Another Big Storm Day - Today Or Tomorrow?

First - another spectacular Mesoscale Covective Vortex at the north end of the Gulf of California this morning. The graphic below shows an IR image, from 0500 UTC last evening, of the generating MCS over northwest Sonora. The 1630 UTC visible image this morning shows the MCV centered south of Yuma. The MCV is moving off to the northwest this morning toward the Mojave Desert.

Conditions have improved somewhat today for strong thunderstorms. The PW here at Tucson continues to run around 1.4 to 1.5 inches (with GPS and TWC sounding in close agreement this morning). There is a nice, low-level anticyclonic circulation centered somewhere in far northwest Sonora - this will keep the BL winds from the northwest here at Tucson this afternoon. Today's PW values are higher to the west and north, so there will be a bit of moisture advection during the afternoon. The steering-level winds are more southeasterly today, at perhaps 10 to 20 kts. Anvil level winds this afternoon are difficult to estimate - it appears they could be anywhere from L/V to easterly at 15 to 20 kts. This leads to the dilemma of possible anvil shading, especially if early storms form over the Rincons or eastern Catalinas. The 250 mb NAM forecast for 5 pm today (immediately below) indicates a long deformation zone extending from southern Arizona eastward to a strong, upper-level cyclone near New Orleans (this feature wll be a player in our local weather several days from now). The forecast 250 mb flow for this afternoon is wildly difluent over northwestern Sonora, indicating a very nice, large-scale vertical motion field. The current NAM forecasts indicate very favorable flow fields over southeastern Arizona for strong storms tomorrow. However, the current U of A WRF-GFS forecast (5 pm composite radar bottom) indicates a big storm day today for the Tucson metro area. The WRF forecasted storms come into town from the higher terrain along I-10 between Benson and Vail and between the north end of the Santa Ritas and the Rincons. The WRF-GFS forecasts these storms to head off toward Phoenix, perhaps posing a threat of another dust-out up there this evening. Very complicated forecast - probably best to call it 50/50 for today versus tomorrow - time will tell.