The first egg was laid in a snowy nest at about 2:15pm on Sunday January 31st. Eagles (and many other birds) will often delay incubation until all of the eggs are laid. This helps ensure that the young hatch more closely together - keeping the youngest hatchlings from being too disadvantaged.
Even in relatively cool weather the eggs remain viable for some time without incubation...a nest full if snow is another matter altogether. To keep the egg from being excessively chilled the female has begun incubation (see picture below). Hopefully the female's body heat will melt away the snow and keep the egg at an optimal temperature (105 degrees). The snowy weather represents a challenge that this pair doesn't often have to deal with but that bald eagles as a species are well adapted for. Some have asked if the female would wait until better weather conditions to lay her first egg - unfortunately once the procees has begun and an egg has entered the female's oviduct there is no stopping it.