Thursday, January 12, 2017

Models Continue To Forecast Wet Weekend

Forecast models continue to indicate a wet weekend for southeast Arizona, as closed 500 mb low digs south along the California and Baja coasts and then turns northeastward across our part of the state. The TUS plumes for QPF from the 06 UTC GEFS (above) have become quite consistent with 100 % POPs for Saturday afternoon and night, although amounts in the forecasts still have large spread. The operational GFS (blue) is now quite close to the ensemble average and indicates nearly half an inch at airport.

The 06 UTC WRF-GFS forecast for composite radar echoes at 5:00 pm MST on Saturday (just below) is quite impressive for eastern Pima County, and the model's forecast for total precipitation through 11:00 am on the 15th (Sunday - second below) indicates a decent, widespread event with maximum amounts up in the White Mountains.

The details will depend upon the actual track that the 500 mb closed low takes (it is currently along the northern California coast). The 500 mb forecast from the WRF-GFS valid at 5:00 pm on Saturday (below) places the low to our southwest, just south of the border. This would be a good track for precipitation here. However, a similar situation, and forecasts, earlier this winter went astray as the low dug further south before turning northeastward - so we'll have to keep close watch as the current low heads south.

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