9:30 AM | ****Severe weather/tornado outbreak on Friday night in the Mississippi Valley…damaging winds gusts Ohio Valley/eastern US later Friday and Saturday associated with strong cold front****

Strong upper-level low will push into the middle of the nation by later Friday and it will become a key player in a severe weather outbreak across the Mississippi Valley region on Friday night. Map courtesy ECMWF, Pivotal Weather

Overview

Tornadoes are running at above-normal levels across the nation so far this season and there is the likelihood for another outbreak on Friday night centered on the Mississippi Valley region. In much the same manner as at the end of the last week, the atmosphere will become very unstable by Friday night in the Mississippi Valley region with a multitude of ingredients coming together including vigorous upper-level support, an intrusion of warm, humid air from the Gulf of Mexico ahead of a strong surface cold front, and an influx of cold, dry air from the north and west behind it. A similar weather pattern late last week resulted in an outbreak of tornadoes across Mississippi and Alabama that tragically resulted in the death of at least 26 people. The powerful cold front that will play a major role in the severe weather outbreak on Friday night will plow eastward through the Tennessee and Ohio Valleys and into the eastern states possibly resulting in damaging wind gusts of 50-60 mph in those sections of the country.

The powerful surface cold front that will contribute to severe weather on Friday night in the Mississippi Valley will then plow to the east later Friday night and during the day on Saturday. While the threat of severe thunderstorm activity may become somewhat diminished, there certainly is the chance for damaging wind gusts in the Ohio Valley and the Atlantic seaboard states from later Friday through Saturday. Map courtesy ECMWF, Pivotal Weather

Details

The number of tornadoes across the US so far this season is above-normal for this time of year and one of the culprits has been the continuation of cold air outbreaks from Canada into the US.  This on-going influx of colder-than-normal air has resulted in the development of a “battle zone” region - across the Mississippi Valley in recent days - with warm and humid air pumped into the southern states aided by persistent high pressure ridging aloft near the SE US coastline.  With the cold, dry air charging to the south and east into the warm, humid air advancing to the north from the Gulf of Mexico, all it takes is for some vigorous support in the upper atmosphere to move overhead to dramatically raise the chances for severe weather. Indeed, this is the pattern that unfolded at the end of last week in the Lower Mississippi Valley/Deep South and, unfortunately, it looks like it will repeat on Friday in the central and northern Mississippi Valley regions with a focus area of concern in the zone from Arkansas-to-Iowa.

Tornadoes so far the season are running at above-normal levels across the US aided in part by the continuation of cold air outbreaks from Canada into the central and eastern states. Data plot courtesy NOAA

The latest in a series of Pacific Ocean storms that will impact southern California today will become a crucial player in the expected severe weather outbreak on Friday night in the Mississippi Valley. The strong upper-level low associated with this California storm will push into the middle of the country on Friday and then to the eastern Great Lakes by Saturday.

As such, upward motion will begin to strengthen later tomorrow across the Mississippi Valley with warm, humid air flowing northward ahead of an incoming strong surface cold front advancing to the east and cold, dry air behind it dropping to the south and east. Once the upper-level support moves overhead on Friday night into this “clash” zone, severe weather can break out and tornadoes are certainly on the table. The threat zone at this vantage point appears to be the central and northern Mississippi Valley regions which would be slightly to the north of outbreak that took place late last week. Farther to the north, accumulating snow is quite likely from the Northern Plains to the Upper Midwest extending from South Dakota to Upper Michigan.

NOAA’s Storm Prediction Center (SPC) has increased the severe weather probability across portions of the Mississippi Valley region for Friday night. Map courtesy NOAA

This powerful surface cold front will continue to plow to the east later Friday night and during the day on Saturday…first across the Ohio Valley and then through the Atlantic seaboard states.  Severe thunderstorm activity cannot be ruled out in this part of the nation and there certainly is the threat for damaging wind gusts of 50-60 mph given the strong low-level winds expected in the vicinity of the surface cold front.

In the Mid-Atlantic region, temperatures ahead of the cold front can climb to 70+ degrees on Saturday in the DC-to-Philly-to-NYC corridor to go along with those very windy conditions. However, on the back side of the front, temperatures on Sunday are likely to be some 20 degrees colder with highs much closer to the 50 degree mark and there will be a stiff NW wind as well.

One final note…there can be a repeat performance next week with another severe weather outbreak on the table in the central US.

Meteorologist Paul Dorian
Arcfield
arcfieldweather.com

Follow us on Facebook, Twitter, YouTube

Video discussion: