Wednesday, January 17, 2018

Last Weekend vs Coming One


Last weekend was about as nice as we can have here - light winds, clear skies, and temperatures in range 75 to 80 F. However, a strong 500 mb shortwave and attendant front will impact Tucson Friday night through Monday the 22nd. Making for a huge contrast between the two weekends.

The above shows the GEFS plumes for QPF (from 06 UTC model runs) at the airport. Almost all the members forecast measurable rainfall at the airport on Saturday. Amounts have a substantial range - from 0.00 to 0.20", with a mean of 0.05". The operational GFS (blue in graph) remains very dry, with amount of only 0.01". The forecast PW plumes for TUS (below) indicate a brief spike to values around half an inch before dry air behind the front dominates. So very cold and windy for Saturday, with chance of light showers around the metro area.



Forecasts of PW from the 06 UTC WRF-GFS (on 5.4 km grid) at Atmo are for 11:00 pm MST tomorrow (above) and 5:00 am on Saturday morning (below). A weak atmospheric river moves southward along California coast, but weakens rapidly once it passes Point Concepcion. This means another in a series of moisture-starved events for southeast Arizona.

Graphic at bottom is from 00 UTC run of the WRF-GFS on the 5.4 km grid for total precipitation through 5:00 pm on January 20th - indicating very little for Arizona and New Mexico.




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