The Tucson morning sounding (above) indicates that cool, outflow air extends up to around 800 mb and that winds in the cool air remained strong at sunrise. Above the outflow is probably the old BL from yesterday, but it could reflect weak subsidence below the thick cloud based at about 700 mb. Regardless, a somewhat classic "onion" sounding that says little about what the day will bring. Would be a good day for a special, early afternoon sounding here at Tucson.
Visible image at 1445 UTC this morning showing the widespread cloudiness, over much of the Southwest and northern Mexico, that further complicates today's forecast situation. Storms overnight in the northern GoC helped to push more moisture northward up the lower Colorado Basin and into California deserts - the outflows were not as dramatic as those over in southeast Arizona. The end result of all this storm and mesoscale outflowing and interacting is that PW now is around 1.75 inches across all of southern Arizona. Another complication is that a leftover MCV seems to be spinning away aove the Safford region this morning.
The two upper-air plots (above) are 250 mb and 500 mb for this morning at 1200 UTC. Note that the upper-level cyclone (see earlier posts) is now centered over the Big Bend country of Texas, with a very pronounced circulation. It now appears to be linked vertically with the weak, inverted trough below 500 mb - this part of the system appears to run northward across the New Mexico bootheel. It appears that 500 mb temperatures are distinctly cooler behind (to the east) this feature - so we can hope for an improvement from the current warm -4C over Tucson. The flow ahead of the upper-cyclone will be weak and diffluent, and it appears that any storms that develop will leave their anvils behind as they propagate westward or southwestward - which is good.
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What will happen today? - there has been enough cooling over Tucson and southeast Arizona that it appears that a new BL will build upward with some capping CIN at it's top. There will probably be CAPE above - although the warm air and MCV aloft make the situation very complicated. New BL days - with CAPE above - can support organized storms when there is decent steering flow and a good outflow kick from mountain storms.
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The morning NAM forecast doesn't indicate much at all for the Tucson area today. However, the early run of U of A Atmo's WRF-GFS indicates signifcant storms developing over southeast Arizona after around 7 pm or so, and continuing well into the night. It is also of interest that the NAM seems to have initialized the upper cyclone, and attendant inverted trough, quite poorly and has the trough probably too far west. Thus, I view the WRF-GFS forecast as a more likely outcome for late in the day.
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