Some Heavy Storms Yesterday

It was a cool day yesterday because of the abundant cloud cover and several days of convection. Highs were mostly in the 80s with some places getting into the 90s. Strongest storms occurred out in the lower Colorado River Basin - Yuma was slammed by the second heavy storm this summer and also recorded 1.62" of rain. Two big storms in Yuma likely translates to a very wet summer for them!

Here in the Tucson metro area there were several strong cells that drifted westward just before dark. Photo above shows one of these to the northeast of the house while it was producing lots of lightning and loud rumbles of thunder. This is as close as it got however and there were again only outflows and no rain here at house. The morning showers and heavy clouds yesterday morning kept things fairly suppressed. There was rain measured at 25 of the ALERT network stations, which translates to about 30% areal coverage. The heaviest measured total was at Rincon Creek with a down pour of 1.81 that triggered flash flood warnings from the NWS.

Things are changing, but slowly this morning. The 500 mb pattern remains ill-defined over most of the US and Mexico, the exception being the strong trough in the Pacific Northwest. The anticyclone is indistinct with weak centers over the Gulf of California and also over the southern Gulf of Mexico. A weak short-wave is over western Arizona and this will be moving slowly into the southeastern corner of the state during the day today. The upper-level short-wave has run east of the feature at 500 mb and extends from western Wyoming south to southern Baja. This will bring increased difluence aloft to much of Arizona this afternoon.

Low-level moisture is little changed; there is moderate CAPE available; and there is CAPE present for parcels in the Tucson morning sounding from the surface up to about 600 mb. Thus, more storms today, some with heavy rains - as per the area of storms currently south of Tucson. Storms from the mountains will try to move east, but winds are so light below 400 mb that local outflows will be able to drive storms in any direction, particulalry toward local maxima of CAPE.