WEST MICHIGAN (April 26, 2014) — If Spring showers bring May flowers, just keep telling yourself that as we head through the next seven or so days. After a day filled with abundant sunshine Saturday and temperatures in the mid/upper 50s, clouds will thicken and lower and dominant our weather from Sunday through next weekend. Why?
Our forecast models are showing an upper level low pressure system (or cold pool of air aloft) that will slowly rotate in to and through the Great Lakes and Midwest. In fact, it will meander in the region for several days creating wind, cloudy skies, and at times waves of rain showers across the area.
It will not be raining all of the time, but at least a few showers are possible throughout the entire 7-day forecast until this system and upper level trough lift out of the region. We’ll also need to watch the potential of some strong/severe storms cropping up Monday/Tuesday as things heat up during the day and the low approaches.
The attached snapshot is from one of our computer forecast models. It’s valid for Tuesday morning and depicts what’s happening around 18,000 feet above the surface and what we refer to as the 500 millibar level. We use this height to identify upper level energy, upper level lows, disturbances, waves, and something called vorticity (the spin of something). A positive spin in the atmosphere (counterclockwise direction) tends to create lift. That’s conducive to the formation of clouds/precipitation.
Note the large low planted over Kansas City, Missouri and the broad upper level trough over the nation’s mid-section. The trough refers to a dip in the upper level flow that allows colder air and unsettled weather over a region. The colder pool of air aloft from this low creates instability. The air closer to the surface is warmer and wants to rise…it has buoyancy. So again, a rising air motion is created. Remember, two easy ways to get air to rise is to destabilize the atmosphere with colder air aloft, or warmer air at/near the surface. These lows tend to be a function of those types of thermodynamics.
These slow, meandering upper level lows can sometimes take many days to move in to and through a region. In our case, it will take the better part of the next week. Get the complete forecast at www.fox17online.com/weather.