Thursday, May 17, 2012

A Big Announcement!

It is with great anticipation and excitement that I announce the return of weather to the Intermountain West after an extended absence.

Yes, there is always weather, but it is May, and we should be seeing the occasional trough passage and airmass change just to keep things interesting.  Instead, it's been slim pickins for quite a while.

That will change tonight and tomorrow.  This morning, we have an upper level trough moving into the western United States.

Today will be warm with perhaps some high-based convection with a slight chance of thunder and local gusty winds.  Late tonight and tomorrow, cooler air pushes into northern Utah, bringing showers and an increased chance of thunder.

Rain would feel oh so good.  KSLC observed .24" on May first, but since then, hasn't recorded measurable rain.  If we get a good shower, make like Tim Robbins in the Shawshank Redemption.


  1. Do the forecast models include any data on current soil moisture conditions and such? It seems like for warm-season precipitation forecasts this could be an important factor in areas like the Great Basin where atmospheric moisture advection is very limited. If you have, say, a quarter or half inch worth of existing moisture near the surface available for evaporation on a given day, you will have a lot better precipitation potential than if the soil surface is completely dry. If this is not factored in, maybe it would be fairly easy to establish several regional measurement points to add something like this to a model.

    1. David

      The NAM and GFS include land-surface models (LSMs) that predict soil moisture, soil temperature, etc. The LSM plays an important role in calculating moisture fluxes to the atmosphere from evaporation and transpiration.

      That's the good news. The bad news is that there are not a lot of reliable soil moisture observations, precipitation inputs to the model are problematic, soil is poorly characterized, etc. Thus, the LSM can be an important source of model error.


  2. Good to know. One thing that originally got me thinking about the importance of this was the very wet month of June in 2009. We had a prolonged series of closed lows and relatively weak upper-level systems, which did not appear to bring in much moisture from the Pacific and most of them had little impact as they initially moved onshore. However, there appeared to be a gradual accumulation of moisture within the Great Basin region which was recycled and led to widespread convective showers during most of the month. Would be nice to see that happen again but I am not holding my breath.