Comments on Last Week

85 degrees.

That’s the temperature swing we saw between last Sunday’s high of 71° and Thursday morning’s low of -14° at Denver International Airport (DIA).

Last week’s cold wallop was nothing to scoff at, especially so early in the season. We broke two all time record lows on November 12 and 13, of -13° and -14° F respectively, and two record low maximums. The record low for November 13 wasn’t just broken, it was smashed. The previous record low was -3° F set in 1916, making the new record 11 degrees colder.

The cold air arrived in a hurry. Last Monday morning we recorded a high of 69° in downtown Denver at 10:04am. By 10:20am we had dropped into the 40s, and by afternoon we had fallen into the teens with light snow.

Here’s a look at the giant temperature swing last week.

Weather5280

Denver also saw it’s first measurable snowfall of the year at DIA, recording 0.1” on Tuesday November 11, and 2.2” on Wednesday the 12th. DIA recorded an additional 1.7” of snow on Saturday, bringing the totals for the week to 4” even. Not a huge snow event for Denver as I think we made clear all along.

Worth noting is that a few locations that did much better with snowfall, however. The Boulder area won big from the Tuesday/Wednesday snowfall with upwards of 8” being reported. The Palmer Divide did best with Saturday’s snowfall as a persistent snow band setup Saturday evening delivering from 2 - 5” of snow -- it was one of the locations we were watching for the potential to bust ‘high’ under banding.

Competitive edge
I was told last Saturday from one of our readers that we were running much colder for the coming week than any other forecast they had seen. Of course, this made me look. Leaving names out of it, this was one of the forecasts I saw on Saturday November 1 (left) for last week’s cold shot. The coldest maximum over the four days was 30 degrees, and forecast for Wednesday. This turned out to be a 24 degree temperature bust. The forecast low of 16 was still 10 degrees warmer than the actual high of 6 for Wednesday.

Denver outlet forecast bust

By Saturday we had already dropped forecast highs into the low teens for Wednesday, and released this chart of blended forecast model daily maximums for the coming week -- nowhere near freezing for Tuesday, Wednesday, and Thursday.

There were other reports of forecasts being off by as much as 40 degrees within 24 hours of the forecast day last last week, which is really inexcusable.

On the right is a forecast from Thursday calling for 3 - 6” of snow in Denver Saturday night into Sunday. We went out with 0.5 to 3” for Denver and stuck with it. Officially DIA recorded 1.7” of snow, with 1.25” recorded at our station downtown Denver. The wildcard was banded snowfall, but this wasn’t a 3 - 6” snowstorm for Denver, as we saw.

The point here is not about pointing fingers -- because, hell, we all blow forecasts.

The point is, at Weather5280, we’re sort of obsessed with getting it right. And it’s not just about being competitive in our forecasts, it’s about making sure our readers are always well-informed.

Brendan Heberton

Brendan is founder of Weather5280. He is co-founder of FreshyMap, and develops software for geospatial data analysis and visualization.

Denver, Colorado
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