A forecast is a prediction. It's an idea about what might happen in the future. This word is usually used when talking about the weather and the climate, but it can also be used in business.
What's the forecast for tomorrow? (This question uses "forecast" as a noun.)
What are they forecasting for tomorrow? (This question uses "forecast" as a verb.)
A meteorologist forecasts the weather.
The person who does the weather on Channel 4 is forecasting a cold weekend.
The forecast is for more snow.
Snow is forecast for tomorrow. (passive voice)
Snow is forecasted for tomorrow. (When "forecast" is a verb, you'll hear people use "forecast" and forecasted" for the past tense and for past participles. "Forecast" sounds better--I think!)
Climatologists are forecasting a rise in global temperatures due to an increase in greenhouse gases in the atmosphere.
Farmers and businesses rely on accurate short-term and long-term forecasts of the weather.
It's difficult to forecast what will happen with the stock market; however, analysts are able to look at trends and make predictions so that investors can make decisions about where to put their money.
Experts on the economy are forecasting a rise in interest rates.