Confusion Ahead (10pm: Not So Much Now)

December 3, 2009


I thought this was something you all could discuss while I get my work (and exercise) done this afternoon.  We were just granted access to new model data via a website here in the Fox12 Weather Center.  Sorry, but it’s only available from our vendor WSI.  They supply the weather info, software, hardware etc…  The data includes ECMWF data out to 360 hours, ensembles, and most important, precipitation.  Of course I immediately loaded up that!  First, it is now the coldest model suddenly AND keeps systems much farther south next week than the GFS.  Above is the Thursday morning image, showing no precipitation making it to Northern Oregon, in fact it shows dry weather through at least next Friday.  Second, I’ll definitely be hesitant to make a big deal out of snow/ice the middle of next week.

What I’m not hesitant to do is reinforce the big message.  An arctic blast is coming Sunday.  All models are on board now.

10pm Update:

Whew!  The cold blast is on track and even looks a bit colder.  All models now in agreement on a major push of cold modified arctic air into (and through) the Pacific Northwest Sunday.  850mb temps on both the ECMWF and GFS are -13 to -15 (forecast of course) from late Sunday through early Tuesday.  That along with strong northeasterly wind should keep high temps below freezing.

Here is something that really surprised me this evening.  Models forecast that first blast of cold air last December with 850mb temps the same or a bit warmer than what we have coming on Monday!  We had a high of 28 degrees on the sunny Monday after the arctic front passed through.  So I dropped the high temp forecast to 30 both Monday and Tuesday.  That may be generous.  Either way it appears our forecast at FOX12 is much colder than others still.  That’s surprising…we’ll see how it turns out.

As for precipitation once the cold air is in place???  The big change in the last 24 hours is the northern stream continuing to dominate most (or all?) of next week.  12z ECMWF and the 00z that I’ve seen to Thursday AM shows no precipitation coming towards us through the end of next week.  GFS is the same now.  The fresh 00z ECMWF also shows -8 850mb temps all the way to Wednesday afternoon.  I may take out the snow/ice in the next 5 minutes in the 7 day forecast.

Chief Meteorologist Mark Nelsen