Several Interesting Days On Tap

YESTERDAY - Thunderstorm activity increased yesterday afternoon and evening - particularly in Cochise County, where there were several special statements issued by NWS for heavy rains and flooding. One station in the ALERT network (Haystack Mountain) reported 0.14"; Ft. Huachuca reported a thunderstorm and 0.37"; and the RAWS at the Headquarters of Chiricahua National Monument reported 0.71". Precipitable water remains around an inch or so at lower elevation stations, so the main driver for the increased CAPE was the ongoing heat-up of the boundary layer and a bit of middle-level cooling. Pat Holbrook noted early yesterday that: Bob, Both GFS and NAM showing a surge this weekend...maybe as early as saturday. Nothing on GYM sounding today so it won't be tomorrow. Pat
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TODAY - Yesterday's discussion still relevant. Surface pressures are falling nicely as the heat-up continues - 24-hour pressure falls this morning over the lower Colorado River Basin are 2.5 to more than 3 mb. Thus, the up-gulf pressure gradient is likely increasing, as is the gradient for middle-level southerly flow. The deeper, subtropical moisture appears to still be over south half of GoC. The Guaymas sounding seems to show a very shallow surge signal this morning and an MCS dissipated over the southern GoC late last evening (see top IR satellite image). The Tucson and Phoenix soundings appear to have a tiny sliver of CAPE, so thunderstorms will again tend to be over higher elevation areas this afternoon.
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NEXT COUPLE OF DAYS - The 500 mb trough along the California coast and the anticyclone over the Southwest do battle and keep an increased gradient for southerly flow through the weekend. The model forecasts agree that the deeper moisture flows northward into the Southwest after 60 hours, with a significant increase in storms and rainfall. The current NWS forecasts indicate 50% POPs for lower elevations in the Tucson area all day Saturday. The NAM forecast from this morning (bottom image) indicates widespread precipitation for the 60 hours ending at 5 pm Sunday afternoon. So looks like interesting weather changes through the weekend.