Monsoon Surge in the Offing

I'm liking what I am seeing in the latest model runs, which advertise a major surge of monsoon moisture and precipitation into northern Utah for Friday combined with forcing from a weak surface boundary to force the action.  Storminess could persist in some areas into Saturday.  

Below is the latest HRRR forecast of surface wind and 1-h accumulated precipitation valid 0000 UTC 6 August (6 PM MDT Friday).  Precipitation is mainly near or northwest of a surface boundary (shift in winds from southwesterly to the southeast to northerly or northwesterly near and behind) draped across central Nevada and northern Utah.  

The flow aloft favors the transport of deep monsoon moisture to this region, resulting in widespread shower (and thunderstorm) activity developing on Friday near and northwest of this boundary.  Showers and thunderstorms may also occur to the south of the boundary, but will be more scattered.  

Total accumulated precipitation through 0600 UTC 6 August (0000 MDT Saturday) shows the heaviest precipitation, with areas > 1 inch and pockets > 2.5" over Nevada (some of this precipitation falls today and tonight, especially over Nevada), but streaks of precipitation > 0.5" extend across northwest Utah.  Strong cells would likely produce more locally.  

The GFS sounding for the Salt Lake City airport at 2100 UTC 5 August (3 PM Friday) shows a stable layer just above the surface due to the shallow, cold northwesterly flow at low levels, but above 650 mb a skinny but deep layer of convective available potential energy or "skinny CAPE."  Total precipitable water is 32.2 mm (1.25 inches), which is fairly high for our part of the world.

Although the surface parcel in the sounding above is the "most unstable", meaning it has the highest CAPE, it is possible that some of these storms may be elevated, meaning that they are developing from instabilities above the surface rather than at the ground.  Mother Nature will provide the details.  And, while it is impossible to predict the precise characteristics and locations of convective storms at these lead times, this is a period where it will be worth monitoring forecasts and being alert to the possibility of severe weather, including heavy rain and flash flood potential. 

One possible fly in the ointment beyond the hit and miss nature of convective storms.  A look at the forecasts above shows that current forecasts call for the action to be greatest near, north, west, and southwest of Salt Lake.  This puts us on the edge of the best action.  Let's hope it doesn't shift northward or westward from advertised.