Central/Western Medium-Long Range Discussion

[Chinook]

22 0-3KM EHI... 22 STP.    One of the craziest soundings i've ever seen, even from the 4NAM. This obviously won't happen, but its hilarious to look at.

It's kind of funny how much this wind profile is different from the surrounding areas (50 - 200 m2/s2 of SRH, 30-45 kt of shear). Seriously, 500 m2/s2 next to 50 m2/s2. Now that it is so much easier to look at the various parameters from the 4km NAM, we see that deep convection on the model can lead to some very different temp/dew/wind profiles near simulated storms.

 

Given the 25kt-35kt of wind at 500mb tomorrow, (as per the 12z GFS,) I would say tomorrow is most likely to have some multicells with hail/wind. The SPC has an enhanced (ENH) outlook for tomorrow for central Texas, which may make sense. Usually something interesting happens when there is 5000 J/kg of CAPE.

 

For the last few days, I thought maybe tomorrow (Tuesday) would be a bigger severe weather day. With marginal winds at 850mb and 500mb, it should be kind of low on the tornado potential, maybe lower potential on high-end wind and hail.

[SluggerWx]

Maybe someone should start a 5/22 - 5/30 Severe Weather Threat thread? Today's Day 7/8 outlook from the SPC indicates they are expecting a larger-scale pattern change more conducive to severe weather next week.

The last few GFS runs show higher 3km EHI values for the period, but they aren't overwhelmingly being supported by high cape values. It looks like SRH/shear are contributing to the higher EHI values, which seems to have been lacking somewhat during prior periods this season.

SPC's note today:
DAYS 6/7 SUNDAY/MONDAY...AN INCREASINGLY SEVERE-CONDUCIVE PATTERN
FOR THE PLAINS IS CURRENTLY EXPECTED AS THE WESTERN STATES TROUGH
CONTINUES TO EDGE EASTWARD AND LOW-LEVEL MOISTURE TRANSITIONS
NORTHWARD. SEVERE THUNDERSTORMS MAY BE POSSIBLE AS FAR NORTH AS THE
DAKOTAS/MN...AND AS FAR SOUTH AS WESTERN OK/TX.

[nrgjeff]

Next week looks like some good storm chasing. Note I do not call for a big outbreak, but I see 3-4 chase days out of a 7 day stretch. Rockies trough is forecast to send out shortwaves for several days. Yes, sounds like SPC is teeing up.

 

Sunday starts with short-wave ridging early but some southern stream jet energy pokes out over the Panhandles late. LLJ responds too. If enough moisture can return in time Sunday evening could be an appetizer. 

 

Monday and/or Tuesday should have some better moisture and wind shear, plus some surface boundaries to locally enhance SRH. Upper level wind fields are not particularly strong, but likely will be plenty for late May. Quality LLJ is forecast away from contamination. Plus no VBV is forecast. One can be reasonably confident that holds with WSW flow upstairs and open waves. If a stronger wave ejects Monday, then Tuesday could be an in between day. Tough to discern this far out.

 

Wednesday or Thursday could go again. New shortwave is shown coming out sometime the middle of next week. Timing is variable run-to-run but the broad pattern is consistent. Perhaps Friday or Saturday something else comes out. For now I like Sunday-midweek.

[bjc3395]

Monday looks like a pretty robust event in OK/KS per 12z euro if you ask me.

[brettjrob]

Euro does look pretty impressive Sun-Tue timeframe. We're finally late enough in the spring that suboptimal timing of shortwave ejections usually won't completely hose a setup, but instead can take a potential outbreak and spread it thinner into multiple localized days - this is the primary reason I enjoy late season chasing about 50x more than March and April, when everything usually has to line up perfectly.

 

Moisture quality for Sun-Mon looks slightly shady on the Euro, while the GFS has been more gung-ho about flooding the Plains with tropical moisture in the medium range. I'm cautiously optimistic that the Euro will trend upward, based on experience. The pattern depicted for the Sun-Wed timeframe isn't anything spectacular - sort of reminiscent of some late season periods in 2013 (May 27-29) and 2014 (early June?) - but the key difference here will be ET, and the likelihood of much better low level moisture than those years ever saw on the High Plains. With quality BL moisture throughout the warm sector in late May, it just doesn't take much at all. I'd be pretty excited for this period as a chasecationer. It would be awesome if something like Bowdle fell out of this pattern, which seems possible - but as long as the trough ejects into the Plains, which looks increasingly likely, a string of localized tornado days should be on tap, for sure. Finding the best storms may not be trivial, but it's hard to beat several consecutive days with hope and opportunity.

 

I'm keeping expectations for any big synoptically-evident days low, given the uncertainties about downstream blocking. But taking the 17/12z Euro verbatim says Monday could actually be that kind of day.

[andyhb]

I'm keeping expectations for any big synoptically-evident days low, given the uncertainties about downstream blocking. But taking the 17/12z Euro verbatim says Monday could actually be that kind of day.

 

If that Euro run slows 6-12 hrs and the 144 frame turns out to be more around peak heating, can't ask for much more than a potent negatively tilted shortwave with a 60+ kt southwesterly/west-southwesterly H5 jet and H85-H7 flow of 40-50+ kts this time of year.

[Chinook]

3-D visualizations of low-swirl, medium-swirl, and high-swirl tornadoes from NCAR

 

https://www2.ucar.edu/atmosnews/perspective/21089/3d-window-tornado

[hm8]

3-D visualizations of low-swirl, medium-swirl, and high-swirl tornadoes from NCAR

https://www2.ucar.edu/atmosnews/perspective/21089/3d-window-tornado

Sick.

[jojo762]

DDC AFD from this afternoon is pretty optimisitc about next week/this weekend, they appear to favor the ECMWF quite a bit... 

 

 

Saturday...12z ECMWF displays continuity forecasting the ridge
axis to pass SW KS Saturday morning, with lee side cyclogenesis
commencing in the afternoon. Forcing for ascent will still be well
west of SW KS, with a 556 dm upper low near San Francisco, with
jet support still in the Great Basin. Still, dryline evolution
should begin Saturday afternoon, and included isolated pops for
isolated supercells in the western zones as ECMWF suggests.

Sunday...Concern increasing for significant severe weather
potential. ECMWF swings an intense upper low/shortwave to Utah
by 7 pm, then into NW Colorado Sunday evening. Dryline will
strengthen further with strong cyclogenesis in NE Colorado.
Scattered supercells look plausible on this dryline Sunday
afternoon and evening. Large hail is likely, per climatology.
Convection expected to continue to some extent Sunday night, as
upper low intensifies to 550 dm near Cheyenne Monday morning.
Possibly a retreating dryline Sunday evening with very strong
forcing for ascent, and this scenario will be watched closely over
the coming days.

Monday...12z ECWMF intensifies upper low further to 544 dm in
Black Hills South Dakota, with an intense dryslot overspreading
western Kansas. Windy and much warmer, at least mid 80s. Severe
weather will likely threaten the eastern zones on the dryline
Monday afternoon.

[OUGrad05]

Monday is a long way off, trying not to get excited at this point.

[andyhb]

Well, there goes the Monday system on all four model runs tonight.

[brettjrob]

Well, there goes the Monday system on all four model runs tonight.

 

Seems like something respectable almost has to come out of Sun and/or Mon, regardless of whether get a MDT/HIGH caliber day. The biggest question in my mind is whether the Tue-Thu period will offer a second round of potential. The ECMWF tonight changed the North American H5 pattern considerably after the first shortwave ejection, so that's really up in the air.

Definitely concerned about this becoming more of an anafrontal flow/shear situation after Sunday, along with the relatively weak anvil level flow over much of the Plains during the whole period. As much as I love just seeing persistent SW flow over rich ET-enhanced moisture in late May, the ECMWF tries to throw every wrench it can into that formula; it also hints at morning convection as a potential problem both Sunday and Tuesday. One would have to think the southern High Plains still hold mesoscale potential several days in almost any scenario, at least.

I don't disagree with you, though. From an enthusiast's standpoint looking for a big outbreak to track, things aren't great, and the clock is really ticking climatologically if next week falls flat. From a chaser's standpoint, I still feel pretty good about next week, with the understanding that late May 2004/2008 is probably out of reach. But it can be a fine line between quality late season mesoscale setups vs. just grasping at straws, admittedly.

[thewxmann]

Meh, from the storm chasing perspective all I can hope for are a few good storms (especially since we're still in a background state that favors less western troughiness). With SWly flow atop a very moist warm sector in late May, we should get at least one or two quality storms. Outbreak not looking as likely, but at least we're not seeing a death ridge.

 

The wrench in all this is we could have a few days ruined by crapvection -- the long SW fetch in the mid-upper levels would imply interaction with the southern stream and its associated, ill-timed disturbances. With such a moist and unstable warm sector, and lack of a hotter EML, any subtle southern stream disturbance could touch off a morning MCS. Too early to get into details about this, however.

[Chinook]

Name this severe weather event! This is the NARR reanalysis for two consecutive days, at 18z. The maps are from before 2015. What happened on these days?

 

 

 

 

[andyhb]

4/10-11/2001. High risk on 4/11 for IL/IA, fairly prolific tornado outbreak in the Plains/Middle-Upper MS Valley.

[Chinook]

That's right. There were 79 tornadoes in two days (according to SPC's Severeplot database) and there was more than $1.3 billion damage from hail across the country on April 10.

 

 

 

 

 

 

 

 

 

 

[SluggerWx]

As recently as the 12z GFS runs yesterday, the start of June had looked pretty inactive after the insane cape values the GFS had been showing for late May.

Today's model runs are the complete opposite.

If the GFS continues this trend for early June over the coming days, the last 8-10 days of May and the first 4-5 days of June look to be active nearly every day on the Plains.

I was trying to plan a chase trip for the 1st week of June, so I've been checking the GFS runs since early June came into range. 

Really interesting change over the last 48 hours for early June on the GFS.

[1900hurricane]

The Pacific jet showing up in medium range guidance sure is nice looking. As others have alluded to across various media, this could help make things rather active later on in June.

[andyhb]

The Pacific jet showing up in medium range guidance sure is nice looking. As others have alluded to across various media, this could help make things rather active later on in June.

 

If we get at least a piece of this ejecting into a typical June warm sector, yowza.

[bjc3395]

Euro shows a pretty significant trough coming onshore hour 240... time to get excited?

[nrgjeff]

Both weeklies and some of the 11-15 day ensembles are starting to hint at a new trough in the Rockies. Some have it unseasonably south. Others have things northern Plains and Upper Midwest which is June Nino-ish. Either way a chaser has to like about a third of the way into June. North would be nice with smaller crowds.

[bjc3395]

Both weeklies and some of the 11-15 day ensembles are starting to hint at a new trough in the Rockies. Some have it unseasonably south. Others have things northern Plains and Upper Midwest which is June Nino-ish. Either way a chaser has to like about a third of the way into June. North would be nice with smaller crowds.

Just curious, where can someone access the "weeklies" and ensemble data?

Thanks!

[nrgjeff]

GFS ensembles and CFS weeklies should be available at NCEP or many free models sites. Euro ensembles and Euro weeklies usually require a subscription somewhere. Euro op is starting to show up on a few free sites though.

[rolltide_130]

Both weeklies and some of the 11-15 day ensembles are starting to hint at a new trough in the Rockies. Some have it unseasonably south. Others have things northern Plains and Upper Midwest which is June Nino-ish. Either way a chaser has to like about a third of the way into June. North would be nice with smaller crowds.

 

Was hinting at possibly as far south into Dixie a couple days ago. Not sure if I buy it but that sure would be something for that part of the country. 

[bjc3395]

GFS ensembles and CFS weeklies should be available at NCEP or many free models sites. Euro ensembles and Euro weeklies usually require a subscription somewhere. Euro op is starting to show up on a few free sites though.

knew of GFS ensemble and CFS, I've been using euro on accuwx but they don't have the ENS I believe. Euro ensemble, at least on a very basic 24 hour interval similar to what pivotal/COD offer, is available on the euro site for free but it's very basic. Anyway it shows a solution further south than what GEFS depicts, with operational euro even further south. Very interesting and encouraging to see. Would not mind a repeat of Thursday's positioning if verified though I'd like to see better timing and less crap. Tl;Dr I wanna chase kansas, maybe Nebraska. Wouldn't mind OK but that would be a rather anomalous event.

[Derek30]

Thursday looks volatile on top of the ridge in southern Manitoba. Reminds me a bit of a certain setup 9 years ago.

Northern Plains also look active next weekend as the ridge breaks down. 6z and 12z GFS depicting a very strong low in ND.

[messier77]

Thursday looks volatile on top of the ridge in southern Manitoba. Reminds me a bit of a certain setup 9 years ago.

Northern Plains also look active next weekend as the ridge breaks down. 6z and 12z GFS depicting a very strong low in ND.

 

Thursday late afternoon/evening definitely has some potential south and east of Regina over the top of the ridge.  Considering that this is my only week of chasing for the year, looks like I might be heading to Canada.

 

[Derek30]

Yeah, E SK looks to be the best bet tomorrow and Thursday. Ridge is overhead for S MB with MCS potential increasing both nights. E SK should see a few supercells with the highest risk on Thursday.

[ZackH]

If stuff does indeed pop in North Dakota on Saturday like the GFS suggests and has suggested for several runs, there will be quite a few nice storms along the warm front axis. Not really any obvious height falls, but a fairly deep low in eastern Montana and lead impulse. 

[Derek30]

If stuff does indeed pop in North Dakota on Saturday like the GFS suggests and has suggested for several runs, there will be quite a few nice storms along the warm front axis. Not really any obvious height falls, but a fairly deep low in eastern Montana and lead impulse.

Keep an eye on Sunday as well. Low progresses east and the trough finally approaches. Should be good forcing along with appreciable moisture and instability.