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06/07/05 TALK: N Plains

  • Thread starter Douglas Mitchell
  • Start date

Douglas Mitchell

Figured this day warranted a TALK thread due to the SPC issuing a Day 2 MOD risk. Wind profile looks good over SE SD, good direction, decent speed and ridiculous instability. GFS and NAM both progging CAPE in excess of 6000 j/kg and LI's greater than -14 from Aberdeen to Sioux Falls. I know its too early to pick a target, but I think I'll be starting the day in Brookings, SD. Hope to see some of you out there.
No suprise with the moderate risk as the NAM has been very consistent over the last few runs for this period. It has also been very consistent placing the the theta-e boundary/warm front in east-central to northeast SD. The 06z NAM places a -13 LI bullseye near Aberdeen by 18z. It fires convection in the 21-00z period. Attempting to find any null factors and there arn't many. An MCS might plow through the Dakotas/MN tonight and the airmass might need some recovery. So many great set-ups are blown by residual cloud in these parts. I'll be starting the day in Grand Forks for my usual bad luck luck shift on a higher threat day getting the MNDoT forecast out so atleast I'll be looking at data all day. I'll be flying south shortly after 2pm to get into a preliminary Redfield-Huron-Watertown-Brookings quad. This will take approximately three hours, putting me there shortly after 5pm. Hoping the cap holds things off until then. By far the best set-up for the Dakotas/MN this year and I don't want to miss it. Will see what the 12z runs offer shortly. Good luck to all NP chasers on this one.
It still looks great in the latest run, and I am probably gonna still be headed for SE SD. Here is a AFD from Sioux Falls...

I just got home last night from my second 3000+ mile four day chase.

With that said, Tuesday makes me want to say hmmm..... I'm very tempted to head out tonight and target somewhere in the vicinity of Mitchell, Sd. It sure is nice to see all this gulf moisture finally make it up into the Northern plains and very nice to see some consistent model runs. Now all we need is for the cap to play along. Good luck to all that chase, I think tomorrow will finally yield some large stovepipes and wedges as long as the cap holds till late afternoon/early evening. If I wasn't so exhausted I would be on my way already.
I have been watching Tuesday for a while now. I would be excited if Saturday hadn't happened. The day is showing good potential though. I am leaving for South Dakota as soon as I get done packing. Right now I am looking at staying the night somewhere in SE to Scentral South Dakota. I have never chased South Dakota before. Does anyone know how good the terrain and road networks are. I was checking maps last night to get an idea of the roads and I saw that there are two huge lakes that run N/S in the target area that could be a serious problem on Tuesday.
I might be leaving early in the morning tomorrow for SD should 0Z model runs hold up on the situation. I have also never chased SD, let alone been in the state of SD before in my life so this will be completely new. I have heard from others that SD is pristine chase territory, but if I do leave early in the morning, I will be heading to Sioux Falls, targetting a Mitchell, SD to Brookings, SD area.

12Z model runs are favorable for an area of E SD, just the NAM has me wondering about cap strength.
I am going to try and get an actual forecast up tonight after the model runs... I'm awaiting the SPC day 2 outlook as well, this mornings models were interesting to say the least. I think I will try to get out there, especially since it isn't going to be a terrible drive from my view. Only 2 hrs out of FSD... Now to my model thoughts.. lol

NAM was still on track with the low in central SD and extreme cape over areas of the northern plains. They did not like to develop precip until after 00z, which may be possible. But, the cap may also break earlier given it did not show much CINH. GFS was just screwy in my opinion.. Throughout their model run they would develop precip. and then just dissapate it in the next timeframe. It was looking a lot like convective feedback to me, which wouldn't be a surprise... I'm sure the local AFD and SPC will have something to say about it.

Overall I say this should turn out to be at least a decent chase day, FSD AFD states a possible significant severe weather outbreak for tomorrow. ABR didn't say more then 2 sentences about anything... To early for target area besides saying somewhere in eastern SD.
I have never chased South Dakota before. Does anyone know how good the terrain and road networks are.

The road network is worthy of an "A" grade. County and farm roads every mile. A perfect grid system but there are numerous small lakes. I-29 runs through east SD for quick moving around. SD speed limits aregenerally 75 on the interstate and 65 on the side roads. Lack of population and chasers tends to keep the roads relatively free of traffic. You might see some slow moving tractors as the planting season is running late due to all the water around. The two lakes you mention are Big Stone and Traverse at the " camel hump" in western MInnesota. Defenitely of serious consideration when route planning. Terrain is worthy of a B+ grade. The area generally flat to rolling hills. Im extreme northeast SD, southeast ND, and portions of western MN, the terrain is as flat as a squirrel on the freeway. Not too many trees in this area except shlterbelts and riparian habitat.

The 12z runs are in and the NAM has changed a bit. Still fairly consistent but it throws in a peculiar mesoscale boundary in southern MN. I'm not ganna latch on to that solution just yet. The GFS and Canadian still favoring northeast SD.
Originally posted by Ben Prusia
I might be leaving early in the morning tomorrow for SD should 0Z model runs hold up on the situation. I have also never chased SD, let alone been in the state of SD before in my life so this will be completely new. I have heard from others that SD is pristine chase territory, but if I do leave early in the morning, I will be heading to Sioux Falls, targetting a Mitchell, SD to Brookings, SD area.

12Z model runs are favorable for an area of E SD, just the NAM has me wondering about cap strength.

Keep an eye out for me i think Im going on this one Ben.. Im supposed to hook up with Ron Gravelle from Ontario Canada up there..

Chasing in SD is pretty nice imho. Even when we do have severe weather, there aren't that many chasers out. I've yet to see a caravan yet. In my little experience so far, it seems a lot of the good stuff drops south.

There is a little construction on I-29 just south of Sioux Falls so it's kind of a bottleneck there. But they've widened to 3 lanes on the north side.

Should be a fun day!
Thanks for the construction update Edward...

Moderate risk by the SPC has elongated north/south and has moved more along the track of the low pressure system. Tornado threat was a little less mentioned in this text. Storms look to become more linear faster is what I get out of it for the most part... Still a decent chase day looking...
Originally posted by Michael Gribble
... I have never chased South Dakota before. Does anyone know how good the terrain and road networks are. I was checking maps last night to get an idea of the roads and I saw that there are two huge lakes that run N/S in the target area that could be a serious problem on Tuesday.

The state is pretty much divided n – s by the Missouri River (large long lakes without many crossings, I think there are only 7 )The western half of the state would probably be considered unchaseable. The eastern half or more so the eastern 1/3 is excellent for chasing. It has a great road network and very flat. But I would definitely recommend staying east of the Missouri River.

Lack of population and chasers tends to keep the roads relatively free of traffic.

Could SD see its first chaser convergence?
oh I've seen plenty of chasers up in SD in the past ... very nice views up there, and the roads are perfectly fine. Bigger question usually is getting across the river, particularly if stuff initiates in O'Neil or northern Nebraska ... that can be a trick. I'm sure tomorrow will definitely see its share as well ... looks like a strong possibility for significant severe at this point ... I'll be up. This week continues to show a lot of potential. Looking forward to seeing everyone up there -

Well, I've been proved this year that my forecasting skills are below the par of most everyone else I know, it seems - but......

Is anybody worried about the possibility of unidirectional shear across large parts of the target area tomorrow?

I was wondering why the NAM does not show much in the way of backing winds ahead or northeast of that low that is progged by 00Z? Indeed, most progged wind directions from south-central NE to north-western IA and south-eastern SD are veered. :? Also - it seems to show winds in the northern half of SD out of the north - suggesting a cold front?

I wonder why SPC has the MOD so far north and east.......the CAPE values are ridiculous throughout most of NE. Also - is a cap of +10oC a bit much for the target area?

Where is everybody targeting??? Are many travelling for this event?

Just the thoughts of a raving madwoman......sitting in OUN all week. And I do mean sitting...... :roll:

A 10C cap doesn't bother me too terribly much, although it's certainly something to take into consideration. It's when you get those +20C caps that I feel you can pretty much toss all hope unless you can manage to get some incredible moisture convergence to help erode it.

That being said: I can see what you're talking about.

Flow is pretty much southerly at the surface until about 0z when a 996 mb low sets in over western NE.

I was concerned about the 850 temps, but surface temps are forecasted to hit the +100F mark in NE which *might* overcome the cap (850 temp of 20 - 25C). Once we overcome that it's smooth sailing for any parcels because 700 temps are only 10C. 500 temps are ice cold so hail will be a concern.

I don't really see a problem in directional shear. 700 and 500 winds are generally southwest with surface winds being south - shifting southeast.

LI of -2 to -6 should be sufficient.

Helicity will be fantastic.

SBCAPE will be insane.

I am not a forecaster by any measure, however. All these numbers mean very little to me.
For tomorrow's moderate area, wind crossover looks pretty good from 850mb to 500mb, moreso in NW IA and NE NE than SE SD, as far as directional shear. However, low level shear looks pretty suspect as 0-1km progged at only 10-15 kts. Looks like since the surface low has a positive tilt, so surface winds don't really back much. Kind of similar to last Saturday's setup over KS, in that respect.

Although good instability further S in NE, reads like SPC believes moderately strong capping inversion is an issue, so proximity to lift from approaching surface convergence in SD may be requisite to break the cap. Surface moisture convergence looks to be concentrated in E Central SD and far SW MN, while more diffuse over NE. However, always the possibility of a mesolow, outflow boundary, etc. triggering something more discrete further out in the warm sector.

Fine sfc backing to the ne of the low along the wf and I don't see any veering ahead of the dryline.


I really don't like those backing 500 winds but that is due to the small wave. East of that in ne SD might be game. I could also see that end up being alot flatter(not so backed) across all of SD over the warmfront. The warfront ops look to be just as far from me as the dryline ops. I'm already starting to hate tomorrow. Both can produce, both can go to hell and one can only be on one. I'm already really paranoid about messing this one up. ETA shuts down the dryling through 6z, but that is of little value to a chaser I think. No idea why I even look at precip forecasts. I need a map and a dart board is what I need. Target right now is w-nw-n from here...somewhere in that direction...hehe.

Yeah looking more at the 18z eta and thinking about SD and warm fronts I will be on the warm front tomorrow. Pierre or bust....
"Bad" forecast be damned, you can bet your ass I'll be on that warm front tomorrow, looking further west maybe in a triangle from Aberdeen/Huron/Mitchell. The models are really tough pinning a precise location, I sympathize with H. I was pulling out my hair last night trying pick a location. Like Tim Marshall (maybe, probably, not really...) once said, "If it's June, and May really sucked, chase..."

EDIT: 0z NAM out, 991 parking over Pierre, everybody and their mothers to the triple-point. CAP maybe an issue, per usual, I'm just hoping that chasing karma will pull through tomorrow.
I'm game for meeting up if any of you are interested. Give me a pm.

Aside from being at work till approximately 4, I'm really thinking we're going to see activity drop south. MLCAPE in the 4000s the further SE you go and surface dewpoints into the mid 60's it looks like. I think we'll see initiation at the points already mentioned, but it just seems like it takes a while for things to get going. Of course my opinion goes with a big disclaimer. We'll see what happens I guess.

Final look for now: Huron to Mitchell, I will be watching. Sticking here and will head west at the first sign of towers.

Good luck all and best wishes for safety.
Argh! This one is killin' me. I'm zonked tired and sore from driving -- but the 0Z NAM is finally showing backed winds again up in northern South Dakota. Not a very strong backed 850, but it's not unidirectional/veering as it was on the 12Z run. NORTHERN South Dakota... argh. What a long haul. If I go, I'll probably target along the warm/stationary front... I'm thinking Watertown, SD is a good target from tonight's NAM, maybe a bit west.
Chase target for June 7

Chase target:
20 mi south of Aberdeen, SD.

Storms will be ongoing to the north and east of an Aberdeen to Watertown line throughout the day, while explosive new convection will form along an outflow boundary just to the south of the target area around 3 PM CDT.

Storm type and intensity:
Supercell storms producing a full spectrum of severe weather, including very large hail and tornadoes. Additionally, very heavy rain will be likely tomorrow night as storms train over the same areas that receive heavy rainfall tonight.

A series of S/WV's embedded in the upper trough flow centered in the NWRN CONUS will eject out ahead of the main vort which will be lifting through WY by 00z tomorrow. At the surface, an outflow boundary will serve as the key focus for tomorrow's weather. There is some uncertainty as to the exact location of this boundary, and NAM guidance is used here as the GFS was too far to the S. MCS development is already underway in NE/SD/ND, and by mid-day tomorrow, these storms will be exiting the NERN corner of SD, laying down an outflow boundary that will be situated along a Mobridge/Redfield/Brookings line by mid-afternoon. NAM and GFS analysis suggests extensive low cloud cover N of US-212 based on H85 RH and UVV fields, however extensive warming of the BL along and S of I-90 throughout the day along with thermal advection into the target area will tend to break clouds up by early afternoon. LCL levels should be in the 1000m AGL range in the target area with the broken cloud cover and outflow-cooled air immediately to the north of the boundary.

Prodigious amounts of moisture and instability will be available for tomorrow's convection. 00Z KABR sounding showed a nearly 150mb deep moist layer along with a surface dewpoint of 59F. Elsewhere in ERN SD, 00Z dewpoints were in the 60F to 65F range, and the 00Z NAM has initialized well to moisture both at the surface and H85 levels. Given advertised widespread heavy rainfalls tonight, it is possible that evapotranspiration tomorrow may result in even higher dewpoints. Guidance suggests MLCAPEs in excess of 4000J/kg by late afternoon, in addition to deep-layer shear to 60kts with the approach of an 80kt H50 jet max, and 0-3km SRH's to 300m^2/s^2, supporting a potentially major severe WX outbreak.

- bill
I don't like the timing of everything as indicated by the 0Z ETA/NAM...and then I looked at the GFS. I wish I hadn't done that.

Anyway, it looks like it could be a pretty late show. In some ways, that's no big deal, as there's plenty of sunlight to work with this time of year (and it gives me extra time to look over things in the morning). But, with the strong cap, I'm worried whether or not our upper level support will arrive early enough to aid in initiation. I'm also worried about the front hanging back too far north and west. SE SD is an easy enough drive (2-3 hours), but Pierre's a different matter.

I'm on the fence.
Tough call ... Quick look at data:

0z GFS: 0-1 km SRH = 175 m^2/s^2 in central SD to 100 m^2/s^2 further to the east; MLCAPE = 3500 J/kg west of Mitchell to 4508 J/kg in Yankton; 0-1 km EHI = 3-4 west of Mitchell, with 7.7 in O'Neil, NE; LCL = 1200 (1000 north of Mitchell); LFC = 1400-1600.

0z NAM: 0-1 km SRH = 90.1 m^2/s^2 in Yankton to 137 m^2/s^2 in NE SD; MLCAPE = 5000 NE of Mitchell; 0-1 km EHI = 3.5 in Yankton; BL-6 km shear = 40.5 east of Mitchell; LCL = 2000; LFC = 1900-2000. Lid strength = 3 most areas, with 1 north of Sioux Falls.

My interpretation of this mess: I was interested in tomorrow until looking at all this tonight - and now I'm just completely on the fence. Instability and shear look great again - BUT don't progged LCL and LFC heights concern anyone? The cap looks do-able even with a relatively high lid because I think the area will see sun and there will be lots of heat. Looks like stronger helicities to the south tomorrow, with more instability to the north (sounds a bit like Saturday). I think I would probably go with the frontal boundary tomorrow - looks like initial storms firing on the DL will possibly be way west, as in the Black Hills. I think high CAPE/shear combo is more than enough to support supercells ... but I do not anticipate a large number of tornadoes at this time due to high bases. It just seems more likely to me that lines of hail producers will likely develop in this elevated environment. This is a borderline call because I really wanted to come up there, but coming down with a cold now and now feeling unsure if it will truly be worth the trip. Somebody will have to talk me into it before morning, I guess ... we've got about four hours or so. :)
Today is about as clear as mud (for a layman like me) - but I've read the Day 1 outlook that Rich Thompson wrote and enjoyed it and agree with it.

I AM concerned about LCL and LFC heights.......I guess that is something that will be resolved later in the day. If I were more knowledgeable, I'd be looking at this morning's soundings.......but I'm not. The models were forecasting a fairly stout cap and I am curious to know whether this will verify or not.......but alarmingly the RUC trend for through the morning at least is to BUILD the cap - almost up to the Canadian border with the +10 line at 700mb. While I know it's June and anything CAN happen - I'm a little concerned about the trend to build the cap throughout the day......that's not going in the right direction.

Of course.......I'm not chasing today.