Someone recently asked me “Can you explain to me how it is that we can get snow for 10 days straight, yet we never seem to get rain for 10 days straight?” Simply put, I can blame it on Lake Effect snow. In a nutshell, lake effect snow occurs whenever cooler, dry air passes over the warm lake, such as the Great Lakes. Last week, there was a thriving cold air setup with a strong northwesterly flow (winds coming in from the northwest caused by a low pressure system that had parked itself in eastern Canada and western New England for much of the week. That low pressure system was also responsible for the rather strong winds that were prevalent last week. Basically, as that cold air moved over the lake, it picked up moisture off the lake, and carried it onto land in Pennsylvania and New York, where it deposited this built-up moisture as snow, and lots of it. Much of northwestern Pennsylvania saw several feet (in upwards of 40 inches) of snow, and these bands did extend far enough south to give much of southwestern Pennsylvania and the western Alleghenies decent accumulation as well (though nothing on that...

While much of the state (namely, the western half) has been pummeled by lake-effect snow over the weekend, there appears to be one exception to notable snowfall accumulation, at least along the Ridge and Valley region of the state and west (not much snow has made it farther east in the state, or at least snow that is sticking to the ground). This region is central Centre County, PA, otherwise commonly known as “Happy Valley”. A look at the modeled total snow depth chart provides the unfortunate news (assuming you like snow on the ground), pictured below. Image Courtesy NOAA This can likely be best explained by the “rain shadow” that the State College area commonly finds it in. Due to the interesting topography of the region, snow (or rain) often does not make it to central Centre County because more of it falls on the windward (“westward”) side of the mountain ridges it crosses. Indeed, you can see a well-defined line of differences in snowfall accumulation along a ridge in the Central Alleghenies from southeastern Somerset County, Pa the entire way to near where I-80 crosses into Centre County. There have certainly been snow flurries in Happy Valley over...

Ah, the changing of the months; the changing of the seasons. It’s official – December is here! (And in case you were wondering, I say the “changing of the seasons” because meteorological winter begins on December 1.) For some reason, this time of year always seems to bring interesting weather. Let’s take a look at some of those interesting events. An Anniversary: 4 Years Since the Last Tornado in Westmoreland County It’s been four years already since the last time a tornado struck Westmoreland County. Don’t get me wrong, there has been plenty of severe weather since then, but December 1, 2006 was the last time a tornado was officially reported. This twister, an F1 (and likely one of the last tornadoes recorded before switching to the Enhanced Fujita, or EF, scale on 2/1/2007) touched down briefly just west of Westmoreland Hospital in Greensburg (Fort Allen area) around noontime. It damaged about a dozen homes before skipping up the central reaches of the county, knocking over many trees. My most famous recollection of the storm also involves downed trees, but was not caused by the tornado. On the other side of Greensburg (Hempfield Township, actually)...

It’s another rainy day across the Commonwealth [of Pennsylvania]. It’s also Thursday. A friend asked me this morning, “is there some sort of meteorological reason why it always rains on Thursdays?” I recalled it did seem to rain on a good number of Thursdays. But how many exactly? I consulted a handy calendar to get the dates of Thursday going back to the beginning of the semester (actually, the Thursday before), which was a total of 12 Thursdays. I then went to the National Weather Service’s Climate Information Site and, using the Preliminary Monthly Climate Data, determined exactly which Thursdays it rained. The results are displayed below: Date: 8/19 8/26 9/2 9/9 9/16 9/23 9/30 10/7 10/14 10/21 10/28 11/4 Rainfall Amount (in): 0.00 0.00 0.00 0.00 0.21 0.00 3.91 Trace 0.23 0.03 0.00 Ongoing Other Details: Trace day after .42 day before .62 day before Trace day after Trace day after Trace day after Some notes about the data: I included the days where there was rain before or after just to factor in...