The large MCS to the east and southeast last night eased an outflow across Tucson that has significantly increased the PW. Above graphic is Univ. of Arizona GFS PW for past 7 days, showing the substantial increase over night. The 850 mb dewpoint is at 13 C this morning, the highest so far for the summer and PW is a bit over 40 mm. The 12 UTC sounding at TUS (skewT plot from SPC below) is the most unstable sounding of the storm season. But with the 500 mb anticyclone shifting from western Arizona toward the New mexico Bootheel today, the winds have aloft have gone light and variable. So moisture and CAPE a plus but no steering flow today.
The early WRF-GFS forecasts storm activity to again remain mostly east and south of the Tucson area. Above is WRF-GFS forecast of total rainfall through 5 am MST tomorrow morning and below is same forecast from the 12 UTC morning run of the NAM. The NAM forecasts much more activity over southeast Arizona this afternoon. The WRF-GFS forecasts a strong outflow from the south at around 5 pm, as well as a huge cirrus shield spreading north from storms to the south. I do not have much confidence in the early WRF today - it has PW a bit low and doesn't seem to have forecast the large area of debris clouds currently over Pima County. All-in-all a very tricky situation for today - will check the morning runs of the WRF to see how they compare to the NAM forecast. But, certainly much more potential for today than we had the last two days!
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