Fall officially began a few days ago, but the jet stream is well north across the eastern United States. This ridge has caused temperatures to soar well into the 80s and 90s for areas east of the Mississippi. These warm temperatures will remain through Wednesday before the transition to near-normal temperatures begins.
By Wednesday, the trough that is responsible for mountain snow across the West will slowly shift eastward. This will send a cool front into the Great Lakes and the South-Central region. This front will eventually move towards the East Coast by early Friday, which will put an end to the summer-like warmth that has engulfed the eastern United States. High temperatures will be 10-20 degrees cooler by the upcoming weekend with the most significant temperature drop near the Great Lakes.
Trough across the West with ridge across the East (Today)
Ridge across the West with trough across the East (Saturday)
Temperatures will still be near to slightly below average, but compared to temperatures that are currently well above average, this will be a very noticeable change. Highs will drop into the 60s and 70s for much of the Midwest, Great Lakes, Northeast, and Mid-Atlantic. Lows will dip into the 40s with a few 30s near the Great Lakes by the weekend. High temperatures across the Southeast will fall into the upper 70s and low 80s. Lows are expected to be in the upper 50s and 60s.
Temperature anomalies (Saturday Afternoon)
The cooler temperature will continue through the weekend before a slight modification occurs by next week. The numerical guidance is hinting at a more amplified upper-air pattern, which would cause more cool fronts to move into the United States over the next few weeks.