Both the GFS and NAM models, from 12 UTC runs this morning, forecast very large height falls at 500 mb as the Pacific S/W cuts off over the Southwest tomorrow. Tucson had a 500 mb height of 576 dm this morning and both models forecast steadily decreasing heights down to about 552 dm by Thursday afternoon - an impressive fall of around 240 m. Will definitely not feel like summer during rest of week. The two images above show predicted 60-hour precipitation ending at 5 pm Friday afternoon - NAM top and GFS operational member bottom.
Neither model predicts much rainfall over southern Arizona, with amounts from less than a tenth of an inch to around a quarter of an inch. However each model predicts several strong vorticity maxima rotating around the cutoff, so the details of how rainfall evolves will be interesting. With strong forcing for vertical motion and dramatically cooler midlevel temperatures, the chances for thunderstorms over southeast Arizona appear quite good. Some rainfall would be quite welcome, since the last rain here at house was on March 23rd. April has brought mostly wind and dust, with trace rainfall from sprinkles and spits on just two days.
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