A Wild End to the Week — Maybe

The oddness of 2020 continues….

As I write this I’m looking outside at heavy grey overcast, occasional rain, and temps in the mid-40’s. The second week of May. All I can say is, a change is coming. And it’s forecast to be in a way we’re not really used to — almost the inverse of how storm systems usually impact us. By that I mean a warm front will ride rapidly north from Tuesday night into Wednesday afternoon, and it’s expected to bring almost as quick a temperature and humidity rise as we usually see things fall behind an early spring cold front.

Here’s an example (for Wichita):

Darksky Net Forecast May 12 through 16
Forecast temperatures (source: Darksky.net) for Tuesday through Saturday

Temperatures remain nearly stable from now (10am Monday until about midnight Wednesday morning. When we pass 50 degrees Tuesday night, that’s the last time we’ll see it this week. The low Wednesday is the 1am temperature. By mid afternoon we’ll have gained 23 degrees, with the dew point remaining within a degree or two of the temperature at any given time.

Now let’s compare a point west of the dryline Wednesday afternoon (Sublette, KS):

Darksky Net Forecast Sublette May 12 through 16
Sublette Temperature forecast for Tuesday through Saturday (credit: Darksky.net)

Although the lows are the same Wednesday morning, the high is much warmer. There are two things at play there: they are in the dry air, which warms more quickly, and there is a bit of compressional heating due to the increasing altitude and the moist air pushing to the west. Let’s look at temperature and dew point at Sublette for a couple of times Wednesday afternoon :

Forecast conditions, noon May 13
Noon Wednesday forecast conditions at Sublette (credit: Darksky.net)
Forecast conditions, 5pm May 13
Forecast conditions 5pm Wednesday at Sublette (credit Darksky.net)

The temperature rises 14 degrees while the dew point falls 13 degrees. That’s evidence of a decent-strength dry line developing, probably not too far away. Here’s one model’s depiction of that:

GFS model High Resolution At 7pm CDT Wednesday
GFS-HiRes Model forecast of dew points, 7pm Wednesday. (credit: PivotalWeather)

The models are still in a bit of disagreement on positioning of the dryline and just how fast the warm front will come north. There is enough agreement that SPC has settled on an outlook area for Wednesday:

Rest of the week

Chances for severe weather stick around each day through Saturday. But beyond Wednesday, specific risks for each day become dependent to a large extent on the evolution of storms each night and particularly how long they hang around in the morning.

 

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