This is for the hardcore weather groupies:
I just saved maps, observations, and other info on our little event last night so I could look look a bit closer in the future when the weather is slower. Here are a few thoughts on the past 24 hours.
1. In general I think our forecast 24 hours ahead of time was pretty good. We said most of the event would be during the night, it would be mainly freezing rain (or all), and the morning commute shouldn’t have any serious issues. Plus we said most of it would occur after the evening commute (partially correct).
What we missed:
1. Snowy start…only because we had very light precipitation to begin with did we avoid a snowy evening commute. The precipitation was a bit ahead of schedule AND it was snow. We could have easily seen a quick dump of 1-2″ that would have made for a December 29, 2009 repeat. Atmosphere overhead stayed far colder than models showed. At 4pm, it was around 26 degrees on the top of our transmission tower in the West Hills (1,800′), the highest resolution model we have (4km WRF-GFS) showed the temp should have warmed to around 37 degrees with wetbulb temps above freezing. That’s pretty bad…models will have to be higher resolution to handle cold air outflow from the Gorge better. At least a close eye on those towers will help. It did about 10 days ago when we had the spotty freezing rain.
Things to remember in the future:
1. I (and everyone else) needs to remember that you don’t get much freezing of roads (that aren’t initially below freezing) until the air temperature gets down to about 30 degrees. I had forgotten about that since the east metro area hasn’t had signficant ice in 3-4 years. My drive across the region at midnight seemed to confirm that. Here in Beaverton it was 31 or 32, but no ice on roads, just everything else. In fact now that I think about it, we don’t get freezing rain that affects traffic (much) west of the West Hills unless it’s associated with one of the big cold storms. Sure, a little ice, but it would have been nice to say that on-air.
2. If the south wind isn’t forecast to arrive until 1-4am (as the best models showed), the temperature won’t really budge until that time. We don’t get “slow warming” in the middle of the night with easterly wind blowing or calm conditions. Not that there was any huge forecast error here, but something to remember.
3. When we have a very warm atmosphere overhead, the temp change will be sudden in most areas. PDX and TTD jumped 10-15 degrees in just one our this morning.
That’s all for tonight…we’ll talk heavy rain tomorrow night I’m sure.
P.S…Yesterday (January 11, 2011) was the busiest day yet for this blog…79,000 visits in 24 hours!
Chief Meteorologist Mark Nelsen