Weather Blog

How to gauge a current snow level

How to gauge a current snow level

I suppose you could just look out your window and see if it's snowing, but for those that are curious to where the current snow level might be, check out this chart:

You can get the latest chart at this link from the UW

This is a virtual temperature graph taken by what's called a temperature profiler. It's akin to sending up a weather balloon, although this uses ground sensors instead of an actual balloon floating through the air with onboard instruments.

This particular one is set at the NOAA building in Seattle's Sand Point neighborhood.

This chart shows the past seven hours' worth, with the black line being the most recent. It's updated every hour.

The line shows how the temperature changes with altitude, shown in meters. (The line actually shows "virtual temperature" -- and you have to subtract about a half to whole degree to get the actual temperature.)

In this instance, if you want to find the snow level, we want to find at what height does the black line cross roughly the 0.5-1.0 degree Celsius peg on the graph's bottom legend. (For those whose physics books are a little dusty, remember that 0 degrees C is freezing -- 32 degrees F)

The color bars refer to the time it was taken, with the answer key in the top right corner, given in UTC time, which is 8 hours ahead of PST and 7 hours ahead of PDT.

So the black line, which is valid at 1 p.m. March 5th, crosses the 1 degree C line at roughly 600 meters, or 1,800 feet. But look back a few hours at the red and green lines (11a.m. and Noon) and it shows a much lower snow level of about 250-300 meters, or 750-900 feet.

Now again, this is taken for Seattle. The snow levels were much lower along the foothills -- closer to 400-500 feet -- due to a Convergence Zone that was intense enough to drive the snow levels lower. (You can read more about that phenomenon on my earlier blog post about how snow is variable around here. Look down under the "Precipitation Intensity" explanation.)

Thus, this isn't necessarily the best gauge for a region-wide snow level when there are individual events going on, but it's pretty good for the Seattle metro lowlands.

If you want to peek back to previous days and hours, check out  this link, or if you want to go back a week, here is a daily snapshot.