Tahoe Weather Discussion.com

So we finally got some decent snow but what now? The forecast has us going back into a pattern similar to what we had for 2 months before the storms with the ridge sitting off the coast keeping the storms to our North. The storms will not be that far North of us and as the ridge shifts back from from the coast a few times over the next week we will see the storms slide down far enough South to bring us a chance of some precip.

It’s nothing to get that excited about as we will most likely see more clouds than flakes. The first system moves into the Pacific NW on Thursday and Thursday night we could see a snow shower with maybe a dusting above 7000 ft. The weekend will be quiet with higs in the 40′s before there is a chance we could see another flake or two on Monday as another storm impacts the Pacific NW. There is a 3rd system on Wednesday. This one has the chance of coming a bit further South but still looks like it would only bring an inch or two at most.

The European model has continued to move toward the GFS for next week so the chance of a cold trough with any bigger storms seems unlikely now. The big difference between the dry pattern now vs. last month is that the Arctic Oscillation is negative as you can see above on the chart. That doesn’t correlate with more snow but it does correlate with high latitude blocking patterns like the one responsible for the storms we just had. The negative PNA does correlate with a trough and stormier pattern but you can see the forecast is for it to go back to postive which tends to be associate with ridging and dry conditions for us unless the ridge is far enough NOrth and the storms come underneath.

You will see that many weather outlets including the NWS blamed the above average snowfall last season on the strongly negative AO and the below average snowfall this season across the US on the strongly positive AO. The negative AO is associated with a suppressed jetstream and increased storms across the U.S. We will have to wait and see if a blocking ridge will setup over Alaska or Canada again in February supressing the jet stream South into the West Coast. The forecast models do hint at this for the 2nd week of February.

Stay tuned for updates and I will have more on the developments of the new partnership I’m working on with a meterologist developing a site that will bring you more tools to feed your snow obsession. BA

First let’s just run through snow measuring real quick. If 3-5 feet is reported over a 4-5 day period that doesn’t mean the snow is going to be up to your neck when you get up on the mountain. The way that most of the resorts measure is using white boards or areas of packed down snow as a starting point before the snow falls. They then take a measurment twice a day, once in the morning and once in the evening. Between each measurement they clear the spot and start over. They will add together the 2 measurements that day for the 24hr snowfall total.

That is an acceptable method usable for data collection by the NWS. What that does however that is different than on the slope or in the trees is it eliminates things that happen to the snow over the course of time like settling and compression from snow piling on top. There is a different measurement for snowpack which is the settled snow on the ground. If you measure twice a day for 5 days, clearing the spot each time, and add it all together you get can get amounts of 4-5 feet. Meanwhile on the ground the snow has settled and compressed down to only 3 feet. The lighter the snow the more dramatic the difference can be. 5 feet of cement is not going to settle that much.

This weekend we had some rain in the middle which would have melted some snow from the first storm. Then you also have people tracking out the snow on their skis and boards. You always hear people denying the reported snow totals by the resorts saying that they didn’t see that many feet when they were there. You will never see us much as is reported for a several day total on the ground, only the overnight total with compressed snow underneath. Now I’m not nieve to the fact that some resorts might put some hype in their number for marketing purposes, but I have worked with a lot of them and gone through their methods and they are pretty legit. If you don’t believe it try it at home with the next storm cycle. Keep a tally of the snow amount on the back deck each 12 hour period, clearing the spot each time. When the storms are over i’m sure the tally is a lot more than what is sitting on the deck in the uncleared section.

The weather will be quiet the next 2 days over CA but not to our NOrth in the Pacific NW. There will be a cold front diving down to our East on Friday that could bring in some light snow showers as it slides inside of us. For next week but the Euro and GFS show another possible weak system sliding by that could bring a snow shower or two. After that the models are all over the place and don’t agree. It reminds me of 2 weeks ago. The GFS shows another weak system for next Wednesday as the ridge stay off the coast keeping any heavy precip to our NOrth. The Euro however retrogrades the ridge back a little allowing a stronger cold storm to dive down the West coast. The Euro has been more accurate in the long-range so we have to give it some merit.

Either way the weather stays interesting next week so we will just have to watch to see how far the ridge shifts back from the coast. The Euro shows a big ridge setting up over Alaska and Western Canada starting around the 5th with storms starting to come underneath into the West Coast for the 2nd week of February. This could be a similar setup as what we just saw and would make sense if the AO stay negative. The GFS doesn’t see it but again it didn’t see it last time either. The GFS does show some more storms sneaking in though with a weak ridge off the coast.

We can look at this more tomorrow as I need to get some sleep. I have been working on lots of new weather related projects that I think you are going to enjoy. I am teaming up with another site that is comprised of avid snow-loving meteorologists, to try and expand these types of weather discussions to other mountainous regions of the country. I will also be linking up this site to a another site where I will have a more brief discussion and snowfall forecasts for each resort a week out. More on all that tomorrow. You can already enjoy the new Weather section over at Unofficialnetworks.com where I have been working with them to post a discussion of the weather for a different region of the country each day through the week and then a powder alert on Friday for where the next big snows will be. You can also find resort specific discussions that I have helped to put together on the Sierra At Tahoe, Northstar California, and Squaw Valley weather blogs linked to their conditions pages. BA