Windy Tuesday, But Whats Standing in the Way of a Nice Weekend?
September 20, 2011 8:30 PM
The first classic wind event of the fall season erupted Tuesday across the Dakotas as an area of low pressure rapidly strengthened as it went by. This rapid intensification really disrupts the atmosphere causing winds to funnel around the low and then shoot out the backside basically like a sling shot effect. Thanks to this, winds gusted over 60 mph in several locations and made for a pretty wild day across much of the area. Check out some of the local wind gusts in the image below and some gusts from across the area on the left. The good news is the winds will begin to subside a bit Tuesday night, and will be slightly calmer through the day Wednesday. However, you can still expect gusts to 30 or 35 mph through the day along and east of I-29. But the more noticeable conditions will be the cooler air with temperatures running 10-20 degrees below average Wednesday with highs expected to only be in the 50’s for many of us. But the big question now is, when will it warm up and how much? Well, these questions unfortunately are not going to be as easy and straightforward as they usually are. Let me explain…
This area of low pressure that’s currently moving by us will move into the Great Lakes region and then turn into a cutoff low. A cutoff low is an area of low pressure that gets cutoff from the steering currents in the atmosphere also known as the jet stream. When this happens, the low can sit in one place for an extended period of time leading to very cool, cloudy, and dreary conditions.
(This is what this low will look like when it becomes cutoff from the jet stream. Take notice that the jet stream is far to the north and that giant L represents the cutoff low.)
But not only can it stall and sit in one place, but without the jet stream pushing it along, it can actually begin to move backwards or west, this would bring the cool weather back to our for the weekend, something we are hoping to avoid. But since forecasting models base many of their predictions by using the steering currents, it can be very difficult to forecast where these lows will go when they become cutoff.
(This is a look at 850mb temperatures for this weekend. You can tell exactly where the cutoff low is located by the batch of cold air that’s located to our east, look for the blue colors. Now if this low begins to move back west, it will bring those cooler temperatures back with it and would prevent much of our area from warming up this weekend)
So as long as that low doesn’t migrate back in our direction, it looks like it will be a very nice and seasonably warm weekend, just look at all of those yellows and oranges that could be over our area…. So if you want it warmer then Tuesday, then hope that cutoff low can move as far east as possible.