Christmas Vacation: More Dull Weather Ahead

December 15, 2011

I will be off tomorrow, and in fact I will be on vacation next week.  Next working day is Christmas Day for me.  No big deal since we just have a short 10pm show and I can come in once the kids are totally absorbed in their new toys and aren’t paying attention to me anyway…

Just for fun, this is the 10 day ECMWF upper-level forecast for Christmas Day.    Look at that upper-level ridge!  Hard to believe it’ll still be around…we’ll see.  Looking farther ahead, here’s the 16 day GFS ensemble 500mb height forecast valid New Year’s Eve.   It’s very smoothed of course because it’s the average of many different ensemble members, but notice the ridge is still there along the western North America coastline.


I’ll be in the area the whole time (relaxing, projects, eating etc…), so you know I’ll be looking at the maps every morning when I wake up.  It’s safe to say there will be no new post unless I see something of interest in the maps.

Merry Christmas!

Chief Meteorologist Mark Nelsen

Record Dry December

December 15, 2011

We’re halfway through December, and we’ve seen all of .06″ rainfall so far here in Portland.  That’s the driest first half of the month we’ve ever seen here!

The next closest was December 1976 when the first 15 days only yielded .32″

Now discuss amongst yourselves…

Precipitation Moving In…Snow For Some

December 14, 2011

Rain and snow is moving in this evening, and some of it is falling as snow, mainly in western Washington and Yamhill counties.   With no warming southerly breezes until after midnight, there’s no reason the hills (Vernonia, Buxton, Timber etc…) couldn’t get 2″ of snow before daybreak.  It still appears to be slightly too warm for snow in the lowest elevations here in the metro area, but only a few degrees too warm.

The Columbia River Gorge still looks setup for snow this evening and overnight.   Easterly flow is weak, but it’s keeping the low level cold airmass in place.  Check out the current temps; they’ll fall a notch or two when the precipitation arrives.

The Next 12 Hours

Portland Metro:  Rain showers, mixed with snow at times…we bottom out around 35 degrees before midnight, then stay between 35-40 degrees through daybreak…No Freezing Tonight.

Coast Range and far western Washington/Columbia Counties…northern Clark/Cowlitz County hills too:  Evening snow…up to 2″ accumulation possible anywhere west of Forest Grove, Banks, and hills around St. Helens and Scappoose.  Warming a few notches towards daybreak, so roads should improve by morning commute time.

Columbia River Gorge:  Snow spreads in, sticking to I-84 east of Multnomah Falls through the night.  Up to 2″ new snow.  Then a slow melt after daybreak.  In the Corbett area and hills east of Washougal, expect freezing rain this evening above about the 500′ elevation.  Up to 1/4″ ice accumulation by midnight.

Chief Meteorologist Mark Nelsen

FOX12 Weather Is Wondering…

December 13, 2011

What kind of social media do you use?  Here’s a poll…choose any that you regularly use.  Of course if your boss makes you use it, it still counts!


Snow Tomorrow: Where and How Much

December 13, 2011

Some of you in the lower elevations will see snow in the air by this time tomorrow night, but I think anyone below 1,500′ will have to be in the Gorge to see it. 

First, the basics:

– Cold again tonight and a real chilly day tomorrow with some fog or low clouds mixed with solid incoming cloud cover by 3-4pm.  We’ll be lucky to hit 40 degrees here in Portland.

– Rain arrives during the evening commute, or slightly later here in Portland.  Sticking snow will be at/above 1,500′.  It’s possible some of you in far western Washington county or northern Clark County could see snow in the air to lower elevations, but I don’t think it’ll stick.

– It starts as snow and stays all snow anywhere east of about Multnomah Falls in the Columbia River Gorge.  A trace to 2″ (up to 2″) is possible from Multnomah Falls out to The Dalles by the middle of the night.


A couple things to note on the models this evening:

1. In the past 24 hours, models have been showing more of a split with the incoming upper-level trough.  More energy heads south of us.  As a result, we don’t get a surface low to the north.  That means no wind tomorrow except for a continuing chilly easterly flow (not too strong) out of the Columbia Gorge.  This would be a great setup for snow here in Portland; no warming south wind, but the airmass isn’t that cold over us and isn’t all that cold coming out of the Gorge either.  And then there is that pesky lack of precipitation issue…see #2

2. More split = drier as well.  Our RPM is showing a grand total of .13″!  The WRF-GFS shows .05-.15″ for the entire metro area and the Gorge too.  Okay, maybe 2″ snow maximum in the Gorge.  What a waste of chilly air eh?  This also doesn’t help with evaporative cooling here in the metro area tomorrow.  You want steady/heavy precipitation to drag the snow level down.  That’s not going to happen.

3. This is the pattern in which we sometimes get surprisingly low snow levels over western Yamhill, Washington, and Columbia counties.  I don’t see the usual “signature” on models for this.  Just not cold enough and not enough precipitation at the same time.

In the Cascades:

Sorry skiers, but this looks pathetic on Mt. Hood.  We need some snow badly;  after this event, the next decent chance is well into the first week of the Christmas Break.  It appears that the biggest two weeks of the ski season (at least in numbers of people) will begin with hard-packed icy stuff off the main runs and a thin snowpack.  Obviously lots of fun for the casual skiers, but no sign of fresh snow.

Chief Meteorologist Mark Nelsen



Looking WAY ahead; La Nina Update

December 13, 2011

Haven’t talked about this in awhile…La Nina:

Where are we?  Still in a moderate La Nina after a moderate-strong event last winter.  This is our 2nd consecutive winter.

NCEP (National Center for Environmental Prediction) says this will probably continue through Spring 2012.  Here is a plot from the CFS2 model, showing the same thing…the negative numbers are La Nina conditions, positive=El Nino.  Note that in AMJ (April-June 2012) it’s still in La Nina territory.

     I found this little nugget (I’m a week late) on Klaus Wolter’s MEI page:  “…Beyond that (Spring 2012), it is worth noting that of the ten two-year La Niña events between 1900 and 2009, four ended up as a three-year event, so I would put the odds for this to occur in 2012-13 at 40% right now. Interestingly, the other six all switched to El Niño, leaving no ENSO-neutral case. Will be interesting to see how 2012 evolves.”  The bold is my emphasis.  Isn’t THAT interesting?  Those of you with more time might have already know about this, but 4/10 double La Ninas (this year) end of going into a 3rd winter of La Nina, but 6/10 went right into El Nino conditions.  There were no cases where this current pattern was followed by a “neutral” winter.


Coldest Night of The Season

December 12, 2011

Last night was plenty cold, as you can see from the numbers to the left, but today was a beautiful day.  

East wind came pouring right over the top of the Cascades and not just through the Gorge.  That broke up the inversion (along with the cold air yesterday), and cleared out the pollutants.  More important for tonight, much drier air moved in…check out the dewpoints well down into the 20s here west of the Cascades.  The wind turns to a “Gorge only” event by tomorrow morning, which gives everyone except areas east of I-205 maximum radiational cooling.  As a result, I think tonight will be colder than last night.   Good chance we’ll see some upper teens in the coldest outlying areas. 

Speaking of east wind, it’s picking up now at the west end of the Gorge with regular gusts up around 55 mph the past hour or so at Vista House.  Someone had unplugged the computer over the weekend, that’s why it stopped reporting by the way.  The wind should peak tomorrow midday, probably similar to or slightly less than the speeds we saw last Friday.

Fog may creep back into the western valleys later tomorrow night and Wednesday morning, then it gets a bit more interesting…

A weak front pushes through the Pacific Northwest Wednesday night and Thursday morning.  Models have been varying on the amount of precipitation and placement of surface low pressure as it moves onshore.  As of this morning, models were all showing the low moving by to the north Wednesday night.  That gives us a southerly wind and mixes out the air in the Gorge quickly by Thursday morning.

BUT, the 00z models are showing more splitting of the upper-level trough, which sends a baggy surface low either right into our area or slightly south.  I see no significant southerly wind in the valleys and no warming in the Gorge through Thursday morning based on this setup.  IF we get thick fog in here Wednesday morning, that’ll keep temps real cold through Wednesday afternoon with no air movement (similar to last Saturday).  When the precipitation arrives, it could still be cold enough for patchy freezing rain or even snowflakes in spots.  Wednesday will defnitely be a “watch the thermometer day”. 

Our RPM model is quite weak with the system, only generating maybe .25″ precipitation, the WRF-GFS is similar.  If the low comes in as the 00z models now show, there will be no scouring of the cold air in the Gorge, so a few inches of snow is likely there by Thursday morning. 

So, some brief weather fun is on the way midweek.

As for the longer range…if last night’s GFS gave me slight indigestion, tonight’s 00z GFS and ECMWF both made me lose dinner.  They both show little or no precipitation through Christmas Day!  Wow…I can’t imagine the ridge and split flow sticking around for another 12-14 days…but it HAS happened in the past (January 1985, December 1985 etc…). 

Chief Meteorologist Mark Nelsen