Friday, September 23, 2016

Drying Out Slowly

Low levels remain very moist this morning, with heavy cumulus about and clouds hanging on the Catalinas.

Yesterday was very unusual regarding severe thunderstorms - all 23 reports from SPC were noted in a small portion of Utah - below.

The blended PW analysis for 12 UTC this morning (from CIRA, above) shows amounts now below 25 mm over southern Arizona. WRF models forecast slight chance for sprinkle showers before drier air moves in from northwest later this afternoon and evening. Below is 06 UTC WRF-GFS forecast for PW valid at midnight tonight, indicating amounts plunging to 10 mm and less over most of state. Weekend should be the coolest we've had in a long time.

This morning the middle and upper closed low is centered over western Utah (above is 250 mb 12 UTC analysis from NCAR), with a strong jet curling across parts of Arizona. Models forecast a strong vorticity maximum to dig down the west side of the low and become a separate closed low, as most of trough heads eastward. By early next week this southern low is actually forecast to be edging westward along the Borderlands (below is 06 UTC NAM forecast for 250 mb valid at noon next Monday the 26th). Will this feature manage to pick up moisture after the big dry out of next 24 hours? We'll just have to wait and see - but it will be the last hope for another rain event before the end of September.

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