Let’s get right to it. I see 2 snow chances over the next 5 days. The first will come with an advancing arctic front tomorrow and tomorrow evening, the second… Monday night.
Tomorrow, a strong arctic front will be approaching the region from the north. Moisture will quickly increase in advance of the front with the latest NAM saying the column will be pretty much saturated already be midday tomorrow. In addition, a couple of short waves (circled regions of the upper left hand chart of the map below) will also be advancing towards the region. These shortwaves and the advancing front will provide some lift to the saturated column and likely producing areas of light precipitation. Here’s that NAM chart valid early Friday evening :
It looks like we’ll have chances for light precipitation starting late morning Friday and last into Friday evening. Looking at the progged vertical thermal profile, it looks like we’ll see the precip begin as snow… mix or even change to rain during the afternoon hours as the boundary layer warms some… then back to snow as the arctic front passes through and squeezes out the remaining moisture in the column tomorrow evening. This does NOT look to be a major event… less than an inch all areas… Here’s the SREF snow plume chart (the mean / black line corresponds to 0.92″ of snow). As a matter of fact even this may be too much because the snow that does fall during the day tomorrow, may not accumulate at all as temperatures will be above freezing.
The second chance for snow will be what we call an overrunning / warm advection event. The ECMWF has been very consistent showing this event for the past 4 runs now. The cold air mass behind the arctic boundary that passes through here Friday evening will still be in place Monday night. During this time period, the ECM shows a strong piece of energy in the southern stream advancing eastward across the plains (circled yellow area on the upper left hand map of chart below).
As a result of this advancing energy, south winds will increase pulling warmer air and moisture northward towards the Ohio Valley. This moisture will then be lifted over the colder-more dense arctic airmass causing thickening clouds and precipitation to form (classic overrunning precip event). Lookong at the thermal profile in place at this time suggests the precipitation would be in the form of snow. The ECMWF spits out what would amount to possibly several inches of snow Monday night over our region. The one thing we’ll have to watch for is the thermal profile as this event nears. Often, the models underplay the amount of warming that occurs with this events so as a result as each new model run comes in, there’s a gradual northward push to the snow area. We’ll watch it close though.