SIR, CAN WE HAVE ANOTHER...

terryswails1
Oct 9
3 min read

What a sensational day Wednesday was. With high pressure perched overhead, dry air and subsidence brought seasonally crisp air and a full day of sunshine. Not surprising with late afternoon humidity values of just 25-30 percent (even drier than that in Iowa City, where the humidity dipped to just 21 percent just before 5:00pm). An air mass like that is not going to support clouds, and it's plain to see there wasn't a single one to be found over the state of Iowa...all day long!

Last night, fair skies and light winds allowed temperatures to plunge after sunset. Lows fell to 37 in Monticello and 38 in Independence. Spencer in northwest Iowa reached 32. The climate guru, Steve Gottschalk in Lowden, Iowa, measured 36 with frost on the rooftops.

Thursday morning, a similar set-up will bring another chance of patchy frost, especially north of I-80 and in the typically cold low-lying drainage areas. The high resolution 3k NAM shows the coldest readings aligned with the river valleys of eastern Iowa and NW Illinois.

After the fresh start, another stunning fall day is anticipated. The dry air will warm quickly and by afternoon highs should reach the upper 60s north to low 70s south. Southerly winds will pick up a bit, with some gusts to 20mph.

Late Thursday night or early Friday, a period of clouds and perhaps some light showers are possible as a weak cold front makes a pass at the region. Moisture is lacking and the window for rain short, meaning the bottom line is it will be light if it occurs at all. Temperatures will be warmer with the addition of clouds, holding in the upper 40s to low 50s. Here's what models are suggesting for amounts.

The EURO

The HRRR

The 3k NAM

THE GFS, last and least on rain potential.

Skies will clear behind the front Friday afternoon, setting the stage for a nice weekend with seasonal temperatures that are mainly in the 60s Friday afternoon and Saturday, warming to the low 70s Sunday. Dry weather should prevail at least into Monday, probably Tuesday.

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AN ENERGETIC LOOK, WEEK 2....

After that, the long wave pattern has a very energetic look to it, with a series of disturbances shown ejecting out of the mean trough centered over the southwest. In the animation below, you can see 3 distinct short waves dig into the 4 corners where they round the base of the trough and slingshot northeast. The wave lengths are short, so temperatures won't have a chance to stay warm after the 2nd short wave passes around the 15th.

Then models are showing the change to cooler weather as the mean trough advances into the Midwest. This was something we've been anticipating for nearly a week. While the GFS was on track with the idea yesterday, the EURO backed away but has now found its way home with the general idea. Confidence is higher for the idea of some chilly temperatures around October 21-24th, but the issue of phasing (the merger of the polar and subtropical jets) will be critical to the amount of cooling. The EURO now looks like this over the next 2 weeks.

One thing that would be good about the energetic pattern, if indeed it holds, is the fact more moisture and better forcing would likely return to the central Midwest with the storm track nearby. The GFS actually shows above normal precipitation in its departures for the period the 14th to the 24th. That would be welcome news, but as I often say, in times of drought, signs of precipitation often don't pan out. Stand by.

Despite some cooler weather in the long range forecast, the mean of the EURO Weeklies still don't show much in the way of snow through November 23rd. That's not all that unusual, as that's about the time when the snow season starts to pick up locally. By the way, the climate guru Steve Gottschalk says the snowbirds (or dark-eyed junco) are back as they migrate south. He has some interesting data on what that means for our first snow. I will have the details in my next post.