Cloudy, Down Day In Most of Southeast Arizona Yesterday

In his model discussion yesterday, Mike Leuthold noted: An area of clouds and a few showers are present over SE Arizona moving south and only the WRF-NAM was able to pick up on this. However, clouds are not widespread enough in the model. Significant moisture remains over much of central and eastern Arizona, but it's bound to be a down day for much of the SE due to widespread clouds and cooling of the lower BL.
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A visible satellite image for 3 pm MST yesterday (19 August 2011), shows that the cloudiness that Mike had mentioned was still hanging over eastern Pima and Pinal Counties. Cloudiness was unusually persistent because of the very light winds in the cloud layer and its initial depth.

A time plot of solar radiation from Atmo (above) shows very limited solar input for much of the day yesterday - whereas, this morning (right edge of figure) is off to a sunny start.

The top sounding above is the WRF-NAM forecasted sounding for TUS valid at 5 pm (0000 UTC) yesterday afternoon. Note that the model forecast indicated that the surface BL would reach upward to 700 mb. Model again forecast a MAUL (see earlier post and and JS comment below) just above the top of the BL. However, in contrast, compare with the observed TUS sounding for 5 pm (immediately above). The actual BL, after a day with limited solar radiation, did not even reach to 850 mb. This is one of the shallowest, afternoon summer BLs that I can recall seeing here.
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This rather extreme example illustrates how important it can be for model initializations to get the clouds right.