Thursday, May 09, 2013

Bit of Cape Around Tomorrow

The early run of the WRF-GFS at Atmo forecasts high-based convection to occur tomorrow afternoon (Friday 10 May) over much of southeastern Arizona. The above forecast is valid at 5 pm MST Friday and shows the forecast of composite radar echoes. The forecast of total rainfall through midnight tomorrow night (below) indicates some light amounts at higher elevations, especially over the Chiricahuas.

Precipitable water amounts remain very low, as per forecast above (in mm), also valid at 5 pm Friday. The forecast skew-T for Tucson at 5 pm (below) is interesting since it shows that we're headed for summer. The forecast boundary layer (BL) is very deep (cloud bases just below 600 mb), but the BL does have a slight amount of CAPE. Steering winds have become easterly tomorrow afternoon also. So, assuming the forecast is accurate, we can expect convective storms over the mountains tomorrow afternoon that will try to propagate toward the west. Because of the dry environment and high cloud bases, these storms will have the potential to produce strong downburst winds, as well as sprinkles, dust, mammatus, and some lightning strikes. Check Jim Steenburgh's post today on mammatus that has some great photos from Wyoming yesterday - link to Jim's blog is at right.

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