Active Severe Weather Pattern Beginning Next Week

[Jim Martin]

 

Day 5 outlook from SPC has portions of the Central and Northern Plains for a severe weather risk 

[andyhb]

I wouldn't have done this yet.

[Chicago Storm]

I wouldn't have done this yet.

Exactly.

 

Already have the below thread, which will probably get some good use most days...

 

http://www.americanwx.com/bb/index.php/topic/46348-short-term-severeflooding-discussion/page-6#entry4116801

[jojo762]

Exactly.

Already have the below thread, which will probably get some good use most days...

http://www.americanwx.com/bb/index.php/topic/46348-short-term-severeflooding-discussion/page-6#entry4116801

the thread for crappy days/random events... Huh. This will probably be a little more than that.. On a couple days at least, I think.

[David Reimer]

Someone can change the title to Mid/Late May storm chances and it'll be a good way to archive the thread later on. Should be a few interesting days from a chase perspective starting up on Sunday and continuing into next week.

[Jim Martin]

Sorry about that.

[thewxmann]

Yeah I think this could be a good bucket thread for mid-late May events, no biggie.

[nrgjeff]

I wouldn't have done this yet.

 

Sorry about that.

 

I think he meant SPC, not you. Monday is really tricky after a morning short-wave. LLJ responds very late if at all. Heck I like Tuesday better than Monday. At any rate Sunday through Wednesday I see about 3 chase days but no big outbreaks. One of those 4 days may be a down day. Then Thursday it shifts east, perhaps jungle perhaps decent Midwest.

 

Sunday looks like jet energy pokes out of the Rockies in time for a High Plains chase. Monday again will depend on recovery from the morning. Tuesday the next wave is forecast to come out. Placing boundaries makes target selection difficult. Wednesday wind fields are a little choppy but another wave is forecast. Details will impact local targets. It will be a target picker's market with no big outbreak.

[brettjrob]

Man, it seems like recent guidance is doing everything it can to minimize the impact of this long string of SW flow days. Nothing really standing out as having great shear or being free from morning MCS effects (I'm looking at you, Sunday).

[jojo762]

Friday, with the final short wave from this whole thing, could be big if the ejection is timed out correctly, and does not shear out before then. 50-70kt at H5 per GFS... Also as long as morning convection and cloud debris does not mess up destabilization. 12Z GFS painted a pretty impressive picture at 00Z/sat.

[OKpowdah]

I usually like to see more upper level confluence to the north/northeast to prevent the strung out SSW-NNE oriented sfc low we see next week. That usually helps in the shear department. One reason I've been cautious about getting excited at all. Though there have been big days with similar configurations. Certainly the ramping up of the STJ makes everything more interesting, on a number of levels. GFS consistently producing dew points in the mid to upper 70s, and astronomical CAPE (cue the "CAPE trumps everything" optimists from 4/26)

[bjc3395]

I usually like to see more upper level confluence to the north/northeast to prevent the strung out SSW-NNE oriented sfc low we see next week. That usually helps in the shear department. One reason I've been cautious about getting excited at all. Though there have been big days with similar configurations. Certainly the ramping up of the STJ makes everything more interesting, on a number of levels. GFS consistently producing dew points in the mid to upper 70s, and astronomical CAPE (cue the "CAPE trumps everything" optimists from 4/26)

Difference is that the low level CAPE in some soundings looks significantly better than anything we saw on 26th. So that becomes a legit argument (not that it trumps everything, but that it amplifies low level vort through stretching).

[brettjrob]

Difference is that the low level CAPE in some soundings looks significantly better than anything we saw on 26th. So that becomes a legit argument (not that it trumps everything, but that it amplifies low level vort through stretching).

 

That might be helpful. Another helpful difference, in my opinion, is that weak shear is better than "bad" shear. A lot of the forecast soundings for this upcoming period exhibit fairly small hodographs, but sometimes the shape is favorable. These are the situations where big CAPE actually can make a difference. In strongly forced and sheared situations like April 26, where the hodographs are a total mess of VBV and looping back on themselves well below 6 km AGL, there's usually not much to be salvaged thermodynamically. Part of that is just because those profiles often imply a large scale environment favoring many storms initiating and running into one another, though.

 

For each day in the Monday-Friday period, I think I've seen at least one medium range deterministic run highlighting that particular day as the one where shortwave timing is favorable, and we actually see a robust sfc low and LLJ. But by the same token, there's virtually no consensus on that happening any particular day. Even so, "big CAPE/low LCL magic" is bound to happen at least once or twice somewhere, if only because of interaction with a boundary or something of that nature.

[jojo762]

Will be interesting to see how Sunday evolves... Dr. Forbes already calling for a tornado outbreak, which is interesting... Not quite seeing that, but he has been doing this a lot longer than myself.

 

Dr. Forbes on Facebook: 

SUNDAY 5/22
Severe thunderstorm and tornado outbreak in central and east ND,
central and east SD, NE, KS, west and central OK, west TX, possibly extreme northeast CO, possibly extreme northwest MN. TORCON - 5 NE, KS; 4 SD and OK areas and northwest TX; 3 - central and east ND; 2 to 3 southwest TX. A chance of an isolated severe thunderstorm in south FL. TORCON - 1

[wildwestpb]

Will be interesting to see how Sunday evolves... Dr. Forbes already calling for a tornado outbreak, which is interesting... Not quite seeing that, but he has been doing this a lot longer than myself.

No, he's calling for a severe thunderstorm AND tornado outbreak. Likely there will be a surplus of wind and especially hail reports that meet severe criteria as well as enough of them to be classified as an outbreak, whereas all it takes to get a tornado outbreak could be 6-9 tornadoes that day.

That seems reasonable given the time of year and the setup it has to work with.

[jojo762]

No, he's calling for a severe thunderstorm AND tornado outbreak. Likely there will be a surplus of wind and especially hail reports that meet severe criteria as well as enough of them to be classified as an outbreak, whereas all it takes to get a tornado outbreak could be 6-9 tornadoes that day.

That seems reasonable given the time of year and the setup it has to work with.

6 to 9 tornadoes is not a tornado outbreak... The 5 Tor-cons across large parts of both Nebraska and Kansas 4 days out make it pretty obvious what he is getting at. Really just splitting hairs there.

[andyhb]

Can we not derail the thread with TOR:CON debates?

[jojo762]

I do not think that two responses derails a thread much... Anyways, from GLD AFD.... They also seem to like Sunday. 

 

 

SUNDAY IS FORECAST TO BE THE MORE IMPACTFUL SEVERE WEATHER DAY  
ACROSS THE REGION. THERE COULD BE TWO ROUNDS OF SEVERE  
THUNDERSTORMS. ROUND ONE WILL FORM ALONG A DRYLINE DRAPED OVER  
NORTHWEST KANSAS AND SOUTHWEST KANSAS. AHEAD OF THE DRYLINE, A MOIST  
AND HIGHLY UNSTABLE ATMOSPHERE WILL DEVELOP, CHARACTERIZED BY SBCAPE  
OF 1500-3000 J/KG AND 850-500 MB LAPSE RATES OF 7-8.5 C/KM. 0-6 KM  
BULK SHEAR ALSO RAMPS UP TO 30-45 KTS, INDICATING A HIGHLY SHEARED  
ENVIRONMENT. LCLS, DEPENDING ON WHICH GUIDANCE MEMBER YOU GLANCE AT,  
ARE EITHER QUITE FAVORABLE OR UNFAVORABLE. 0-3 KM HELICITY AHEAD OF  
THE DRYLINE ALSO INCREASES SIGNIFICANTLY, UP TO 200-350 M2/S2.  
FAVORABLE HODOGRAPHS ARE ALSO A FACTOR INCREASING CONFIDENCE IN  
SEVERE WEATHER. ALL THIS BEING SAID, SEVERE SUPERCELL THUNDERSTORMS  
APPEAR LIKELY AHEAD OF THE DRYLINE. ALL MODES OF SEVERE WEATHER  
COULD BE EXPECTED WITH THESE STORMS...INCLUDING THE POTENTIAL FOR  
HAIL LARGER THAN 2" IN DIAMETER, SIGNIFICANT DAMAGING WINDS AND A  
FEW TORNADOES (POSSIBLY A STRONG ONE TOO). LATER IN THE EVENING, A  
COLD FRONT SHOULD SURGE SOUTH ACROSS THE HIGH PLAINS. THIS STRONG  
FORCING MECHANISM COMBINES WITH REMAINING INSTABILITY, LEADING TO  
ADDITIONAL THUNDERSTORM DEVELOPMENT (ROUND 2). THIS ROUND WOULD BE  
CAPABLE OF LARGE HAIL AND DAMAGING WINDS.  

[OKpowdah]

That might be helpful. Another helpful difference, in my opinion, is that weak shear is better than "bad" shear. A lot of the forecast soundings for this upcoming period exhibit fairly small hodographs, but sometimes the shape is favorable. These are the situations where big CAPE actually can make a difference. In strongly forced and sheared situations like April 26, where the hodographs are a total mess of VBV and looping back on themselves well below 6 km AGL, there's usually not much to be salvaged thermodynamically. Part of that is just because those profiles often imply a large scale environment favoring many storms initiating and running into one another, though.

 

For each day in the Monday-Friday period, I think I've seen at least one medium range deterministic run highlighting that particular day as the one where shortwave timing is favorable, and we actually see a robust sfc low and LLJ. But by the same token, there's virtually no consensus on that happening any particular day. Even so, "big CAPE/low LCL magic" is bound to happen at least once or twice somewhere, if only because of interaction with a boundary or something of that nature.

 

That is a wicked good point.

[wildwestpb]

6 to 9 tornadoes is not a tornado outbreak

http://www.spc.noaa.gov/publications/edwards/defpaper.pdf

Current commonly accepted definition of a tornado outbreak is 6-9 for a small outbreak, and increasing from there in magnitude and/or amount - however there is no official definition from the SPC or NWS as to what constitutes a tornado outbreak.

[Chinook]

So far this year, there haven't been any severe storm reports in South Dakota. Perhaps that will change on Sunday. The GFS shows 0-6km shear looks around 30-35 kts, with higher values near the cold front, and 2000-3000 J/kg of CAPE in eastern South Dakota.

[andyhb]

Flying into Denver on Sunday. That GLD AFD/the overall setup intrigues me since I'll be driving E and staying the night in Colby.

[jojo762]

Flying into Denver on Sunday. That GLD AFD/the overall setup intrigues me since I'll be driving E and staying the night in Colby.

DDC AFD is also pretty good for Sunday-- as far as tornado/supercell prospects go. Looks like your first day, might be your best day this whole week, but who knows... Lots could change for every day.

[andyhb]

I definitely think it's too early to call that. Any subtle shortwave trough and amplification of the flow fields in the following days and there's likely going to be some pretty nuclear updrafts with the amount of instability that's going to be in place there.

[jojo762]

I definitely think it's too early to call that. Any subtle shortwave trough and amplification of the flow fields in the following days and there's likely going to be some pretty nuclear updrafts with the amount of instability that's going to be in place there.

Monday looks pretty good across S/SW OK, GFS appears to show a possible S/W and some STJ influence there on Monday within the 21-00Z timeframe, leads to pretty nice MLVL flow, and while LLVL shear is not that great, the hodographs have nice curvature to them, but the crazy 4000-5500J/KG MUCAPE values it is showing along with 0-3KM CAPE of 100+J/KG could definitely help make up for that, any morning convection would likely leave behind a nice vorticity pool and perhaps a couple OFB as well which would also help quite a bit.

[David Reimer]

<rant>I deal enough with the TOR:CON BS over on social media. Never thought I'd have to put up with that garbage on this forum - but times change I guess. Calling for a severe weather/tornado outbreak five days out on a fairly marginal setup is just another example of the media-bias in trying to get attention and ratings.</rant>

 

There should be at least one or two decent chase days next week if things can come together. Knowing 2016 the days we expect to be 'decent' will be garbage and the day we think is the most marginal will produce a tornado outbreak. FWIW most folks classify a tornado outbreak as 10-20 tornadoes - depending on your source. 6 to 9 tornadoes isn't an outbreak although can be noteworthy if in a heavily populated area. 10+ tornadoes in a 100-150 mile area is a 'regional outbreak' IMO. I don't expect we'll be seeing any outbreaks over the next week - except on the most marginal day. Goodness... I've turned into one of those grumpy old storm chasers I laughed at years ago. 

[KSWx]

<rant>I deal enough with the TOR:CON BS over on social media. Never thought I'd have to put up with that garbage on this forum - but times change I guess. Calling for a severe weather/tornado outbreak five days out on a fairly marginal setup is just another example of the media-bias in trying to get attention and ratings.</rant>

 

There should be at least one or two decent chase days next week if things can come together. Knowing 2016 the days we expect to be 'decent' will be garbage and the day we think is the most marginal will produce a tornado outbreak. FWIW most folks classify a tornado outbreak as 10-20 tornadoes - depending on your source. 6 to 9 tornadoes isn't an outbreak although can be noteworthy if in a heavily populated area. 10+ tornadoes in a 100-150 mile area is a 'regional outbreak' IMO. I don't expect we'll be seeing any outbreaks over the next week - except on the most marginal day. Goodness... I've turned into one of those grumpy old storm chasers I laughed at years ago. 

 

 

After review I'm giving this post an 8 on my proprietary POST:CON Index. It has also reached Forum Storm status so in compliance with our new forum storm naming policy I hereby dub this post "Forum Storm Reimer" 

 

-

 

But in all seriousness I agree wholeheartedly, this forum has always been a nice escape from the madness/ignorance of social media and the hype-casting lately has been a bit overdone.

[bjc3395]

You are calling Sunday a marginal setup?

OK.

[David Reimer]

You are calling Sunday a marginal setup?

OK.

 

Today is Thursday. Sunday is four days away. Four days may not be 'distant' when compared to synoptically-evident events but Sunday is not a slam dunk by any means. Every 'big' setup forecast days in advance this spring has found a way to crap out. I don't care if it looks like the next super outbreak - I'm not going to get into the hypecast game when it only got in the range of the 12km NAM this morning. So yes - until we get closer I consider Sunday and every day next week marginal. I got my hopes up for other events this Spring that were supposed to be epic and turned out to be marginal. No reason not to expect the same for Sunday at this point. With time and as confidence in a particular solution increases I'll reevaluate.  

[bjc3395]

Today is Thursday. Sunday is four days away. Four days may not be 'distant' when compared to synoptically-evident events but Sunday is not a slam dunk by any means. Every 'big' setup forecast days in advance this spring has found a way to crap out. I don't care if it looks like the next super outbreak - I'm not going to get into the hypecast game when it only got in the range of the 12km NAM this morning. So yes - until we get closer I consider Sunday and every day next week marginal. I got my hopes up for other events this Spring that were supposed to be epic and turned out to be marginal. No reason not to expect the same for Sunday at this point. With time and as confidence in a particular solution increases I'll reevaluate.

well it's a good thing you're not an ops guy, that is absurd logic.