Yesterday (Thursday, July 18th) was very suppressed across southeast Arizona, much as the early WRF-GFS forecast indicated it would be. Rainfall across the ALERT network was zilch (0 % coverage) during the past 24-hours ending at 6 am MST. Graphic above is detected CGs for the same 24-hours. Thus, the significant tropospheric cyclone/inverted trough has produced little weather in this area for three days now - certainly hope for an improvement next couple of days.
There has been a significant surge of low-level moisture from the GoC into the lower Colorado Basin after about 11 pm last night. This morning VAD data from the Yuma Doppler radar (above) show strong south-southeast winds up to about 3,000 ft MSL. As easterly winds have weakened, PW values have increased across all of southern Arizona and values range from around 1.5" east to 2" or more out west. Below is early WRF-GFS forecast of PW valid at 5 pm MST this afternoon - model forecast indicates little change from conditions this morning.
The model forecasts a fair amount of CAPE (>1200 J/kg) at Tucson at 5 pm this afternoon (see forecast skew-T above), but with a unidirectional wind profile, that is not particularly favorable for much of Tucson metro area, unless storms develop nearly overhead. If storms develop, they will try to propagate toward the west but anvils will tend to spread out ahead of the cores - not good for lower elevations. The early WRF-GFS forecasts an upturn in storm activity today (forecast of total rainfall through 5 am tomorrow morning shown below). Rain amounts are not large and best amounts are in Santa Cruz and central to western Pima County (as well as along the Colorado River out near Parker). It also appears that the model forecasts storms forming over the Rincons and Santa Ritas, but these do not propagate very far to the west. However, the model does forecast much more activity for all of Pima County tomorrow and the next day, with very heavy storms forecast for the lower Colorado River Basin.
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