Micro climates
Big differences in our weather over a small area
Micro climates allow us opportunities to experience significant weather differences over just a few miles.
Much of Southwestern Pennsylvania lies in what we call the lower elevations. This includes the western half of Fayette County and all of Greene County. The eastern half of Fayette County houses our local mountains and the weather in these two zones can produce dramatic differences.
The highest elevation is 2,993 feet on the Chestnut Ridge and the lowest is 740 feet at Point Marion.
Elevation is the key ingredient, and the difference in weather over just a few miles can be dramatic. Temperatures decrease with elevation at a rate of 4 degrees per thousand feet so a temperature of 40 degrees in Point Marion or nearby Uniontown can be about 9 degrees colder on Chestnut Ridge.
In the past few weeks we got to see the effects of this difference just by looking up the Chestnut Ridge and seeing the slower appearance of spring growth as one looks up the mountain. Spring comes about two weeks later along the Ridge than it does in the lower elevations.
In addition to the difference in temperature and vegetation there are a lot of other variants.
Mountains enhance precipitation as air is forced upward and as it rises it produces more clouds and more rainfall. Uniontown averages 40 inches of rain per year whereas Chalk Hill in the mountains sees an average of 54 inches. Snowfall in our lower elevations averages 38 inches per season and in the mountains it is 88 inches at Chalk Hill and ridge tops see well over 100 inches.
This increased rain and snow also produces more clouds and less sunshine than lower elevations. Fog is another problem, as mountains frequently see fog when clouds and precipitation hug the higher elevations, restricting visibility, making for dangerous driving conditions.
Another interesting weather phenomenon is the “Mountain Wind” which is a downslope wind that forms when winter and spring storms are centered to our south allowing for a wind out of the southeast that accelerates like a ball rolling downhill. Winds may be 10 to 20 miles per hour at the top of the mountain but can reach 40 to 50 mph, and sometimes higher, as they reach Hopwood, Point Marion and Connellsville.
If the wind stays from the southeast we usually get snow turning to rain however if the wind shifts a bit to the east and especially the northeast we get a significant snowstorm.
In the summer, mountain areas offer a respite from the heat and humidity as temperatures are frequently 5 to 10 degrees cooler than Uniontown and lower elevations and is the reason so many head to the mountain to recreate and cool off.
Mountain areas average about one day per summer above 90 degrees while lower elevations usually see at least 10 of these afternoons.
Record high temperatures are 103 for Uniontown and 95 for Chalk Hill.