Yesterday I posted an article (see by clicking HERE) about the in-depth meteorological process that goes into the generation of a general forecast for the public.
Today I wanted to do a reality-check and go back to see how well I did with that forecast and what actually happened. Let’s hope I passed.
I was happy to see that the local weather observations changed from ice pellets to light snowshowers. This indicated that my suspicions about the lack of an elevated warm layer aloft was correct. Whew – my first check mark.
The Morning Drive
My drive into the city was fascinating – from a meteorological standpoint. From Echo Bay to the eastern edge of the city I drove through several changes in precipitation type. I went from snow, to rain, back to snow and then rain again. My elevation did not change and my surface temperature (from my cars temp readings) did not change. Outside temperatures were near +1C. How did this happen?
For snow to form it requires the activation of ice nuclei. This occurs around -10C. Without temperatures that cold we end up with what’s called supercooled water droplets in the atmosphere that exists in below freezing temperatures that do not freeze or create snow.
Yesterday the vertical profile of the atmosphere cooled with height. The higher you went the colder the temperature. So yesterday when I drove through the areas of snow it was an indicator that the cloud depth was deep (high) enough that it reached into the area below -10C for snow to form. So how did I get periods of rain then?
When I drove through shallower clouds the cloud tops were not high enough to reach -10C, likely only several degrees below freezing. So snow never formed and these supercooled water droplets simply fell to the surface as rain since surface temperatures were above freezing.
This whole process was evident when I looked aloft to the various dark clouds and could see tall deep clouds mixed with more shallow clouds. Mystery solved – check mark number two about my fear that moisture in the snow growth region would be a forecast challenge for the day.
Where Was My Widespread Afternoon Snow?
By mid-morning, it became evident that there was a lot of dry air winning out against the moisture from Lake Superior. I was seeing little to no evidence that overall upper-level forcing (QG) was occurring to generate or enhance precipitation. By noon some strong bands of snow moved into the Sault and I was relieved to see the timing of precipitation was on-track. (check mark #3!). I was disappointed to see that the strong winds and snow were behaving like transient squall lines that came and went with periods of sun between this scattered lake effect activity. I knew right away my idea of some widespread light snow was not going t happen (first failing grade today.)
Temperatures did come in for +3C, so another checkmark. The snow did come and go in brief blasts but never did come close to accumulation or any slush (another ‘x’).
Halloween did play out as expected with temperatures falling towards freezing with northwesterly winds pushing windchills down below freezing and the odd lingering scattered flurry.
The observations shown above from the Sault airport show the kind of hit and miss day it was for flurries and snow. The most important part and the most frustrating part of meteorology is that you are always learning and nobody knows it all. Mother Nature can be humbling but I keep coming back for much because it’s what I love.
Thanks for following along and I hope you enjoyed this peek into some behind-the-scenes meteorology. I’m hoping I received a passing grade and put out a public forecast good enough that it had value for folks to plan their day.