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Sun, clouds, snow, sun.. and more snow! Here’s a closer look at today’s changeable weather.

Weather Blog

ROCHESTER, NY (WROC) — As stated in the previous blog about snow in April, we’ve been settled into a colder and more active weather pattern that has continued to bring a few snow showers to the forecast. Today’s on and off snow were due to a mix of two different phenomenon; daytime heating and lake effect snow, one of which being slightly unusual for this time of year. Here’s what happened today:

Take a look at the visible satellite image from earlier this morning. We started off with mostly sunny skies especially in and around Rochester. You can even see the snow cover on the ground from yesterday’s snow showers around the Finger Lakes if you look closely. 

As the day progressed, the sunshine melted away the leftover snow and allowed the ground to heat up enough to produce bubbly, convective clouds over the land. This daytime heating and instability mixed with a westerly wind direction over the lake all came together, and was enough to create just the right conditions for multiple bursts of snow showers. Some of these flurries dropped visibility down quite a bit in some spots. You can see what the radar image looked like later on in the day as these scattered snow showers developed.

To put this in perspective, we typically get lake effect snow when cold enough air passes over the warm waters of the lake, and this usually shuts off by the time we get to April as the temperature difference between the relatively warm lake and the cold air above it isn’t enough to fuel the instability in the air. A good rule of thumb to follow is that if you have a temperature difference of around 13 °F between the air above the lake and the surface, you can indeed get lake effect.

The current lake-wide average water temperature of Lake Ontario is around 41°F, and the air flowing over us at roughly 850 millibars, or over 4,000 feet above our heads is around -10 °C, or 14 °F. With this set up, it came as no surprise for us to see these scattered lake enhanced snow showers today especially with the cold air mass currently in place. We even have more snow showers in store before the week comes to an end.

~Meteorologist Christine Gregory

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