I live in the Los Angeles area, at sea level. Nearby we have tall mountains where I like to go hiking. I've noticed something strange about the NOAA forecasts, which is that the forecasts in the mountains seem to predict day-night temperature differences that appear implausibly small. Example:
NOAA forecast for where I live, at sea level
NOAA forecast for the high elevation area (9000-10000') surrounding a nearby summit
These are live, so here are a couple of static screenshots for today and tonight:
The day-night difference is predicted to be about 20 degrees at sea level, but only 8 degrees on the mountain, at about 10,000'. This is a pattern that I've seen repeatedly in the forecasts, not just when the weather is changing or something. For the sea-level temps, I'm able to verify with a thermometer that the forecast is just about right for this morning, and in general the daytime temps at my house are about right, i.e., I believe the 20-degree difference at sea level based on empirical data.
The tiny 8-degree difference for the mountains just seems impossible. I don't bring a thermometer with me when I hike, and I don't think there is any actual weather station on top of any of our local mountains, but for instance when I visited this mountain last Friday, it seemed obvious to me that temperatures were increasing rapidly as the day went on.
Admittedly I don't have hard data for the temperatures in the mountains. Am I just wrong? Is there some actual physical reason that diurnal differences in the mountains would be so small compared to the ones at sea level? Or is there some bias in the way NOAA's software works, perhaps because they have ground station data at sea level, but not at high elevations?