Sunday, December 18, 2016

Temperatures Tonight

Edited to add morning observations: Have added the 06:00 am MST observations from MesoWest for comparison to yesterday's WRF-GFS forecast for same time. The forecast was certainly on with the signficant warming trend. But it was also too agressive with the wind forecast, so midtown ended up cooler than forecast, while the east side was warmer. Temperatures across lower elevations of metro range from 57 F to 35 F or 22 F spread. Airport came in at 50 F at 06:00 am, but with low of 42F during a calm period. all of this just illustrating the forecast difficulties for low temperatures in situations like this.

A follow-up to yesterday's post about the tricky forecast situation for tonight. This morning's 12 UTC WRF-GFS forecast of surface conitions around the metro area above is valid at 06:00 am MST tomorrow morning. Because of the easterly winds (and also cloud cover) predicted by the model some early morning temperatures are more than 20 F warmer than were temperatures this morning. The high cloud that has moved overhead this afternoon has been well-forecast by the model. Forecast of OLR below is valid at 03:00 am tomorrow morning and keeps fairly thick high cloud overhead. So the model forecasts a night tonight that will be radiatively much different than last night.

Current NWS forecast low for the airport tomorrow morning is at 35 F. The WRF-GFS tends to over-forecast the nighttime winds and keep the temperatures a bit too high, and this may be the case tonight, but the clouds are playing in sync with the winds, so it may well be very much warmer at sunrise tomorrow.

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