6/24/08 FCST: MO/KS/IA/IL

[Michael O'Keeffe]

Looking at the WRF model it looks as though a decent setup may be in store for much of N/C Missouri and adjacent areas of E KS/S IA/W IL. A zonal flow situation looks to play in as a 20-30 knt. SSW LLJ pushes into the region. Deep moisture, SE surface winds, CAPE between 3000-4000+j/kg, and 0-3km helicity around 200-300 m2/s2. So all in all it seems like a pretty good severe weather setup mainly over NE KS/NW MO attm. If it verifies I wouldn't be surprised to see a few naders in N MO/NE KS and possibly S IA/W IL.

 

[Bill Schintler]

Chase Targets for Tuesday, June 24

Chase target (north): Judson, ND (18 miles west of Bismarck).

Timing and storm mode:
Storms will develop between 5 and 6 PM CDT, with high-based supercell storms likely.

Chase target (south): 10 miles east of Marysville, KS

Timing and storm mode:
An elevated storm complex will be ongoing in eastern and southeastern Nebraska during the majority of the day. Surface-based storms will develop between 4 and 5 PM CDT, with severe multicell storms the dominant mode. An isolated tornado or two cannot be ruled out, especially within embedded supercells.

Synopsis:
ULVL flow will deamplify slightly over the nest 24 hours as the ERN Great Lakes trough shifts E and the WRN CONUS ridge flattens. The visible satellite indicates an increasingly SWRLY ULVL flow from WY into the NEB panhandle and the WRN Dakotas. The strongest flow will remain over ND through MN, while well to the S of the jet stream, a S/WV and associated mid-level speed max will translate from KS through MO. Associated with the SRN S/WV will be a large area of mostly elevated convection what will be ongoing during the morning hours in ERN and SERN NEB.

Discussion (north):
A SFC boundary will sharpen along the ND/SD border during the afternoon in response to forcing provided by an intense mid-level S/WV and elevated convection will move from ERN MT into WRN ND. Storms should become SFC-based as UVM spreads into the region with H7 omegas increasing to -3 to -4 ub/s along with ERLY upsloping LLVL flow N of the boundary. SFC dewpoints will climb into the lower-60’s F under persistent upslope flow, with moisture pooling over WRN ND. 40 kts of deep-layer shear will be sufficient for storm organization, despite modest instability with MLCAPE’s of 1000J/kg.

Discussion (south):
Overnight, a nocturnal MCS will develop after 07Z along and N of the KS/NEB border owing to WAA and isentropic lift, and remnant boundaries left from this convection will set the stage for afternoon storms on Tuesday. In NERN KS, SFC-based convection should fire along an OFB laid out by the morning storm complex as a remnant MCV translates E through the area. This convection may be more of a SWRD growth of the ongoing MCS. A sizable thermal gradient from SW to NE will develop in response to differential heating with significant convective debris remaining over NRN MO, SERN NEB, and into IA. Storm motion should take these storms along the boundary where storm inflow will be backed. Moderate instability will develop as modest mid-level lapse rates of 7C/km overspreads SFC dewpoints of around 70 F while contributing towards MLCAPE’s to 2000J/kg. Moderate directional shear will exist throughout the SFC-4km layer with 35kt H7 flow on top of backing LLVL winds NE of the OFB. The LLJ will increase to 40-45 kts after dark, while aiding in the maintenance of the storm complex while it tracks ESEWRD into NWRN MO.

- bill
9:20 PM CDT, 06/23/08