The 500 mb anticyclone will be shifting westward the next two days, relocating near the Four Corners by mid-week. Such a shift can be accompanied by subsidence on the south side of the anticyclone. Currently PW values are around an inch and a half across lower elevations of southern Arizona. However, the early run of the WRF-GFS forecasts lower PW (PW forecast valid at 4 pm MST above), as easterly flow prevails at low-levels this afternoon. Surface observations and TUS morning sounding indicate this is possible. The model forecasts a complete shutdown of deep convection across southeast Arizona today (total rainfall forecast by WRF-GFS through midnight tonight is shown below). The model forecasts storms only out over southwest Pima County. In contrast, the current run of the NWS NAM forecasts storms over at least higher elevations of much of southeastern Arizona. So, a considerable difference in the current model forecasts.
The WRF-GFS forecast sounding for 5 pm MST this afternoon is shown below. The winds aloft are forecast to be easterly at all levels, and the diurnal west winds in the boundary layer are absent. The sounding indicates no CAPE, but somehow the analysis routine is indicating moderate CAPE. I'm not sure what's happening here, but will be certain to take a close look at the 12 UTC model runs from Atmo.
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