Day 7 of Missoula, MT (KMSO)

Good radiational cooling led to a quick dip down to 35F last night. Mostly sunny skies led to a quick warmup, apparently boosted by vertical mixing with cool advection and westerly winds, leading to a high of 77F so far. The cirrus has also been rather thin. West-northwesterly winds are strengthening a bit now, so far maximum of 10 kt. Clouds will thicken tonight, with mostly cloudy skies (mostly mid to high level clouds) preventing as quick of radiational cooling as the past few nights, leading to a much warmer low even with general weak cool advection. The wind will also weaken this evening as we lose vertical mixing from sunshine, and with mid to high-level clouds dominating (though with some breaks) tomorrow as well, there won’t be too much vertical mixing, and winds even aloft are not that strong. So tomorrow’s winds will likely be weaker than today’s but still out of the west-northwest. Clouds will clear more at the end of the day tomorrow but perhaps too late for any additional warming. Note that these mid to high level clouds are not as thick as the low level clouds that sometimes prevent any nighttime cooling or daytime warming from happening, but will be enough to alter the model biases. It is not clear if the low will occur tonight or at the end (Friday 06z). Mostly clear to partly cloudy skies (some mid-high level clouds returning possible) and light winds at the end will lead to good radiational cooling, but it seems like it often doesn’t cool down overly much initially at Missoula, and it might have to wait until after 06z to get the truly cold temperatures. The slightly cooler air mass and cooler high temperature will give it a head start though.

 

Source: PivotalWeather

Also, something that we usually don't have to think about for days 7 and 8: The unseasonable warmth and dryness has led to wildfires growing in the western U.S., and some of the smoke will be overhead Missoula all day tomorrow, perhaps enough to lower the high by like 1F or so for day 7. It won't be particularly thick tomorrow so it won't be like many degrees. It might actually be thicker on day 8, but we shall see.

 

 

Source: PivotalWeather