IEM Daily Feature
Tuesday, 19 February 2013

100% Chance

Posted: 19 Feb 2013 05:41 AM

Those of you that fervently monitor the NWS forecast may have noticed something interesting this past Sunday. For some locations in the state, the NWS had a near 100% chance of precipitation forecasted for Thursday. Is it common to see a 100% chance forecast at four days out? The featured chart shows the frequency of this confident forecast based on the afternoon zone forecast for Polk County (Des Moines). Based on data back to 1 Jan 2009, this would appear to be the first time it has happened for the day 4 forecast for Polk County. The chart nicely shows that forecasters get more confident of predicting a 100% chance as the event gets closer. Today's forecast for Thursday remains at 100%!

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Tags:   zfp   forecast   nws