So in the last week, after I released an update to my iPhone app that integrated Darksky weather, I'm seeing multiple cases in which Darksky forecast / current conditions are totally blowing it. The issue is precipitation type. My coverage area is the western part of Virginia. The forecast difficulty here in winter is almost always the type of precipitation we will get.
Last week Darksky predicted 2-4" of heavy snow, where no other weather forecasts said snow (and the NWS watch was for mixed winter weather - sleet, freezing rain type stuff). For the entire day Darksky said it was snowing. Minutely said things like "Heavy snow ending in 30 minutes", etc. We did not get one flake of snow from that system. The ground temperature was a little below freezing, and we got lots of rain, with some freezing rain with ice accumulation, which is very typical here.
Now today we are getting snow. 2-4" of it. It is snowing right now. DarkSky's current condition and minutely forecast: "Heavy rain for the hour". The temperature is 36 F but we are getting snow. As forecast by the NWS and others.
So I can only conclude that Darksky is extrapolating minutely type forecasts from radar, and naively determining the precipitation type by the ground temperature.
After some searching I came across this research document from 2016. Darksky consistently ranked second to last (7th out of 8 ) in weather forecast accuracy.
https://www.forecastwatch.com/wp-content/uploads/Three_Region_Overview_2010_201606.pdfI am in the process of reimplementing my backend to work with the new NWS raw forecast data. I won't have "minutely" data, but the hourly has looked very good in my tests. It is not great when a forecast is wrong, but it's downright embarrassing when the current conditions are totally wrong as to the precipitation type -
all day long.
I just wanted to point this out for those using Darksky. Perhaps in areas where the precipitation type is more simplistic (all rain or all snow) the accuracy is better, but for this part of the country, where cold often meets warmth, they have been exactly backwards in the precip type.