Central/Western Summer Medium/Long Range Discussions

[Ian]

Woo storms

[HM]

This has been and will continue to be a valuable lesson in how to properly use tropical forcing for diagnosing medium to long range patterns. There were a lot of forecasters banking on the PNA-styled pattern continuing and the MJO blasting through phase 6-7 etc.

 

When the MJO reinforces the climo signal (stagnant walker cell forcing), magical things can happen for chasers.  

 

[Srain]

This has been and will continue to be a valuable lesson in how to properly use tropical forcing for diagnosing medium to long range patterns. There were a lot of forecasters banking on the PNA-styled pattern continuing and the MJO blasting through phase 6-7 etc.

 

When the MJO reinforces the climo signal (stagnant walker cell forcing), magical things can happen for chasers.  

Thanks for your input in our Region the past several weeks, HM. Good luck and successful chasing to all those headed out!

[andyhb]

Thanks for your input in our Region the past several weeks, HM. Good luck and successful chasing to all those headed out!

 

Yeah I second this, hopefully this will keep up.

[Ian]

I'm worried the weekend storm will become a vortex of doom now. Need another 0z GFS injection.

[andyhb]

I'm worried the weekend storm will become a vortex of doom now. Need another 0z GFS injection.

 

I wouldn't be overly concerned about that, that thing wouldn't need to move overly far to at least open the High Plains for moisture return.

[Ian]

I wouldn't be overly concerned about that, that thing wouldn't need to move overly far to at least open the High Plains for moisture return.

Well this weekend initially looked sorta similar so there is that. I'm not ready to buy this becomes a good season just yet tho. GFS has moisture issues much of the run behind the sys.

[HM]

The ensemble mean from the GFS and ECMWF still keep the general idea of trough--ridge--trough across the CONUS post-weekend potential / storm system into early next week. Maybe a reload by the end of next week/ Memorial Day Weekend?

[Dsnowx53]

The ensemble mean from the GFS and ECMWF still keep the general idea of trough--ridge--trough across the CONUS post-weekend potential / storm system into early next week. Maybe a reload by the end of next week/ Memorial Day Weekend?

 

 

I have generally been having these thoughts as well, but I'm definitely hoping that the 12z Euro is wrong. It has the initial wave turning into a gigantic cutoff low over the east, which prevents eastward progression of the upstream ridging. This seemingly puts the High Plains in a "screw zone", as the trough out west is too far west, so there is really only a height gradient out in Wyoming and such. The models have trended weaker with the Central Canadian block and barely even show a resemblance of it now. 

 

I'm not worried just because I still expect the wave to slide into Canada instead of becoming a giant cutoff, but with this season, you never really know. 

[Ian]

I have generally been having these thoughts as well, but I'm definitely hoping that the 12z Euro is wrong. It has the initial wave turning into a gigantic cutoff low over the east, which prevents eastward progression of the upstream ridging. This seemingly puts the High Plains in a "screw zone", as the trough out west is too far west, so there is really only a height gradient out in Wyoming and such. The models have trended weaker with the Central Canadian block and barely even show a resemblance of it now. 

 

I'm not worried just because I still expect the wave to slide into Canada instead of becoming a giant cutoff, but with this season, you never really know. 

 

scary pattern. seems it's either pretty good or terrible. i think the LR has been consistently overmodeling that lakes area vortex tho.. so i guess i'd not expect it to just chill either but if it's going to this is the year..

[Dsnowx53]

scary pattern. seems it's either pretty good or terrible. i think the LR has been consistently overmodeling that lakes area vortex tho.. so i guess i'd not expect it to just chill either but if it's going to this is the year..

 

 

Indeed. It's looking like either days and days of tornadoes for the western high Plains, or days and days of ridging. I liked the initial zonal look better and what the 6z GFS and previous Euro ensemble runs were showing. 

 

The Euro ensembles last night still looked pretty decent, but it's showing too much/too deep of EC troughing for my liking. But yeah if the models are overdoing the Lakes Vortex, that should be enough for the trough in the entire east to retreat to the northeast, ridging to slide a bit eastward towards the southeast, and put the High Plains back in the downstream side of the trough. 

 

But as you said, if any year could screw us over, it would be this one. 

[Ian]

Indeed. It's looking like either days and days of tornadoes for the western high Plains, or days and days of ridging. I liked the initial zonal look better and what the 6z GFS and previous Euro ensemble runs were showing. 

 

The Euro ensembles last night still looked pretty decent, but it's showing too much/too deep of EC troughing for my liking. But yeah if the models are overdoing the Lakes Vortex, that should be enough for the trough in the entire east to retreat to the northeast, ridging to slide a bit eastward towards the southeast, and put the High Plains back in the downstream side of the trough. 

 

But as you said, if any year could screw us over, it would be this one. 

 

Think more ens means than not are not holding that vortex around long or at all. There is a general building of the central US 500 ridging at times but for the most part the axis stays east of the high plains which should keep moisture running up that area. Those are notoriously tricky setups tho.. but can repay you with multiple days of great stuff.

[HM]

I have generally been having these thoughts as well, but I'm definitely hoping that the 12z Euro is wrong. It has the initial wave turning into a gigantic cutoff low over the east, which prevents eastward progression of the upstream ridging. This seemingly puts the High Plains in a "screw zone", as the trough out west is too far west, so there is really only a height gradient out in Wyoming and such. The models have trended weaker with the Central Canadian block and barely even show a resemblance of it now. 

 

I'm not worried just because I still expect the wave to slide into Canada instead of becoming a giant cutoff, but with this season, you never really know.

Don't worry about the op euro. It has a tendency to over amplify in the day 8-10 range. You get a sense of that too when looping through the frames. Given the time of year, cutoffs are inevitable. But I wouldn't discount that next Pacific trough or this pattern quite yet. Also, the new ensemble mean should calm your nerves about the op.

[Ian]

Don't look at the 18z GFS heh.

[andyhb]

Don't look at the 18z GFS heh.

 

The good thing I notice is that with whatever strange things the long range models do with this closed low in the West, it does revert back to western troughing eventually.

[HM]

I didn't know where to put this; but, you can see by this loop when the MJO takes over between 5/12 and today:

Notice how the flow which was meridional / slow turns zonal in both hemispheres in the loop, taking their fire hoses more toward the East. This is a classic response when forcing is in the eastern IO / Indonesia region.

[Dsnowx53]

Don't look at the 18z GFS heh.

 

 

And don't look at the 00z GFS, either, lol. 

[wxmeddler]

And don't look at the 00z GFS, either, lol. 

 

I'll take North Dakota for 500 Alex.

[brettjrob]

At least the GEFS mean still eventually allows sustained southwest flow over the C/N Plains by ~12-15 days from now. The degree of eastern troughing and northerly flow into the eastern Gulf is a tad concerning, but a gravy train of upslope setups would likely be a lock in that scenario, at minimum.

[Dsnowx53]

At least the GEFS mean still eventually allows sustained southwest flow over the C/N Plains by ~12-15 days from now. The degree of eastern troughing and northerly flow into the eastern Gulf is a tad concerning, but a gravy train of upslope setups would likely be a lock in that scenario, at minimum.

 

 

The progged pattern kind of reminds me of the early June upslope tornadoes that Wyoming and Colorado received last year. Still obviously hope that the trough can shift a bit further east with time, as well as the EC troughing being a lot more shallow in depth. 

[nrgjeff]

A significant multi-day severe weather episode should commence Saturday. Will it be a classic sequence? Still too early IMHO to drill down details, but the pattern looks favorable. Looks like Saturday may be somewhat isolated, with ridging still lingering around the Plains, but the cap should be breached. Could be outflow and/or retreating WF from Friday intersecting DL on Sat. Sunday looks like a nice high instability set-up with cooling mid-levels and good shear. DL and WF could both light up Sun. SPC notes that Monday we have a second jet streak coming out of TX/OK into the southern part of the system. Despite the closing off up north, action may continue with the secondary jet streak south - esp if outflow boundaries - Mon. Details murky on Tuesday but it could continue somewhat in the Lower Missouri Valley, Ozarks, and/or Ohio Valley. It won't be all 3 Tuesday, with lots of uncertainty for Tue. However Saturday through Monday looks like a pretty good signal for the Heartland.

 

EDIT: Meant to put this in the severe thread. Will keep it here since most of my thoughts already expressed in the severe thread, though I'm on the bullish end of the spectrum over there.

[HM]

The data is putting up an omega block over Alaska, holding a trough on either side which includes the Pacific NW. The situation with the downstream ridge and cutoff low will not be ironed out until a few days before hand, so relax. Anyone planning on chasing at the end of May / early June will be fine as long as that N PAC scenario is correct.

 

This is playing out on the modeling as we discussed before. The comparison to 1990 gives an example of what kind of tornadic episodes could occur with something like this. Clearly, we should have no problems going forward advecting strong EMLs into the northern Plains/Midwest to kick off summer (of course I know you guys are worried about return Gulf flow which also should improve by later next week).  

[HM]

One last statement about the long range: an interesting retrograding period may bring the S-C Plains another window a bit later into June. I wouldn't call it amazing, especially given the time of year, and the signal is not as strong or clear as this weekend was at this range.

 

As the North Pacific repeats what it did last month, the blocking will retrograde slowly, getting into the WPO position sometime at the end of the first week or second week of June. At the same time, the wavelengths will get shorter with the arrival of summer and the tropical forcing will be over the Atlantic-Africa-IO sector again. But in mid-June, this can actually lead to a trough formation over the Rockies/S. Plains, assuming the wavelengths are short enough.

 

So while the northern Plains / Upper Midwest may be the place to be for chasing at the end of the month / early June (on the north side of the ridge), there may yet be another window for areas further south.

 

Something to think about for you June chasers.

[Ian]

gfs is pretty beautiful. i'd lock that in without question lol. high plains in between bigger events.. almost nonstop action. model must be on crack.

[wxmeddler]

gfs is pretty beautiful. i'd lock that in without question lol. high plains in between bigger events.. almost nonstop action. model must be on crack.

 

Every single day there is an area with at least 3000 j/kg of CAPE somewhere in the plains through the entire 384 run... Wow.

[Dsnowx53]

gfs is pretty beautiful. i'd lock that in without question lol. high plains in between bigger events.. almost nonstop action. model must be on crack.

As long as our original thoughts are right about that EC low not cutting off, and instead getting out of the way, then we should be looking good.

[wxmeddler]

00z Euro builds in a massive death ridge by hr 180 and it sticks around till the end of the run. The only game in town is in ND, MT or Canada.

[Stebo]

gfs is pretty beautiful. i'd lock that in without question lol. high plains in between bigger events.. almost nonstop action. model must be on crack.

 

Yeah that was an amazing run, pattern kept reloading with substantial CAPE day in and day out. With no real end in sight even at day 16.

[Dsnowx53]

00z Euro builds in a massive death ridge by hr 180 and it sticks around till the end of the run. The only game in town is in ND, MT or Canada.

The ridge axis though is in the eastern Plains, so it's really not a bad run for a lot of the north and western high plains regions. Obviously not as good as the GFS but I'd imagine that chasers would still manage, especially via upslope.

[Ian]

The ridge axis though is in the eastern Plains, so it's really not a bad run for a lot of the north and western high plains regions. Obviously not as good as the GFS but I'd imagine that chasers would still manage, especially via upslope.

 

yeah it's not horrible. not necessarily amazing but probably relatively OK. as long as you don't get that ridge pumped way up and axis west of like 105-110 it's workable at least when waves pass by etc. one issue at times might be that heights tend to rise day to day on some models.

 

those high plains days are tough because they look like crap from range a lot and they are nerve inducing but huge payoff if you get a good one or string of good ones. 

 

i loved how the gfs just kept piling moisture into places like the black hills last night. i doubt it's right but those would be fun chases.