Can it rain more in a valley than on a hill?

Question

An odd question, but my mom and I have noticed that when it is raining, it always seems to be raining more in towns nearby that are at a lower altitude. Is this possible?

Answer 1

Good observation. Here is what I believe may be going on - and there may be other factors as well to keep in mind. First towns may have a bit of a so-called heat island effect which generates convective currents over and around the town/city which in the presence of instability of the atmosphere can intitiate precipitation. Valleys are typically more protected and are in the shadow of surrounding hills or mountains which due to their orographic lifting creates more rain on the windward side of these hills or mountains and less rain on the lee side. What I would suggest you do is collect some data from archived newspapers or weather observers near you and in those nearby towns and look to see what is really happening. If indeed the valley locations are receiving more precip I believe it would be worth a good science fair project indeed and some of the possible reasons I have given above could be evaluated as well as a few other possible reasons you may find in the data.

Answer 2

Interesting observation and good question. The answer typically depends on the wind direction. But as with most things in meteorology, there are always exceptions. Below is a description of what could be happening.

It certainly is possible for one side of a hill/mountain to see more precipitation than the other side or on top. It all depends on the direction the prevailing wind is blowing. For example, Denver, CO which sits on the leeward (downward) side of the Rockies experiences far less precipitation per year than areas in the mountains or on the western slopes of the Rockies. The main reason for this has to do with many Pacific storms that come in from the west will produce precipitation on the western side of the mountain but downslope (drying) as the storm moves over the Rockies. You can see from the link below on the second page there is an annual precipitation map of Colorado. It shows the variance that was described above. I hope this helps.

http://ccc.atmos.colostate.edu/magazine/winter2001.pdf

Answer 3

It's called orographic lift. As coulds pile up against moutains they rise. As the clouds rise moisture condenses and it rains. Some times quite a bit! So yes it does rain more in the hills than in the valleys. The valleys may get more water but it's just run off.

Answer 4

Maybe, you can get some kind of air inversion that concentrates some clouds, but only under unusual conditions. It would get more water flowing through it though.

Answer 5

yes