Ask the Meteorologists:
Posted July 21, 2008 9:39 a.m. EDT
Updated July 22, 2008 1:51 p.m. EDT
We were wondering if you could explain a weather phenomenon that we are experiencing in Fairview, just outside of Asheville. We have had drought conditions for the last 2 summers. We notice that it is raining all around our immediate area, but not on us. The rain front comes to within a mile of our immediate area, and then seems to break apart. WE have watched this for 2 years now- can you give us a reasonable explanation - construction, development, pollution?
MIKE MOSS SAYS: Joe and Nicole, The entire region has been in a drought as you mention, with some of the worst conditions acroass southwestern NC. Of course, that is a fairly large scale phenomenon and what you describe is much smaller scale, a variation that is local to your region. One issue that may be playing into your perception is that Asheville, and central Buncombe county in general, is located in a topographicaly-induced "rain shadow" area in which higher terrain, especially to the southwest and northeast, enhances precipitation production in those locations by forcing moist air upward, which then warms and dries out as it flows downhill into the relatively lower altitudes. This doesn't result in no rain at all for the Asheville/Fairview, region of course, but it would add to the sense that there are often significant rain-producing cells nearby that fail to produce precipitation in you area. Just to give you a sense of the kind of impact those terrain effects have, the area from around Asheville up into central Madison county (around Marshall) to your northwest only averages 40-45 inches of rain per year. Only about 15-30 miles to your southwest and west, the yearly average is more like 60-90 inches, while there is an average of about 50-70 inches per year a similar distance northeast and southeast. I can't be certain that this is the effect you're noticing or if there is some other shorter -term set of circumstances involved, but this seems like a reasonable starting point.