If it seems a little warmer than it should for the second week in October, you’re not going out of your mind (okay, well maybe not for this reason). It’s been warmer than normal for most of the country, and we’ll stay that way for the next couple of weeks. The abnormal warmth is doing more than just keeping us from shivering—it’s also keeping the trees from changing colors.
This afternoon’s outlook from the Climate Prediction Center shows decent odds of abnormally warm temperatures across almost the entire United States continuing over the next two two weeks, with higher odds of above-average temperatures out toward the Intermountain West.
While these fall-flavored maps may make it look like we’re going to melt away, remember that they only show you the forecaster’s confidence in above- or below-average temperatures, not the actual temperatures themselves.
Warmer colors show higher odds of temperatures coming in above average; in the darkest shading over Utah, for example, the average daily temperature is around 55°F this time of the year, meaning that you would normally expect a high of 65°F and a low of 45°F, give or take a few degrees. In this case, you could probably expect highs around 70 and lows around 60. By no means excessive—kind of nice, really!—but not normal, either.
The culprit behind nature’s anti-fall bias is a big ridge in the jet stream that will camp out across much of the United States and Canada in some form or another for the next two weeks. Weather under ridges tends to stay calm, clear, and warm.
You can see the iconic ridge in this GFS model image valid for this Sunday:
And the GFS thinks that the bulk of the ridge will slide west by next Thursday, a time period that’s typically toward the edge of model fantasy land, but fun to look at anyway:
The East Coast—especially the Mid-Atlantic and Northeast—stands the best chance to see near-average, chilly October weather beginning this weekend as a series of cold fronts rudely shove their way through the region over the next week or two. Everyone else stays warm(ish).
Abnormally warm temperatures through the fall also has an effect on foliage, much to the disappointment of leaf peepers near and far. We’re at or just past the historical peak in color in interior sections of the Northeast, for example, and many of the leaves up there are still green or just now changing color.
The National Weather Service office in Caribou, Maine, posted a stunning picture to their Facebook page the other day showing the difference between this year’s color compared to the same date on 2012 and 2013 at Hanson Lake in Presque Isle. The trees in this part of northern Maine—typically vivid by now—look like the trees in North Carolina should by this point in the year.
It’s been a weird year for both quiet and active weather, and given the ever-strengthening El Niño, there’s no reason to believe the interesting trends won’t continue through the rest of fall (“fall”) and winter.