Outflow from the northeast last evening was strong enough to kick off several small thunderstorm cells over parts of the metro. Here at house there was a nice lightning show around 9:00 pm MST. But several stations in the ALERT network picked up measurable rain (above is for 24-hours ending at 8:00 am this morning) - airport actually had .08". Yesterday's 06 UTC WRF-GFS forecast was quite good, but with the storms getting further into eastern Pima County than had been forecast.
Storms in Sonora developed into a huge MCS (as Mike L. had mentioned as a possibility in his discussion yesterday). IR image below, sent over by Jim Means, shows the MCS cloud shield at 05 UTC last evening. The plot of detected CG flashes second below (from Atmo and Vaisala) is for 12-hours ending at 06 UTC last night. The active storms went into the GoC and caused winds and dewpoints to surge at Yuma beginning a bit before midnight. This surge is one of the complications for today - cool air is over southeast Arizona and the push from the GoC is very warm with lower pressures currently to west. How far east will this air make it today?
The 500 mb analysis (above for 12 UTC from SPC) indicates a mid-level, inverted trough from central Baja northeastward into New Mexico. This weak feature was probably at play during the development of the MCS last night. The TWC 12 UTC sounding plot (below) shows both significant increase in PW (up to over an inch and a half) and also outflow cooling. The sounding remained affected by the MCS and local thunderstorm activity. Another key question is that of how the sounding will evolve today - a special 18 UTC sounding could prove very useful; however, there is no mention of possible thunderstorms today or tonight in current NWS forecast for TUS.
Both versions of 06 UTC WRF forecasts from Atmo keep thunderstorm activity east and south during the day with little forecast for eastern Pima County. However, both versions forecast a nocturnal MCS across our area after midnight - above is GFS version and below is NAM version, both valid at 2:00 am tomorrow morning. The other various WRF forecasts indicate several features converging over the metro area by midnight: the surge boundary from west, an outflow from the south-southeast, and an outflow off the Catalinas.
Complicated mesoscale details fairly far out in time - but will undoubtedly be interesting to see how all the various features actually develop and interact.
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