More Chilly Weather Ahead; Maybe Some Rain Too

December 11, 2011

I’m back in the saddle now through Friday, which apparently means dead weather yet again.  Here are the highlights:

1. Ridging along or just off the West Coast is going to continue through the foreseeable future.  I almost felt my dinner come back up this evening (slight gag reflex) as I looked at the 16 day GFS maps…yuck.  The ridging or splitty flow is there through the whole period.  For sure there will be no significant change for another 7 days.

2.  We’ve got a very cold air mass overhead right now.  850mb temp at SLE this evening was -6 degrees C.  That’s plenty chilly, but now we have cold and dry air returning at the surface from both the north and through the Gorge.  Dew points have been falling at Kelso, Troutdale, and The Dalles.  East wind has returned to the west end of the Gorge as well (V. House sensor offline, will try to reboot tomorrow!).  The atmosphere overhead warms tomorrow afternoon through Wednesday.  At the same time the low-level pool of cold air east of the Cascades thickens up.  It wasn’t scoured out by this weekend’s weak system;  high temps at Yakima, Tri Cities, and Hermiston had trouble getting out of the 20s.  That increases surface pressure over there.  WRF-GFS shows about 6 millibars easterly gradient through the Gorge by Tuesday morning.  Assuming it goes a bit over that, we should get gusts 30-40 mph in the eastern Metro area and 55-65 in the western Gorge.  I’ll guess a 70 mph gust at the Vista House sensor Tuesday midday (just for fun).  That easterly flow will give us a sunny day Tuesday here in the Metro area!

3.  One system slips through the ridge late Wednesday and Thursday.  Timing for precipitation arrival appears to be narrowing down to Wednesday night.  At that time it should be a little too warm for frozen precipitation (snow or frz. rain) in the western lowlands of Oregon and Washington.  For sure the NAM and ECMWF look that way with a surface low pressure center going to the north (warming south wind in valleys).  The WRF-GFS and GFS are a bit cooler with the center coming inland almost right over us (east wind ahead of it).  The largest difference would be in the Columbia River Gorge.  The colder models imply a decent and guaranteed snowfall all the way down to river level east of Multnomah Falls.   The warmer northern route of the low would still be cold enough for snow in the Gorge, but a west wind would develop behind the low, with warming on Thursday.  I should point out the GFS does not even mix out the cold air pool eastside Thursday; it just rebuilds again Friday-Saturday.

4.  If you haven’t put on your studs yet, you don’t need to worry, I see no need for them here in the western valleys the next 7+ days.  Sure, more of the morning frost, but no freezing rain or snow, unless you live right beside a steam plant…

Chief Meteorologist Mark Nelsen


Coldest Year Since 1985…So Far

December 11, 2011

Some spare time this evening between shows.  I started wondering what the cool spring and cool summer, plus now a cooler than average November/December means for our yearly temperature.    Quite a bit…we’re running with the coolest average yearly temp we’ve seen in 26 years here in Portland.  Now this graph shows the average of the entire Oregon Climate Division #2 (areas between the Coast Range and foothills of the Cascades) through November.

What does it mean? Newsflash: It’s been chilly this year!

This only applies to the Pacific Northwest; check out the graph for the entire USA.   The incredible summer heat and warm spring temps in the eastern part of the USA gave the country another above average year, another one in a long string of warm years since the late 1990s.