SEVERE THREAT GOES UP FOR SATURDAY.
Saturday still promises to bring the threat of severe weather to parts of the central Midwest. However, questions remain about the extent of the severe potential as well as the precise location. Friday's early models showed a slight shift to the southeast on the track of the surface low so the SPC risk outlook was revised in that direction.
Friday nights data has trended back to the northwest so the models are doing some last minute fine tuning regarding the position of the storm. Here's the latest SPC outlook which has increased the risk outlook to enhanced and pushed it back NW into my area.
Based on what I've seen Friday night the greatest potential for severe weather in my local area exists near and southeast of a line from Dubuque to Cedar Rapids and back to Oskaloosa. One of the big factors in what ultimately happens is how much heating and instability can be achieved ahead of the surface low and triple point. If there is too much grunge from morning convection that risk could be diminished in my region. The grunge issue will not be resolved until mid to late morning Saturday so it's a wait and see situation until then.
One thing that's a positive for supercells and potentially tornadoes is the amount of bulk shear. Some models are coming in around 60 kts. That's big and we'll need to keep a close eye on that Saturday.
The GFS is showing the storm center over eastern Iowa near Cedar Rapids by evening and from there it deepens and races towards Milwaukee at midnight. Here's the GFS surface depiction at 7:00pm
Here it is 6 hours later at 1:00am.
No matter what happens, there will be thunderstorms and the risk of heavy rain near the track of the surface low. The GFS shows this for total precipitation.
Here's a larger regional perspective.
Behind the low the pressure gradient really tightens and stiff northwest winds will gust to 35 mph. That in turn will tap much cooler air and bring a brisk brand of weather for Sunday. The sun will emerge but highs around the Midwest will generally hold in the 50s.
Sunday night the risk for scattered frost exists with lows in the mid to upper 30s. About 10 days ago I thought this might be our first freeze but the depth of the cold air is less and it's moving fast. Thus, the growing season will continue!
Longer range some fine weather is expected to dominate much of the period October 16th through the 23rd. A zonal flow will result in drier conditions and above normal temperatures. Here's the day 4-9 temperature departure at 5,000 ft.
Beyond that all signs point to a developing EC trough that will bring a substantial cool-down. Look at the big change in temperatures in the day 11-16 period.
That's the lay of the land as of late Friday night. Keep and eye on the severe weather situation Saturday afternoon and evening, especially in SE Iowa, WC Illinois, and NE Missouri. Otherwise, have a sensational fall weekend. Roll weather...TS
