Tuesday, September 27, 2011

Cool frontal boundary exits our area today leaving cooler & generally dry conditions today. Upper level low pressure remains relatively stationary over northern Illinois, keeping abundant cloud cover and occasional rain in the forecast Wednesday & Thursday. The system will finally exit to the northeast early Friday as a stronger cold front invades from Canada. Reinforcing Canadian front will keep good chance for rain showers Friday. Cool, dry air on the backside of the front will bring more fall-like weather for the first few days in October. 

For today & tonight... Drier & more comfortable air mixing in from west to east behind the cool frontal boundary that crossed the mountains last night. Residual low level moisture & rainfall persisting along the eastern slopes slowly drying out as the weakening frontal boundary progresses north & east. A few peaks of sunshine and highs in the low 70s are on tap today. A few light mountain showers are possible this evening & overnight but much of the area will stay dry with deeper moisture pool well to our west. We'll keep variable clouds & patchy fog overnight with temps with lows falling into the low/mid 50s.

Great Lakes low pressure will continue to plague the Midwest & Mid-Atlantic states Wednesday & Thursday. Temperatures will become gradually cooler each day, especially with reinforcing cold front arriving this weekend. Mainly cloudy skies, highs in the low 70s & spotty rain showers are on tap during the day Wednesday. Skies will stay mostly cloudy with scattered rain & lows in the low/mid 50s Wednesday night.

Rain will become more widespread during the day Thursday as that Great Lakes low pressure system finally presses eastward. Skies will stay mostly cloudy & highs will only reach the upper 60s Thursday. Then another better defined line of showers will blow through after midnight into early Friday as that reinforcing cold front swings into our area. A few leftover showers are also possible during the day Friday as low level moisture lingers in the mountains into Friday night.

Remnant low level moisture may trigger a few weak showers Saturday morning. Otherwise the weekend forecast will stay cool and dry as the Canadian front pushes over the mountains & into the Carolinas Saturday. Strong high pressure will allow for plenty of sunshine this weekend. But highs are expected to only reach the upper 50s/low 60s over the weekend. Lows will fall into the low/mid 40s. Saturday night will be the coldest with lows falling to near 40. Cool, dry weather will last through a good part of next week as well.