Cutoff Over Southwest Through 72 Hours

Summary of yesterday: There were some light sprinkles over central Tucson at midmorning yesterday. Numerous thunderstorms erupted by early afternoon, especially to the northwest of here in south-central Arizona, where there were a couple of marginal severe storm reports. Large storms also developed across Santa Cruz County and moved northward. When they reached to near Green Valley, they mostly crashed and shifted off to northeast. These storms threw out a very large, strong, and dusty outflow that appeared to result in a large are of subsidence over and west of the Tucson area. Thus, the afternoon and evening was devoid of storms over much of southeastern Arizona - the models obviously did not verify well for this part of state. Light showers and thundershowers developed well after midnight and moved through the Tucson area just before sunrise this morning. Again, the midnight model runs did not pick up on these showers either. Across the ALERT network about 80% of the stations of the stations had rainfall - mostly early this morning, although the southern stations had rain yesterday afternoon also. Amounts were quite light - 0.09" here at house; only 10 stations had amounts of 1/4" or more, with one station (Tubac) reporting a total of 0.51".

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Top figure shows the dual cutoffs at 500 mb over the US - if interested, scroll down to the "Looking Ahead" post and you'll see that the ECMWF was vastly superior in the long range forecasts for this situation, when compared to the GFS.

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Tucson sounding this morning was taken within the band of showers and is not representative of the larger-scale - temps were too warm and there was only a bit of CAPE. Other soundings indicate temps at 500 mb this afternoon of -10 to -12C. PWs are increasing over southeast Arizona and decreasing over southwest Arizona, where dry air has pushed in from the west at low-levels.
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The SPC has a slight risk area over Arizona for today and a large area of strong storms is currently underway southeast of Flagstaff in the Rim Country. I also see a new storm has already developed over south Tucson - so looks like an active day.

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Bottom two images show the midnight WRF and morning NAM rainfall forecasts ending near midnight tonight and both are very similar!