A ridge of high pressure is dominating our weather leaving little or no chance for valley precipitation for at least a week and probably longer. The trend is to move out of our 45 day stormy pattern and into a much drier, warmer pattern. There will still be small storms to pass through our area and leave snow in the mountains, but now would be a pretty good time to wash the car.
The first of those small storms will graze our area this Saturday, then on Tuesday of next week, with a little bigger storm coming in the following Thursday. These impulses will have no measurable effect on the valley but will serve one very important purpose; to change the air. The valley is notorious, this time of year, for trapping cold air, especially when there is warm air aloft, like now! The cold, moist air in the valley is producing thick morning fog. Combine that with 20 degree temps, and the fog freezes on some roadways. These storms move the air out of the valley and replace it. The high pressure systems also are able to warm the air in the valley, but that takes time and usually the air cools again at night. This entire process is called a temperature inversion and we will be experiencing them for quite some time to come.
Here is a quick look at the latest NOAA PNA chart, which suggests that what I am saying is true:
Remember, as the PNA goes negative, we move into a much stormier pattern. The opposite holds true for positive PNA readings. You can see that we have mostly been in a stormy pattern since a week before Thanksgiving and that trend is beginning to change.
For you powder hounds out there, it looks like a week from Thursday could bring a decent shot of Sierra snow. Take a look at GFS for Thursday, January 13th:
As of now I would say the 14th would be a pretty decent powder day. However that is over a week away. I will keep an eye on this one, along with any changes in what now appears to be a much more mild pattern for the Lake Tahoe area.
Stay Tuned ...