Snow? When the Temperatures Are > 20C?

The gubmnt weather office shows very useful radar screens for our area, but the folks there really need to change their precipitation measures from "snow" to "rain". 

Here's a screen shot from this afternoon. Note the word "snow" in the heading and in the scale along the right side, even though the current temperature is 22C [72F].

Comments

[Patrick Carroll]

The radars are programmed to interpret echoes as rain or snow on a seasonal basis. The switchover from warm to cold or cold to warm season interpretation can result in the apparent confusion shown here when the programmed precipitation type does not match reality.

Environment Canada determines the optimum date when the switchover from cold to warm or warm to cold season interpretation takes place. As the above example shows, the timing can be off due to unseasonable weather.

From their web site:

What is the difference between PRECIP-Rain and PRECIP-Snow images?

In general, rain is more easily detected by radar than snow. In order to better represent the precipitation during the warm season, a certain relationship is used to relate the reflectivity to a rainfall rate (in mm/h – PRECIP-Rain). During the cold season, a different relationship is used to relate the reflectivity to a snowfall rate (in cm/h – PRECIP-Snow). However, it should be noted that just because the reflectivity is being represented in mm/h doesn’t mean that the precipitation shown on the radar is rain or if the reflectivity is being represented in cm/h that the precipitation shown on the radar is snow. The precipitation in most of the more densely populated areas of the country can still show a high degree of variability throughout a good portion of the fall, winter and spring allowing for rain, freezing rain, ice pellets and snow to occur alone or in some messy combination. Therefore, it is always important to relate the precipitation you are seeing on radar with what the current weather conditions are and what the forecast is in the coming hours to get the best sense of what may fall out of the sky in your area.

[Rick]

Interesting... I find the Exeter radar images less detailed than our southern friends' radar images. I have not seen the Exeter screen in a few years but it looks exactly as I remember it. I hope a software update is in the works. Until then, I prefer the looped images offered by NOAA. Just click on the word 'Loop' next to your region. You can then click on the map for a closer look from a nearby city. Here in sunny London we can use the radar images from Detroit, Cleveland, or Buffalo. Folks in Goderich will have to settle for the Exeter radar.

http://radar.weather.gov/