The power of dry air
Winter is still a month away and mid-Missouri has already seen numerous winter weather events.
In just a matter of two weeks, more snow has fallen than what we saw all last year. While several opportunities for snow existed last year, in the end, dry air ending up eating away many of our snow chances.
It’s easy to be pessimistic about snowfall chances, especially when you factor in snowfall the last two years. Before the snow we’ve seen this November, the combined total from the past two years was less than 6 inches, an 84 percent drop from a typical two-year period.
Several factors played a role in our dry winters, but none were as evident as the dry air that encompassed a large portion of the Midwest. By definition, dry air is air that simply has less water vapor.
The lower the water vapor content of air, the more room there is for evaporation when liquid falls through it. This is what mid-Missouri experienced the past two years during many of its snowfall events.
At times it seemed like it would snow, as seen by many radars and even on the ABC 17 Stormtrack Weather App, but when glancing outside all that greeted us were overcast skies and quiet conditions. Eventually, a few light snow showers did end up occurring toward the end of the event, but not enough to cause significant accumulation.
This is the power of dry air.
Much like cold, dry air can sap moisture out of the skin and leave it chapped, that same air can eat into our snowfall chances and leave just a dusting when 2 to 3 inches was anticipated.
As with any cold air intrusion, there will always be some level of dry air, but it’s the depth of that dry air that can significantly impact snowfall amounts. As snow falls through the atmosphere on the way to the ground, it commonly comes in contact with dry air, which evaporates the snowflake, releasing water vapor back into the air. As water vapor is released into the air, the moisture content of the surrounding environment increases as well. As this occurs, the layer of dry air shrinks in size, with snow eventually making it to the surface.
Because it takes time to overcome dry air, the shallower the layer the better your chances of seeing a decent snowfall event.
While no two snow events are the same, drier air always accompanies cold air, which in the end can make or break a forecast.
