Upper level analyses Friday evening showed a dip in the jet stream evolving over the Great lakes region. Resulting northwest wind flow will bring the area temperatures more typical of mid-May, making this the only weekend this month with sub normal readings. The six days comprising the first three weekends of the month averaged 9.5 above normal, and included three days of 90-degree heat. Highs Saturday and Sunday will struggle to reach the low 70s, a level nearly 10 degrees below normal. Cold air aloft is also expected to prompt afternoon cloud development. Vertical cloud growth will be limited on Saturday, with only isolated sprinkles possible. Conditions are to become more unstable Sunday, allowing clouds to become tall enough to produce thunderstorms capable of producing brief downpours and gusty winds.