A summer-time weather pattern is over taking Kansas City and much of the Midwest.
The jet stream, the wavy, high altitude river of winds that steer storms, is shifting north this week. It will soon take up its typical summer-time residence across the northern plains, closer to the U.S.-Canadian border.
Since winds are created by temperature and air pressure contrasts, the jet stream is stronger during the winter. That's when we find greater contrasts of temperatures and pressure between the United States and Canada. There is less of a contrast during the summer months, so the winds aloft weaken and will soon blow at their slowest speeds of the entire year. That transition will be happening over the next three weeks and will begin the dog days of Summer.
The dog days are from late July through late August and coincide with Sirius, the dog star, rising before the sun. But we won't have to wait that long for it to feel like the dog days as stagnant weather pattern develops by this weekend.
Weaker winds aloft mean can mean stagnant weather. You know what we're talking about. Hazy, hot, humid days that seem to stretch on for weeks. It can often be very dry but occasionally thunderstorms will develop across an area or thunderstorm complexes will form at night and bring much needed rain.
This time of year in Kansas City and the central plains, up to 70% of our summer-time rain can come from night-time thunderstorms. Sometimes those complexes leave behind small boundaries that act like mini cold fronts. Our in-house computer model hints at one of the boundaries sparking showers and thunderstorms Wednesday evening.
It won’t be a lot of rain, maybe a quarter of an inch of less. Heavier rain is forecast in eastern Missouri where a small storm will stall through the middle of the week. Back here in Kansas City, except for pop up afternoon thunderstorms, it could be a hot & dry start to July.
The stagnant weather pattern may not break down until closer to the middle of the month. There are some indications of better thunderstorm chances around the 12th or 13th of the month.
Anyway, the Climate Prediction Center released it's 8 to 14-day outlooks today. Above average temperatures are likely for Kansas City.
And below average rainfall.
That definitely looks like a summer-time pattern. Hang in there, autumn is just three months away. That's like saying at mile 20 of a marathon that you're almost finished. We've still got a long way to go.