Tuesday, May 05, 2015

Quick Look At Today

Even though the main short wave at 500 mb is now to the east of Tucson, fairly high PW continues to our west (above is CIRA blended PW from 12 UTC this morning). Temperatures remain quite cool at 500 mb and main forecast challenge for today will be where afternoon thunderstorms actually develop.

The Yuma sounding from 12 UTC this morning has considerable moisture up to just above 500 mb, while the morning sounding from TWC (below) continues with deeper moisture and some CAPE. Winds are westerly aloft through both soundings, which is not a good steering direction for lower, desert elevations.

This morning's NAM forecast of 850 mb winds and PW is shown below for 3:00 pm MST this afternoon. Even with weak subsidence behind the short wave, deep drying does not occur within the model's forecasts until during the night tonight. Best chances for thunderstorms over southeast Arizona will be over and east of the higher mountains. Here at the house we sometimes get a storm under this kind of flow regime, if deep convection develops over Kitt Peak and/or the Tucson Mountains. 

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