Deadly tornadoes possible this weekend, discussion/analysis

[WXBUFFJIM]

Good Friday everyone. Since the memorial Day weekend is approaching, it's best to mention the threats this weekend because they will be very real across the Nations midsection. Things will go downhill in big hurry this weekend with severe weather including destructive and deadly tornadoes. Anyone with travel plans and cookout plans need to be mindful of this and take immediate action if a warning is issued because this will be a very dangerous situation. We look at some of the most major outbreaks of the past and compare it to this outbreak on an analysis stand point, its' looking very bad. On a scale of 1-10, this weekends outbreak is getting pretty close to a 10 with something possibly as bad as May 3rd, 1999. Thia one means business and we got to keep an eye on it.

Taking a look at the analysis this morning shows a very strong upper trough plowing into the western United States this morning. There was even rainfall down into San Francisco, which is unheard of for the month of May. This same storm system will produce very heavy wind whipped snow in the Wasatch. Snow levels today will be around 9000 feet in the Wasatch of Utah. Then snow levels will drop off very rapidly with the approach of the upper level cold pocket. Extremely heavy snow is expected for this area later today through tonight with 7-14 inches expected. Some local spots could see over 14 inches of snow with this storm. When we see something like this in the Wasatch or the Rockies in late May, that means business back east into the nations mid section.

Looking ahead to Saturday shows an unseasonably strong and broad upper trough shifting east across the Rockies with the upper level low centered over eastern Montana. There will be two surface lows, one centered over the South Dakota/North Dakota/Minnesota border. Another low will also develop over western Kansas where the triple point will set up between the cold front and the dryline. Very moist air building north from the Gulf of Mexico will combine with extreme instability and shearing profiles to result in long lived destructive tornadoes. The area of greatest concern on Saturday will be from eastern Nebraska and western Iowa southward through east central Kansas and possibly even further south if the cap breaks in Oklahoma and north Texas as well. However eastern Nebraska/western Iowa southward into central Kansas will see the greatest instability on Saturday. Upper divergence will maximize in that area adding to lift in the atmosphere. Veering shear profiles will also be in place in that area. As a result, we need to be on the lookout for dangerous, destructive, and killer tornadoes in this region.

The upper trough continues eastward on Sunday across the Midwest and becomes negatively tilted, thus adding to the wind fields already present. Destructive and deadly tornadoes are possible Sunday from lower Michigan and Wisconsin southward through Illinois, eastern Iowa, Missouri, and northern Arkansas. Later in the day Sunday, supercells should evolve into a major windstorm known as a derecho across the Ohio Valley. Wind gusts over hurricane force could be widespread in the Ohio Valley area on Sunday night.

The severe weather threat will likely potentially reach the Mid Atlantic coast by Monday with wind damage, large hail, and a few tornadoes likely from Pennsylvania southward through the Delmarva, the tidewater area of Virginia as well as the eastern Carolinas.

This is shaping up to be a wild weekend with deadly tornadoes likely. When we start talking the killers, the f3,f4, f5, the huge wedge tornadoes that are a half mile wide or more, that means business ladies and gentlemen. There will also be flooding concerns along the banks of the Mississippi River and it's tributaries. Areas on the Mississippi River and Des Plains River just to name a few need to watch out this weekend for sharp rises in river levels due to heavy rains from this upcoming storm system. For the sake of the holiday weekend, don't cancel your plans, but please check on the weather if you live in the areas mentioned above Saturday through Monday because this will likely be a very dangerous and life threatening situation. More updates will be given soon on this outbreak.

[Guest]

Great analysis, Jim!

This could be one for the books. Here, locally, ever since yesterday, 60 hours out, our NWS has placed "severe" wording in the forecast for Saturday/Saturday night. I have not seen that happen in a long time; 60 hours out is outrageous and means things are appearing obvious with the models!

Plus, my area is in a 2nd Day Moderate risk; those have distinct possibilities of being raised to high.

Still, I can't get over with hearing "some storms maybe severe" several days in advance in the PUBLIC forecast!

[Brett Adair]

Jim is right on with the analysis. This could be one for the books. Late season upper air trof with EXTREMELY cold air aloft is going to dig and bring the most diffluence with it I have seen since 5-4-03. I will be posting a more in depth model analysis of the situation soon...

[Cumulonimbus]

I posted this yesterday and it is worth mentioning it again today. To make Jim's point perfectly clear, I live in Seattle, Wa and a tornado occurred in sw Washington yesterday afternoon. It was only an F0 but tore part of the roof off a barn. Western Washington doesn't get tornados and this is the 2nd one this spring. Very cold air aloft is moving east and like he said it DOES mean business. A tornado in western Washington shows you how potent the cold air already is.

So please, pay attention to the forecasts and stay safe.

Alex

[WXBUFFJIM]

To see a tornado at all in Washington state is quite rare. Just last week we saw a tornado near Spokane, Washington. The average number of tornadoes Washington state sees in an entire year is 2. They saw 4 this year already. To see a tornado that is damaging in Washington state is a statement. To see over a foot of snow in the Wasatch above Salt Lake City as well as the Yellowstone National Park in LATE MAY is a statement. That means there will be major severe east of the rockies this weekend, that's the bottom line.

Be safe everyone. We got one helluva tornado outbreak on the way in the nations midsection this weekend. That's about the only way to describe that in words.

Jim

[Stephanie]

Great summary as usual Jim! I hate to see Iowa and Nebraska in the line of fire again after all they've been through already.

[Wnghs2007]

What about Georgia. I think we have a good chance of Severe on monday. Nothing is in stone yet but I do believe that we might see some storms. Here is why below

http://www.wxcaster.com/CONUS_ETA_SVR_CAPESRHSWEAT_84HR.gif

[shaner]

Hmmm,....not liking that low pressure right over SW Ontario. I hope we don't get a repeat of last weekend.

[WXBUFFJIM]

The only problem with this system is the negative tilt of this, thus the severe wx will progress eastward rather than staying over the same places. So there will definitely be more severe real estate. We hope for the best. But unforuntately in this situation where we have a holiday weekend, we should prepare for the worse too. Some of the data I'm getting is definitely an indicator to a tornado outbreak.

Jim

[yoda]

Does that mean we will see some of the severe weather too in D.C.? I would like a tornado or two to spice up my weekend!

[USAwx1]

Jim is right on with the analysis. This could be one for the books. Late season upper air trof with EXTREMELY cold air aloft is going to dig and bring the most diffluence with it I have seen since 5-4-03. I will be posting a more in depth model analysis of the situation soon...

I definitely concur with the both of you. my area of PRIMARY concern WRT tornadoes is along the warm front ----east of the SFC low where the flow is southeasterly in the low levels, backing around with height which should help contribute to lowest 3 KM SRH values exceeding 300 m2/s2, overtop of good boundary layer moisture and SFC dewpoints in the upper 60s, to near 70, yielding STRONG instability with mean layer CAPE above 3000 J/kg.

0-6 KM deep layer shear of >45 KT and aforementioned strong instability combined with good SR inflow ( 2 * sqrt(CAPE) + SR inflow > 85 KT) will likely contribute to vigorous convective updrafts with LG hail and tornadoes, SOME INTENSE. the severe threat will increase eastward overnight along the warm front as LLJ veers and strong isentropic lift increases across the WRN OH valley.

[Cumulonimbus]

Here is an article rleating to not one, but TWO tornados in western Washington yesterday afternoon. Nothing like you get back east, but significant for us. Even an F0 has some punch to it.

ASSOCIATED PRESS

TENINO, Wash. -- Two small tornados touched down in southwest Washington, damaging barns near Tenino and La Center but causing no injuries.

The twisters Thursday afternoon apparently were spawned by a 10-square-mile storm cell embedded in an intense cold front that brought heavy rain to much of the western part of the state, the National Weather Service said.


"It was very common across the area today to see extremely heavy rainfall with localized low visibility and ponding of water on roadways," said Mark O'Malley, a weather service meteorologist in Portland, Ore.

At one point visibility on Interstate 5 was cut to 50 feet, State Patrol troopers said.

Jeff Rood, a meteorologist with the weather service in Seattle, said the tornado near Tenino struck around 3 p.m., covering about a quarter-mile along the ground in a minute or two.

"My wife comes over, hollering, 'The barn's gone!'" Marv Dupper told KIRO Television of Seattle.

NOTE: This article has been updated since it was originally published in the newspaper.
Crumpled strips of metal roofing were hurled about, one high into a tree, and Dupper said a piece of lumber punctured the roof of a building on his property.

Louise Richardson of Tenino told The Olympian of Olympia she was driving a school bus with three students at the time.

"We saw a funnel cloud and a lot of debris flying around," Richardson said. "They asked me if it was a tornado and I said it sure looked like one to me.

Kathy Estes, a Thurston County Emergency Management official, told Northwest Cable News the tornado came out of nowhere.

"There was no forecast. There was no warning," Estes said. "It was just an instantaneous event here."

The twister outside La Center hit about 4:30 p.m. and tore part of the roof off a barn, said Wanda Likens, a weather service meteorologist in Portland. No one was injured, but the woman who reported the damage said her horses were spooked and didn't want to go back to the barn, Likens said.

According to weather service statistics, Washington averages 1.8 tornadoes a year, but Thursday's were the fourth and fifth to touch down in the state in the past four weeks.

A tornado was reported May 21 in Spokane during a storm that also brought lightning, hail and heavy rain, another was reported in East Wenatchee on May 19 and one was reported April 27 near Sumas.



This is the system that is heading for the midwest at this time.

Alex

[WXBUFFJIM]

That is a definite statement for folks east of the rockies starting tomorrow and lasting through the weekend.

Jim

[simplykristi]

What is the possibility of severe weather for the greater KC area?

Kristi

[snoopj]

What is the possibility of severe weather for the greater KC area?

Kristi

Were doomed. Grab some beer, a lawn chair, and watch your house blow away. Might as well go out with a little gusto.

Seriously, I have no idea. Looks like a very good chance Saturday through Sunday in the KC metro area.

--snoopj

[Wnghs2007]

What is the Chance of Severe weather in North Georgia. No one seems to want to respond to my thread so I guess I would ask the question in this thread.

[simplykristi]

Really don't want to watch my house blow away. But grabbing a beer and sitting back sounds good to me! If we do get some serious sweather here, I want to be able to get pictures. Just need to get my digital camera charged up.

Kristi

[USAwx1]

Really don't want to watch my house blow away. But grabbing a beer and sitting back sounds good to me! If we do get some serious sweather here, I want to be able to get pictures. Just need to get my digital camera charged up.

Kristi

Sounds great to me too, Kristi, i'll fly out and join ya......LOL.

In KC specifically, the threat is pretty high especially for tornadoes and yes, even some destructive tornadoes as well.

The 18z MESOETA sounding at KTOP valid 0z SUN revaled EXTREME INSTABILITY with LI and SI values both below -8 to -11, TT's ~60, and Surface based CAPE values > 5000 J/kg.

EVEN w/ loss of daytime heating, strong LLJ evident on BUFKIT soundings should good 850-700mb isentropic lift going, which coupled with impressive > 45 KT deep layer shear and favorable LLVL wind fields will allow for thunderstorms to remain above severe limits well into the evening and overnight hours.

Also noted dry air intrusion near 700mb (DD at 13.2 DEG C and RH < 40%) above rather rich boundary layer moisture evident on the 0z sounding at TOP, as SFC dewpoints climb to around 24C which would not only favor tornadoes, but downburst, and wind damage potential also, enhanced by 700-500mb lapse rates of 7.5-8.0 DEG C/km.

Still however the GREATEST threat for DAMAGING TORNADOES will be along the warm front where winds in the low levels are out of the southeast.