I'M IN THE MOOD FOR MISCHIEF...
Back to back days of sunshine and temperatures above the freezing mark made for good sledding and even some thawing around the region Tuesday. Low level moisture from melting snow and nighttime cooling may combine with weak surface winds for more shallow areas of fog or stratus early Wednesday. This should burn off in most areas allowing for at least partial sunshine and afternoon temperatures comparable to Tuesday. Where the snow pack is deeper highs will hold in the mid 30s while low 40s are likely in the far SW where a minimal coating exists.
This was the snow cover we started the day with Tuesday. The days melting did not change it dramatically.
It really shows up nicely in the hi-res GOES satellite imagery. All that white over Iowa and Illinois is the snow pack.
You can see the impacts snow cover has on temperatures below. Late in the day Tuesday readings over the deeper snow field were in the low to mid 30s. Just outside of it they jumped into the range of 40-45. The reflective nature of snow does not allow the suns energy to absorb into the soil as it would with bare ground keeping temperatures colder. This reflective impact on solar radiation is "known as the albedo".
That leads us into our next weather maker which leads to some wintry mischief. It's been a long time coming considering the last day with measurable precipitation in most of my area was January 1st. We'll run the streak to 13 days before rain or snow arrives Thursday.
The system I'm referring to has some nice dynamics but moisture is somewhat limited and the track is not ideal for forcing to overcome that issue. We discussed this yesterday. That said, the system is going to cut-off allowing it to slow down and spin its way directly across my area through Friday night resulting in a prolonged period of forcing and at least light precipitation.
Spokes of energy rotating around the vortex will generate occasional periods of snow. The first batch arrives late Thursday afternoon and could begin as light rain before transitioning to light snow. Amounts during the day look light with minimal snow accumulations confined to my NW counties. Later Thursday night and Friday as the system settles overhead and inches east the cold core of the energy will be overhead. That, along with spokes of vorticity rotating within the circulation will generate additional periods of snow showers or even snow squalls. The potential is there for an inch or so but much will depend in the precise position of the circulation center and the location of a dry slot. Right now the broad brush approach is for most areas to see accumulations of 1 to perhaps 2 inches, with the heaviest focused on my far northern and western counties (where a few 3" amounts are possible). The 12K and 3K NAM have even higher totals but for now I consider them outliers. Currently I expect the heavier and more impactful amounts will remain just to the northwest of my area. We still have time to monitor trends as we are just getting into the 24-36 hour window before it begins. As of now, here are what various models are showing. These are not forecasts, just model output that allow us to make forecasts. You will notice amounts are lower over eastern Iowa and Western Illinois where the upper air low and associated dry slot is centered over the heart of my area.
The Canadian GEM
Now what I currently consider the outliers for snow accumulations starting with the 3k NAM
The 12k NAM
As the storm advances east it will generate some brisk NW winds by Friday and with time draw progressively colder air into the Midwest over the weekend. By early next week some good old fashioned January cold will be in place. Yes Virginia, winter is alive and well. After all, it is mid-January! Roll weather...TS