Severe Thunderstorms In Borderlands Yesterday

Edited to add: Forgot to mention that TUS reached 100F yesterday, tying the record for consecutive days with highs of 100 F or higher - 39 days.

Email from Art Douglas this morning indicates that he measured 3.73 inches of rain and that hail at his place was 3/4 inch diameter (not 1 1/2 inches as reported below).

Heavy storms occurred yesterday afternoon and stayed mostly in the Borderlands, much as had been forecast by the early WRF-GFS. The SPC issued a severe thunderstorm watch that covered mostly the low deserts, including the Tucson and Phoenix metro areas, and the Borderlands west of Cochise County. This watch did not verify well, as both CAPE and steering flow ended up being marginal for storms to propagate through the deserts. Across eastern Pima County there was lightning and thunder around midnight with generally light anvil rain. Here at house we had 0.07" in the gauge this morning. Across the ALERT network 44 sites had rainfall but amounts were very light, except for the two southern most stations (see latest 24-hour rainfall across the southwest portion of the network - above). The plot below shows CG lightning strikes for 24-hours ending at 5 am this morning. Most of the heavy storm activity stayed in southern Cochise and Santa Cruz Counties and in Mexico.

Very severe storms struck from Sierra Vista south. Carr RAWS reported 2.38" of rain. Ft. Huachuca observed a wind gust to 82 mph and there were a number of wind, hail, and flooding reports. Art Douglas left a message that he had had 2 inches of rain and severe-sized hail - he reported that the creek in Ash Canyon was flooding. There were reports of severe hail near Nogales also.

This morning's skew-T for TUS is shown above. The easterly steering-level flow has increased markedly overnight - finally. PW and CAPE are high. Skies are mostly clear or covered with thin cirrus this morning, so that debris clouds are not a serious problem. The forecast sounding for Tucson (below - valid at 2 pm MST from the early WRF-GFS) indicates conditions that are very favorable for storms to move into the low deserts today. The easterly winds are essentially uni-directional which is the only con I see in today's setting. High-elevation storms should produce easterly outflows and gusts that will lead to propagation into the deserts. Appears that the boundary layer lifted parcel will have theta-w of 24 C or higher, which is nearly always associated with severe thunderstorms here in the Tucson area. So, a significant potential for severe thunderstorms with wet downbursts and heavy rains this afternoon for much of southeast Arizona and northwestward toward Phoenix.