7/13/06 FCST: NE / SD / ND / MN

[Ryan Pfannkuch]

Thought I would see if anybody else had some thoughts on the potential along the sfc trough moving into eastern SD/NE Thursday afternoon....it always seems like this time of year some nice suprises happen out in the O'Neill area so I cannot completely ignore this one.

The 18z WRF shows storms developing/moving southward down the Hwy 14/Hwy 81 corridors during the afternoon with some nice low-level turning according to forecast soundings for the Norfolk area BUT no more than 30kts of flow at 500mb limiting deep shear. I'm sure LCL's will be up there with sfc temps fcst into the 90s but moisture also shouldn't be as much of an issue as it has been so many times before this year. I've seen enough interesting things happen in this area during July-August on big CAPE days that even the marginal deep layer shear could be good for some decent structure on some big hailers.

Although I am far from committing to chasing at this point, it might be kind of tempting to play the Niobrara-Norfolk corridor and see what the day brings. I'll put it this way, how much less would I see than I did in May/June in the eastern NE/IA area?

 

[Justin Walker]

Looking at the 12z NAM from the 12th holds some possibility of a chase day. The deep layer shear is better the further south you go into southern NE and northern KS. The best backed winds are across northern KS but the mid level flow is only 25 knts, but add in 15 knt southeasterlys at the sfc and might have a chance for supercells. Helicity values will be in the 300-400 m2/s2 range. The moisture is good with upper 60 Td's across the region. Sfc temps will be high, approaching the upper 90's, leading to high bases. This is almost enough to lead me away from Denver, but I will decide in the morning. :unsure:

 

[Scott Olson]

I'll definately be out tommorow. Strong instability should be present across parts of the Eastern Dakotas/Eastern Nebraska. With at least 30kts of deep layer shear and 25-30kts of 500mb flow. That's on the weak side and im not to impressed with the 850 flow. But still the directional shear appears to be adqueate for some supercells. While temps are hot and LCL's are high, they really aren't any higher than most setups this year. Models have been indicating intiation near SD/NE border moving SE into better moisture. Im not sure if I believe the 75Td forecast for E NE from the NMM WRF. But if that does materialize, we would be looking at a 15 degree defecit at 0z.

Given strong 0-3km CAPE, moderate helicity across the region, decent shear vector orientation and LCL's that while high, aren't extreme. It does appear a decent threat for some supercells in NE Nebraska & Eastern South Dakota. I'll most likely be focused on NE Nebraska.

 

[Mike Hollingshead]

I tried not to post anything on this as I'll just jinx it, but I'm not having much luck. I really like tomorrow in nc NE. The 0z trend is certainly a nice one. It now moves the stronger flow(which increased itself) over the sfc trough. The 500mb temps are a smidge cooler and 700 is still very much in check. The concern is that low level flow. Does anyone have any thoughts on what it does to the low level flow between 18z and 0z? Does it kill it on the model because of convection? If at 0z it is what it shows at 18z I think tomorrow could be a very fun day somewhere. My current target is O'Neill NE. A word about tomorrow, watch for those boundary anchor storms that grab it and ride it south or even ssw. My 2 July tornado days in nc NE were that way.

Also about tomorrow, there were some posts about the highway between O'Neill and Valentine being a long mess of construction. I wonder how much of that is still going on. I guess one really doesn't have any other option if you wind up in O'Neil and want to go west.

 

[Jeff Snyder]

Does anyone have any thoughts on what it does to the low level flow between 18z and 0z? Does it kill it on the model because of convection?
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Looks like a good possibility to me. The NAM blows up QPF across a couple areas in NE, and you can see the complicated effects of this convection on many different fields and levels. For example, check out the 2m T field valid at 0z tomorrow... Or many of the 850mb fields... Or even the 500mb fields (like 500mb vort). Of course, that solution may verify if the convection forms exactly where indicated. Otherwise, it's tough to get a grasp on the specifics of the synoptic-scale environment given the model's modification of the forecast environment owing to convection.

 

[Justin Turcotte]

Tossing ND and MN into the mix. Convection in northeast ND this morning should provide a differential heating boundary to interact with the surface trough this afternoon. Perhaps some locally enhanced low-level shear in northeast ND and northwest MN along this axis during the afternoon. Holographs along the trough suggest the potential for supercells. Damage reports along with a replay of radar from yesterday evening suggest a tornado hit Coleharbor, ND petty hard. Not much different in the cards today, only the threat will be further east in or near the Red River Valley. A pretty good H50 punch in southeast SD and northeast NE combined with stout instabily should allow for some rotating storms there as well. Preliminary targets would be Hillsboro, ND and Norfolk, NE.

 

[Mike Hollingshead]

MD out for the area now

I guess I just wonder how extensive this early stuff will be and how much will be able to fire later to the west of this area. I'm shifting my target south more to the highway 91 area and plan to chase some of this early stuff on the way west and figure out later wether or not there will be more ops to the west/sw.