For the last several days, we’ve been keeping a close eye on the potential for some spooky winter mischief near or just before Halloween. A low pressure system is expected to develop off of the leeward side of the Rockies early next week, and will gradually strengthen as it pushes eastward into the Great Lakes region Tuesday and Wednesday. This low pressure system will be ahead of an upper level cut-off low, which will supply the surface low with ample amounts of energy and upper level divergence (aka, help the storm rapidly strengthen). As we move into the Halloween time frame, cold air will begin to wrap around the back side of the low (we call this cold air advection). This rapid injection of much colder air on the back side of the system will cool the air at the middle and lower levels of the atmosphere.
With this, we have the POTENTIAL for a mix of wintry precipitation or snow, primarily across Wisconsin, Illinois, and Michigan. Operations model data remains highly variable in the timing, location, and amounts of wintry precipitation at this time, but it is worth watching. And yes, it’s way too early to even think about discussing snowfall accumulations (I don’t suggest looking at the weather model maps for this because they’ll change dozens of times before the event). Here is a map of the current potential tracks of heaviest snowfall based on the latest model data:
There are a few very key things to remember with early season wintry precipitation: 1- Models have a cold bias toward climatology this time of year, which often causes model forecast temperatures to be too cold in the longer range before they eventually correct themselves as the event approaches. 2- Ground temperatures are in the upper 30s to middle 40s, so most wintry precipitation that does fall would melt. An exception to this would be if snowfall rates were high, or a LOT of snow was anticipated. Otherwise, impacts would mostly be kept to grassy and elevated surfaces. 3- Uncertainty remains HIGH with this system, whether ANY wintry precipitation will occur, and where. Check back over the next five days as we get in more reliable data.
If data continues to trend toward the verification of this event occurring, we will be starting our affected winter clients a few days early so you are prepared for the event. Please complete your renewal process as soon as possible! If you’re not currently a client but are interested in our services, contact us today at firstname.lastname@example.org.