Fall Forecast: Next three months of weather & winter preview
Thursday, September 21, 2017, 12:24 - The Summer of 2017 will be remembered very differently, depending on which part of the country you call home. West of the Rockies, scorching heat and persistent dry conditions prevailed, as temperature records fell and places like Seattle saw an unprecedented streak of rain-free days.
East the Rockies, this past summer was characterized by a lack of persistent or extreme heat. For most areas rain was more plentiful and in some cases excessive, particularly for the Gulf Coast where tropical moisture provided ample fuel for heavy downpours, and devastating hurricanes Harvey and Irma shattered records.
Now that summer has run its course, we turn our attention to the next three months to see what the fall season has in store. Where will heat linger, and who has the best chance to see crisp autumn air take hold early? And where do we expect to see the most active storm track in the upcoming season? We have all the details below (and a preliminary look at winter temperatures as well) in The Weather Network’s 2017 Fall Forecast, which covers the months of September, October, and November.
National Fall Overview
We expect that the fall season will feature near normal or above normal temperatures across most of the United States. However, fall is well known for its temperature rollercoasters, and it is rare for any region to lock into a pattern for most of the season. Regions that are warmer than normal for the season will still see periods of cold weather, but the periods of mild weather will outweigh the periods of cooler weather.
A good example of this can be seen in our pattern map for mid to late September. This map is quite different from the map for the fall season as a whole, especially the western half of the country.
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Regional Temperature Specifics
From the Upper Midwest to the Northeast we have already seen several shots of autumnal weather during August and early September, which has even brought a very early frost to some areas. However, warm weather is not gone for good across this region.
Fantastic fall weather is expected to dominate mid and late September and continue well into October, providing more than the typical number of warm sunny days and great opportunities for outdoor activities and enjoying the fall foliage. Of course, shots of cooler air are still inevitable, and as we head towards November we expect a return to a typical late fall pattern with classic fall storms and a few reminders that winter is just around the corner.
While the West will take a temporary break from being the warmest part of the country, above normal temperatures will still dominate the season near and west of the Rockies.
Near normal temperatures are expected to be widespread from the Plains to the Appalachians, though slightly cooler than normal temperatures may linger over the lower Mississippi Valley, especially where the ground is rather wet.
The East Coast is expected to see near to above normal temperatures this fall, including warmer than normal conditions for most of the major metros. This will be thanks in part to warm water temperatures in the western Atlantic basin. This warmth will also bring lingering summer-like humidity, and the threat for excessive rain from any tropical systems that track near the region.
Of course it’s important to keep in mind that fall is a transitional season. Much like the spring, this is a time of year when big changes are par for the course. The months of September, October, and November are when we see some of the largest temperature changes throughout a typical year. Most cities across the country lose a few degrees from their average high temperature each week in the fall, and that trend to underlie the pattern this year as always.
While the upcoming months are famous for their classic fall storms, the first half of fall is expected to be less active than normal across most of the country – the one key exception be areas that are impacted by tropical storms and hurricanes. However, a more typical pattern is expected late in the season.
Looking at the precipitation map for the fall season, overall rain and snow amounts are expected to be near to below normal for the season across much of the country.
Dry conditions may persist for much of the interior Northwest, leading to concerns for worsening drought. However, precipitation should slowly trend towards normal for the Pacific Coast, as the stubborn ridge that brought heat and drought through the summer breaks down.
In the Desert Southwest, rainfall may even be enhanced by moisture from recurving eastern Pacific tropical systems, thanks in part to the very warm water temperatures off the coast.
The eastern two thirds of the country can expect precipitation near normal overall for the fall season. However, with the active hurricane season in full swing, we can’t rule out impacts from additional tropical systems – which could tip some localized areas, even inland, well above normal this season. And while we don’t expect the second half of the hurricane season to be as active as the past several weeks, all the favorable conditions for tropical development that we have seen through the late summer will still be in place in the early fall.
With lingering warm water near the Eastern Seaboard and Gulf Coast, we certainly can’t rule out additional impactful landfalls this year.
Towards the end of the season, November should bring a few classic fall storms – which have a reputation for bringing widespread strong winds and heavy rain. This also introduces the potential for some impactful winter weather before Thanksgiving.
For more details on the 2017 U.S. Fall Forecast, be sure to watch the video that leads this article.
Looking even further ahead, here is a look at our preliminary forecast for the upcoming winter.
While there are several similarities to last year in the global pattern, we expect some differences in how this winter will evolve.
We don’t expect this winter will be as severe near the West Coast, which should mean less snow for the lower elevations in Washington, Oregon, and northern California. The Cascades and Sierra won’t match last year’s epic snow totals either, but there should still be more than enough accumulation for a strong ski season.
The coldest air relative to normal is expected to settle into the Northern Plains, Upper Midwest, and western Great Lakes. Meanwhile the southern tier can look forward to a milder than usual season.
An active storm track is expected to bring more Colorado Low type systems into the Great Lakes and Northeast which may mean more snow and mixed precipitation for the region. But at the same time the lake waters are not as warm as last year, which could reduce the amount of lake effect snow squalls this season.
There are mixed signals for now on how long we will have to wait for the arrival of persistent winter weather. However, once winter does arrive we expect that it will be more persistent than it was last year east of the Rockies where January and February were very mild.
We will continue to monitor global patterns and refine this forecast as the fall season progresses. We will have much more detail on what to expect this winter in our next seasonal outlook, which will be released at the end of November.