Snow Showers Tonight

November 18, 2011

Some excitement across the Portland Metro Area this evening as the band of heavy showers moved through.  Sticking snow on the hills, cooling temps, chunky rain even in the lowest spots…meteorological winter has arrived apparently.

The good news is that the coldest atmosphere of this event is moving in now through tomorrow morning.  The bad news is that precipitation intensity doesn’t look too high the next few hours. 

The earlier models had shown the surface low coming inland almost right over us.  The brand new 00z NAM and our 00z RPM both show the low either over us or to our south overnight.  Keeping most precipitation down in the Valley.  Due to the movement of the low, the south wind is going to totally cutoff very soon.  It’s already gone light east here at the station.  That always helps to get snow a bit lower.  But our RPM shows little or no precipitation after about 11pm.

So the rest of the night through tomorrow AM is really going to be about watching the radar.  If you get a heavy shower to pass right over you, maybe a dusting?  Sure feels like December out there with the chilly air and snowflakes mixed in!

Chief Meteorologist Mark Nelsen

A Cold Friday; Big Snow in Cascades

November 18, 2011

Mountain snow has been even heavier than expected; Automated sensors show about 22″ new at Mt. Hood Meadows since yesterday morning and possibly 26″ up at Timberline!  That’s 2 feet already with more to go! 

The snow level did drop a bit further overnight, and the freezing level right now is around 1800′ over Portland based on the top of our transmission tower (1900′) at 31.8 degrees this morning.  That’s a very chilly airmass.  When you get heavy showers at that temp, sticking snow can push a good 1,000′ lower.   In fact take a look at the 10am ODOT cameras at Shorty’s Corner (1200′) just east of Sandy and Quartz Creek (1,100′) in the Coast Range.  Both had or have snow on the side of the road. 

For the rest of today, sticking snow should generally remain well above 1,000′ with the minimal daytime heating.  But anyone could see flakes mixed in the rain or just plain flakes with such a chilly atmosphere.  There are no travel concerns in the lower elevations through this evening here in Western Oregon.

Tonight there is a little “fly in the ointment” as they say.  First thing I noticed on the satellite looper this morning is that low pressure center offshore is farther south than models showed it placed.  It’s a minor but important detail. 

I’ll be at work a bit early this afternoon, eagerly awaiting our 18z RPM run to see if it shows the low coming inland farther south as the two UW mesoscale models show.  More later…

Chief Meteorologist Mark Nelsen