First Alert Weather In-Depth: Ingredients for a cold night

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ROCHESTER, N.Y. (WHEC) — Only two days ago we had summer weather here in Western New York, but tonight we are talking about temperatures that are going to be dropping into the 30s.

It is interesting to note that the record low temperature for Wednesday morning is 30 degrees, which goes back to 1981. We do not foresee a record, but it is worth mentioning.

There have to be a couple of ingredients for the temperature to drop during the overnight. Number one is the wind speed. The winds need to come down dramatically as we go through the wee hours of the morning. The second is the cloud cover. As we go through the late afternoon and evening the clouds are expected to slowly dissipate. So why are the clouds so important?

We get that incoming solar radiation and then as have that cloud deck and we get into the nighttime hours the longwave radiation escapes into the atmosphere, but the clouds act as a blanket on the atmosphere. If we get some clearing, will exit the atmosphere and that is when the temperature will fall.

So how chilly is it going to get tonight? Again, we expect the low temperature in Rochester will about 39 degrees. But south of Routes 5 and 20, in those deeper valleys, the temperature will be in the low 30s. It is no surprise that we have a frost advisory in effect for some folks southwest of Rochester. The question is when we get the warmer weather again.