Good afternoon everyone! I wanted to get started discussing the freezing fog threat that is expected to exist over the eastern two-thirds of the region this evening and increasing through the overnight hours into Tuesday morning. Weak southwesterly winds will help to drive slight warm air advection within the circled region below that will likely result in areas of dense freezing fog given temperatures at or slightly below freezing. Slick spots are expected to develop within areas that observe the denser pockets – something to keep in mind if traveling.
A weak shortwave trough that will be lifting into the northern portions of the region this morning is the driving force for the slight warm air advection out ahead of the system. The energy will be rather weak, but will provide enough saturation in the lower levels of the atmosphere to initiate patchy freezing drizzle, especially in IA, this evening through the overnight hours. Patchy freezing drizzle coupled with areas of freezing fog could make for a mess of things (slick spots) in IA during this timespan.
Due to these threats, the National Weather Service in portions of eastern IA have issued Winter Weather Advisories for the threat of freezing drizzle/fog through 9am CST Tuesday. Eastern IA will have the greatest focus for this threat, hence the advisories. However, as previously stated, don’t be surprised to see patchy freezing drizzle and especially fog west of those locations spanning the remainder of IA.
Simulated radar through 12pm CST Tuesday: Increasing warm air advection over fresh snowpack along with the entrance of a shortwave trough will initiate patches of freezing drizzle in northern IA by 6pm CST this evening and continuing in a southeast direction through the night across central and eastern IA. There is the chance eastern NE could observe freezing drizzle but will be isolated in coverage due to less saturation. Areas of freezing fog will be more of a threat in those areas. By 6am CST Tuesday, areas of freezing drizzle will still be prevalent in eastern IA with portions of far northern MO also working in patches of this threat. Most of these risks will diminish by noon Tuesday, but lingering pockets of freezing fog could still promote a few slick spots.
The freezing fog risk will shift southward Tuesday night into Wednesday morning (shown below in the darker shades) with eastern KS and northern MO having the highest chances to observe fog and hence some slick spots. Elsewhere, the threat won’t be zero as patchy freezing fog will still be possible in central NE and southern IA. The slight warm air advection over this fresh snowpack is definitely keeping it interesting in the region!
Another weak system with more moisture will work into the region late Wednesday through Thursday morning, providing the chance for a light wintry mix. Warmer air to the south will help to keep most of the light precipitation as rain in southern KS/MO while warm air overriding cold air at the surface will increase the threat for light freezing rain in northern KS/MO. Scattered snow showers are expected along the northern periphery in eastern NE into IA. We could be looking at a light glaze of ice before all is set and done in the areas that observe freezing rain with this system.
We’re watching a more impactful system Friday through Saturday which will leave the entire area “at play” for impactful wintry precipitation. The highest risks for significant wintry precipitation includes the northern half of MO and the southern half of IA (almost the same places that got hammered over the last weekend). Shown below is a latest simulated radar from the GFS Parallel for the late week storm, with some areas receiving a heavy dose of snow. The second image below represents what was shown from this morning’s update which still aligns with our latest thoughts. Given how far out this system remains at this time, more adjustments in track and intensity will be likely over the next few days, so definitely keep checking back for our latest thoughts. One thing is for certain, a potent upper-level trough with an associated arctic high pressure system will dive in behind this system and bring a dose of much colder air late weekend into early the following week.
If you have any questions do not hesitate to reach out! Have a great evening!