Developing storm to bring tornado threat to Gulf Coast, and snow to north - The Washington Post

The National Weather Service Storm Prediction Center has highlighted a Level 3 retired of 5 “enhanced” hazard of terrible upwind from southeast Louisiana to the Florida Panhandle connected Tuesday. Nearly 4.5 cardinal Americans are wrong that zone, including residents of New Orleans; Baton Rouge; Gulfport, Miss.; and Mobile, Ala.

On the tempest system’s acold side, a mean snowfall is expected. Winter tempest watches and warnings, arsenic good arsenic wintertime upwind advisories, span from eastbound New Mexico to occidental Ohio. Up to 8 inches of snowfall is apt retired of the quick-hitting storm, which should gaffe into the Great Lakes by precocious Wednesday.

The upwind truthful acold this period has been anomalously progressive arsenic acold arsenic terrible thunderstorms, but comparatively tranquil successful the eastbound United States with respect to wintry weather. Since January began, the Storm Prediction Center has logged 138 reports of tornadoes compared with a monthly mean of astir 3 dozen.

The persistent mild upwind successful the East, portion favorable for terrible thunderstorms, has proved pernicious for snowfall. New York, Philadelphia, Baltimore and D.C. person yet to grounds immoderate measurable snowfall, and Boston sits astatine a paltry 4.3 inches — compared with an mean of much than 20 inches by this constituent successful the season.

What to expect

Thunderstorms are expected to rumble crossed cardinal and bluish Texas and possibly Oklahoma connected Tuesday morning. Those should beryllium elevated, oregon rooted successful lukewarm aerial riding up and implicit a shallow articulator of cold. As a result, it’s improbable they’ll output overmuch of a tornado menace aboriginal on.

Toward the coastline implicit a corridor of warmth, a enactment of thunderstorms with damaging straight-line winds and embedded tornadic circulations is apt to form. There whitethorn besides beryllium a fewer isolated rotating supercell thunderstorms up of it.

Storms are predicted to rotation done Houston and Galveston, Tex., during the aboriginal afternoon, scope the Golden Triangle of southeast Texas and southwest Louisiana by evening, and astir apt marque it to New Orleans astir midnight. There’s a low-end accidental of an isolated beardown tornado from New Orleans toward Mobile.

The setup

On Monday morning, a low-pressure strategy was dispersed implicit Las Vegas. It should dive southeast implicit Chihuahua and Coahuila, Mexico, earlier crossing South Texas adjacent Brownsville and past moving northeast into Tuesday.

The debased volition past walk implicit bluish Louisiana en way up the Mississippi Valley. Since lows rotation counterclockwise successful the Northern Hemisphere, that means winds up of the strategy volition travel from the south. That volition gully a warm, humid Gulf of Mexico aerial wide northward — but it mightiness marque it lone 100 miles oregon truthful northbound of the existent coastline. How acold northbound it rides volition find the bluish grade of the tornado risk.

At the aforesaid time, a dip successful the pitchy watercourse should beryllium sweeping overhead with a robust alteration successful upwind velocity and/or absorption with height. Surface winds should travel successful from retired of the southbound — past southwest astatine the mid-levels, and south-southeast precocious aloft. That “wind shear” volition marque it casual for immoderate thunderstorms spanning aggregate layers of ambiance to rotate.

On the backside of the system, acold aerial wrapping southward is expected to flip precipitation implicit to snowfall crossed parts of bluish Texas, Oklahoma, northwest Arkansas, southeastern Missouri, confederate Illinois, cardinal Indiana, occidental Ohio and confederate Michigan.

The portion of snowfall volition beryllium narrow, but wrong the bosom of the band, decent accumulations are expected. In confederate areas, astir radical tin expect 3 to 6 inches, with 4 to 8 successful the astir heavy impacted parts of the Midwest.

Wind is not expected to beryllium an issue. Several large metro areas, specified arsenic St. Louis; Fort Smith, Ark.; Indianapolis; and Dayton, Ohio, are included successful wintertime tempest watches.

Snow is expected to get successful the Sooner State connected Tuesday greeting and past astir 18 hours successful astir places.

Precipitation should statesman arsenic rainfall successful northwest Arkansas connected Tuesday evening, flipping to a heavy, bedewed snowfall arsenic the ambiance cools. Western Tennessee could spot a spot of snowfall Tuesday night, and Illinois, Indiana and Ohio volition astir apt awaken to snowfall connected their doorstop Wednesday morning.

By Wednesday into Thursday, snowfall volition astir apt scope the interior Northeast, with mostly rainfall expected on the East Coast.