A large MCS over Sonora last evening and night (above is 06 UTC IR image from NCAR RAL) has helped push higher dewpoints northward into southern and southwestern Arizona. Lightning strikes for 12-hours ending at 7 am MST this morning are shown below. Note the strikes south of Phoenix that occurred early this morning.
Outflow from this MCS passed Nogales around 10 pm MST last night and eased into the Tucson area around midnight - below is T and Td time series from Atmo. At 7 am Td ranged from 58 F at TUS to 74 F at Yuma - increases of 20 to 35 F - similar to increase observed yesterday at Hermosillo. A large area of debris cloud from this system covers much of southern Arizona this morning.
The GPS PW time series for last 5 days (above from NOAA ERSL) shows a steady increase during the past 24-hours, with a small jump when the outflow moved by. Some light thundershowers developed before sunrise between Sells and Phoenix, reflecting a layer of unstable air aloft. The morning skew-T plot of the TUS sounding (below - from SPC) shows the elevated layer having CAPE extending from 700 to 500 mb. The models are tending to keep afternoon storms again mostly in Cochise County but conditions are obviously more favorable for storms today across all of southern Arizona. Note that the early run of the WRF models at Atmo seems to have had problems, perhaps in initialization, with low-level moisture and the forecasts seem far too dry in the boundary layer.
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