Model Image links are to the Forecast Hour. To determine what time/date
the image is for, add the number of hours to the initial model time. For example, to see the forecast graphic for 24 hours from now, use the
24 link. If the model time is 5 pm Sunday, the forecast 24 graphic is for 5
pm Monday.
The National Weather Service always operates on "Z time" (variously
called Greenwich Mean Time or Universal Coordinated Time) which does not observe
Daylight Saving Time. This allows all meteorological offices around the world
to be able to refence the same time, without having to deal with time zones
and adding or subtracting hours.
www.weather.gov 
