Monday, December 03, 2012

Models Forecast Pattern Change By Weekend

The long-range, global forecasts indicate a pattern change over the weekend. The 144-hour 500 mb forecast from the GFS (above - valid 5 am MST on Sunday the 9th) indicates a short wave and strong vorticity maximum digging into the Southwest. The GFS is more aggressive with this short wave than is the ECMWF, which forecasts an elongated vorticity maximum digging southeastward across western Colorado (144-hour forecast for 500 mb below). It appears that quite cold low-level air will move southward behind this system. The two forecasts are fairly different west of the Canadian coast, where the GFS has forecast stronger ridging while the ECMWF has forecast the next wave eastward more quickly. The evolution of the details during the week will determine whether or not we end up with a chance for some weather in southeast Arizona.

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