The weeks of Oct. 17 and 24 will be the best this autumn for fall foliage in Pennsylvania, according to a national prediction map from SmokyMountains.com, an online guide.

The map uses an algorithm to analyze several million data points and outputs approximately 50,000 predictive data pieces. Data input into the algorithm came from National Oceanic and Atmospheric Administration historical temperatures, historical precipitation, forecast temperatures and forecast precipitation; historical leaf peak trends; peak observation trends; and historical model outputs from previous years.

That data then enables a program to forecast county by county the precise moment when peak fall will occur.

The end-user can easily select a date on a slider at the bottom of the map to learn where fall will be peaking for that week.

The results for Pennsylvania show the week of Oct. 17 as peak fall foliage in the northwestern quarter of the state, the Laurel Highlands, and the mountain areas of southcentral Pennsylvania; past peak only across the northern tier and northeastern corner of the state; and near peak across the rest of the state.

For the week of Oct. 25 the map predicts past peak across the northern tier, the northeastern corner of the state, the northwestern quarter of the state, the Laurel Highlands and the mountain areas in southcentral Pennsylvania, but at the peak for the rest of the state.

“Similar to any meteorological forecast, leaf predictions will never be 100 percent accurate,” said David Angotti, creator of the map. “However, after publishing our predictive fall foliage map for nearly a decade, we are quite confident in our data sources, process, and algorithm. Our experience combined with a scheduled mid-season update has us especially confident about this year’s predictions.”

Other predictions for Pennsylvania by the map include the following:

Users of the online map also can check on individual counties across Pennsylvania and across the entire country.

For the first time this year, SmokyMountains.com will be adding a midseason update to the map in late September.

“Due to the complexity of applying a humongous, multi-faceted dataset, we have historically published our map annually without mid-season updates,” Angotti explained. “However, for the first time ever, we plan to release a mid-season update in late September. By applying the midseason update, we believe the accuracy and usefulness of the tool will be increased.”