1:00 PM | *Much colder weather pattern setting up for the eastern two-thirds of the country to close out October*

Discussion

Big changes to cold are coming for much of the eastern two-thirds of the country during the last couple weeks of October. Temperatures have run at well above normal levels so far this month in the Midwest, Appalachians and Northeast, but much of that will be negated over the next couple of weeks; especially, from the Upper Midwest to the Appalachians.

An unfolding weather pattern change will bring about a deep upper level trough of low pressure centered over the Upper Midwest and a strong ridge of high pressure along the US and Canadian west coasts. The combination of these two upper level features will promote a flow of air from north-central Canada right into the northern sections of the US and these cold air masses will gradually spread eastward to the eastern seaboard. Last night’s GFS ensemble 500 millibar height anomaly forecast map (above) for next Thursday, 10/24, shows this upper level pattern with the deep trough represented by the blue and the strong ridge shown in red (map courtesy Penn State e-wall). This pattern will bring progressively colder air masses to the Upper Midwest, Great Lakes and Northeast US and very likely the first snows of the season from the Upper Midwest to the Appalachians over the next couple of weeks. The greatest departure from normal will be across the Upper Midwest and Great Lakes regions where the core of the cold will set up. One final note - no matter who wins the American League Championship Series - Boston or Detroit - it looks like there could be some chilly times during the World Series while playing in the American League city.

[NOAA 6-10 day outlook]