6/26/10 FCST: NE/SD/IA/MN/KS

[Brian Stertz]

From looks of 12z NAM, there appears to be a nice bullseye on the boundary from NE Nebraska into extreme SE South Dakota and NW Iowa. Timing looks to be mid-late afternoon with strong instability on both sides of the boundary. 40-50 kts. deep layer shear and 0-1km VGP should be favorable for tornadoes given the moist/warm (not hell capped) airmass in vicinity of the roughly e/w oriented boundary. Things may transition to more cold pool outflow dominated storms & supercells as the front begins to sag south and southeast further into NE/IA after 6-7pm time frame. Sure looks to me like a decent June setup. Will keep a watchful eye on tonight's data....

 

[Kevin Walters]

I was looking at the same area as well. Climatology favors tornadoes in this area in late June. Any storm that deviates due south could become tornadic.

 

[Kyle Masters]

Looks like the main threat for tornadic supercells will be near and east of the surface low, progged to be just N of Yankton, SD by 4 P.M. and the stationary front in place now. I'd say a good place to start off today would be Sioux Falls, as that has interstate and highway access.

At least the road network around here is pretty solid, but a word of warning to anyone who's chasing in this area - there are several washed out and still flooded roads in the area, for example US Rte 18 is closed. And with the 1-3 inches expected to come from these storms, more will be closed. Keep a sharp eye.

 

[Bill Schintler]

Chase Target for Saturday, June 26

Chase target:
Worthington, MN

Timing and storm mode:
Storms should develop by 5 PM CDT. All modes of severe weather is likely, including a tornado or two.

Discussion:
An outflow boundary from an early morning MCS extends from north-central IA into eastern IA. Further west, a synoptic cold front extends from Marshall, MN to Valentine, NE. Outflow from ongoing elevated convection in eastern SD is serving to reinforce the cold front. A warm front will sharpen along the IA/MN border by 00Z A WF/OFB triple point near Worthington, MN should be the focus for surface-based convection by late-afternoon. Capping should persist through 21Z with shortwave ridging in place. By 00Z, another in a series of H5 shortwaves will arrive to provide necessary forcing for convection. An axis of strong instability will develop, with MLCAPEs in excess of 3000 J/kg between I-90 in MN and US-30 in IA. Deep-layer shear will should increase to 40-50 kts as an H5 shortwave overspreads western MN and northwestern IA. Enhanced helicities exist along and north of the warm front and outflow boundaries.

Bill Schintler

11:23 AM CDT, 06/26/10

 

[Fred Dearborn]

Tornado watch box is up,seems kinda early to me.Currently south of Vermillion,SD. grabbing lunch and headed north/northeast.Skies are all clear here.