Severe weather pattern setting up last three days of week

Note that we've posted a weekend summary and some recent photos on the madweather web page, with links posted on the blog this morning.

Conditions remain very moist this morning; however, the TWC sounding is about 5mm too high in IPW according to the FSL comparison site. The 12Z sounding is quite strange, exhibiting the off-the-surface moist spike that Mike Leuthold pointed out about a week ago. Many of the 12Z soundings for last several weeks show this same artifact - particularly on calm mornings. This morning's sounding exhibits an adiabatic layer off the surface and then a sharp inversion to about 890 mb. This same layer has the strange Td structures. These data in lowest levels probably reflect the local conditions on the roof of the NWS building, and the moisture spike may result from similar contamination.

Regardless, moist and unstable and a calm troposphere again this morning. Only 11 of the Pima County Alert gauges had precip yesterday - making it the driest day since last Friday - with the significant amounts being on the mountains. The amount of anvil that the early mountain storms produced was truly amazing, but of course left all the lower elevations under thick anvil for much of the afternoon. Looks like anvils will tend to spread toward south and southwest today also.
Upper-level difluence increases this afternoon and evening as the inverted upper trof approaches. This feature directly affects southeastern Arizona tomorrow afternoon and steering level winds finally pick up. The 500 mb temperatures with this feature are -8 to -9C, i.e., very much cooler than have been observed at TWC for many days!

The best vertical shear for organized, propagating MCSs is forecast by the NAM on Thursday afternoon/evening as the winds at high levels - 200 mb - turn to south-southwest as remnants of Dolly approach the Big Bend. Wind shear predicted by the NAM remains very favorable on Friday afternoon. Very difficult to call which day will bring the most intense storms to southeast Arizona for rest of week, since local and small scale features and the previous day's events will be playing a big role each day. But it will be very interesting to observe what actually evolves.