Chase Forecast: June 5

With the potential for a significant severe weather outbreak increasingly likely over parts of Iowa, specifically western Iowa, I will be on my way to the storms throughout the afternoon tomorrow. Latest SPC discussion indicates that there are some questions still to the evolution of the forecast, and in the storm evolution once they do fire tomorrow afternoon. Nonetheless, as the SPC also mentions, it does appear that a 'Significant/damaging event' will take place over the plains tomorrow.

Forecast models continue to have some struggles with the placement of surface features, most notably the warm front and low pressure positions. Last nights' consensus was to have the low placed in eastern South Dakota by 00z, with warm front extending eastward through South Dakota and into southern Minnesota/Wisconsin. This mornings' model runs took a slightly more west and south approach, leading to the extension of the moderate risk in the latest SPC day 2 westward. The 12z NAM indicated good timing on the 500mb jet and vorticity axis in correlation to 00z and the likelihood of storm initiation. The placement of the warm front was oriented from southwest to northeast, unlike previous model runs, and stretched from northeast Nebraska, along the IA/MN/SD intersection and then into southern Minnesota. The low pressure center at this time seemed to be much further south, in vicinity to the Norfolk, NE. This solution would still yield significant severe weather, it would however move the risk to mainly eastern Nebraska and western Iowa, and not include portions of SD/MN as much as previously thought.

The 12z GFS run is slightly east when compared the NAM in the 500mb jet and vorticity axis. This does not have a negative effect though, as the overall setup remains the same with good support throughout the levels for thunderstorm development in the late afternoon and evening hours. The surface setup with the GFS model run indicated less of a change when compared to last nights' runs. Low pressure still centered along the NE/SD borders in vicinity to Yankton, SD. Associated warm front extends east/northeast from the low over southeast South Dakota and into southern Minnesota. This is much more in line with current SPC forecasts and remains fairly consistent with previous models, thus is likely the favored model currently.

Ideal target area will be anywhere along a line from near Yankton, SD southward along the dryline throughout eastern Nebraska. This line is likely to include areas such as Norfolk, NE; Columbus, NE; Grand Island, NE; Hastings, NE; etc... My current chase plans include the morning at KICD Radio in Spencer, IA before departing in the early afternoon to head westward. Dependent on where the surface features are placed, continue west near the SD/IA border or drop south along highway 60 towards the Sioux City area. More updates are likely tonight and tomorrow regarding the severe weather threat both late tonight across Iowa, and the threat for tomorrow.