Moisture From The East

This morning (Sunday, July 8th) there is a band of heavy, middle cloud, with some light sprinkles, covering most of south-central and eastern Arizona (above is visible satellite image for a bit before 7 am MST). This has moved in from the east, as the 500 mb anticyclone strengthens over the west, with one of its several centers over the Great Basin. The outflow predicted by yesterday's WRF-GFS did move westward through the Tucson area, but not until around 9 pm - four hours or so later than predicted by the model. Nevertheless, weak advection and strong moisture recycling, with outflows, has brought better moisture in from the east.

This morning's Tucson sounding (above from SPC) has almost 35 mm of PW; however, CAPE is marginal. The best aspect of the sounding is that middle-level steering winds are quite decent, from the east-northeast. This means that higher elevation storms will try to propagate into the deserts this afternoon. The early WRF-GFS forecast of PW, valid at 6 am (below), appears quite accurate, with the leading edge of the moist intrusion reaching almost across Pima County.

With the heavy cloud cover present this morning, the details of what happens this afternoon and evening will hinge to a high degree (pun intended) on how much clearing and heating occurs across the lower elevations of Pima County (note that yesterday there was NO rainfall measured in the ALERT network). The graphic above is WRF-GFS forecast of incoming solar radiation (W/m**2) valid at 9 am MST this morning - the high values indicate that the model forecasts clear skies across most of southeastern Arizona by then. This obviously isn't going to happen so quickly. An optimistic evaluation is that the model is again 4 or 5 hours too "quick" on what it forecasts for today. The model predicted total precipitation through midnight tonight is shown below. rainfall amounts are best at higher elevations and to the south and east. It does appear that chances are much improved today for  gusty storms, perhaps some dust, and some showers in the metro area - how much storminess? Watch the temperatures and the sunshine.