Tuesday, December 22, 2015

Quick Update For Christmas Day

The ECMWF and GFS operational forecasts for 500 mb are now very similar through the afternoon of Christmas Day. Shown here are 96-hour 550 mb forecasts from 00 UTC last evening, both valid at 5:00 pm MST on Christmas (ECMWF above and GFS below).

The 06 UTC plumes from the GFS ensembles for the 21 members continue to be interesting. The temperature plumes above continue to forecast a strong cold front passing TUS in the late afternoon, or early night, on Christmas Day. The model is forecasting high temperatures on the 26th to be around 15 F colder than those on the 25th.

As for QPF forecasts below, there is still substantial variance among the different configurations of the GFS model. While all the members forecast light showers and sprinkles at the airport from this evening through Thursday morning, the precipitation with and following the cold front ranges from less than a tenth to almost seven tenths of an inch. (The WRF high-resolution forecasts from Atmo at 06 UTC this morning continue to keep precipitation from now through Thursday mostly to the north and in the Catalinas and Rincons.) The operational version of the model (blue trace) remains quite dry compared to many of the forecasts. Most of the models are forecasting the precipitation during the night following the frontal passage; however, some members have the precipitation falling mostly on Saturday. The snow level would be very low by Saturday morning, so it continues to look like an interesting weather-weekend.

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