The last six days have averaged close to fifteen degrees warmer than normal, with the last five days having morning lows warmer than the average high for the day. The upper level ridge that brought the unseasonably warm air to move so far north is breaking down, allowing for cooler air to arrive from Canada. As a result we'll see temperatures much closer to normal for the rest of the week.
Today's forecast is pretty straightforward in that the back door cold front that is the leading edge of the cooler air will plow into a low pressure system arriving from the Midwest. As the Midwestern storm tries to ride up and over the cold air mass we are likely to see some light rain this afternoon and evening. That rain is much needed, as October's precipitation is already almost an inch below normal. This afternoon's high will only reach the lower 70s, which is still several degrees warmer than normal but not the extreme warmth that we've seen for almost a week.
As the high moves in from Canada it will shunt the Midwestern storm off to our south and the rain will taper off overnight. Clouds and an easterly wind will keep Thursday's high in the lower to mid 60s, which would make it the coldest day in the city since early June. Friday will also see a mix of sun and clouds and a high in the mid 60s. Much warmer weather is expected this weekend, with highs in the mid 70s on Saturday and close to 80 on Sunday.