Why first cold snap is almost always underestimated by NWS

[WxDen]

Why is it the first true cold snap is almost always underestimated by the NWS even enlight of the models depicting it? The first frost here is never predicted here by them. The temps from the cold shot have been several degrees colder than they predicted. Why is this? Is it that they look at the "normals" and just think that it can't get that cold this early?

[JCT777]

Good question. Maybe they do not think the model-predicted cold temps at the upper levels of the atmosphere will translate down to the surface, since it is early October and the sun is still not too low in the sky. So perhaps they have overestimated the surface temps for this reason. It's my novice theory, anyway.

[PTrackerLA]

I think you might be on to something. High temp was supposed to be 78 today but at 2:20 we're only 70 and will probably only go up a degree or two more. You won't hear them mention that they were wrong most of the time either. The low tonight is supposed to be 53 but I wouldn't be surprised to see upper 40's. It's pretty rare to have such consistent coolness like this in early autumn also.