More Action Ahead

January 5, 2011

Okay, we can move on from the big “ice storm” now.  Looks like in the end it was just a marginal event with almost no evaporational cooling effect in the lowest 2,000′ or so.  I would argue that mesoscale models did great with the mid-upper levels of the atmosphere (above 1,500′), but were horrible in the lowest layers.  Consider that we never did get a southerly wind or for that matter even a drift of south wind today.  Imagine if it would have been 5-8 degrees colder to start…Portland would have been an icy mess all day. 

Moving on…the front on Friday is sure looking less juicy on recent model runs.  Plenty of chilly air behind it Saturday, but snow levels only down around 1,000′ and minimal post-frontal showers.  The weather will just turn chilly, dry, and breezy later Sunday through early Tuesday.

The interesting action is Tuesday and beyond.  There appears to be an epic battle shaping up across the eastern Pacific and western North America.  A converging of the mild and moist westerly Pacific Jet and the very cold northerly jet on the back side of a very strong upper-level high over Alaska.  The interaction of these two will probably make a mess of models for days to come.  We could easily just stay in the mild westerly flow, or see the northerly flow take over…who knows 6 days ahead.  The 00z GFS was similar to the 12z ECMWF with several wet low pressure systems interacting with the cold air starting Tuesday.  BUT, the new 00z ECMWF totally swamps us with the milder southwest flow.  As I said…who knows?  I can remember a bunch of these situations in the 1990s with models flip-flopping around 3 days before the event.  Regardless, the weather action is going to really pick up again after Monday.

Chief Meteorologist Mark Nelsen

Spots of Freezing Rain This A.M.

January 5, 2011

A quick look at what’s going on this morning (from half-asleep eyes):

1.  No snow…temps are too warm above, note the hills around town have moved well up away from freezing.

2.  Very little precipitation of any type so far.

3.  Little to no “wet-bulbing” going on with such light precipitation, temps and dewpoints are gradually rising (especially dewpoints) in just about all areas.  About half of us in the metro area even appear to have passed the possibility for significant icing as the temp has moved above freezing.

Add these together and it now appears a signficant icing of the Metro area for the morning commute is unlikely.  Definitely localized icy areas though, but even those will just last a few hours.

Be careful on sidewalks and a few side streets, but in general I think we are in pretty good shape; could have been much worse!

Chief Meteorologist Mark Nelsen