Tonight Looks Like Another Tough Forecast For Low Temperatures

Edited to add: From Mike Leuthold - Bob, I have identified a issue with WRF over-forecasting these easterly wind events. I changed PBL schemes awhile back to correct an issue of winds that were too weak during synoptically forced strong west wind events. Fix one thing, break something else. As of 12Z, I've gone back to the old PBL scheme and if you look at the 12z model runs, you will see lower wind speeds. Still enough to keep temperatures elevated where winds blow and much warmer than the 2pm NWS Tucson metro zone forecast of 41-46.

 http://www.atmo.arizona.edu/products/models/wrf_d02_3/tus_station.html

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Cold here at the house this morning with a low temperature of 34F (versus 46F at the airport).

The early runs of the WRF model today are forecasting strong winds from the east to set in during the night. Above graphic shows WRF-NAM forecast of 10-m winds valid at 4 am MST on the 7th. The matrix below shows high and low temperatures forecast by early WRF for today and tomorrow. Note that the model forecasts a low of only 63F at the airport tonight.

In contrast, the NWS current grid point hourly forecasts for today and tomorrow call for considerably colder lows. Forecast above is for the grid that house is within and below is for the TUS grid point. Forecast low tonight for the house is 40F, while it is 44F for the airport (about a 20F difference in the two forecasts). The grids indicate east winds, but gusts don't set in at airport until after sunrise.

The range in lows will probably again be quite large and depend upon the nocturnal winds that occur locally. For example, here at the house cold air often develops early enough in evening that east winds are kept aloft by the stable, cool pool.