BALTIMORE — A few Marylanders were given a late wintry surprise yesterday as a few snow showers made their way into the state in the afternoon and evening, but if you looked at a thermometer or a weather app, the temperature was reading well above freezing.
So, would this not be too warm for snow to survive?
Surprisingly, the answer is no.
Snow can fall when temperatures are above freezing but only when the conditions are just right. It is all dependent on relative humidity. Looking at yesterday's conditions during the afternoon snow showers, the wet bulb temperature (a measure of temperature and humidity) showed that it was comparable to 36 degrees. AS for the evening showers, conditions were even cooler and the wet bulb temperature was at 34 degrees.
This allowed for any snowflakes to make their way down to the surface to survive their fall.
The next key component was the strong winds aloft that helped drag in enough moisture off Lake Erie to produce these snow showers.
We pointed out the winds at 700 millibars (around 3,000 feet in elevation) to show just how strong the winds were as it carried over moisture from the lake.
Winds were howling at 52 knots, or 60 mph, at that height giving the airmass enough momentum to overcome the Appalachian chain and bring us those snow streamers.
You will also notice that there was an ample amount of moisture in the airmass just below 3,000 feet in the "dendritic growth zone" where snowflake formation takes place between -10 to -20° F.
Again, this case of snow was just right to see those snow showers which certainly made the wintry surprise a little more magical.
