Cool snap coming into central and eastern U.S. next week? GFS forecast temperatures compared to 1981-2010 average next week (WeatherBellModels.com) Computer models looking out about a week from now are advertising the arrival of unseasonably chilly air in the Midwest, a piece of which could make it to the East Coast by late next week. Both the European and GFS models suggest the jet stream will carve out a large trough over Midwest extending into the Ohio Valley around Tuesday of next week. And the North Atlantic Oscillation is forecast to tank well into negative territory. When the NAO is negative, it is typically an indicator of a large dip in the jet stream over eastern North America and colder than average temperatures. Most members of the GFS ensemble model forecastthe North Atlantic Oscillation to dip into negative territory in mid-to-late September. (NOAA) How cold are we talking? Highs in the arrowhead of Minnesota and the upper peninsula of Michigan may not get out of the 40s. These areas and locations further south could see their first freeze. Around Chicago, highs may struggle to exceed 60 with lows near 40. These temperatures are 15-25 degrees below average. Often times these early season outbreaks of chilly air moderate as they head east and sometimes models overdo their intensity this many days out. The GFS simulates more of the cold will make it east compared to the European model. But a deeper taste of autumn may arrive in the mid-Atlantic in just over a week. It's not out of the question highs are challenged to reach into the 70s with more widespread 40s at night in the D.C. metro region. We'll keep you posted.