07/08/04 FCST: Northern Plains

Larry J. Kosch

As requested by Mike Hollingshead, a FCST thread for 07/08/04 has been started. Post your forecast discussions here. Thanks. 8)
 
http://weather.cod.edu/forecast/ETA/etaUS_...2_thetae_78.gif

http://weather.cod.edu/forecast/ETA/etaUS_...2_thetae_84.gif

Get that trend to change and get that to yank itself nw into the area in nc SD and there could be a very nice show up there Thursday afternoon. I don't exactly understand why it's doing what it's doing with the sfc flow, but it is out there a ways. So if I'm going to ignore anything it will of course be the sfc.

http://weather.cod.edu/forecast/ETA/etaUS_..._3km_hel_84.gif

Sfc and 850 flow changes a bit and this should go nw with it, and the instability and would be setting right under this.....

http://weather.cod.edu/forecast/ETA/etaUS_..._500_spd_84.gif

It's wanting to push some sfc feature east, then between 18 and 0z it starts to back the sfc winds.

http://weather.cod.edu/forecast/ETA/etaUS_...2_thetae_72.gif

http://weather.cod.edu/forecast/ETA/etaUS_...2_thetae_78.gif

http://weather.cod.edu/forecast/ETA/etaUS_...2_thetae_84.gif

Again.... I myself do not get this and beings it's so far out it might be more realistic to think we could take that 18z frame out of the middle there and assume a good se flow all day taking that juice much further nw. That would be GREAT.

Thoughts, reasoning? With the strong 500mb winds coming out would this result in a sfc reflection briefly?

For the cape lovers out there......

http://weather.cod.edu/forecast/ETA/etaUS_...S_0_cape_84.gif

I'm placing that centered over PIR for my model....lol. And all that helicity is going with it.

Mike
 
Nevermind I see what it's doing. You can see the wave it kicks out. It shows up well at 700 and 850mb.

http://weather.cod.edu/forecast/ETA/etaUS_..._850_spd_72.gif

http://weather.cod.edu/forecast/ETA/etaUS_..._850_spd_78.gif

I hope it doesn't happen, but if it does I'd be sure to be on it.

I just want to be west further under this with some instability too...

http://weather.cod.edu/forecast/ETA/etaUS_..._250_spd_78.gif

Plenty of speed at 500mb though with the lead wave kicking out.

http://weather.cod.edu/forecast/ETA/etaUS_..._500_spd_78.gif

I guess if I can imagine the cape being more nw without any lead disturbance I can imagine it being further north with the lead disturbance. Just stay west of northern MN though!

Also..... Wednesday could be a pretty nice day too in southern SD down into NE if anyone wants to start a thread.
 
By the looks of it, for us in Canada, the best bet is gonna be southern Manitoba on Thursday. That's gonna be tough to get to for me so I'm looking at maybe chasing Wednesday afternoon unless this will be the "storm of the year" type of system (which I doubt).

Someone give me a reason to take the day off work and maybe I will make a day of it on Thursday. I'd rather chase close to home, but if tornado warnings begin early in the day, I will be kickin myself for not going. :?

Jared
 
After tonight's 0Z run, which is very simlar to the previous solution, I agree with that Thursday deserves serious attention. I also noted that the 84 hour output shows the main system digging in and organzing a dry line at 12Z Friday morning. A two-day show is worth the drive for me if the solutions hold up.

I guess the most remarkable features right now are the strong dynamics aloft (though southern SD could be in a more favorable region relative to the jet I suppose) and the extreme instability. The warm front in ND is a possible play as well, though low level wind fields taper off up there per the 0Z. Have to see how it shapes up.
 
Thurs/Fri Setup

Keeping up with the model output for Thursday & Friday's potential severe wx setup, ETA's been wonderfully consistent in the past few runs with the extreme intabilites (>5500 j/kg over e. central/northeast NE) and a *tropical* moisture regime over a large area from southeast SD, all of eastern NE, western IA, & most of ne/n.central KS. Coupled with the extreme instability, the way the dynamics are setting up later this week (sfc winds backing over the whole area & 850s strong from the south), I wouldn't be surprised if SPC upgraded to a MDT risk over eastern NE & s.central/southeast SD in the next Day-2. At this time, the only factor that concerns me is how far north & west the 500mb trough stays. The areas with the most instability seem too displaced from the strongest mid-level winds for any supercells that do form to tap into the upper support they'll need to stay strong. Hopefully though, the ETA will change it's mind about that in the next day, and we'll have a nice jet streak plowing into all that instability. :p
 
I'm hoping that instability will meander down into southeastern NE. I'd much prefer to do some local stuff than take Ye Olde Bucket of Rusted Metal outside of any area further than a few counties over.
 
Too much explaining for a late night....zzzzzzzzzzzzzzzzz
 
SPC for Friday

UH-OH!! :shock: Looks like the SPC has pushed the "much-anticipated" Northern Plains action back to Friday. The SLIGHT risk for the Northern Plains is now listed in the Day Three box. That means a prolonged chance for storms in the Central Plains. Better change your chase plans. :roll:
 
uhhh its listed as slight for the day two and day three.. Why would anyone change their chasing plans?
 
KFSD seems to agree with the projection. See below

“A SIGNIFICANT SEVERE WEATHER EVENT IS POSSIBLE ACROSS PARTS OF
THE AREA ON THURSDAY. LOW PRESSURE WILL DEVELOP OVER THE HIGH
PLAINS THURSDAY MORNING. AS THIS OCCURS...A WARM FRONT WILL MOVE
NORTH FROM KANSAS INTO NORTHERN NEBRASKA AND NORTHWEST IOWA BY
THURSDAY EVENING. THE ATMOSPHERE ALONG THIS WARM FRONT IS
EXPECTED TO BECOME EXTREMELY UNSTABLE THURSDAY AFTERNOON AND
EVENING.â€￾

http://iwin.nws.noaa.gov/iwin/ne/special.html
 
Perhaps we might see some local Omaha area action. I was out of town during the big Hallam storm that came through the area.. but perhaps this could be a good show :)
 
http://www.wxcaster.com/modelskewt.php3?mo...&STATIONID=kgri

12z eta run for grand island. I'd think anywhere in ne NE or se SD should work. ETA keeps blowing up this convective bomb in ec NE but this is getting too far south of the better mid-upper flow for my liking. I hope this takes place further nw and also that the low levels improve. Almost too much backing further north. I would suspect a big ol back building day could be in the works if this happens further south. That front needs to get it's butt north that is all there is to this. If I had to go somewhere now it'd be Norfork Nebraska just to stay south. It'll be easier to fix the goof from the south then it would from the north tomorrow. I'm getting images of July 20, 2003 in my head and I do not care to repeat that day.
 
Mike,
I agree. There's a well-defined instability axis (LIs -12 to -14) that's forecast to extend over n.e. Kanasas leaning back to just west of the GRI area. Dews supposed to be in the 70s across the entire area, and CAPEs stay nice & high straight into SE Nebraska as well. As the warm front advects into northern KS/ s. central NE, hopefully synoptic lift from the front combined with the shortwave moving through will spark off a few sustained supercells before dark tomorrow. SPC highlights the strong cap as their biggest concern, but I'm sure all that instability will break through before late. Hopefully that GRI Skew-T will actually verify & yield some explosive supercells around that area. Man, I'm printing out that sounding & FRAMING it! :shock:
Jon
 
Guess I'll be the only one to add some negativity to this forecast - but I think R. Edwards discussion is spot on. Very potent cap - note the 700 mb thermal ridge axis lies right over the region of interest at 00Z:

http://www.wxcaster2.com/CENTRAL_ETA_700_G...WINDRH_36HR.gif

I'd ignore the trough / moist anomaly over western IA into eastern NE - this feature is pretty suspect, as it is a continuation of convection from western Dakotas tonight - the hard right turn 12Z Thursday is a new feature in the morning ETA that is not supported in previous runs or in other models. Expect the complex to skirt northern SD. SPC also discounts this convective feedback feature in IA/NE. Expect instead for there to be a lack of sharp boundaries present across NE during the day, and w/o any upper level support (instead shortwave ridging - adding to the cap strength), I'd be surprised to see convection much before dusk along the WF. Agree also w/ SPC that convection should begin over the Black Hills region, where better moisture should be present than forecast owing to overmixing by the ETA. If I could be anywhere, I'd probably play the storms rolling off the Hills as they approach the better moisture axis - perhaps somewhere from VTN to PHP. Back further east, storms probably have the best chance in the 01-03Z time frame w/ the decoupling of the boundary layer, w/ consistent model guidance suggesting the SUX area. Otherwise, looks like convection to the NW should roll out into the LLJ axis over E NE overnight.

Others are welcome to hack/comment on my forecast - which is of course subject to change as the real atmosphere starts to reveal its cards.

Glen
 
You folks are all hyping the positives, granted there is extreme cape and instability. However there are negatives and concerns to consider. Note that the 700mb temps will be high and may prevent convection. In the areas that have the best sfc to 850mb flow there is no decent 700mb and especially no 500mb flow. The upper jets are weak and mostly absent which could eliminate storm venting. IMO there will certainly be some hail monsters and some high winds from storms with no vent collapsing into microbursts. Tornadoes could occur (big maybe) near magical boundary intersections if there are any or more likely IMO behind the boundary in cooler air - these being very diffuse and spread out tornadic events.

If the 500mb and up winds can come further south and intersect the boundary area and convection can initiate in that area then certainly there is a chance. Right now I don't see a strong showing of this on the models though.

Will SPC go Moderate? I think they will base that on their belief for where convection will actually occur and what the risk is in that area. My guess is they will go Moderate initially probably in a fairly small area to cover their butts, and if convection and ingredients don't seem to be coming together they will downgrade to Slight.

I think this could potentially be a significant severe event based primarily on instability if a large area becomes uncapped and convective. Once again primary risks will be large hail, damaging downbursts, and a few scattered tornadoes possible.
 
Originally posted by Bill Tabor

If the 500mb and up winds can come further south and intersect the boundary area and convection can initiate in that area then certainly there is a chance. Right now I don't see a strong showing of this on the models though.

I would have been saying the same thing as you last year, but not after experiencing some of the events this year... Last year I would have said that we needed >55kts at 500mb for a good event. However, this year certaintly didn't have too many of these setups. For example, check out the conditions near the 6/12 Mulvane supercell... Winds were, by more typical cyclic tornado events, relatively weak, with general 25-40kts flow above ~800.. For most decent chase days this year, mid-level flow has been 35-50kts...

More importantly, despite relatively weak mid-upper flow, 0-6km shear is still progged by the ETA to be quite favorable for signficant supercells: http://www.wxcaster2.com/CENTRAL_ETA_250M-...VECTOR_36HR.gif ... General 40-55kt 0-6km shear is very favorable for supercells, especially given the strong/extreme instability. I longer put much into absolute wind flow. Rather, I put more into 0-6km bulk shear, which has worked well so far this year...
 
Hey if anyone is coming up for this event, drop me a line...i live up here in SE SD and know my way around quite well. Maybe I'll see some of you out there! Keep you're eye out for the black monte carlo driving in circles trying to find the best observation point.

Anways, the numbers seem to be adding up, I'm expecting a signifigant event. The models are reminding me of a souped up picture of June 24, 2003, but hey, I doubt that'll happen again. Time to go dust off the camera!
 
Now I asked 3 days ago if the cap was going to be a big issue and a chaser to be named later said "no" as he droolled all over the floorboards of his truck while stuffing it with supplies for a 2000 mile road trip. I just hate to think that he may end up driving all that way for nothing, but boy if that cap should break - KABOOM!!!!!!!! :blob6:
 
Originally posted by Anthony Petito
Perhaps we might see some local Omaha area action. I was out of town during the big Hallam storm that came through the area.. but perhaps this could be a good show :)
Omaha got some wind and small hail but no real action that day. The city of Omaha has been REALLY lucky this year and with as many high risks as there have been in this area I always worried its luck would run out.

As far as this system goes, I just charged the camera, got tapes and got the laptop ready to go.
 
Hm, enticing day, but a big risk for a bust. 7000+ J/kg suggested by the ETA near HDE by 00Z ? Mind boggling! Not worth much though with 14+ C 700 hpa air. I'm more inclined to play as far east as I absolutely can. May take til 8 PM or so for shortwave energy/warm front to break cap near H14 in C Nebraska.

I like southern Nebraska, but just too many questions until we see the sun rise and get some real data. But boy, if it's sunny north of the warm front tomorrow, watch out. Right along I80 and points a bit north are where I'm interested in. As long as the 700 hpa winds are 15 kts + and the 500 hpa winds are 30 kts +, any storm that develops will have a very good chance for deep rotation. (I might be a bit different in that I love events between 30-50 kts at 500 hpa, and not a fan of anything stronger, because it makes storm motion too fast.) The low level tornado parameters are fantastic. UL winds typical for July in Nebraska, more typical forecast soundings for supercells that sit and drop 5 inches of rain in one area.

Finally, I am really intrigued by subsiding air ETA projects ahead of the shortwave. Might keep us mixed a bit but will also keep us mostly sunny. I am thinking as of tonight of starting near Superior, NE, playing the southerly warm front, and seeing what happens from there. Will stay home as absolutely long as I can. There may also be a high plains play near the surface low out to the west. 14-15 C 700 hpa air isn't as big of a problem out there it seems. I'm not that gutsy though.
 
Yeah when you say the mid-levels are too weak one should look at some historic events and see what CAN happen. Due south sfc winds at 10knts and 30-35knts at 500mb might not be that great. Back those sfc winds and 850 flow and that 30-35knts become much more favorable. As for all the cap talk. Screw the cap. It's nearly pointless to even look at the thing, I mean seriously. If you are a chaser, you CHASE the cap. I'd worry more if it was weak then if it were insanely stout. I've seen too many days where the cap was progged to hold all day into the night and crap went up early, while I sat at home feeling sorry for myself. No thanks. I'll drive and kick myself for 5 minutes if it holds(10hours driving today doing just that)...beats the hell out of kicking myself for days, months, years? For forecasting for others, ok, fine lets forecast what we think will happen with the cap. If you are a chaser, you'll learn to not waste too much time fussing over the cap. Fuss all ya want but you're best off going and finding out 'the hard way'. And ya know, same almost goes with weak mid-level flow. Amazing what a storm propegating and back building down a boundary does not need.

Mike....here's to the positives.....(1 being it's not winter)
 
Originally posted by Jeff Snyder+--><div class='quotetop'>QUOTE(Jeff Snyder)</div>
I would have been saying the same thing as you last year, but not after experiencing some of the events this year... Last year I would have said that we needed >55kts at 500mb for a good event. However, this year certaintly didn't have too many of these setups. For example, check out the conditions near the 6/12 Mulvane supercell... Winds were, by more typical cyclic tornado events, relatively weak, with general 25-40kts flow above ~800.. For most decent chase days this year, mid-level flow has been 35-50kts...[/b]

I don't have quite as high of a threshold as >55kts at 500mb. I've always put the minimum closer to 20kts to 25kts or so. True Mulvane had about 35kts 0-6km shear.

<!--QuoteBegin-Jeff Snyder

More importantly, despite relatively weak mid-upper flow, 0-6km shear is still progged by the ETA to be quite favorable for signficant supercells: http://www.wxcaster2.com/CENTRAL_ETA_250M-...VECTOR_36HR.gif ... General 40-55kt 0-6km shear is very favorable for supercells, especially given the strong/extreme instability. I longer put much into absolute wind flow. Rather, I put more into 0-6km bulk shear, which has worked well so far this year...

As I understand it 0-6km shear is calculated by summing and then averaging the incremental layers of air in 50mb increments from near srf to 500mb. This results in an overall average value for calculating the shear across this area. However the problem with this as I see it is significant layers could be missing and the value would still look reasonable. However it would still be possible to kill tornado potential. I certainly don't rely just on the bulk shear values, and I think that's one of SPC current problems with their forecasting tools. I had a conversation with Rich Thompson and he mentioned that parameters such as the STP can be misleading because they don't always look at individual layers of air. He said he plans to revamp it so that if values fall below a certain threshold then the parameter would go to zero. Anyway 0-6km is still something to consider in the mix.

For Thursday I was down on it because I saw 500mb being near 20kts - possibly lower on the 12z ETA for the 7th. The upper jets were almost absent as well. Looking now at the latest 0Z run I see it is showing slightly more favorable 500mb, 700mb, 850mb and surface IMO, the upper winds are still a bit lacking though and CINH is still questionable. I notice however that the ETA does show precip and so does the WRF for portions of NE that I would be interested in.

I'm thinking there could perhaps be a few torns in NE if convection breaks out, but the very slow upper winds may mostly prevent the supercells from lasting long enough to do it well. I think upper winds and cap is the greatest threat right now - all else is basically a pseudo reasonable go.
 
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