Elevations & Snow

December 3, 2005

I saw something interesting tonight on another station. A forecast for sticking snow above 800′. The official NWS forecast for tonight is 500-1000′. By the way, when we say "snow level", we mean the elevation to which snow will stick…it’s usually colder as you go up in elevation. So does that mean that one station or forecaster can more accurately predict how low the snow is going to go? Not really. In situations like tonight…where a solid stream of cold showers are moving inland (at over 30 mph!), and the low level wind is southerly…we tend to see a general snow level the same from the beaches all the way to the Cascades. You could argue that it’s about 1,000-1,500 at this moment while I write this close to midnight Friday night. And that’s what I forecast tonight. But when the wind isn’t too strong, a very heavy shower moves through and the melting snowflakes can bring the snow level lower than expected otherwise. Last night, coming over Sylvan at 11pm (780′ elev.), it changed to almost all snow in a tremendously heavy downpour. I almost panicked, thinking this would be the end of all of us and a surprise snowstorm. There was probably sticking snow to 1,000′ in that shower, but then it moves on by and the light southerly breeze warms things back up a few degrees. The point is that the snow level in situations like this could be 1,500′ one moment and 800′ the next. It’ll always drag lower when the precip really comes down hard. I have 1.5" on the ground at my home tonight at 1,000′, while I doubt there is any Skyline & Barnes in Portland. Mostly likely heavier showers moved through here as they ran into the Cascades (it’s a very wet place!). FOR THIS REASON, I usually stick to 1000′ increments, but sometimes 500′ if necessary, in my forecasting. Saying 250′ or 750′ or 800′ or anything along those lines that implies accuracy that we don’t really have. Just one opinion of course, but have a good weekend! Mark


Elevations & Snow

December 3, 2005

I saw something interesting tonight on another station. A forecast for sticking snow above 800′. The official NWS forecast for tonight is 500-1000′. By the way, when we say "snow level", we mean the elevation to which snow will stick…it’s usually colder as you go up in elevation. So does that mean that one station or forecaster can more accurately predict how low the snow is going to go? Not really. In situations like tonight…where a solid stream of cold showers are moving inland (at over 30 mph!), and the low level wind is southerly…we tend to see a general snow level the same from the beaches all the way to the Cascades. You could argue that it’s about 1,000-1,500 at this moment while I write this close to midnight Friday night. And that’s what I forecast tonight. But when the wind isn’t too strong, a very heavy shower moves through and the melting snowflakes can bring the snow level lower than expected otherwise. Last night, coming over Sylvan at 11pm (780′ elev.), it changed to almost all snow in a tremendously heavy downpour. I almost panicked, thinking this would be the end of all of us and a surprise snowstorm. There was probably sticking snow to 1,000′ in that shower, but then it moves on by and the light southerly breeze warms things back up a few degrees. The point is that the snow level in situations like this could be 1,500′ one moment and 800′ the next. It’ll always drag lower when the precip really comes down hard. I have 1.5" on the ground at my home tonight at 1,000′, while I doubt there is any Skyline & Barnes in Portland. Mostly likely heavier showers moved through here as they ran into the Cascades (it’s a very wet place!). FOR THIS REASON, I usually stick to 1000′ increments, but sometimes 500′ if necessary, in my forecasting. Saying 250′ or 750′ or 800′ or anything along those lines that implies accuracy that we don’t really have. Just one opinion of course, but have a good weekend! Mark