Holbrook's Flight Scheduled To Depart At 4:20 PM Today!

First - as noted above, Pat Holbrook is scheduled to depart TUS on a flight to Boise at 4:20 pm this afternoon. He has had lots of exciting, and delayed, flights this summer because of thunderstorms - so this is a factor to consider today.

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Tucson's morning sounding is shown above (top) from the SPC. It is a marginal sounding for storms locally. Wind profile is not at all good (but I know, we've had two good storm days this summer with bad profiles). CAPE could be better - need some continued increase of low-level moisture or some middle-level cooling.

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As for the 500 mb evolution dilemma - see middle image, which is the NAM forecast valid at 5 pm this evening. The model forecast indicates the tail of the Wyoming/Colorado shortwave is left behind to become part of the weak upper-low off Baja. The model forecasts the Baja feature to pull slowly north toward southern Arizona. The lower-tropospheric cyclone remains west of the Colorado River, so that winds below 700 mb remain south to southeast during the day. A chopped up pattern, but one with several interesting alignments.

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So, the models forecast a fairly active storm day - particularly before 5 pm. The bottom image is from the 0600Z run of the WRF model, showing total accumulated rainfall in the forecast through 5 pm. Thus the WRF indicates a very active afternoon, particularly over the higher elevations of all of Pima County, with the heaviest storms occurring out west over the Tohono O'odham highlands - which is the same answer the NAM forecasts (although almost all of the morning NAM's forecast rainfall is out west over the highlands).

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Current NWS forecast of 40% POPs today and 30% tonight for zone 33 seem quite reasonable, in light of the model forecasts. Here at the house, I'd say the probability of rain is pretty close to zero, unless something were to develop very nearly overhead, which is also a low probability event.