October 21, 2014

Severe weather likely tonight, could become a derecho

Severe weather is expected in Missouri tonight, and now the National Weather Service is concerned storms could come together to form a derecho.

This graphic from the National Weather Service shows the potential threats from severe weather tonight.

This graphic from the National Weather Service shows the potential threats from severe weather tonight.

A derecho is a long-lived, widespread, straight line wind storm. Such events have drawn national media attention including last week, when a derecho that swept across several midwestern states caused multiple tornadoes, heavy rain and widespread damage and has been blamed for five deaths and numerous injuries.

Meteorologist Mike July stresses that the formation of such a storm is possible and not definite.  Whether a derecho forms or not, severe weather is likely, and he wants Missourians to be prepared.

“Continue to monitor your local media because storms haven’t formed yet, and once they begin to form we’ll kind of see how they evolve,” says July. “If they begin to show signs that we look for, then we’ll have to maybe ramp things up a little bit.”

If the system evolves as some computer models say it will, it could produce winds of 70 miles per hour or more.

“Right now we’re kind of thinking in excess of 75 miles an hour winds are certainly possible, and it’s highlighted from an area southeast of Nebraska all the way over to St. Louis, so it’s a fairly wide corridor,” says July.

The public can often be dismissive of straight-line winds as a threat, but a prolonged straight-line wind even can be as damaging or more so than a tornado.

“In a tornado, if you kind of think of it in real estate coverage, it’s a small area that it covers,” says July. “If you’re talking about a true derecho, it could very well be, from the north end to the south end, it could be 100 to 200 miles long, and along that entire length you’re getting damaging winds.”

There is also a threat of flash flooding.

“We’re talking about one to three inches of rain possibly, and even from a localized area, four inches of rain,” says July. “We have multiple hazards to be concerned about this evening.

For National Weather Service information for your area, visit these NWS pages.

In northwest and western Missouri:  Kansas City (Pleasant Hill)

In northeast and eastern Missouri:  St. Louis

In southwest Missouri:  Springfield

In southeast Missouri:  Paducah, KY

Scotland and Clark counties:  Davenport, IA 

Slight risk for severe weather Thursday and Friday in Missouri

The National Weather Service’s Storm Prediction Center is warning of a slight risk for severe weather for much of Missouri Thursday and a smaller portion of the state on Friday.  Missourians are encouraged to watch for weather updates and be aware of changing conditions.

This graphic from the National Weather Service's St. Louis Office shows where the Storm Prediction Center says there is a slight chance of severe weather Thursday and Friday.

This graphic from the National Weather Service’s St. Louis Office shows where the Storm Prediction Center says there is a slight chance of severe weather Thursday and Friday.

The National Weather Service says storms could move into southwest Missouri after midnight Thursday morning and begin impacting northwest Missouri by around daybreak. Storms the morning carry some risk for severe weather, primarily from hail.

Meteorologist Steve Lindenberg says later Thursday storms could become stronger if enough instability is present.

“During the afternoon and evening we could get additional strong to severe weather with large hail and damaging winds the primary severe weather risk,” says Lindenberg. The Weather Service does not rule out the possibility of isolated tornadoes Thursday.

The front that will produce these storms is expected to move slowly and linger in the state Friday and into the weekend, presenting the possibility of more rounds of thunderstorms Friday and perhaps Saturday and Sunday. A slight chance for severe weather remains for Friday in most of the southern half of the state.

The Storm Prediction Center says the predictability of severe weather for Saturday and Sunday is too low to offer an outlook.

Forecasters are also concerned about the possibility of minor flooding in the next few days, but major, widespread flooding is not anticipated.

For National Weather Service information for your area, visit these NWS pages.

In northwest and western Missouri:  Kansas City (Pleasant Hill)

In northeast and eastern Missouri:  St. Louis

In southwest Missouri:  Springfield

In southeast Missouri:  Paducah, KY

Scotland and Clark counties:  Davenport, IA

Weather Service warns of possible life-threatening storms today

Most of Missouri will have one round of severe weather to contend with today, that could include tornadoes, damaging winds, hail and flooding. Some of Missouri will have two.  

This graphic from the National Weather Service Office in St. Louis shows where the Storm Prediction Center in Oklahoma says there is a risk for severe weather today.

This graphic from the National Weather Service Office in St. Louis shows where the Storm Prediction Center in Oklahoma says there is a risk for severe weather today.

National Weather Service Meteorologists say storms today will be life-threatening and are urging Missourians to prepare now for severe weather. Governor Jay Nixon (D) has declared a state of emergency in response to the storms already happening and those to come.

A tornado watch has been issued for 21 counties in southeast and south-central Missouri, for storms that have already prompted a tornado warning in Arkansas this morning. Those storms are anticipated to sweep northeast from southwestern Missouri through the St. Louis area.

These storms could produce large hail, damaging winds and tornadoes. Flooding is a possibility locally in southern Missouri, and more so in central and east-central Missouri where heavy rain has already fallen overnight.

Then for this afternoon will come storms that have caused the Storm Prediction Center in Oklahoma to say much of central and southern Missouri has a “moderate” risk for severe weather.

This graphic from the National Weather Service in Pleasant Hill illustrates the threats of severe weather today.

This graphic from the National Weather Service in Pleasant Hill illustrates the threats of severe weather today.

Today’s threat of tornadoes is the highest the state has been under so far this year, according to Meteorologist Jayson Gosselin with the National Weather Service in St. Louis.

“Unfortunately there will probably be at least one tornado in the state and there could be quite a few,” says Gosselin.

“It looks like it should warm up by this afternoon and get very unstable and a cold front will head from west to east across the state. Out ahead of that and along it we’re expecting thunderstorms that are going to be capable of very large hail, very strong winds as well as tornadoes possible.”

Storms are expected to form in Kansas and Oklahoma before sweeping through the state, first as discrete supercell thunderstorms, which Meteorologist Ryan Cardell with the Weather Service Office in Springfield says are generally the most dangerous.

“They can produce large hail, damaging winds and possibly stronger tornadoes,” says Cardell.

Farther east, storms are expected to gather into a line.

“At that point the threat will switch over to being more of a straight-line wind threat with isolated tornadoes. That will happen early in the evening sometime.”

Flash flood warnings have already been issued in a swath of central and eastern Missouri where rainfall totals have ranged from between 2.5 to more than 3 inches from storms overnight. Gosselin says if more heavy rain does move through, more flash flooding issues are likely.

“Everything is very saturated now,” says Gosselin.

“This is a good time … before the storms have formed … to dust off your emergency plans,” says Cardell. “Make sure that’s all ready so that when the watches do come out you can kind of start heightening your situational awareness to where the storms currently are, if they’ve formed, things like that, so that way you’re kind of ready. When the tornado warning happens you’ve got one foot in place heading into your disaster plan.”

For information for your area, tune in to your Missourinet affiliate station and visit these Weather Service office websites.

In northwest and western Missouri:  Kansas City (Pleasant Hill) and on Twitter @NWSKansasCity

In northeast and eastern Missouri:  St. Louis and on Twitter @NWSStLouis

In southwest Missouri:  Springfield and on Twitter @NWSSpringfield

In southeast Missouri:  Paducah, KY and on Twitter @NWSPaducah

Scotland and Clark counties:  Davenport, IA and on Twitter @NWSQuadCities

Several rounds of severe storms possible Tuesday through Thursday

Missouri could experience severe weather several times in the next couple of days.

This graphic shows the chances for general or organized thunderstorms for Tuesday (left image), Wednesday (center image) and Thursday (right image) according to the Storm Prediction Center in Norman, Oklahoma.

This graphic shows the chances for general or organized thunderstorms for Tuesday (left image), Wednesday (center image) and Thursday (right image) according to the Storm Prediction Center in Norman, Oklahoma.

The National Weather Service says storms today are expected to develop in southwest Missouri before pushing into central and northern Missouri in the afternoon and evening.

“We’re not expecting that to be severe,” says meteorologist Jenny Laflin at the Service’s Pleasant Hill office, “but as we go into the overnight hours we could see some additional development and some strengthening … and that’s where we’d look for severe potential, mainly between midnight and 8 a.m.”

Laflin says storms overnight should be widespread but only a few are likely to become severe, producing large hail. There is a lesser chance of damaging winds.

The greater chance of severe weather begins Wednesday.

“We have a warm front that’s lifting into the area and it’s just going to kind of park over central Missouri,” says Laflin. “We could see strong development across that boundary during the afternoon but our main window for severe weather is during the evening and early overnight hours, expecting large hail, damaging winds and potentially an isolated tornado or two.”

Laflin says the atmosphere Wednesday is predicted to be much like it was Thursday, when one thunderstorm in northwest Missouri produced three tornadoes that damaged several homes and outbuildings.

Meteorologist Ryan Cardell with the Weather Service’s Springfield Office says there will also be a chance of severe weather Thursday, and it will be more focused in the southern half of the state.

“That’s when the main upper-level dynamics are going to come through sweeping the main frontal boundary through the area from the west,” says Cardell. “That is probably going to be the better chance for any higher-end severe weather, like tornadoes.”

Cardell says heavy rainfall in localized areas could result in flooding as well, but severe weather is considered the primary threat.

For information for your area, tune in to your Missourinet affiliate station and visit these NWS pages.

In northwest and western Missouri:  Kansas City (Pleasant Hill)

In northeast and eastern Missouri:  St. Louis

In southwest Missouri:  Springfield

In southeast Missouri:  Paducah, KY

Scotland and Clark counties:  Davenport, IA

Weather Service finds evidence of three tornadoes from Thursday storms

The National Weather Service office in Kansas City has completed its assessments following yesterday’s storms. It believes one supercell thunderstorm spawned three separate tornado touchdowns along about a 35-mile path from around Weatherby to east of Spickard in northwest Missouri.

The first tornado touched down at about 3:03 p.m. about 3 miles east of Weatherby. It traveled more than 9 miles in about 12 minutes and left a damage path up to 200 yards wide. It produced EF-1 damage, meaning its winds are estimated to have reached up to 110 miles per hour.

The last of three tornadoes in northwest Missouri on Thursday, March 27 2014 touched down in Crowder State Park and passed north of Trenton. (photo from Facebook)

The last of three tornadoes in northwest Missouri on Thursday, March 27 2014 touched down in Crowder State Park and passed north of Trenton. (photo from Facebook)

The second tornado was on the ground for less than three miles after it touched down at 3:22 p.m., north of Jameson. It caused EF-2 damage, with winds estimated at up to 130 miles per hour before lifting off the ground after 5 minutes. 

The final tornado touched down in Crowder State Park northwest of Trenton at 3:55 p.m. and traveled more than 13 miles northeast to east of Spickard in 20 minutes. It left a damage path up to 500 yards wide and also produced EF-2 damage.

No injuries have been reported but homes, outbuildings and trees were damaged.

See more from the National Weather Service’s Assessment of the March 27, 2014 storms

“We were really fortunate with this event,” says Warning Coordination Meteorologist Andy Bailey of the fact the storms caused no injuries despite the damage to homes and structures. “There were probably half a dozen to ten houses that were pretty heavily damaged along the path. I know of at least one mobile home that was completely destroyed.”

Bailey says it is possible other tornado touchdowns have gone unreported.  Anyone who wants to report additional damage to the Weather Service for assessment can contact the local county emergency manager, or can reach the Weather Service on its Facebook page.