2012: 4th Wettest Year In Portland

December 27, 2012

This one probably doesn’t surprise you…are you sitting down???  It’s been VERY wet the past 2 months (actually a bit longer).  The October-December rain total is around 22″ here in Portland, that’s way above average as you can see:


In fact you have to go back to the first few days of October to find a dry spell longer than 3 days.  That was the end of the driest 3 month period ever recorded in Portland!  What a change…

The wet end to 2012 and the wet spring have pushed us to the 4th wettest calendar year ever here in Portland.  Observations at the Portland Airport go back to 1940:


Notice that we are nowhere close to the record wet year 1996.  That year we had flooding in February, November, and then again in late December (after a pair of damaging ice storms here in Portland).

It’s extremely unlikely we’ll get the 1/2″ to push our total to #3, so it’ll remain our 4th wettest year since 1940.  We don’t combine rain totals from PDX with those downtown because it’s a wetter location.  Those records go back to the late 1880s in several locations downtown.

Where do we go from here?  MUCH DRIER.  Not totally dry, but every little rain through the next week.  In general over the next week we either have upper-level ridging over us or weak systems splitting as they approach.  Yes, the dreaded SPLIT-FLOW.  For us weather geeks, this means SEVERE BOREDOM.  No stormy weather, no snow, ice, extreme cold/warmth etc…

No sign of an early January arctic blast either on any model.  Wayne Garcia asked again today if he needs to put on the studded tires; and again I said “don’t bother”.  This may be one of those winters where the lowest elevations don’t get snow, or it may be one of those where we get a severe arctic blast and snowstorm the last week of January…who knows.

Chief Meteorologist Mark Nelsen

Latest First Frost Ever in Portland

December 26, 2012

Today I looked out at my still green banana trees and other bushes untouched by frost just a few days before the New Year.  I thought…this is weird!  It is!


Many parts of the Portland Metro area still haven’t seen frost, and when we do finally get a frost, it’ll be the latest ever recorded at PDX.  Those records go back to around 1940.  So yes, a very mild Fall and early Winter so far.  The previous record was December 24th, 1999.

Your next question might be, have we ever gone the ENTIRE winter without frost in Portland.  A “San Diego” winter?  Yes and no.  No, not in the 70+ years at the Portland Airport location.  But before 1940 records were kept officially in downtown Portland.  It appears that about once every 10 years (on average) there is no frost until at least after the New Year at that location.  And at least once we’ve seen no frost the entire winter!

Check out what happened during the Great Depression.  There was a normal late-winter frost on February 14th, 1933.  But that was the last frost of Winter 1932-33.  The following winter (33-34) there was NO frost.  I noticed LOTS of 50+ degree days all through December and January.  Then, we went all the way through the next Fall and early winter with no frost!  Folks were probably thinking the world was falling apart here with a 2nd unprecedented mild winter.  Then finally, on January 3rd, 1935, a frost.  A little less than 3 weeks later a severe (but short) arctic blast hit.  For two days the temperature didn’t climb ABOVE 21 degrees.  Wait, there’s more.  The 3rd day it jumped back to 51 degrees, and 3 days later, on January 24th, it hit 65…in January!  Weird…

Chief Meteorologist Mark Nelsen

Christmas Day Snow Totals

December 25, 2012

A snowy day across a good chunk of the region, but not in the lower elevations west of the Cascades.  I-84 is a real mess from Pendleton all the way into Idaho right now, more snow coming up tonight:




Keep discussing weather on other posts.

Merry Christmas! Snow Storm In the Gorge

December 25, 2012

Everything is working out just about right forecast-wise this morning.  East wind has been ramping up the past few hours, bringing cool air through the Columbia River Gorge while a lot of moisture is moving inland.  I see snow briefly mixed with the rain before sunrise out in Washington County, but now it’s all rain for most of us.  Snow has fallen up in northern Clark County and some snow briefly this morning from Sandy out through the Hoodland areas.   But, unfortunately for the kids, no White Christmas in just about the whole metro area, as forecast.

In the Gorge, temps are about 1-2 degrees warmer than I would have expected (32-33 at river level right now), so the freeway (at 9am) is mainly clear with just slush.  Plenty of snow sticking as soon as you get above the river level.  Here’s a pic from Ryan Yecny from the 500′ elevation at The Dalles.  Already 3″ snow on the ground there!  581400_4485918180794_634945367_n


Then take a look at the latest view from freeway level at Cascade Locks:CascadeLocksWB_pid620  That MAY change in the next hour if the snowfall rates become heavier.  Note the Cascade Locks observations the past few hours showing a temperature drop from 4-8am:  http://www.wrh.noaa.gov/mesowest/getobext.php?sid=LKSO3&table=1&banner=off.  By the way, I like that observation because during heavier snowfalls it’s the only spot in the Gorge that shows snowfall accumulation.  With those 1-2 degree warmer temps, I’ve got extremely marginal freezing rain here, it’s slushy on the deck and roof (rain freezing there), but not anywhere else.

Some of you here on the blog were getting worked up around 3-5am about a forecast bust around the time the precipitation started; you have to wait a couple of hours at least in the Gorge for the temps to drop and heavier precipitation to cool the air mass.   “Reverse Wishcasting” will get you in trouble too.

Chief Meteorologist Mark Nelsen

Snowy/Icy Gorge Christmas Day

December 24, 2012

A Christmas Day snowstorm is coming for the Gorge, and some spots near/in the Coast Range.

It’s Christmas Eve (Day) and what do you know, it’s still raining…we’ve seen just under 50″ of rain here in Portland this year and it appears it’ll probably go down as the 2nd wettest year on record here!  Of course that would be 2nd after the 63″ we received back in 1996.

Here are the highlights for those just wanting the basics:


  • I-84 through the Columbia Gorge will likely be very snowy after daybreak Christmas morning and through at least early/mid afternoon.  A nice Gorge snowstorm for those of you already there.
  • Hwys. 6/26 will be snowy tomorrow morning over the Coast Range passes (a good 4-6″ new snow), then improve rapidly by midday as the snow level jumps to around 3,000′.
  • I-5 north & south through Oregon and Washington should be okay, just a little snowy over Siskiyou Summit to California. 
  • No snow headed north to Seattle, or at least not enough to affect freeway travel if there is.


No interesting weather through the middle of tonight, we just dry out as the day goes on.  Enjoy the brief dry spell.

  • A very wet storm arrives before daybreak west of the Cascades Christmas Morning.
  • Precipitation may briefly mix with snow in the metro area 3-6am (when we are sleeping), but then all rain as the freezing level jumps quickly after 8am.
  • Sticking snow is unlikely in the metro area EXCEPT possibly out around Banks, Forest Grove, Gaston, Vernonia.  A trace to 2″ possible in those areas if everything works out just right.
  • Just a few degrees too warm elsewhere.
  • It will be ALL SNOW east of Multnomah Falls in the Columbia River Gorge…8-14″ possible from 6am to 6pm!
  • Freezing rain is likely above 500′ west of Multnomah Falls (but not in metro area), heavy ice accumulation (1″) possible up around 1,000′ during the day.
  • After 10am, all areas west of the Cascades (except western Gorge) will see only rain as warmer air moves in, raising the snow level up to around 3,000′.

I’m still on vacation today, but just couldn’t keep quiet when I saw a good setup for a Christmas Day Snow Storm in the Gorge.  I am finally getting tired of the rain, I just noticed we’ve only had one completely dry day this month too.  Hard to believe it’s now the wettest year since 1996 after 80+ days of almost all dry weather;  those people nagging me about “covering up a developing drought” back in early October look REALLY silly now!

Last night was fun with sticking snow briefly in some spots on the east side of the metro area; it’s interesting that without this blog or discussion on Facebook one wouldn’t have known about it via the observations; no metro area official observation showed snow or even a rain/snow mix.  I ended up with a quick 1.5″ here at home.

Nice map for 6am tomorrow:mgWeb_WRF_20121224-120000_ANW_ECONUS_F00250000_PgeneralSfcPres_R4km

Tomorrow we’ve got a real juicy system moving in with a surface low working its way up the coastline; it’s far enough south that it draws in a surge of colder/drier air working across Eastern Washington overnight.  By 10am tomorrow morning, models show 7-10 millibars easterly gradient through the Columbia River Gorge!  It’s going to be a very cold and windy Christmas at the west end of the Gorge.  Gusts 60+ mph are likely there.  BUT, by 7-10am, warmer air will have already worked in to the atmosphere overhead (as noted in the highlights).  So this is a situation where if you wanted snow or freezing rain in the metro area, you need a little longer period of cold east wind to start and/or you need the airmass coming through the Gorge to be colder to start with.  We’ve seen situations like this in the past where the cold air gets pulled towards a surface low offshore and we get a nice ice or snow storm in the metro area.  But this is when it’s truly modified arctic air moving down from the northeast.  Think temps already down in the 20’s in Hood River and The Dalles to start with.  Not from radiational cooling (like we’ll see tonight) but the actual cold airmass.  This time the air will be just a little cooler than what’s already in place today; that’s why it’ll be really tough to get anything frozen outside of the Gorge.

IF we do get a mix or briefly all snow in the metro area, the timing isn’t so great either.  Our RPM has it here by 4am, the WRF-GFS a little slower, but not much.  Most of us will be asleep at that time (I know I will be!).  Any chance for that disappears quickly after sunrise too due to the warmer air moving in aloft.

As for the Gorge, wow…no sign of the snow level rising above the surface until the evening at the earliest.  Think of it this way:  The cold airmass eastside is deep enough to meet the 3,000-4,000′ snow level at the crest of the Cascades.  So whatever falls should fall as snow the entire day as the whole column of air stays near/below freezing; that’s why I went with the big snow totals.  Jesse should be happy in Stevenson, looks like a big dump there! 

For those of you at the west end of the Gorge (like me), it’ll be a thin layer of air right near freezing.  But warmer air above means a Silver Christmas.  Probably marginal for freezing rain near 500′, but around 31-32 degrees at 1,000′.  A narrow band of elevation will see a Christmas Day ice storm with thick accumulation.

I haven’t looked farther ahead on the weather maps, but I work late tomorrow afternoon so I can do that then.  Holidays at a tv station are REALLY slow…

Chief Meteorologist Mark Nelsen

Merry Christmas; Some Days Off

December 20, 2012


I had yesterday off and don’t work again until Christmas Day; no postings until then unless a hurricane hits.

I don’t see any real exciting weather in the next week, so enjoy the holiday!

Chief Meteorologist Mark Nelsen

Sticking Snow Unlikely Metro Area Tonight

December 18, 2012

It’s one of those weird nights, in which we are forecasting little to no snow (less than today) in the metro area yet the NWS is forecasting 1-3″ (more than today) for the morning commute tomorrow and has a Winter Weather Advisory up.  We’ll see how it turns out by daybreak tomorrow.

For those just tuning in for the basics, here is our graphical overnight forecast, read the details below:


  • Steady rain/snow returns to western Oregon and Washington by midnight.  For most of us, especially north of Salem, it’ll be mainly snow falling, not rain.
  • However, it’ll be just 3-5 degrees too warm (35-38) in the Eugene to Vancouver corridor (lowlands) for the snow to stick. 
  • The morning commute should just be wet in the majority of the metro area.
  • Better chance for sticking snow 1am-4am in Columbia County (Vernonia, St. Helens, Scappoose, & Rainier).  Also northern Clark County (possibly Battle Ground, Amboy, La Center).  We could see a trace to 2″ in all these spots.
  • Tomorrow looks very windy and very wet with south wind gusts 30-40 mph and heavy midday-evening rain.

So why am I so “anti-snow” this evening, especially considering the NWS is forecasting a bigger event than last night?

1. Upper levels are plenty cold to start, but even at 1800′ right now (top of TV tower), it’s 30 degrees.  In a well-mixed atmosphere, one would expect 37-38 down at sea level.  That atmosphere does not cool in the next 8 hours, in fact it warms dramatically after 4am.

2. Precipitation rate on models is very light through 4am.  If we’re going to drag the snow level down to the surface, the precipitation had better be at least moderate, preferably heavy.

3. No dry air coming in from the Gorge; actually no real cool air coming out of the Gorge anyway.  Gradients are flat right now and will go to maybe 3 millibars easterly by 4am when it goes calm again.  Either way, the Gorge is not a factor and will not help get us the usual evaporative cooling.

4.  Southerly wind just above the surface will be increasing through the night, with temps holding steady through 3am, then a big jump after that time.  No matter what happens down at the surface, the 1,000-2,000′ temps go well above freezing before sunrise.  Model soundings, cross sections, and meteograms show temps at the surface holding steady or rising the next 6 hours.

Our 00z RPM is pathetic generating very light snow totals as a result of these points:


Wait, there’s more to talk about…

Strong Wind

…in the warm sector tomorrow, quite a strong and gusty south wind up the Valley.  I could easily see gusts 40-50 mph down at Salem during the day, and maybe 30-40 mph here in the Portland area.  That should be fun.

Heavy Rain

We’re really going to get soaked tomorrow.  Models showing a cold front just about stalled over us in the evening and early overnight hours Wednesday.  Our RPM is showing a good 1″ through 8pm, then another 1″ in the following 6 hours.  The WRF-GFS is similar with very heavy rain 7-10pm.

Post Front Heavy Snow Tomorrow Night?

This one has been hinted at by several mesoscale models the past 36 hours.  Immediately behind the stalled cold front tomorrow evening, the atmosphere suddenly cools with the very heavy and steady precipitation.  There is an area of snow levels just about down to sea level as a result.  Last night our RPM was hinting this would occur on the east side of the metro area.  Tonight the WRF-GFS paints heavy snow from 10pm-4am along the east slopes of the Coast Range (Gaston to Banks to Vernonia area).  Note the foot to 18″ forecast by that model over the N. Coast Range?  This will be a very interesting feature to watch.  In fact if you look at the WRF-GFS meteogram for Portland, it drops temps down into the 30s under the heavy precipitation, although it doesn’t generate sticking snow.  Tonight may not be our last brush with snow!


Beyond that…I don’t see a setup for snow as we just have weaker and cool weather systems through Christmas Day.

By the way, Andrew from Silverton pointed out this disparity in forecasts has occurred before.  I had forgotten about the big snowstorm forecast 2 days after Christmas 2007 that never happened.  Some fun old reading on the blog there.  And of course the big event the day the blog started back in 2005.  A winter storm warning was up for a big snowstorm, but I was forecasting no snow, that was a very stressful night.  In both cases it hardly snowed or none at all.

Chief Meteorologist Mark Nelsen