There is the beginnings of a possible change in the pattern this morning…. One that won’t immediately bring us significant snow, but one that, at the least, begins the process with retrogression of the longer range.

In the short term….. The big east coast storm is now moving out to sea and the wave length is opening up across the CONUS, thus the west coast ridge will temporarily weaken.  The ECMWF has the 2nd weak upper low sliding down the west coast rather then moving into the pacific northwest diving toward the Rockies. This is a major change in the way the EC handles that weak system. The importance of this, is that now, it is at least closer to the thinking of the 06z and 12z GFS and this mornings 12z NAM. Now all the models generate at least a little light snowfall over Mammoth Sunday. It is not expected to be much…..possibly a dusting to an inch or two, but at least something.  Of more importance is the notion that in back of this weak short wave is the sharpening of the west coast upper ridge back out to 135 west, next week. This may be more significant as we go into the month of February as some sort of retrogression in the long wave is the most likely scenario prior to either a storm coming into the Sierra from the Gulf of AK or some undercutting of the westerlies. However with that said the deterministic 12z run of the GFS progresses the long wave back to the west coast again next week. However, a significant number of both the ECMWF and GFS ensembles create retrogression to 140W.

Additionally toward the end of week 2, the GFS REXes up over the Aleutians at 160w by the 8th.  This is some thing new and will have to be watched……as if it is persistent and strong enough, the down stream effects would be profound.  All the models are saying, is that a change is coming in the next couple of weeks. However, it does not mean significant snowfall for Mammoth yet.

Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.