Tough Forecast

Yesterday - Hot! as per WRF forecasts two days ago. Phoenix 113F and Tucson 108F. Storms yesterday were mostly locked to the mountains. Two regular reporting stations had light rain (Douglas and Nogales); 15 ALERT stations had rain and these were mostly around the strong thunderstorm shown in the 01Z Tucson radar image (top) that was centered in the southern Catalinas and foothills. This storm produced three rain reports of a bit more than half an inch and also a severe downburst along the Catalina Highway (so, first severe thunderstorm of summer in Tucson area - I think). There was rain also at 6 RAWS stations and amounts were very light, except fo 0.38" on Mt. Hopkins. Here at house nothing, except that I observed lightning for the first time this summer - off to far northeast around 8 pm.

Today - Continues moist with little change in PWs and much cloudiness over all the Southwest and north to the Great Basin. System that brought severe storms to southern California yesterday is spinning along north of LA but main moisture is north in central Sierra Nevada and Great Basin (bottom satellite image). Middle image shows the heavy morning cloudiness here in Tucson. Tucson morning sounding is a bit cooler at 500 mb due to the tremendously deep boundary layer growth yesterday (see Jim Toth's comment below). There may a tad more CAPE at lower elevations. Low-level winds are strong southeasterly and upper-level winds are easterly, with some middle-level northeasterly steering flow. Big question is what will conditions look like this evening? The morning NAM shows a piece of inverted trough from Big Bend area affecting southeast Arizona after 00Z, and a somewhat supportive shear profile for propagating storms into lower elevations. So, today's storminess may depend to some degree upong the role of all this cloud cover and how long it will persist. The NAM now forecasts, again today, that tomorrow will bring better storms and rains, but shear profiles become less favorable as anticyclone becomes quite vertical north of here. So, main conclusion is that it's a tough forecast today, but strong storms with decent rains should be on the upswing today and perhaps through the weekend.