The early morning rains have left behind a messy synoptic situation for Arizona today. The 500 mb vorticity maxima that yesterday's NAM made an important player for today has vanished and been replaced by a new convectively-induced vortex that is situated just off to the east of Tucson. The visible satellite image (top) shows that all of Arizona was covered by heavy cloud at sunrise, and that a nice slug of moisture will be moving into Utah later today. Much of northwest Mexico has cleared out though, and this will essentially be the wild-card in how today's weather evolves over southeastern Arizona. The large clear area over northwestern Mexico is exactly where this morning's NAM has initialized a large moisture maximum at 700 mb, leaving the model starting out with a dubious analysis.----------------------------------------------------
The morning Tucson sounding from SPC (middle graphic) indicates no CAPE and is of an onion character, having been highly modified by the MCS debris and light rain. This sounding, with heating later today will have to build a new boundary layer surface upward. The sounding will develop some CAPE but will require a good outflow kick to release the CAPE - thus the important question of what will develop over northern Mexico and Sky Islands of southeast Arizona. The SPC had outlooked a very large area with a risk for severe thunderstorms today, but the latest update has wisely dropped that. However, things could become interesting later today in the Canyonlands of Utah and perhaps along the Borderlands. Winds remain mostly south-southwesterly with some speed shear in upper-troposphere; the sounding's north-northeasterly winds around 700 mb reflect the convective vortex to Tucson's east. Today's NAM forecast for precipitation ending at midnight tonight (bottom graphic) has become a mere shadow of what it was forecasting for this period the last several days - so, we'll have to watch carefully how things evolve later today, and I look forward to seeing what the WRF runs come up with this morning!
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