Very Cold Tonight; Then Sprinkles/Flurries Again Monday

December 30, 2012

Brrr!  It’s getting cold out there quickly this evening.  Already down to or below freezing at 10pm across the entire metro area.  East wind areas are a little above freezing.  It’s going to be a very cold night with clear skies until almost sunrise:

FCST_Tonight_Metro

Then a very weak system moves inland and dies right overhead during the afternoon.  Some models (not all) are producing some very light precipitation.  Our RPM is mostly dry with just a few hundredths on the west side of the Willamette Valley.  But other models squeeze out a more widespread few hundredths of precip.  Soundings are cold enough for just about all snow.  But even if we do get precip, it’ll be too light to stick in the lowest elevations since we’ll be above freezing.  But not by much.  Tomorrow’s cloud cover after a cold night means highs only into the upper 30s! 

Bottom Line: It’s going to be a cold and gray end to the 2012 with possibly a few afternoon sprinkles or flurries.

Here’s why I’m not too excited about real snow…lack of precipitation.  Even the “wet” WRF-GFS produces around .10″:

or_pcp24_36_0000

The 00z NAM-MM5 produces less than .05″, and as I mentioned our model produces almost nothing.

Whatever happens or doesn’t happen tomorrow, it’s done by 7pm as skies clear and we head to at least a 3 day period of cold temps, clear skies, and very strong east wind.  The air mass east of the Cascades is getting cold; single digits in many areas that don’t often get that cold tonight in north central Oregon.  Just got an email of single digits above Lyle already on the High Prairie.  That’s really cold and all that cold air will be coming through the Gorge the rest of the week.

Someone asked me today what I thought about long-range models occasionally looking colder beyond Day 10.  The 00z GFS has ridging either over us or just to our west through the 15 day period, nothing exciting there:m500za_f360_bg_NA  That 00z ensemble mean at Day15 has that stupid ridge just to our west where is has been at times over the past month. 

Now the 12z ECMWF ensemble chart

tseries_850t_000-360_Portland

does show a considerable number of members want to put us in a cooler pattern beyond Day 10.  Something to keep an eye on.  I am fairly confident that we won’t see a big arctic blast in the first 7-10 days of the New Year.  Beyond that, who knows.

Chief Meteorologist Mark Nelsen