About Rain and Melting Snow

By: Lee Grenci, 1:43 PM GMT on March 25, 2015

Just a quick note on the topic of rain and melting snow in early spring.

When it rains on a snowpack in early spring, it would be easy to attribute the rapid melting of snow directly to warm raindrops falling on the snow. It can be shown, however, by invoking the conservation of enthalpy, that warm rain falling on snow cover increases the runoff by only 10% (raindrops directly melting snow). Thus, it would take sustained downpours to directly melt a rel...

Weather Forecasting Thermodynamics

Updated: 3:18 PM GMT on March 25, 2015

Spring Snow Sticking on Roads? ... Repeating the Party Line

By: Lee Grenci, 3:09 PM GMT on March 21, 2015

A lot has changed with regard to broadcast meteorology since I started my stint as an on-air meteorologist (WPSU-TV) in the mid 1980s. If some of the local network affiliates and the 24-hour news programs are any indication, on-air weathercasters utilize much less atmospheric science in their presentations, structuring most if not all of the forecast around computer models. For example, weathercasters show short-range computer animations of clouds and precipitatio...

Weather Forecasting Radiative Transfer

Updated: 6:21 PM GMT on March 21, 2015

Disappearing Acts

By: Lee Grenci, 8:50 PM GMT on March 13, 2015

I had meant to post this last week, but better late than never. There were nice two examples of "disappearing acts" in the Southwest...snow cover over a portion of Texas and Oklahoma and upslope fog over western Texas and a portion of New Mexico. Before you look at the loop of visible satellite images (below) from 1415 UTC to 2015 UTC on March 5, 2015, check out the two areas to which I'm referring on this annotated visible satellite image at 1415 UTC.

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Synoptic Meteorology

Updated: 6:02 PM GMT on March 14, 2015

Ice, Salt, and Time Machines

By: Lee Grenci, 2:16 PM GMT on March 05, 2015

The sleet and freezing rain that encased central Pennsylvania Tuesday night and early Wednesday morning meant that I spent several hours clearing off my driveway and the back patio (see picture below). I've had just about enough of winter weather, although, as I was chipping away, I got an idea for a blog.


The old man chipping away at ice on the back patio...back-breaking work!

The ice on the back patio was particularly tough to remove, ...

Winter Weather

Arctic Front: Late Arrivals

By: Lee Grenci, 6:19 PM GMT on February 24, 2015

A good question from George about the late arrival of Arctic air in the DC area on Monday, February 23:

On a peripherally related note, do you have any thoughts on the delayed arrival of the arctic air here. It seemed to get hung up in the mountains for several hours which is typical, yet often missed. I was too busy with other things to be watching it but local forecasters were fast with its arrival (predawn rather than the verifying rush hour timing).

Synoptic Meteorology

Updated: 12:50 PM GMT on March 02, 2015

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About 24hourprof

Retired senior lecturer in the Department of Meteorology at Penn State, where he was lead faculty for PSU's online certificate in forecasting.