6/10/2010 FCST: WY/NE/SD/CO

[Dean Baron]

Surprised tomorrow hasn't been brought up yet. SPC currently has a 30% non-hatched area over the northern half of NE and southern half of SD with the new SWODY2 coming out shortly. Looking at the new WRF I like western Nebraska the best. Front pushing east/southeast with good moisture and surface heating. MLCAPE AOA 3000 for the majority of the area with pretty good 0-3km and decent 0-1km helicities. H85 winds out of the SSE, H7 out of the SSW, and H5 out of the SW. The WRF also has a little compact vort max over the eastern NE panhandle by 00z, I dont know how long that's been on the models for, but I like it. H7 temps are warm thru 18z but cool from north to south by 00z, but still pretty warm say south of Highway 2 in Nebraska. GFS has a bit of a different solution, keeping the center of the low farther to the south in northeast CO/northwest KS but still wraps a large swath of strong instability around to the north of the low. IMO it's harder to define a boundary on the GFS, and upper level winds look suspect on the GFS. Fow now I will go with the WRF and target Bridgeport, NE. GFS also shows cooling H7 temps from north to south in the same general area across NE as the WRF shows. Gonna leave tonight, it's a long haul out there from Minneapolis.

 

[Logan Karsten]

I too am surprised a thread hasn't been made for this potential event. I pretty much agree with everything you said Dean. Low-level wind fields look very favorable for tornadic supercells to fire across north-central and western Nebraska late tomorrow afternoon.

 

[jamesmseitz]

I thought about starting this but I started Friday..... That said. I too think that the cool pocket will erase the cape and the window for tornados exist as well before the MCS. Leaving Twin Cities at the crack of dawn (which is about 5 am up here )

 

[Eric Bucsela]

I thought about starting this but I started Friday..... That said. I too think that the cool pocket will erase the cape and the window for tornados exist as well before the MCS. Leaving Twin Cities at the crack of dawn (which is about 5 am up here )

Erase the cap or erase the cape? Actually, I don't think either will be a problem. When I first glanced at this setup, I thought of May 29, but only because of the region (~Sidney to Valentine NEB) and the cold front. But I think this one will be much better because the zone of overlap for good shear and CAPE is much broader and pre-frontal. My prelim target would be around Hyannis NEB (same as May 29!).

 

[Rob H]

Fow now I will go with the WRF and target Bridgeport, NE. GFS also shows cooling H7 temps from north to south in the same general area across NE as the WRF shows. Gonna leave tonight, it's a long haul out there from Minneapolis.

Leaving from MN in the next few hours as well. The 00z NAM is shifting everything slightly south and is leaving me scratching my head. At least the WRF and the GFS seem to agree somewhat. The WRF progged reflectivity is showing two beautiful cells going up on the WY/NE border @ 21z and moving ESE into NE - I would love to see that verify. I'm torn between the warm front and the upslope play, but based on the last two weeks, I'm liking the upslope odds better. Anything on 385 (Bridgeport included) doesn't sound like a bad start.. I just hope things don't move into Cherry County.

 

[Andrew Stoller]

I hate to be the party pooper, but I've been cap busted the last 2 days in CO, and 700 mb temps are the same or worse then yesterday per the RUC. However, today the western trough is closer so we may get some aid via that with some energy ejecting out. Also, the RUC is trending much further north with the surface low which once again places the main upslope regime into the Laramie range. Don't be surprised if you find yourself in Goshen county WY again!

:edit: although the RUC is showing the surface low further north, the east west portion of the dryline is still along the Palmer Divide with a nice cell showing up around Denver by 21z, so it's once again a crap shoot whether to go north all the way, or linger south.

 

[Andrew Stoller]

OK, after further analyzing things, all the models and water vapor imagery show a well timed impulse coming through CO and into western NE by 00z, so that could possibly get something to break through the cap. Given the cap and the timing of the impulse, it might help keep any convection very discrete and explosive in one particular area. SPC sure seems to think so.

 

[Jerry Prsha]

CAPE

Given the cap and the timing of the impulse, it might help keep any convection very discrete and explosive in one particular area. SPC sure seems to think so.

I can't help but focus a bit on the eastern portion of the Moderate Risk area; around Kearney because of such high RUC predicted CAPE values. ...Perhaps a bit south of that location right around dusk?

I also think the MOD Risk will be stretched North through central NE through early nighttime hours.

 

[Adam Adkins]

CO should be added to this thread. The RUC breaks out the main precip in CO and moves it east into Nebraska from there. Good CAPE and good shear profiles certainly warrant CO in this thread.

 

[Skip Talbot]

I can't help but focus a bit on the eastern portion of the Moderate Risk area; around Kearney because of such high RUC predicted CAPE values. ...Perhaps a bit south of that location right around dusk?

Watch out for the cap off to the east. The RUC is showing it to be pretty stout out that way, but there is good erosion near the panhandle into Wyoming. Your best shear and upper level dynamics are going to be further west closer to that trough as well. I'm staying put in Kimball, NE for now where I the RUC forecasts extreme instability, backed surface winds, and 40-50 knots of deep layer shear. With the cap eroding by late afternoon and the trough nosing in, I imagine wiill see storms start to pop late afternoon early evening across eastern WY. Keep an eye on CO for more isolated/discrete activity although shear will be weaker down there.

I also think the MOD Risk will be stretched North through central NE through early nighttime hours.

I agree, there is strong instability forecasted all the way into South Dakota and the deep layer shear is greater up there as well.

 

[Mike Kovalchick]

HRRR model would suggest Weld county, CO and points to the East is the place to be today. It has been showing the Southern end of a line of storms being there..suggesting capping further South will keep convection in check. Since Weld county has reported more tornadoes than any other county in the U.S over the last several decades, it might be on to something! (Landspout country obviously but with the high dewpoints that are forecast for the area-some real tubes should happen.)

 

[Adam Adkins]

What I am trying to determine is whether or not the CAP will be broken and storms will fire in Colorado today. I made the mistake of chasing CO yesterday only to realize that the CAP was not to be broken. To me is almost seems like it will be even MORE DIFFICULT to break the CAP today than it was yesterday - and if it didn't even break yesterday - then I question the sanity of anyone trying to chase northeast CO today. It will certainly make me very cautious. But another very interesting thing to me is that the CAP doesn't decrease up north - it is uniform from CO into WY. Does anybody have any thoughts as to initiation in northeast CO?

And I recognize the RUC breaks out a supercell in northeast CO, but is shows that cell strong then erodes it to nothing. Could this be a result of the CAP killing it?

 

[Mike Kovalchick]

What I am trying to determine is whether or not the CAP will be broken and storms will fire in Colorado today. I made the mistake of chasing CO yesterday only to realize that the CAP was not to be broken. To me is almost seems like it will be even MORE DIFFICULT to break the CAP today than it was yesterday - and if it didn't even break yesterday - then I question the sanity of anyone trying to chase northeast CO today. It will certainly make me very cautious. But another very interesting thing to me is that the CAP doesn't decrease up north - it is uniform from CO into WY. Does anybody have any thoughts as to initiation in northeast CO?

And I recognize the RUC breaks out a supercell in northeast CO, but is shows that cell strong then erodes it to nothing. Could this be a result of the CAP killing it?

The ouflow surge has messed up the low-level wind field. When a good upslope flow gets re-established this afternoon..along with height falls coming in the West..initiation should be on the lee side of the Front Range. Mid-low winds are strong enough to propagate storms off the foot hills into the Plains.

If the height falls don't arrive until later or if ESE wind upslope doesn't get established as expected..a cap bust would be in the cards.

 

[Jesse Risley]

What I am trying to determine is whether or not the CAP will be broken and storms will fire in Colorado today. I made the mistake of chasing CO yesterday only to realize that the CAP was not to be broken. To me is almost seems like it will be even MORE DIFFICULT to break the CAP today than it was yesterday - and if it didn't even break yesterday - then I question the sanity of anyone trying to chase northeast CO today. It will certainly make me very cautious. But another very interesting thing to me is that the CAP doesn't decrease up north - it is uniform from CO into WY. Does anybody have any thoughts as to initiation in northeast CO?

And I recognize the RUC breaks out a supercell in northeast CO, but is shows that cell strong then erodes it to nothing. Could this be a result of the CAP killing it?

I think you would have to look at the strength of both the H3 and H5 for evidence of a shortwave that might provide the synoptic lift necessary to overcome the CINH.

Daytime heating will also be a key factor, because if the convective temperatures can be realized, the CINH would be less of an issue. Due to the fact that synoptic scale models are trying to resolve mesoscale details, it will be important to watch these mesoscale features very closely this afternoon.

While the upper level dynamics are not momentous, you're going to have good localized dynamics (convergence and shear) INVO the low. The 00z RUC sounding near the NE/CO/KS border shows a massive dry air intrusion, which should bolster lapse rates. While surface winds might be somewhat mediocre, there should be more than enough lift to generate supercells across the region later this evening.

 

[Warren Faidley]

TARGET: NE CO. Think the secret today will be refining surface features by around 20-21Z to pinpoint "sustained" convective target. Per SPC forecasting products, most unstable area ATM is in NE, CO and slightly to the South, well within favorable shear. Like yesterday, I would not be surprised to see a storm or two form between DEN and PUB. The cap might be an issue, but the broken CU field looks better than yesterday's capped off appearance. I did notice LCL's are in the 2k range in SE WY and SW NE. This might be a problem later further north.

W.