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6/17/08 FCST: CO/NE/KS/OK/TX

Joined
Mar 19, 2005
Messages
558
Location
Independence, MO
The early part of this week should see a series of typical early summer northwest flow severe events over the western High Plains as upper disturbances ride down the lee side of the ridge of high pressure currently parked over the Great Basin. While there will likely be severe wx over the area over a course of several days, Tuesday looks to have the greatest potential for significant severe wx, including possible isolated tornadic supercells.
An instability axis will be oriented northwestward from the Red River Valley to eastern Wyoming. There will be a fairly stout capping inversion in place, however it should erode from northwest to southeast along the instability axis during the mid to late afternoon hours, with initiation taking place on the higher terrain of eastern CO/WY and moving southeastward into portions of western KS and the OK/TX Panhandles with time.
Very strong directional shear will be present across the entire target area, but the southern portion of the target area will have anemic mid-level flow, resulting in initial supercells quickly transitioning into linear segments with damaging wind/large hail the primary threats. Further north across northeastern CO and western NE, the mid level flow will be enhanced thanks in part to a nice little 55 knot mid level jet streak moving down the ridge in the early evening hours. This combined with strengthening low level flow and mid 50's dewpoints should provide an environment favorable for persistent supercells, some of which could be tornadic given the favorable combination of strong directional shear, copious moisture return values (for the High Plains) and moderate to strong instability.
The latest model trends are keeping convection fairly isolated, which could mean we actually might see something that we have yet to see this season - DISCRETE TORNADIC SUPERCELLS! I hope I haven't jinxed it by saying it... lol. While this will probably be a very localized event, I wouldn't be surprised to see a mini-outbreak across the NE Panhandle and northeast CO with a half dozen or so tornado reports.
Something similar to the rogue tornadic supercell of June 27, 2006, which produced a total of 8 tornadoes as it tracked from southeast of Scottsbluff, NE to northeast of Sterling, CO and occurred under very similar conditions (NW flow aloft, mid 50's dewpoints and strong directional shear enhanced by a mid level jet streak) wouldn't be out of the question on Tuesday evening.
Will be keeping a close eye on the situation as it evolves into what could be a potentially decent backyard chase!
 
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I too am keeping an eye on tomorrow's setup and am excited that it may be in my own backyard for a change. Eastern Colorado doesn't usually see very high dewpoints like other places, so anything in the mid 50s and above is worth watching. Whenever the flow at the surface is from the east or southeast and the flow at or above 500 mb is from the northwest the turning with height is in place and tomorrow appears to fit that description. If we can clear out the low clouds (unlike today) and get some sun to the surface, we could have a few discreet cells develop either off of the Cheyenne Ridge or the Palmer Divide as described above my Mr. Farnik. The parameters that supercells prefer seem to be shunted to the eastern part of Colorado, so anything that develops along the front range will be moving into a more favorable environment for sure. I'll be watching and waiting on this one and am initially targeting Limon for tomorrow.

Mark
 
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Whenever the flow at the surface is from the east or southeast and the flow at or above 500 mb is from the northwest the turning with height is in place and tomorrow appears to fit that description.

I love turning with height, but not once it nears or exceeds 180 degrees. That's often a killer with nw flow setups. I've seen those enough times and can't think of anything cool I've seen(though I'm sure worthwhile examples exist). Crap vents into it's own inflow, and it just never seems good. If it's nw flow, give me southerly sfc. That or just give me weak sfc and let it deviate along its core's path.

I'm not thrilled with tomorrow, but have been wanting to go west anyway. Will probably target an area near Pine Ridge SD. Hopefully a little better moisture can slide up there between now and then.
 
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