Mid-50s, sun returns Thursday after cold couple of days

Weather Blog

Temps this afternoon through the atmosphere will range from 46 to 48-deg at the surface (i.e. ground level) down to a record 31-below at roughly the 18,000 ft. level.

The lowest temp on record at that level at the Davenport, IA (one of our closest upper air sites) at that level of the atmosphere is just under 27-below–so we’re talking about record cold readings aloft). That’s an extraordinary vertical temp drop through the lowest 18,000 ft. of the atmosphere approaching 80-deg.

Closer look at the Wed afternoon CAPE forecast off the National Weather Service’s HRRR model

In practical terms what all this means: Any heating which occurs down here at ground level will produce air which is dying to ascend and cool–and to do so vigorously. This produces a situation is which the rain and snow showers which occur may well do so with gusty winds as air rushes in to replace the rapidly rising columns of air. This steep vertical temp drop increases the case for small hail formation with any rain and snow which occurs.

Lightning also becomes a possibility in a few of the more vigorous snow/rain showers since the cloud towers in this situation will be composed of a mix of raindrops and ice–a situation which separates electrical charges, the basis for lightning occurrence.

And another interesting side bar–such an unstable atmosphere has been known to spin up waterspouts on occasion out over the “comparatively warm waters” (water temps are running from 46 to 51-degrees) of Lake Michigan.

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