A lot of sunshine with a few afternoon clouds will pair with very warm temperatures this weekend. A strong ridge of high pressure moves onshore pumping temperatures into the mid-70s in Reno both Saturday and Sunday, and the heat will be enough to pop up a few afternoon clouds starting on the mountains and drifting into the western valleys. A weak cold front passes by to the north Monday cooling us back into the 60s, but it’s not likely it will produce any showers this far to the south.
When talking about floods, many people wonder how an El Niño affects our chance of having floods. While it may seem like our odds would increaseevery time an El Niño rears its head, that hasn’t been the case historically. In fact, large widespread flooding events are no more, and maybe even less likely to occur here in western Nevada during an El Niño. That’s not the case in southern California, where an El Niño does increase chances of flooding, but not this far to the north.
There are lots of other factors which come into play. You can also get flooding due to debris flows. That becomes very important around our neck of the woods after one of our numerous wildfires. After a severe burn, there little or no vegetation on the ground, and any good rain will run off very quickly, usually taking a healthy slug of mud, then sticks, and then like a good avalanche, downed trees. These can dam up and divert rivers, causing catastrophic flooding. That’s one of the reasons forest officials make such an effort to re-vegetate burned out areas.
Here’s another mechanism: Ice Jams. In the northern tier states (especially New England), the winters are cold enough to freeze over the major rivers. Most of the time, the spring thaw occurs without any problems, but in some areas, a rapid breakup of the icepack can act like a debris flow, damming up the river and causing deadly and damaging floods. In the last 30 years, at least seven people have died, and damages average 125 million dollars annually.