Even though the country is nearly three weeks into meteorological fall, what is known as astronomical fall will begin on Sunday when the Sun is directly over the equator.
This moment marks the time of year when daylight and nightfall are relatively equal in length and many Americans begin yearning for cooler days and crisp nights.
Unfortunately, Mother Nature does not always follow this pattern, as warm temperatures across much of the Lower 48 are expected to continue.
Since the start of meteorological fall, most observation sites outside the Southeast have experienced a generally warm autumn, with many locales reporting temperatures 4 to 8 degrees above average.
The warm weather has undoubtedly led to an extended mosquito season, and children are returning to school without the need for extra layers of clothing.
The question many are asking is whether the warm weather will continue, and when the country will see a break in the pattern.
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Weather experts at both NOAA and FOX Weather concur that ridging across parts of North America will play a significant role in keeping temperatures at or above average through the first week of astronomical fall. This includes the Pacific Northwest and the Northeast, where temperatures are expected to be well above average.
Questions remain regarding the Southeast and whether any tropical moisture can cool temperatures below their typical levels. If an influx of moisture fails to materialize, this region could also experience thermometer readings that are at or above average.
According to forecast models, the first significant fall cooldown is unlikely to occur before the first full weekend of astronomical fall, but there is some hope on the horizon.
Satellite observations and model forecasts indicate that zonal winds associated with the polar vortex are weaker than usual for this time of year.
Without a tight belt of winds concentrating the cooler air around the Arctic, cold air masses will tend to escape and move south into lower latitudes. However, exactly where the influx of cold air will occur depends on the positioning of features such as high and low-pressure systems, as well as the jet stream, which essentially act as a conveyor belt.
If the weather features do not align properly, other regions, such as Europe and Asia, might receive some of the cooler air until the pattern reverses.
Additionally, the clash of air masses usually brings the threat of a second severe weather season across the eastern half of the nation.
A stronger jet stream can enhance the scope of severe weather outbreaks, leading to damaging winds and even tornadoes.
With an overall warm, zonal air mass in place, thunderstorm activity will still exist, but chances of a widespread outbreak are minimalized.
Here again, the tropics can play a significant role in activity, but the certainty of large features such as tropical storms or hurricanes are unpredictable outside of the 5-7 day forecast window.
Original article source: Here’s what the weather looks like for the first week of fall
