6/23/05 FCST: Central/Northern Plains

Bear with me in my first mediocre forecast...There are a couple factors that are worrying me with this setup - the cap and LCL heights.

0z Fri NAM puts a substantial amount of energy in eastern SD, but it seems like there's nothing there to feed it. Southwestern MN looks a little better. CAPES are at least in the 2500-3000 range. Marshall's(KMML) and hodograph looks like the fish symbol (icthus). But Worthington(KOTG) and Pipestone(KPQN) seem to have a better CINH and EHI values.

I think we're going to see more of what Mike H. saw last night in Vermillion. Quick stuff that looks really interesting.

Synopsis: Coming off the boundary above Mitchell to Huron, things rapidly build on top or just west of the SD/MN border. Pipestone seems south enough to get some moisture flow however it might be too late as the pattern of late has been to develop far to the NW and come SE or directly E.

EDIT: Apparently the models have changed and all but killed my target area. SPC changed the slight risk zone and moved it more northerly.

2nd EDIT: SPC dropped the slight area into my TA again, however I'm thinking things are going to be coming off that boundary pretty quick. If I were going out tonight - I'd stick here and see where the towers pop up first and then get going.
 
Good forecast.. No outbreak or anything but we should keep alert for what little the weather has to offer.

I have been browsing the AFD's and HWO's for the Plains through to the Great Lakes and there is some concern that the NAM is overestimating the amount of CAPE that will be available over the next few days.
 
Great job Ed. Yeah it looks like the CAP may supress convection with 700mb temps progged at 13-14c. Doesn't look like forcing will be enough but that could still change. Front should be draped from just north of Marshall, MN to Lake Andes, SD by 0z. NAM indicates substanial Convective Inhibition remaining in SW MN. I'll focus on two areas.

Lake Andes: NAM has little CINH remaining at 0z and also has QPF output for this area. This also conicedes with the remaining pops in the FSD CWA. NAM shows good moisture convergence just north of this area. Instability should be plentiful.

Granite Falls, MN- Watertown, SD- NAM substanially cools/removes remaining convective inhibition by 0z. While this could very well be overdone it is definately an area I will be watching tommorow. Decent VV's and moisture convergence may get something going in this area before dark.

Tempatures tommorow are forecasted in the ridiclouis range with 100 not of the question. Weak 0-6km shear isn't that supportive of supercells and LCL's approaching 2k are not to supportive of tornadoes. But if the cap can be overcome the high instability, 200+ m2/s2 0-3km SRH & 20kts 0-1km Shear may support a minimal tornado risk and some severe storms.

-Scott.

Disclaimer: Forecaster is by no means an expert.
 
Chase target for June 23

Chase target:
Minot, ND.

Timing:
Storm initiation by 2PM CDT along a Minot, ND to Brandon, Manitoba. Storms will move rapidly to the E towards MN through the early evening, reaching an International Falls to Bemidji line by 8 PM

Storm type:
Fast moving line with embedded supercells. Severe winds to 80mph will be the primary SVR threat.

Discussion:
In NWRN MN/NERN ND, it now appears unlikely that a significant MCS with attendant outflow boundaries and other Day 2 FCST complicating factors will affect the area overnight given strengthening cap along with veering LLJ between 06Z and 12Z. As of 04:30Z, convection had yet to initiate in either ND or NRN MN, while the MT MCS associated with S/WV there was tracking NE towards CAN and weakening.

As for Thursday, confidence is higher for convection to fire along the CF in NERN ND and track towards NWRN MN towards the evening. Mid- and upper-level forcing will be more then sufficient to overcome strong CAP by 20Z, and expect storm initiation along a YBR(CAN) to MIB line. Storms will move rapidly to the E at 30kts, and a line with embedded supercells will reach an INL to BJI line through 02Z. SFC heating may be slightly hindered by thin CI shield, especially in the WRN areas, however MLCAPE’s should still reach 3000J/kg in the target area. Shear parameters also look impressive: deep layer shear as high as 50kts in the NRN areas along with (0-3km)SRH’s to 150m^2/s^2. DVN NWS BLEP technique suggests severe wind potential to 80mph given FCST thermodynamic profiles.

- bill
 
14z NoDak surface chart looks intriguing as winds are backed to the east- southeast ahead of the low. Arc of cloud on space pics above this apparent boundary. Also looks like a prefrontal trough in the western portion of the state where the dews drop from the 70s into the 50s. 12z RUC and NAM seemingly place this loosely defined intersection in northeast NoDak - southern Manitoba around 2 to 3pm. There may be a little enhanced tor potential here if the surface winds continue with any easterly component. Stout enough cap should offer a window of discreet cells but monster instability combined with frontal forcing should also lead to rapid transition into linear mode. SWODY1 looks good. Maybe add a small 5% tor area in addition to the 2% in norteast ND, northwest MN.
 
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