How are long-term forecasts created (beyond 10 days)?

Computer models which meteorologists use to forecast the weather are made up of complex mathematical equations.

Different models, and therefore different equations, determine the forecast period. The further out a computer model runs, the less dependable it becomes (due to the "chaos theory").

We always emphasize that long-term models should be used primarily for the trends they exhibit, not specifics.

They may give us some insight on global patterns or trends that may be developing, like the patterns and trends of El Niño and La Niña years.

We always, always take long-term forecasting with a "grain of salt".

» More Homework Help Questions

Interactive Radars

Regional Headlines

This Week's Circulars


Regional Radar Image

Live Traffic Cameras

Cameras provided by PennDOT

Historical Averages

High Low
Current 82°F 62°F
Average 65°F 42°F
Record 91°F April 28, 1990 30°F April 28, 1934