Little Change Since Yesterday

Yesterday, thunderstorm activity across southeast Arizona was very limited and restricted to mostly high elevation zones. We had thunder here at the house around 4 pm from a storm on the western Catalinas, but it quickly fell apart and could not move off the mountain. At 6 pm 18 ALERT stations had measured precipitation, and there was no additional rain after 6 pm. So, high coverage over Catalinas and Rincons but only some outflows in the Tucson metro area. Above is the regional radar coverage (from NCAR RAL) at 4 pm MST - this is the most active, hourly chart of past 24 hours. The water vapor image (below) for 9 pm MST yesterday indicates little activity over northern Mexico and the Southwest - exceptions are a small complex of storms over the Four Corners and a large MCS over southeastern Colorado.

There is little change today. The PW values are around 1.25" across southern Arizona, but with somewhat smaller values toward New Mexico. The morning visible satellite image (above for 6:45 am MST) again shows heavy morning cloud cover, and some likely showers, over most of southern Arizona, with clear skies only in the far southeast. This morning's Tucson sounding below (12 UTC from SPC) is very similar to yesterday's. The wind profile is essentially light and variable, with steering winds diminished relative to yesterday. Note that the lifted parcel shown will not be representative of this afternoon's deep and drier boundary layer (BL). At best, I can estimate a sliver of CAPE at low elevations.

The early WRF-GFS forecast of rainfall from now until midnight (below) is similar to yesterday's - not much in southeast Arizona except in the mountain zones. The WRF-GFS forecasts early convection again, with most activity before 2 pm. This is probably a few hours too fast, as was yesterday's forecast. Not much to latch onto in this chopped up pattern - it is hard to forecast out past 24-48 hours, since the synoptic pattern remains weak and without significant features, except of course the 500 mb anticyclone over Utah.