We use two forecast services. Snowforecast.com and Weather Underground. The later gives a forecast based on our local weather station. However, it has limitations.
Our primary service is Snowforecast.com. It is much better at forecasting temperature, conditions and precipitation type.
Weather Underground is good at forecasting precipitation and the general amount. They are not good at predicting temperature. Their assumption is based on Smithers and the higher the elevation the colder it should be. The forecast does not account for the many inversion that we experience. So, a forecast temperature around 0°C and snow may actual turn into a warmer day with rain.
POP and narrative are from Weather Underground. Combining the two makes our forecast more inclusive.
The precipitation/rain gauge measures rainfall in millimetres. To be able to measure snowfall, a heater has been installed to melt the snow and measure it as rain.
A tipping bucket electronically records precipitation electronically. It has a funnel, like a simple rain gauge, but the funnel leads to two tiny "buckets." The two buckets are balanced (somewhat like a sea-saw) and each holds .2 mm of water. When one bucket fills, it tips down and is emptied while the other bucket fills with rain water. Each tip of the buckets causes the device to record an increase of .2 mm of rain.
Snowfall measurement determines the equivalent amount of water in a unit of snow. To obtain this ratio, the snow must be collected and melted into water. Generally, 10 mm of snow produces 1 mm of water. However, it can take up to 100 mm of loose, fluffy snow though as little as 2-4 mm of wet, compact snow can produce a millimetre of water.
The model for estimating snow depth will include the effects on snow depth of precipitation rate, snow density, wind speed, and ambient temperature. All measurements necessary for the estimate are taken from the Davis Instrument Tip Bucket Rain Collector and Wind vane with potentiometer Wind Direction Sensor.
The factor used to estimate snow depth for snowfall today is based on the average of measurements over the last 24 hours.
The factor used to estimate snow depth for snowfall this month is based on the average of measurements over the current month.
Snow Conversion Data
Kevin V. Galloway, Scott D. Landolt, Roy M. Rasmussen National Center for Atmospheric Research Boulder, CO
This situation will occur under the following circumstances;
The current data is over an hour old. This indicates a power disruption at the weather station location. The weather server will resume once power is restored.