The heavy valley rains from earlier will turn to snow over the next few days…enough to cause a Winter Weather Advisory to be posted for the Reno area until noon Friday. Total valley accumulations will vary greatly depending on the elevation, but could range from a couple of inches near the airport to as much as a foot in the upper foothills. In the mountains, a Winter Storm Warning will extend through the weekend into Sunday afternoon, with high winds and heavy snows once again making mountain travel anything from difficult to impossible. By the end of the weekend, Lake Tahoe could see another couple of feet of snow, with 5-6′ possible in the upper elevations near the crests.

Temperatures will drop dramatically, likely not exceeding 40 degrees through the middle of next week.

There’s a lot of stormy weather left this week, with a wet and warm storm gradually transitioning into a somewhat less wet and somewhat colder storm. Significant rain below the 8,000′ snow level overnight tonight into tomorrow morning has caused an Areal Flood Advisory to be posted for the Lake Tahoe area, as some leftover snow is still clogging up storm drains. As we go through the day on Thursday, snow levels will gradually lower to about 6,500′, and then drop all the way to the valley floor by Friday, although the deepest moisture will be past us by then.
High winds will continue to plague the valleys, and the High Wind Warning continues for western Nevada through Thursday. High wind gusts of 60 mph are possible, with even stronger blasts in the wind-prone areas.

As the valley rain switches over to snow late Thursday night into Friday, precipitation amounts will lessen, but a few additional inches of snow over the course of the weekend is not out of the realm of possibility.

Winter weather will come charging back into the region this weekend, and the National Weather Service has issued a mountain Winter Storm Warning from Friday afternoon all the way through Monday. There are two separate systems coming through, the first of which will bring snow above 6,500-7,000′ on Friday afternoon through Saturday. Another storm front will come in later Sunday, this one colder, which will drop snow levels all the way down to the valley floors. The mountains will provide enough lift to keep precipitation up there going almost continually between the two storms, and although things may ease up a bit Saturday night into Sunday morning, it is best you get any mountain travel out of the way before late Friday afternoon. By the time the second storm ends we could be looking at another 4-5 feet of snow in the upper elevations of the mountains.

In the valleys, initially there will be a fair amount of shadowing late Friday, but enough spillover early Saturday to make some rain almost a sure bet. The second storm Sunday night into Monday could create some commuting issues with slippery roads Monday morning.

After a mild and dry stretch to nearly finish off January, it looks like some wetter weather will work its way back into the region. Tuesday should stay mostly dry and mild, with only a few showers possible up in the mountains. Precipitation chances increase slightly Wednesday and Thursday with a couple of weak systems moving through, with stronger storms moving through Friday and Saturday. Snow levels should remain above Lake Tahoe until the weekend, when they will drop to somewhere between the lake and the valley floor.

A series of powerful storms will make travel across the mountains difficult if not impossible late Wednesday through Thursday. In the short term, the valley is under a Winter Weather Advisory tonight into early tomorrow morning, with accumulations of up to a few inches in the valley with more possible in the foothills. Wednesday starts with a bit of a break, before a very powerful storm brings high winds and heavy snow to the mountains (and possibly significant rain to the valleys.) A Blizzard Warning is in effect above 7,000′ for the mountains from 7 pm Wednesday until 7 am Thursday. A Winter Storm Warning is also posted starting 4 pm Wednesday running into early Friday morning. Conditions dry up Friday and Saturday before the next storm (not as strong this time) comes in on Sunday.

After closed passes, heavy snow and high winds, the weather conditions will calm down as we head into the work week. Warmer air will move into the region and scattered rain and snow showers will decrease Monday morning after heavy snow causes a very difficult time getting across the Sierra. Temperatures will be mild through the rest of the work week (near the 50 degree mark in Reno) with the next storm moving through on Wednesday, with mountain snow above 6,500’ and valley rain.

Many have asked me what the difference between freezing rain and sleet is. Sleet is basically snow that starts to melt on the way down, and falls as a mix of rain and snow. Freezing rain is precipitation that has completely melted into rain on the way down, and then falls into cold air at the surface that is below freezing. This rain usually freezes rapidly as it hits the ground, and is perhaps the most dangerous winter weather pattern. How do you get it?

In general (and perhaps obviously) you need to have warm air aloft on top of cold air at the surface… along with (again obviously) some rain. This can occur a couple of different ways. A warm front will always shove warm air up over colder surface air, and is a relatively common way to get freezing rain in the central plains states. Here in Nevada, these cold air inversions that we have been having can also trap enough cold air in the valleys to create freezing rain, although it is fairly rare.

After a dry and warm Friday, the weather pattern will change as we go into the weekend, with a series of storms lined up to come through. None of the storms are particularly strong in and of themselves, but cumulatively they could add a nice boost to the mountain snowpack. The strongest of the storms gets going Saturday, with snow levels that will approach the valley floors, but it isn’t likely we will get any valley accumulations, and we will see significant shadowing out due to strong southwesterly flow over the mountains. A Winter Storm Watch is posted for the mountains starting early Saturday morning and going through Sunday morning. Snowfall amounts will range from a few inches at Lake Tahoe to a foot or more on the passes.

The weather remains unstable through the middle of next week with scattered valley rain and mountain snow.