Difference in precipitation percent chance

I was monitoring the weather for a station in downtown Alexandria, VA, in particular, what was the forecasted chance of rain for Saturday. WWL shows 62%. When I select More under the Tomorrow icon I get an entirely different number, 30%. You can see WWL to the right and the website I went to for more info showing Saturday to the left. Is this an anomaly, or can it be attributed to the station I selected? Not sure how the data shown on the webpage relates to the forecast given in WWL. I’m using WWL 6.1.09. Thanks

Check out the daily and hourly forecasts for your selected weather station at WeatherBug.com. If you compare the maximum POP in the daily and hourly forecasts, you’ll see they don’t match up. When that data is downloaded into Weather Watcher Live, I alter the POP in the daily forecast to match up with what is in the hourly forecast. I chose to do that because the POP predictions in the hourly forecast always seem to be more accurate.

I think I’m confused. Guess I don’t quite understand. I thought the hourly readings seem to match pretty closely the Saturday daily, but you have to compare to the hours after 8AM. In other words, it is 62% up till 9AM, then it drops to 27%. To confuse things even more if you click the Weekend Forecast, 7-Day, or Detailed it is now showing 50%, but the hourly hasn’t been updated yet to match.

See the image below. The circled numbers are the highest POP predictions in the morning/evening.

I’m not sure what you mean by the 50% in the detailed forecast.


Sorry, not following this, but don’t worry about it.

Here are the important points to take away:

1) The top, left image is the daily forecast. The images to the right and bottom are sections of the hourly forecast.

2) Only one hour is left in Friday’s hourly forcast (top, right image), so the maximum POP is 62%. That number is the POP for “Fri Night” in the daily forecast.

3) If you scroll down the POP column for Saturday morning’s hourly forecast (middle, right image), you’ll see the maximum POP is 62%. That number is the POP for “Sat” in the daily forecast.

4) If you scroll down the POP column for Saturday afternoon/evening’s hourly forecast (bottom, left image), you’ll see the maximum POP is 27%. That number is the POP for “Sat Night” in the daily forecast.

The POP values listed in the daily forecast are always the maximum POP predictions for that period of time. If the POP goes from 27% to 6% (like in Sat Night’s hourly forecast), 27% will be displayed.

I think that helps, especially the last part about using the highest value for the period.

It was late last night when I was looking at it, but I was trying to figure out why your WWL looks different and thinking maybe that was part of the reason I wasn’t following.


I’m using the new Splendid2 skin. It’ll be included in the next Weather Watcher Live release – sometime next week.