Wednesday, March 3, 2010
9:50 P.M.

Hey everybody! So I have some absolutely fantastic news for skiers and snowboarders! For the first time in a really, REALLY long time, it looks as though we could get into a snowier pattern for the Cascades. Why are we going to see snow later on there as opposed to other times? The answer is all in the jet stream. Take a look at this picture of the jet stream. The jet stream is the "highway" for the storms; they ride from west to east along it. The reason why we have had a fairly mild winter is because the jet stream has been splitting right around us as a result of high pressure centered off of our coast.

This is an example of the split flow pattern that we have seen so regularly this year and is the forecasted atmospheric conditions for 00 UTC Sunday. Since there is a split flow at that time, there will not be cool conditions. The cool pattern will resume when the jet stream looks more like this. This graph shows the 06 UTC Wednesday atmospheric conditions.


See the difference? The latter one has the jet stream entering from a much higher latitude - the Gulf of Alaska as opposed to off the Oregon/Californian coasts. Also, there is no split in the jet stream over us. There is one in the picture though. Can you identify it? It is way down south.
Let's take a look at the weather conditions forecasted. From now on to Sunday, where a jet stream similar to the first picture is in place, warm and dry conditions will be in place over the region. However, from Monday on, we will be under the influence of the jet stream from the Gulf of Alaska, bringing us cool and showery conditions.

Our first shot at precipitation will come later Sunday but our first shot at mountain snow will come after that as we are under the influence of post frontal showers. Here is a picture of another system early Wednesday morning (1 A.M.). You can clearly see the main front pushing through, and by then, it should be cold enough that even the main front will have snow in the passes with levels possibly as low as 1500 feet. See the showers behind the front? Those will fill into the area later and cause snow in the mountains and showers down here. With strong sun angles and an unstable atmosphere I wouldn't be surprised if some of these showers grew quite strong or had some ice pellets. We'll see.
Peace and love,
Charlie