The morning TUS sounding (above 12 UTC 7 July 2012) seems to exhibit the extreme low-level dry bias that is common with NWS RRS sondes. However, the current GPS/RAOB comparison (below) indicates only a small difference in the two measurements of PW. So, it appears that the day starts out with PW less than inch.
The WRF-GFS forecast of the Tucson sounding at 5 am also indicates dry low-levels. There is higher PW to the east along a weak, south to north inverted trough at 500 and 700 mb. The model forecasts an active early afternoon along the New Mexico/Arizona border (radar composite forecast for 2 pm below), with storms from the high elevations trying to move westward and southwestward. However, model forecasted CAPE stays marginally low over eastern Pima County. Some storms eventually make it to the Rincons and then fizzle out.
The WRF-GFS forecast of the Tucson sounding at 5 pm this afternoon is shown below. Note that an outflow from the east has made it into the Tucson area, but the surface CAPE (dashed-red moist adiabat) could not likely be realized. Thus, model suggests storms at higher elevations northeast through south, but wind and perhaps some dust, along with anvil sprinkles and spits, here in the Tucson metro area. Forecast vertical wind profile remains chopped up and chaotic. Model remains fairly depressing through Monday.
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