Storms Possible

North view from Kitt Peak this morning shows a line of mid-level build-ups, as moisture begins to return.

The 500 mb closed-low remains well west of northern Baja at 12 UTC (above). Models continue to forecast the system to be ejected northeastward, bringing an open trough across Arizona tomorrow. Note - comments on this NWS 500 mb analysis: the observation plotted for Guaymas is clearly bad but got thru whatever quality control there is for plots, but was not used in analysis; cyclone center over Great Basin placed very badly; and height contour over Mexico/GoM is a mess.

Current NWS forecast for probability of measurable rainfall 

(above - 0.01" or more) indicates increasing chances this afternoon through tomorrow.

I took a look at the 09 UTC WRF-RR forecasts. Forecast of radar echoes (above) is valid at 9:00 pm MST this evening. Forecast of total precipitation through 6:00 am tomorrow morning is below - very light showers indicated for Tucson metro area. Second below shows same run's forecast of total rainfall through midnight on the 6th. The WRF forecast keeps tomorrow's more significant rain well north to northeast of our area.

I took a look at the forecast soundings for Tucson in the model run and they look like they'd support storms tomorrow - apparently the forecast brings subsidence behind the short wave into play before it can develop storms. I would go with the sounding forecasts and expect storms in the area tomorrow - will watch to see what actually happens.

Took a look at he SPC outlook for thunderstorm areas today (green shaded areas right of bold line), and it appears that Las Vegas office did not want to be included in the area over the Southwest - will watch this also.