In Joliet, IL, the weather is overcast and cold. We are traveling today, but have not picked an endpoint for today’s travels, other than to say that we will likely end in Kansas or Missouri.
The National Weather Service (NWS) in Chicago forecasts a miserable day today, with a high of 29 F, with flurries, wind and overcast skies for the Joliet area. I will be happy to leave that unpleasantness behind. The NWS has also issued a number of Flood Warnings across the state due to the high water levels in the Mississippi and tributaries.
The visible satellite imagery shows that as we drive south, we will exit the cloud cover.
The enhanced infrared satellite imagery does not provide much new information along today’s route and has been excluded from today’s post.
The water vapor satellite imagery shows a dry stripe of air. We will ride along the dry stripe from central Illinois through Kansas City.
The 12Z upper air sounding from Lincoln, IL, shows a moist layer near the surface, but extremely dry air aloft. There was only 0.19 inches of precipitable water present in the column today and no Convective Available Potential Energy (CAPE). A thermal inversion near the surface lowered the 0-3 km average lapse rate to 2.6 C/km.
The deep-layer shear was 77 kts, and the low-level shear was 35 kts. Almost all of the shear was due to speed changes, and little due to directional changes.
The surface observations (from the SPC Mesoscale Analysis Map) show the clockwise winds around the high pressure system. The cloud cover is contained in northeastern Illinois, though the cold temperatures extend throughout the entire region.
The surface pressure map shows a 1036 mb high pressure system over western Oklahoma, though the pressure gradient is not steep through the Great Plains or Midwest.
Synoptically speaking, the 300 mb NAM chart (from Unisys) shows
a split-flow pattern across the center of the country today. The streams recombine over Missouri, and there is a sharp bend in the northern-most jetstream across Illinois this evening. Perhaps the shear will shift to more directional shear versus speed shear in this region this evening.
The 500 mb NAM chart shows that my entire route will experience Positive Vorticity Advection (PVA) this evening. Notice how the wind direction vectors cut across the vorticity gradient.
The 700 mb NAM chart shows no rapidly-rising air along our route this evening. This chart has been excluded from this post.
The 850 mb NAM chart shows some weak Cold Air Advection (CAA) through Illinois, but the Chicago area will experience more of this than I will. The gradient is strongest near Lake Michigan.
Overall, I expect an unpleasant day today. I don’t expect much precipitation, based on the lack of clouds and the 700 mb chart, but the cold temperatures, and the potential for some wind as the high pressure system moves northeast will make today a day for staying indoors.
Thank you for reading my forecast.
The upper air soundings and mesoscale analysis plots are from the Storm Prediction Center website.
The forecasted upper air soundings are from TwisterData.com.
The surface observation and upper level charts are from Unisys Weather.
The satellite data is from NASA – MSFC