September weather outlook pits warm forecasts against cool signals

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The FOX Forecast Center is eyeing a complicated weather pattern heading into September, with competing signals emerging as to what to expect during the first month of meteorological fall.

While NOAA’s latest monthly outlook calls for a likelihood of warmer-than-average temperatures across most of the country, several of the most-used computer models suggest temperatures may not be as warm as expected.

Guidance from global models such as the Global Forecast System (GFS) and the European Centre for Medium-Range Weather Forecasts (ECMWF) continues to point toward significant troughing across the eastern half of the United States – a pattern that has led to record lows and one of the coolest ends to summer since the 1980s.

Early September temperature outlook

(FOX Weather)

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NOAA has highlighted the Rockies, Southwest and New England as regions potentially seeing some of the greatest warm anomalies, while no one across the Lower 48 is expected to see below-average monthly temperatures.

On the precipitation front, the agency identified communities across the Southeast, Florida and the mid-Atlantic as being at an increased likelihood for precipitation – likely a result of stalled frontal boundaries and increased tropical activity.

There is also some support for increased rain chances across the Pacific Northwest as the region transitions out of its typical dry season and into the wet season.

September temperature & precipitation outlook

(NOAA)

According to NOAA’s outlook, most of the country could be in line to see precipitation accumulations that are either at or below average, which could have a significant impact on the vibrancy of fall foliage.

Leaves begin changing color when trees receive less daylight, but factors such as cloud cover and drought play a role in how vibrant displays become. 

The absence of chlorophyll allows yellows, oranges and reds to emerge, creating the peak color many regions see in October.

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Average Peak Fall Foliage

(FOX Weather)

Climatologically, August’s warmth typically lingers into September before larger-scale cooldowns take hold later in the month, but since the last month of meteorological summer wasn’t on the warm side across much of the eastern half of the nation, climate patterns are a bit out of sync.

If NOAA’s outlooks are accurate, then what the country is experiencing now is commonly known as "fake fall," with a return of summer-like weather toward the middle and end of the ninth month of the year.

Again, the warm signal in NOAA’s outlook appears to be more robust than some model depictions.

Months such as September during the fall, December in the winter and March during the spring tend to be some of the more difficult months to issue extended forecasts for because of the changing nature of the globe out of and into seasons.

NOAA’s August forecast proved accurate for much of the Southwest and New England but underestimated the extent of cooler-than-normal weather east of the Mississippi River.