It's a Trough

The models are advertising the slow movement of a mid-latitude trough across the western US this week.  It's not an unusually deep one, and we've had some weak troughs move through the area recently, but this is one of the better "put together" troughs we have seen in a long time.  

The overnight GFS forecast has the trough approaching the California coast later this afternoon (0000 UTC 9 September with rain in the California and Orgegon Coastal Mountains.  Oh to be there for this frontal rain.  It just warms the cockles of my heart to see it!

As exciting as that is to see, the trough moves very slowly across the western US and is not a strong one.  The result for us will be a few days of light-moderate southerly to southwesterly flow at mountaintop level and a bit of enhanced southerly flow for the valleys.  A few pockets of monsoon moisture might be embedded in this flow, but at least right now, hit-and-miss thunderstorms look to predominate through Thursday.  

By 0000 UTC 13 Sep (6 PM MDT Friday) though, the trough is centered over central Idaho.  The weak front associated with it appears to be a locus for thunderstorm development, which in this model run, occurs over northeast Utah and western Wyoming.  

At such lead times though, don't get too caught up in the location details.  We can count on a cooling trend after Wednesday as the trough approaches and perhaps an uptick in precipitation chances.  The NWS is currently forecasting a high for Friday of 74 at the airport.  Won't that be pleasant, even if we don't see much in the rain bucket.