Friday, January 19, 2018

Temperature And Precipitation For Weekend

There remains little uncertainty that the approaching weather system will bring much colder temperatures for Saturday afternoon to Monday the 22nd. Precipitation amounts however remain much more uncertain wrt various model forecasts, even though event is now only 24 to 36 hours away.

Above is 500 mb forecast (on 5.4 km grid) from the 06 UTC WRF-GFS run at Atmo - very cold, short wave approaching from the  west at 5:00 pm MST tomorrow. Below, from same forecast on 1.8 km grid, is forecast of surface plot at 5:00 pm tomorrow afternoon. Main changes in model forecasts have been to slow down the system some, and delay the quick hitting precipitation event into late afternoon and evening.

The forecast plumes of 3-hour QPF below are from the Short Range Ensemble Forecasts (SREF) viewer at SPC - from a 09 UTC run of the system of 27 members. The fast hitting (some of members forecast entire event to be over in less than 3-hours) rainfall at TUS has shifted toward 5:00 to 8:00 pm.

As for amounts: the SREF mean total is only 0.03" to 0.04"; the GEFS mean is .07" to .08"; and the wetter, deterministic WRF-GFS run comes up with 0.20" at airport.

So bundle up tomorrow afternoon and watch how this all evolves.

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