I just noticed the switch of forecast data on the national LDL. At about 3:41 PM ET, the forecast temperature data for Tuesday was missing, but Wednesday was still present. And then at about 3:42, the LDL froze on Sacramento for about a minute. When it finally got moving again, the forecast for Wednesday and Thursday was showing.
I don't know what or where the national LDL is getting it's data from. I had thought it was running on Viz, but now I'm not too sure, because it wasn't showing the customary "-" for missing data.