Clouds will be on the increase Sunday in advance of an approaching cold front that promises to bring the first taste of fall's chillier side as we enter the last workweek of September. Once the front begins to clear the area to our south on Sunday post-frontal precipitation will arrive in its wake, bringing with it the first chance of appreciable rainfall in our region in well over a week. Sunday's high temperatures may be the last of those to reach the mid to upper 70s for the remainder of the intermediate-range forecast period. Most parts of the Tri-States are poised to pick up 0.50" - 1.00" of rainfall from this upper-level trough and its associated surface cold front, although a few areas may end up with slightly less, and some isolated locations may see more than 1.00" of rainfall.
Cooler air that currently lies well to our north will buckle equatorward and slide into our region in association with a change in the upper-level jet stream pattern. This will signal a deviation from the rather warm early fall temperatures we've been enjoying, as daytime highs will be 10-15 degrees cooler most of next week, with overnight lows feeling much more archetypically autumnal just in time for October's arrival on Thursday.