Each situation is different, but the reason I always try to explain how predictable a given circumstance is, is because I know, personally, I'd like to know in advance if the forecast might change or is secure. In this case, for this coming weekend, the forecast definitely may change. The reason for low predictability comes from the handling of the jet stream winds aloft - the fast river of air that steers storms and separates cool from warm air. Of dozens of possible solutions, the greatest agreement on a similar forecast for the jet stream one can find for the weekend is only about 20% - that's quite low. Essentially, this means that 80% of the solutions show something *different* from the "most likely" forecast!
Predictability Is Low for the Upcoming Weekend - Stay Tuned to Forecast Updates
Every once in awhile I explain a bit about forecast confidence and predictability of a weather pattern - the forecast for this upcoming weekend is one of those times. Chances are good, some of you will read this and recall hearing this upcoming weekend should be nice, while others will recall hearing a chance of rain, depending upon which forecast outlet you utilize (of course, I always hope the answer is NECN!). Why the difference in forecasts? Can the forecast change?
You can imagine, if the jet stream pattern that steers storms is unpredictable, then surely the exact placement of frontal boundaries at the surface will be quite uncertain, as well - and that's why, in my Monday night broadcast, you saw me explaining the placement of a stalling front offshore is important to the Friday through Sunday forecast. I'll keep you posted if anything should change from the rather optimistic forecast I'm currently offering, of just a chance of a Friday shower east, a quiet and fair Saturday, and scatterd Sunday afternoon storms.