Inversimageddon Almost Finished; Freezing Rain On The Way

I know, it’s not a real word, but the past 7-10 days have been quite interesting considering we’ve been near/under a dry upper level ridge!  50s, 60s, and even some 70s in the higher elevations and 30s down below; a very strong inversion.   You folks in the central and southern Willamette Valley have been stuck in the muck (fog and cold air) for about 10 days!  Check out Salem’s numbers:


Andrew from Silverton noted earlier that if Salem stays below freezing again tomorrow, it’ll be tied with 1979 for 6 days at/below 32.  And the most 32 or lower days since that time; yet no record low temps.  It has just been consistently cold, but not “arctic cold”.  We’ve definitely had much colder weather in the past 30 years, but it lasts just a few days each time.

Absolutely nothing changes in our weather through Tuesday night, so another day of sun here in the metro area and fog/clouds in the Valley.  But, there is relief in sight…a weather system gives us a mild southerly wind along with some rain very late Tuesday night and the first part of Wednesday.  That means Wednesday afternoon we’ll see the usual showers and sunbreaks…get the sunglasses ready Salem, it might be blinding!

The transition from the current cold weather at the lower elevations to mild temps and moisture is an issue though.  As I said, nothing will change through late tomorrow night.  So temps will drop off into the 20’s to around freezing everywhere between the Cascades and the Coast Range below 1,500′.  Above that level up to around 3,000′ temps remain above freezing through Wednesday afternoon.  Uh-oh, I smell freezing rain coming on…

This is what I’m showing at 10pm tonight, it covers the highlights:


  • Why freezing rain and not snow?  Much too warm above for snowflakes to survive; we are in a very shallow layer of cold air here at the surface except in the Columbia River Gorge.
  • How long will it last?  Not long, all models show a pretty decent southerly breeze blowing up the valley well before noon; with such a warm airmass overhead it shouldn’t take much to wipe out the thin layer of cold below.
  • How much does it take to make roads icy?  Very quickly…can be 5 minutes.  Freezing rain is liquid rain that freezes on contact, so it happens really fast.  I spent 1976-1982 living in the Mt. Angel area and saw freezing rain just once.  It started sprinkling in the morning at my bus stop and 5 minutes later the bus was starting to slide on the road.  What a downer that we made it to school and they didn’t cancel!  The point is that unlike snow, freezing rain can change road conditions very quickly.
  • Will it affect the Wednesday PM Commute?  No, 40s by midday all areas west of the Cascades and probably even the far western Gorge too.  This isnt’ one of those situations where the cold air takes forever to leave, a south wind should move it out quickly as mentioned above.

What about the Columbia River Gorge?  In one way the forecast is easier here; it’s plenty cold for freezing rain from Troutdale eastward.  In fact east of I-205 is the one part of the metro area where I think freezing rain is just about guaranteed for the Wednesday AM commute, even if the rest of the metro area somehow escapes it.  It is a little tougher with respect ot precipitation type.  I think freezing rain is “a lock” from Troutdale to Bonneville Dam, and it may just be freezing rain all the way to Hood River too.  There is small chance it starts as snow from Cascade Locks to Hood River; tough call.  I’ll have a better idea Tuesday.  There isn’t much moisture at the eastern end of the Gorge so there might not be much of anything east of Hood River.

Enjoy one last real sunny day in the Portland area tomorrow before more typical weather comes back.

By the way, I borrowed the Inversimageddon word from a poster on the Western Wx Forum.  I hope you don’t mind!

Chief Meteorlogist Mark Nelsen

72 Responses to Inversimageddon Almost Finished; Freezing Rain On The Way

  1. Marcus says:

    ZR advisory posted it is accuweather tho we shall see!!!….???

  2. Mr. Donut says:

    Whoa, “real” clouds over PDX for the first time since???

  3. Marcus says:

    12z euro hrs 120-192 look like low snow levels at best to me then back to possible ridging!:/

  4. Marcus says:

    Once again KGW has snow almost everyday on their weather app???

  5. 925mb cold pool is sliding west up against east slopes Washington Cascades and now 0c to -1c over/west of The Dalles

    Looking at the NWS/NCEP 12z Pacific Surface Analysis along with Mesoanalysis seems to suggest the TTD-DLS gradient may surge again up over -10mb later….If the ridge doesn’t break down that is, and I do not think it is going to as fast as models show…. Never does…..

  6. W7ENK says:

    Looks like the ice roads in Estonia are opening to traffic, as of last week.

    I wish just once in my life to have ice roads open across the Willamette and/or Columbia Rivers.

  7. dothgrin says:

    It was clear most of the night in the Aloha area and it is currently 21 degrees. If the clouds get in before the cold scours out, there will be a pretty decent cold pool at the surface going into the evening, especially for the areas west of the Willamette.

  8. Longview 400 ft says:

    I believe up here tomorrow in the morning might be to warm for any freezing rain. Just looking at the satellite view and see that the clouds have made it past the coast line.

  9. Cold pool over the Columbia Basin and eastern Washington has really expanded and deepened over the past 24 hours. 925mb temps are now -8c with -2c over the eastern Gorge. 4 hr trends show this area has grown noticeably and now edging west into the Gorge.
    4hours ago

    This is significantly colder and more sprawling compared to 24 hours ago. Colder and drier air is funneling west through the Gorge. I’d have to think the cold layer is gradually deepening over the area.

    KPTV Tower Temps show that at least the low level cold pool over PDX metro has indeed deepened.
    Upper Sensor(1818′) 42.6
    Middle Sensor(1473′) 29.1
    Lower Sensor(1818′) 27.7
    Temperatures above 1500′ are still warm, but it is colder down below compared to 24 hours ago. This is undoubtedly going to cause problems should moisture arrive later.

  10. gidrons says:

    Latest sounding forecast at PDX:

    Temp is above freezing when the precip is supposed to start.

    • Not sure temps warm all that much today as the air mass is even colder a bit, and clouds should increase capping things. As long as this east wind continues it is pulling progressively colder air over us and keeping our dewpoints low.

    • gidrons says:

      That’s true, there’s a big gap between DP and temperature. I wonder how much the program is accounting for evaporative cooling.

    • Mark Nelsen says:

      Models have been showing us as staying above freezing the past 5 days too though; they are clueless this time around the lowest 1500′.

  11. Tyler Mode in Battle Ground says:

    I’m headed out to photograph the icy falls before it all melts away…

    • David B. says:

      Enjoy! I did that during the 2009 cold snap. In my opinion, Horseshoe Falls gets the best ice formations (though they’re all interesting and worth seeing). Hopefully it’s been cold enough for good “ice volcano” formations to build up at the bottom of Multnomah and Latourell falls.

  12. gidrons says:

    Awww Mark, I’m disappointed you waste time reading western forum.

  13. W7ENK says:

    Sunrise this morning… WOW!

  14. ocpaul says:

    My wife’s dog blog has been calling this an in-fur-sion.

  15. Tyler Mode in Battle Ground says:

    21 here in BG. Was 18 yesterday. Mostly clear skies save for a few high clouds.

  16. JClack says:

    21.7 degrees this morning when i left for work, in clackamas near high school. The fog cleared and calm wind remained allowing me to drop to my lowest temp of the season so far.

  17. W7ENK says:

    23 degrees, and so much frost it looks like a quarter inch of snow! Everything is covered in white, including the roads. I’ve never seen anything like this before.

    • W7ENK says:

      Down at thr lower part of Milwaukie, and there’s nothing. Just a few sparkling patches here and there.

  18. Wow…. east wind went from being just gusty to now raging. A big increase…. I see TTD-DLS is just over -8mb, so it is down from the peak yesterday of -10mb, but this is the strongest wind I’ve had yet, sooo I assume the cold layer is deepening east side, or inversion weakening….

    • Another interesting thing is occurring. My temp has been very steady around 32.8 to 33.3 when the east wind was gusting 25-34mph keeping things mixed, but now that it has increased over 35mph my temp is falling now 31.6, 16 dewpoint.

    • alohabb says:

      I kinda think this cold layer might be so thick that it takes longer to scour out and freezing rain becomes a bigger issue than we think. I’m at 20 degrees right now and that’s the coldest I’ve seen all season. This will be the part we remember for this winter ,no snow but a freezing rain mess

    • W7ENK says:


  19. bgb41 says:

    1/21/2013 Oregon (All) Temperature Summary

    High:74 at CINNAMON(4834 ft)
    Low: 51 at RED MOUND(1753 ft) & GOODWIN PEAK(1800 ft)

    High:7 at NYSSA(2172 ft)
    Low: -18 at Lakeview /Center (4750 ft )

    Largest Diurnal Change: 57 degrees
    CRAZYMAN FLAT (62/5 ) (6100 ft )
    DW9630 La Pine (56/-1) (4256 ft)

  20. Marcus says:

    00z euro cooler but the real cold slides to the mid west and then the east coast! Just doesn’t seem to be our year:/

  21. 32.7 here even with gusty east winds, dewpoint 16.

    925mb cold pool over the Columbia Basin/eastern Washington is significantly colder than it were 24 hours ago. Right now -7c, last night at this time it was barely -3c.
    Slightly colder and drier air(lower dewpoints) is funneling west through the Gorge thanks to a colder air mass below 4000′ over eastern Washington

  22. Marcus says:

    Shocking another cold spring!ugh!

  23. AdamInAumsville says:

    My numbers the last 10 days…

    Hi Lo

    12 35 20
    13 30 27
    14 36 27
    15 38 32
    16 36 32
    17 36 32
    18 35 29
    19 33 27
    20 33 25
    21 32

    It’s been lovely. /sarcasm

  24. Thanks for the update, Mark. It sounds like it might be pretty bad out my way, maybe. Also, for those who saw today’s 12z ECMWF the last few frames weren’t all that bad really. Ridge 140-145 W, Trough over us, Southeastern US ridge, and bitter cold to our north. It led me to be a bit optimistic for tonight’s run….

  25. My nasal passages are in hibernation, waiting for that warm, moist southerly flow. Burning eyes, scratchy throat………. We’ve had way too many funky days since the Jan 1st. Way too many. Bring on the rain and onshore breezes!

  26. W7ENK says:

    The whole area around the I-205/SE 82nd/Hwy 224 interchange is an icy mess right now. Super-thick frozen fog, and the road surface is covered in so much frost it looks like it snowed!

  27. Heisson Rob says:

    We’ve been using “fake cold” here. How about “pooled cold”?

  28. bgb41 says:

    Andrew in Silverton coming through with the climate research from ’79. What a stud!!

  29. Lurkyloo says:

    You in, ‘Poose?

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