Over the past week and in forecasts for the next 10 days the overall pattern remains in some ways similar to what we have seen all winter. The flow is very high amplitude, with strong upper-level ridges and troughs. This can be seen in the dynamic tropopause analysis below, which is essentially a map of jet stream level winds with areas of locally low tropopause pressure (warm colors) indicating ridges and areas of locally high tropopause pressure (cool colors) indicating troughs.
What has changed, however, is that the mean ridge position has shifted upstream to what I'll call its "happy place" over the central Pacific Ocean. As a result, we will see several amplifying upper-level troughs digging into the western U.S. over the next 10 days. This is a much colder pattern than we have seen all winter.
It is also a more "active" pattern. Forecasts for the next 7 days show a series of weak but frequent storm systems moving through. Total accumulated water equivalent produced by our downscaled NAEFS product for Alta ranges from 1 to 3 inches of water. The former would be a bit below average, the latter almost double.
The Steenburgh Effect is in full force.