The weather will be calm today as it decides what to do tomorrow through Thursday as a large, messy storm system takes shape. There are no hazards, watches, advisories or warnings at this time, although we may see them later today. Below is the short-term discussion from the NWS Weather Forecast Center:
By Wednesday night and into Thursday, the aforementioned upper-level trough is forecast to eject into the Southern Plains and spawn an area of low pressure near the Texas Panhandle with an expanding precipitation shield found toward the northeast. At the same time, a slow moving cold front is anticipated to bisect the country from the Great Lakes to the Southern Plains. The precise location of this cold front as it sinks southward on Thursday will be crucial to determining which locations see significant snow, rain, or a wintry mix. At the moment, the greatest chances for disruptive snow extends from south-central Kansas through central Missouri, northern Illinois, and into central Michigan. Areas of sleet and freezing rain will likely be found just to the south of the heaviest axis of snow, but rather high uncertainty remains regarding where exactly the transition zone will set up. Residents are urged to stay tuned to the latest forecast so quick preparations can be taken before the storm begins.
Keep in mind these are just guesses at this point:
Forecast discussion
- Good deal of uncertainty remains for Wed-Thu System Not much going on for today preceding the more potential noteworthy event for Wed-Thu. Some lingering light snow showers continue this morning for western areas. This is the result of sufficient over- lake instability and a westerly component to the wind in the cloud layer. These snow showers are expected to taper off as the flow aloft becomes more southerly, and the sfc flow will be from the SE. Some partial clearing is expected with the low clouds blowing out, and lingering mid and high clouds holding in. There is good consensus that there should not be many significant impacts on Wed for the entire area, as pcpn should be all rain during the daylight hours. Temperatures will be comfortably above freezing as the rain develops overhead over the course of the day. The only potential impact there could be hydrology related with the rain and melting snow. We will address that more in the Hydrology section below. The uncertainty begins Wednesday night, and then continues through the end of the event around Thursday evening. The uncertainty comes in with regards to p-type and heaviest precipitation axis/p-type amounts. The remaining uncertainty, and still a decent amount of time before the impacts would arrive late Wed night/Thu morning will keep us from issuing any watches at this time. What is known is that we will see a gradual changeover of rain to a wintry mix before going to all snow. This occurs as colder air is drawn to the SE, and undercuts the warmer air aloft for some uncertain amount of time. Many of the international models/ensembles indicate that this window of mixed pcpn will be shorter, vs. a longer potential in the american guidance. That then goes along with where the heaviest pcpn axis ends up being. That is just another layer of complexity. The collaborated forecast will reflect somewhat of a middle of the road scenario. That would be rain, changing to a little potential freezing rain, then snow. The heaviest axis would be generally across the southern half of Lower Michigan. Our thoughts of where this might trend would be a little more to the south. We believe that the further north solutions may be too far north for two reasons. These reasons are there will be drier air feeding into the area from the NE, and the further north solutions look to have the mid level wave over-developed, which brings the sfc low a little bit further north. The sfc low is only a part of the forcing, as this event will be largely driven by a coupled upper jet scenario. This system looks quite similar to the event from Feb 2nd, with the difference being the presence of a mid level wave this time. - Clipper system expected for later Friday The pcpn will wind down quickly Thu evening, with a brief break in pcpn Thu night and Fri morning. We will get back into the NW flow once again, and a clipper will drop SE through the area. The brunt of pcpn with that clipper will likely stay north of the area closer to the core of the wave, with some light snow down here. - Quiet and seasonable for the weekend and Monday Once the late Fri/Fri night clipper moves east of the area, we should see a fairly quiet and tranquil period through most of Monday. The Polar jet retreats far enough North to keep the unsettled weather up there. The upper flow off of the Pacific will bring in a more mild air mass, vs the arctic from the North that has dominated more recently.
Hydrology
We are monitoring two different concerns with regards to hydrology with the upcoming system. The first will be snow melt and rainfall on the front end of the upcoming system. Then the ice jam potential aspect with the break up of ice with the up and down nature of the temps along with runoff expected. The good news is that the rivers are generally running around normal, or even a little below normal over the Muskegon River basin. This is good going into a melt/rain event like this. Much of the area has less than 2 inches of water in the snowpack, with a little over 2 inches toward the lakeshore. Much of this will probably melt and run off with the ground frozen everywhere. The good news is that new pcpn in the form of rain that would runoff would be less than an inch. Heaviest amounts likely further south. With rivers running at or below normal, they should be able to handle this. A good chunk of the pcpn will come as snow, which will not add to the runoff at this time. The uncertain part of this is the ice jam part. There is not a lot of ice on the Kalamazoo River, so there is less of a threat there. The Grand and Muskegon basins do have more ice, and could end up breaking up. Then it all comes down to how much breaks up, and then hangs up in the typical areas. We will continue to monitor this, but there is not a significant concern for now.
