If you’re looking how to forecast snow, then you’ve come to the right place. In the following guide I’m going to be showing you which parameters need to be met in order to see snowfall down to lower levels across the United Kingdom. For the purpose of this guide I am going to be using the Wetterzentrale GFS charts which can be found by clicking on the link below. When you click on the link, it will open up a new window within your internet browser.
500hPa Air Temperatures
Firstly, we’re going to have a look at the 500hPa air temperatures to find out whether they’re suitable for snowfall. These can be found by clicking on the “500hPa Bodendruck” in the link above. Generally for snowfall, we want these temperatures to be around -27c or below. You can see this being shown in the chart below. I’ve drawn circles around the temperature readings.
850hPa Temperature Readings
Once we’ve looked at the 500hPa temperatures and we’ve seen temperatures are cold enough to support snowfall. We then move on to take a look at the more important 850hPa temperatures. You can do this by going onto the Wetterzentral website and clicking the “850hPa Temperatur” tab. To support snowfall to sea level, we typically want to see these temperatures of -7c or lower for snowfall. However snow can fall when 850hPa temperatures are at -5c or below during heavier showers if all other parameters are perfect. You can see this by clicking on the image below.
We now move on to look at the Dew Point temperatures. These MUST be at 0c or below. If the Dew Points are above freezing then the snow is likely to be more sleety in nature. We can view the Dew Points by clicking on the “2m Taupunkt” tab on the wetterzentrale website. Here is what that chart looks like. I’ve circled the temperature reads you will need to pay attention to. I’ve left the bottom temperature reading un-circled so you can see the boundary line between the freezing dew points and the above freezing dew points.
Dam Air Thickness
Last but not least, we must then take a look to see whether Dam Air Thickness is suitable to support snowfall. Typically we want to see the 528 (Light blue line) Dam Line across the United Kingdom. You can see this by clicking on the “Mittl.Wolken” tab within the Wetterzentrale site. I’ve circled the line on the graph below in yellow.
If ALL of these parameters are in place, then we can begin to start looking at the precipitation charts to see whether any Precipitation coincides with these cold conditions. We can do this by clicking on the “Niederschlag” tab within the Wetterzentrale website. The blue represents Precipitation, if all the boundaries above are in place, then it’s very likely going to fall as snow. The darker the blue/purple the heavier it’ll be.
And that concludes my basic snow forecasting guide. If just one of the parameters above is too warm, then snowfall is unlikely. However under certain conditions not impossible. Please use the above as a guide only. This guide is to be used for cold spells within a three day timeframe. Looking at the specifics further out than that will lead to inaccurate forecasting.