend.

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