7/20/06: FCST: WY, CO, SD, NE

[Justin Walker]

In addition to storms over the great lakes, the WRF is forecasting a 40-50knt speed max moving through southern Montana and northern Wyoming. A weak sfc low develops in the afternoon to help back sfc winds from the SE. SSE to S 850mb winds at 20-25knts will help enhance lowlevel shear. Moisture will be in place with low 60's Tds all the way to the I-25 corridor and upper 50's in southeast Montana. This will give CAPE values of 1500 J/Kg in Montana and southern WY/northern CO values in the 2500 J/Kg range. LCL heights will be workable with T-Td spreads of roughly 20-25 degrees. We should have supercells develop early with a couple of tornadoes, then transitioning to MCS's after the cold pools rush out. I will be going out targeting most likely somewhere in eastern WY.

 

[Justin Walker]

The 0z run of the WRF tonight doesn't bring the shortwave quite as far south as yesterdays run. The 50 knt flow stays in Montana decreasing down to 25 knts over northern Colorado. The deep layer shear will be sufficient for supercells tomorrow all down the frontrange with 55knt in Montana to 40 knt in extreme SE Wyoming. The 0-3km helicities values will be in the 250-300 m2/s2 range, but the lowlevel shear will be on the weak side across SE WY and N CO. By 18z there is a CAPE bulleyes north of Cheyenne of 3000 J/Kg. That is quite a bit of instability for that elevation. There will be wwa throughout the day strengthening the cap, so it will hold most likely hold convection off until late afternoon. My target will be up I-25 to SE Wyoming.

 

[Terry Tyler]

Well, i just got a look at the SPC mesoanalysis, and the forecasted sounding for that area...The only things im liking is the 4000+ CAPES, and 65+ Tds. Probably going to be some pretty big hailstones up by Sterling, Ogallala, but it looks like the deep-layer shear isnt going to get much more than 40kts. The directional shear is ok, but i think im going to stay near the urban corridor for today. It looks like stuff is coming over the foothills, and might get better organized as it crosses I-25 into better moisture.

 

[Jonathan Merage]

Sitting at the Holiday Inn, Cheyenne. Initially we were hoping the incoming shortwave would hit northeast of here, since we're still lacking any good upper support. Now it looks like the best chances for supercells will probably be into the Tri-State area (CO/NE/KS).

At this time, LCLs, LFCs, & sfc flow look the strongest in that area. However, this being the High Plains wouldn't be too surprised to see a supercell spin off the foothills & rapidly develop a lowered base as it moves into the higher Tds, sfc flow & instability. In fact, we're watching a couple strong towers that just shot up to our NW. Cores look to be over northern Larimer County. Ughh--it's HP :wacko:
Will provide updates as we go...