Monday, May 11, 2015

Weak Short Wave From Mexico Tomorrow

A weak middle and upper-level short wave will be approaching from northwest Mexico tomorrow. The 15 UTC water vapor image above shows the feature over over central Baja this morning. The early run of the WRF-NAM model at Atmo today is actually forecasting radar echoes associated with this feature to move across southeastern Arizona late tomorrow. The forecast below is of composite radar echoes forecast for 10:00 pm tomorrow evening (Tuesday, May 12th).

The model's forecast of precipitable water (above, also valid at 10:00 pm MST) forecasts little moisture with this feature - keeping amounts tomorrow around half an inch. The forecast soundings indicate high cloud bases, with a deep and dry boundary layer. However, the model somehow manages to get rainfall down to the ground, as per its forecast of accumulated precipitation through 5:00 am on the morning of the 13th. 

Given the lack of moisture at low-levels, my guess would be for an unsettled afternoon tomorrow, with perhaps a few sprinkles across eastern Pima County. South and east of here there may be some better showers that dampen the ground. More significant showers and thunderstorms are forecast for the Big Bend country and eastern New Mexico.

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