How much snow for Philly, Darby, Haddonfield … your town? The National Weather Service will pinpoint it

Not so long ago, National Weather Service snow forecasts tended to err on the side of ambiguity — something like, 1 to 2  inches in the city, 2 to 4 in the northern and western suburbs.

The more-localized estimates were left to the likes of AccuWeather.

These days? As you can tell from the handy snow map posted with Emily Babay's snow story, the forecasts have become far more specific. But that's only the beginning.

To see how much things have changed, check out the Mount Holly weather service office site.

With the lunchtime update, you'll note that the main map now has the Philly metro area in a deep blue "winter weather advisory" zone and now is calling for 2 to 4 inches.

But if you want to get more deeply into the forecast, so to speak, click on the Winter Weather section.

Scroll down to the table labeled "chance of snow accumulation." It shows that Philadelphia, for example, has an 87 percent chance of getting at least a tenth of an inch and a 67 percent likelihood of up to 2 inches, and 2 percent chance of 4.

As they say in those TV infomercials, hold on, there's more. Go to the county option, and you can get similar readouts for several towns in each county.

Switching to "all" gives them for 136 towns for which the office lists forecasts.

You also can opt for a potential range of accumulations for all the towns.

The accumulation probabilities are "objective" for the most part, says weather service meteorologist Sarah Johnson, based on mathematical calculations from numerous computer models, with a dash of subjectivity.

Such specificity, however, can't guarantee accuracy. As we've seen again and again, snow accumulations are hard to nail.

They depend on variables that include the water content of flakes, temperatures through several layers of atmosphere, and even the size and shape of flakes.

Computers, like humans, have their limits.