September morn – Lows early Friday dipped to mid-September levels and as cool as the lower 50s outlying. 52° Mt Comfort, 53° Tipton & Crawfordsville. While later tonight new clouds spill increase associated with a storm complex in lower Michigan, there will be plenty of clearing overhead to aid in another very mild night.
Early Saturday morning lows are expected to lower well into the 50s and IF the wind is light enough, we will dip below 60 degrees in Indianapolis for the FIRST TIME since late June.
Why a light wind? With the breeze from the northeast, the warmth of downtown is pushed southwest, out over the airport where the official sensor/thermometer resides for the city of Indianapolis. The “urban heat island” effect (the concrete and asphalt of the city absorb and hold on to the warmth of solar radiation longer than outlying grassy areas) means the temperature will run warmer than those in outlying locations. Winds that go light or shift slightly east or southeast will bring a dip by daybreak.
Friday’s temperatures were more typical of mid-September and this pattern has staying power.
The “hot dome” has migrated west allowing for a cooler “northwest flow” here well into next week! With the hot dome west, around the periphery of the heat are “waves” or disturbance that dive into the eastern U.S. The first of two this weekend arrives early Saturday morning. Better rain and storm chance accompany the second one Sunday morning.
Weekend rain chances reach peak coverage early Sunday (30%) then diminish. Overall threat for rain drops going forward as a milder and drier pattern takes hold.