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andyhb

Central/Western Medium-Long Range Discussion

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Meanwhile south of Wichita...

Quote

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 730 PM CDT FOR SOUTHERN
COWLEY COUNTY...
    
At 645 PM CDT, a confirmed tornado was located near Arkansas City,
moving southeast at 15 mph.

HAZARD...Damaging tornado and golf ball size hail.

SOURCE...Emergency management confirmed tornado.

Probably won't be anything long-lasting or too photogenic, but the storm's reflectivity presentation looks lovely.

ICT_2343.png

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CFS still really wants to bring a small area of 50kt SW flow to parts of KS/NE next Saturday. GFS also has it but has been very consistent with an ugly crashing cold front surface pattern and no SLP really able to wrap up. So we go from February in April, to July in early-mid May, back to April in mid-late May? Seems legit.

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On the plus side 2013 and 2016 were good chasing. We don't need high tornado counts. We need tight clusters, but I think everyone knows that. Just a rosy glasses reminder.

This week I see the following targets. Thursday DCVZ would be my choice. Action is forecast farther north, but I'll take some geography to increase success rate. Friday could be the first true DL event of the season; or, it could turn into a cluster fast on sub-68 dewpoints. Saturday looks a little bit like Monday in Kansas (OFB); or, CF/DL farther south but with moisture risks. Saturday is still way up in the air 5 days out.

Next week hints of a midweek shortwave are noted. Attm it looks like slightly less than Fri/Sat but it's also a week out. Could improve or fall apart but something to watch.

Memorial Day weekend looks awful on the GFS ensembles; however, Euro/Cad have the door open for another trough. GFS is trying to latch onto some bearish Pacific forcing, but a slower evolution would favor the Euro/Cad. Time will tell. Nothing looks spectacular, but at least late May chances are there.

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Looks like this season will come down to June.

Given trends and what has happened thus far, one can't really be that excited, but we'll see...

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Mulling over some NAM forecast soundings for Friday over KS/NE (obviously still at the very end of its range so take it for what it's worth). The biggest weakness I see is of course the modest deep layer shear. However low level directional shear and mid-level lapse rates look quite good. Still not sure if I'll bite on it, but based off that Euro run Friday-Saturday would be the only play of my vacation window.

If only that 500mb shortwave with the small pockets of 45-50kt southwesterlies could be a little faster (on the GFS, too). It seems to want to lag the warm sector until the cap is filling in after dark, however that could imply a small window of time shortly after 0z when everything lines up. As we saw on the 1st, sometimes that's all it takes.

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First NAM run for Saturday in range, and it actually agrees with 6z GFS with Iowa/MO having some impressive parameter space. (Yes, I realize its 84 hour nam, but this agreement at least gives something to watch for)

 

 

GFSMW_con_scp_090.png

ehi01.us_mw.png

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Yeah. Honestly, after hitting rock bottom over the weekend, things are looking up a bit for the coming weekend into the following week. Should be at least a few opportunities. Saturday in particular has my eye now that the GFS actually forms a surface low.

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15 minutes ago, CheeselandSkies said:

Yeah. Honestly, after hitting rock bottom over the weekend, things are looking up a bit for the coming weekend into the following week. Should be at least a few opportunities. Saturday in particular has my eye now that the GFS actually forms a surface low.

CFS disagrees lolcfs_bchiclet.png

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5 minutes ago, largetornado said:

CFS disagrees lol

I've been checking this daily, I'm not sure if I buy into it being anything to consider when it comes to Plains activity. The red contours the other Friday were super impressive looking on the mouseover square for then but nothing happened in that spot. That was 1-5 days before. Its experimental (the dashboard) and I'm trying to find a pattern.

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3 hours ago, ChrisBray said:

First NAM run for Saturday in range, and it actually agrees with 6z GFS with Iowa/MO having some impressive parameter space. (Yes, I realize its 84 hour nam, but this agreement at least gives something to watch for)

 

The GFS shows a decent synoptic setup for severe weather on Saturday, with CAPE of 4000 J/kg in OK and KS. There is a cold front, warm front, and dryline. There could be 70-73 degree dew points in Oklahoma. 0-6km shear values increase from 18z to 00z.

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29 minutes ago, Chinook said:

The GFS shows a decent synoptic setup for severe weather on Saturday, with CAPE of 4000 J/kg in OK and KS. There is a cold front, warm front, and dryline. There could be 70-73 degree dew points in Oklahoma. 0-6km shear values increase from 18z to 00z.

With quite the stout cap to go along with it. I think Saturday the only hope is further north with stronger forcing. I haven’t looked to closet though tbh.

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Moisture is going to continue to be a limiting factor (as will weak shear in the deep layer). Moisture is pretty meh for the time of year thanks to the ULL in the gulf. Unfavorable trajectories should persist for quite a while. Ie, plains dealing with recycled/processed moisture rather than rich Caribbean trajectories. 

While Friday and Saturday could yield fun chase days, think that overall ceiling will be tempered by lack of richer low level moisture. 2018, you never cease to amaze. 

 

Severe opportunities should continue into parts of next week, perhaps shifting north. Ensembles depict potential activity for the northern plains closer to Memorial Day 

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Friday looks to have the best potential (over favorable terrain) in the coming days, particularly over Kansas. Tomorrow looks like a mess up north (northern Plains), while the southern Plains may struggle a bit with storm longevity. Not to mention that outside of the Dakotas, deep layer shear appears marginal (only around 30kts in the 0-6km layer). You'll probably get some locally enhancement in climo-favored northeastern Colorado, but that's about it. (A conditional threat may exist along a warm front in the eastern Dakotas, but that seems fairly conditional)

Saturday looks to be just a little too late/east. A closer look at a consensus of guidance (which I will lean more toward the Euro) favors increasingly unidirectional mid/upper level flow and capping issues. An area that may have the best potential will probably fall near the lower Missouri Valley (northern Missouri and surrounding areas). I'm not sure that the eastern Kansas dryline setup will work. Sure, if the system slows a bit and we see a stronger signal for backing of low-level flow, then maybe, but we've seen similar setups fumble this year in such a scenario.

With respect to the CFS, that might be a hiccup, but when it shows such low "values" for SCP during peak season, that's a major red flag. Taken verbatim, the latest CFS would be pretty dull next week, although you'd probably still have at least a day or two thread the needle somewhere, either along remnant outflow or terrain-aided.

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I don’t have much to say about Friday but one thing: outflow boundary. 

 

global and mesoscale models indicate a SEward propagating upscale growing segment will move through SW Ne and N/W Kansas. This is depicted well by the 3km NAM and falls in line with low level flow anticipated. In the wake of the decaying activity Friday morning... all eyes will be on this boundary. 41510820-D509-4B4E-B2AA-8003981BF752.gif.c50034e4f7a7771f2f0c1cf4480c725f.gif

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Also for next week, the Euro is really ugly. The 500mb maps suggest virtually ZERO 500mb flow of 30+ knots in the Plains. A major failure of the calendar if it verifies. 

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One should include reasoning regarding why one agrees or disagrees with data.

2 hours ago, largetornado said:

CFS disagrees lol

 

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GFS looks decent for saturday in NE KS, but everything else is atrocious for any type of semi-legit severe potential. The Euro looks especially garbage for Saturday. Nice mid-level jet punching the warm-sector but low-level winds are depressing and even instability and moisture are seasonably underwhelming. 

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Here's something a little off topic. I have noticed today that the 18z 3-km NAM products, as shown on PivotalWeather.com and College of Dupage, have taken from 18:00z till 23:00z, 5 hours, and they're not even completely done. This does not take so long for the 00z 3-km NAM products. Is NCEP just processing that much more computational stuff during the mid-day time?

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1 hour ago, Chinook said:

Here's something a little off topic. I have noticed today that the 18z 3-km NAM products, as shown on PivotalWeather.com and College of Dupage, have taken from 18:00z till 23:00z, 5 hours, and they're not even completely done. This does not take so long for the 00z 3-km NAM products. Is NCEP just processing that much more computational stuff during the mid-day time?

Think it’s an issue with the feed 

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ECMWF and its parallel are finally starting to slow down for Saturday. GFS about to score a coup? NAM also slowed down more at 06Z. Storm mode is still in question with an ongoing MCS that is not forecast to die in the morning. However, in contrast to Friday, dewpoints will be there Saturday. Northeast Kansas is good chasing terrain. NW Missouri is even OK if it crosses the River, but be mindful of crossing well in advance. Plan ahead for both safety reasons and not losing the storm.

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Starting to really get interested in Saturday. Might have to make a short trip. Nuclear CAPE owing to impressive BL moisture on the order of 70+ degree surface DPs and 8.0-8.3C/KM Lapse Rates, with relatively impressive directional shear with winds out of the southeast at the surface veering to SW at 6km. Upper-level winds are fairly tame so venting and supercell mode *will* be a problem. But low-levels look sufficient for mesos on the NAM and GFS. Have not looked at the euro yet but I will take Jeff's word for it that it looks better. FWIW, 4km NAM shows a mixed storm mode with bows and supercells across NE KS/SE NE into NW MO Saturday afternoon and evening. A bit concerned about a morning MCS, but ultimately believe it would put out a boundary that would probably be the biggest play of the day with surface winds likely being locally more backed and moisture pooling along the boundary. Will have to wait and see, as there has clearly been a trend of setups falling apart come D-day, but saturday is starting to look like a more interesting day in model land, the opposite of what we have been seeing -- given that it is mid/late May. 

KTOP has a good discussion:

Quote
Next, we then turn our attention to Saturday afternoon and evening.
The evolution of convection Friday night/Saturday morning will play
a key role in severity, mode and location of thunderstorms Saturday
afternoon/evening. At this point in time, model consensus continues
to suggest a surface low/warm front/dryline intersection in central
to north central KS with the main upper low remaining west of the
CWA through 00Z Sunday. That being said, weak mid-level height falls
coupled with weakly capped MLCAPE values between 3000-4000 J/kg,
should foster thunderstorm development along the dryline after 21Z
Saturday afternoon. The primary hazards look to be large hail and
damaging winds, some significant, given the strongly buoyant and
modestly sheared environment. A mesoscale-driven tornado threat is
certainly possible, especially on any outflow boundary from Saturday
morning`s convection. Further thunderstorm development is expected
after 00Z as the main upper low ejects across the central Plains.
Stay tuned to subsequent outlooks as confidence is low in boundary
positions and the evolution of Saturday morning`s convection.

 

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Middle of this week looks like a doable 3-4 day stretch in the Northern Plains. Tue/Wed feature a LLJ somewhat backed approaching/over the region. Moisture may be JIT on Tuesday but should be there Wednesday. Note that 65F dews is enough up there. I will not attempt specific targets due to mesoscale details, but generally Wyoming, Montana, Nebraska and the Dakotas. 

Late this week SPC even mentions a short-wave for the Dakotas, Minnesota and Wisconsin Thu/Fri. Nebraska and Iowa could be involved. Best forcing looks north, but boundaries may sag south still with just enough flow aloft. Is the season over in the heart of the Alley? Time will tell, but it looks like the North is perking up even if it's a little early compared to climo.

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8 hours ago, nrgjeff said:

Middle of this week looks like a doable 3-4 day stretch in the Northern Plains. Tue/Wed feature a LLJ somewhat backed approaching/over the region. Moisture may be JIT on Tuesday but should be there Wednesday. Note that 65F dews is enough up there. I will not attempt specific targets due to mesoscale details, but generally Wyoming, Montana, Nebraska and the Dakotas. 

Late this week SPC even mentions a short-wave for the Dakotas, Minnesota and Wisconsin Thu/Fri. Nebraska and Iowa could be involved. Best forcing looks north, but boundaries may sag south still with just enough flow aloft. Is the season over in the heart of the Alley? Time will tell, but it looks like the North is perking up even if it's a little early compared to climo.

Could be a decent stretch into next week as well with a rather strong ridge encompassing the eastern US and prolonged SW flow aloft for the northern Plains and southern Canada 

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I feel like this is all of us, and the rest of the storm chasing community this season. It's actually quite remarkable how incredibly boring and awful it has been across all the various tornado hotspots (i.e., Plains and Dixie Alley).

297.png

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