Downslope Wind Today

Solid stratus deck in most of the Columbia Basin...notice it's pushing up through the "Lava Butte Gap" south of Bend.

We’re in more of a downslope wind event today compared to the last two days.  That’s where we get wind coming right over the Cascades as well as through the Gorge.

1.  Cascade west slope locations are significantly colder than yesterday at this time.  Wanderer’s Peak SE of Estacada was around 40 at this time yesterday; it’s 27 today.  Horse Creek SE of Molalla was 64 for a high yesterda at 3,400′.  Today it was 30 degrees colder!  Only 34 for a high.  Cold air is spilling right over the top of the Cascade crest from the cold pool (shows as low clouds on satellite image) east of the Cascades.  Notice most of Clark county is windy today too; yesterday it was calm in most spots.

2. Peak wind gust last hour on the Glen Jackson bridge was over 50 mph, but Corbett (in the west end of the Gorge) has backed off with only gusts to 40 mph in the last hour.  Steve Pierce was up at Crown Pt. at noon and says a person recorded a gust to 74 mph.  Real windy, but not as wild as you would expect up there.

3.  Wind direction at PDX is east…a true “gorge wind” at PDX is from the ESE, or about 120 degrees.

10:30pm Update:  00z models are looking drier for tomorrow…good news.  I took the gamble that we probably won’t see any moisture tomorrow in the forecasts.  I DO notice the 00z SLE sounding is pretty darn close to snow.  So if we see something it could be either a sprinkle OR a flurry.  I still think we’ll stay dry anyway.  Our RPM model shows a second surge of moisture coming up from the south after dark tomorrow evening, but it tends to be to wet so…well…you get the idea.

Otherwise pretty quiet through Tuesday morning with east wind easing off a bit more.  PDX-DLS gradient has dropped from around 11mb. last night to about 8mb. this evening so the wind has backed off and won’t be nearly as strong tomorrow.

Tuesday COULD be interesting since we still have easterly flow as a strong front moves inland with lots of moisture.  This might produce signficant snow in the Gorge and maybe some spots from Portland north could be a mix if the precipitation moves in early.  Definitely more active weather on the way later in the week too.

Mark Nelsen

223 Responses to Downslope Wind Today

  1. Rob "Wrath" S.E. Portland says:


  2. Rob "Wrath" S.E. Portland says:

    Justin, I agree after looking at 00z WRF sounding the inversion is gone.

    Some additional thoughts….

    So my thinking is overnight tonight the easterly gradient backs off a tad perhaps down to 3 to 3.5mb by morning. Then high clouds move in after sunrise and increase during the day capping max high temps. Then as the stronger frontal system approaches I think this could increase the gradients for a time up towards 5-6mb(Models aren’t showing this, but that is usually how things play out with approaching lower pressure and the leftovers of the cold dome over the Columbia Basin). I think it will be crucial to continue a PDX-DLS gradient of 3.5mb or stronger to keep the drier air/lower dewpoints filtering into the area because generally as the clouds thicken and moisture arrives the dewpoints will climb too, so we need the continued outflow to compensate for that.

    Close call…..

  3. Matthew says:

    For the 29th-30th of Dec appears to be our best chance for frozen precip in the whole 384 hour gfs. With a frontal system movng into the area by day tomarrow with some offshore flow lasting into the early morning Wednesday time frame, than a change over to onshore flow as the low passes north of our area, with a southwestly flow at the 925 mb level. 850mb levels appear cold with about -4 to -5c at 850 through the 31st…So 1,500 feet snow levels appear to be likely. Afterwards off and on rain for the next 300 hours….Huge amounts of cold air into the eastern United states too.

    I believe that things will remain like we’re having now until at least the second to the third week of January. I believe that Late January could have a switch, in which will allow a ridge to develop off shore near 145-150 west and finally give us another shot at some arctic air. But that could change of course, so hope for the best. I don’t expect much to happen with the tuesday-thursday time period.

  4. Andrew (Ellensburg, Wa) says:

    How about this for some snow drifting haha.

  5. Anthony Bertolo - Gresham 500' says:

    I will agree with Justin, this doesn’t look like a freezing rain event at all. Most of us will likely just see a mix, and it isn’t likely anything will stick. I don’t see a good enough setup to keep the south winds at bay for very long at all.

  6. muxpux says:

    ghcsweather, where are you talking about?

  7. Battle Ground Brian says:

    28 degrees now , calm wind

    Still spots of ice this afternoon on Hamilton Hill on the Northeast side of BG Lake i.e.(259th st).
    High temperature of 39.3 here was much cooler than surrounding areas.
    It was horrible driving conditions this morning in my neighborhood with widespread black ice.

  8. I posted one of the two pics this morning showing how ice formed a pattern last night on my patio table top. The second link shows the pattern somewhat duplicated on the lid of the bbq.
    One comment suggested that the ice followed fingerprints on the table surface. That wouldn’t explain the similar pattern on the bbq. Mysterious and beautiful.

  9. boydo3 N Albany says:

    Kind of an interesting article regarding the
    Arctic Oscillation. Could colder winters be in the forecast?

  10. Rob "Wrath" S.E. Portland says:

    Hmmmm 18z has moved precip now to late Tuesday night/Wednesday morning.

    NWS also says this


    I’m still a bit concerned for a period of ZR east of I-205.

    • ghcshweather says:

      Well, up this way it pretty much looks like a rain to snow back to rain event. Where I live usually does pretty good with these setups with a surprise inch or two of snow. We have 925’s at or below zero, 850’s around -2 to -3 and light offshore flow at the onset that continues for a few hours tomorrow evening, could be a fun evening up this way.

    • couldn’t agree more!
      we had something like this a year ago!

    • Justin (Brush Prairie) says:

      Rob, ZR is NOT a threat with this system. If we get anything it will be either rain or snow. Even though 925mb temps will be a bit above freezing, the 850 and 900mb layer of the atmosphere looks like it will be supportive of snow which usually means wet snow can fall down to the surface. At this point the 00z NAM and GFS look supportive of a cold air damming event with sticking snow potential for the westside and maybe even eats of I-5 if the south winds hold off.

    • Stevengibson says:

      So could we see anything in the Salem area?????

    • could be sad for salem.. :/
      however maybe..just need those east winds!

  11. Anthony Bertolo - Gresham 500' says:


  12. Andrew (Ellensburg, Wa) says:

    Went target shooting up in the coast range above Timber Junction, just got home. It was 32 degrees there with about 2 inches of snow in the hills above town, was surprised that there was that much. Highway 26 was icy in the shady spots.

  13. Snow-Zone/Monmouth-Elv200' says:

    32.5F with the fog rolling in… ready for some snow sometime this winter.

  14. Having a heat spell…Temp has now reached 44°

  15. Gidrons says:

    18z GFS is about done. Possible New Year’s Day wind storm…just enough to knock out power for the Rose Bowl.

  16. Snow-Zone/Monmouth-Elv200' says:

    37.4F with sunny skies, a lot cooler than what I thought it was going to be especially with all the sun.

    • Gidrons says:

      That’s something you don’t see everyday

    • biochemist says:

      The pattern looks like finger prints run across the glass and the ice crystalized in a different pattern where the skin oils were left. I’ve seen patterns like this in petri dishes where fingers have touched.

  17. Photo taken this morning. It is our glass table top on our patio. The moisture on the table top turned to ice, forming this amazing pattern. The light is my camera flash. The pattern you see is from the ice forming, as the surface is without texture. Beautiful how God designed creation!


  18. Jerry says:

    Tuesday= at best sleet or ZR maybe mixed with snow. This is for east side metro only imo and wont last long… I hope I am wrong, but it doesnt look likley.

  19. WEATHERDAN says:

    In the El-Nino winter of 76-77 we had a lot of weather just like this. Dry weather and strong inversions. Nov-Jan had less than 5 inches of rain. Very little snow on Mt Hood, and temps around 40 during the day and 20 at night. With freezing levels around 10,000 feet.

    • Matthew says:

      Thats how I base my boring winter thinking off of. I think we get less than 2-3″ of snow this winter.

    • I remember driving up to Timberline in January of 1977 and there was very little snow…

    • Battle Ground Brian says:

      Looking back at records, the longest snow free spell in recent history was 1974-1977. My family moved from Southern California to Milwaukie, Oregon in May 5, 1974.
      I had just turned 5 years old and never had seen falling snow from the sky in my life.++
      42 Months later, I finally saw my first snow on (Nov.19, 1977). I remember the excitement waking up that morning to see 8-9″ on the ground. It was 50 degrees by 11pm that evening, and the snow disappeared very quickly. I will however, never forget that day.
      To date this is still the deepest snow ever in November in Portland. I also find it quite amazing that significant snow happened again in 1978 in November.

  20. Snow-Zone/Monmouth-Elv200' says:

    Now with some extremely thin fog moving in temp now down to 34.3F…. I like this, still pretty cool as we move into the afternoon hours.

  21. Snow-Zone/Monmouth-Elv200' says:

    Sitting at 35.8F right now.

  22. EA_TTD says:

    Marybeth, I would suggest leaving about 11. The precip isn’t modeled to be in the Gorge until 2 or 3 at the very earliest; that could change but I think if it does, it’ll be bumped back later. Leaving at 11 will have him at The Dalles by 2 and out of any potential snowfall. Models show very little in the way of precip east of Mt. Hood.

  23. marybeth7362 says:

    My dad is visiting here in Mt Angel and needs to head home through the gorge tomorrow. Anyone have any clues what the weather and roads will be like, and what would be the best time to go? Thanks!

  24. 34.6 bright degrees….So far, this month has been one of my coldest months ever..

    In the background lurks the image of another dry winter???

  25. Hour 168 Euro 12z showing a low making landfall in Central OR coast, AND I MEAN A NICE LOW

  26. Timmy_Supercell (Hillsboro) says:

    This Fall/Winter so far has been kinda different from any other I’ve seen. I don’t recall sunshine covering 3/4 of December.

  27. WEATHERDAN says:

    I don’t fret about those computer models for one reason. They change so rapidly. One day the 184 hr thickness is 520. Next day it’s 546. Then the next day it’s back down to 526. Already I see a change at about 312 hours on the iges-gfs. They have us in a Northerly flow but with a thickness down to a minimum of 536. I expect over the next few days it will bounce around to anywhere between 516 and 544. What will most likely happen though is just some typical sunny winter weather. You know, low 28 high 42. But one never really knows. Just keep an eye out for January 10th-14th.

  28. JohnD says:

    Yeah I also am intrigued about what could transpire tomorrow afternoon/evening in e. county–even if only briefly. Probably nothing–but with the e. wind still going you can never know for sure.

    ALSO I am thinking more and more that this is simply going to be a dryish ho-hum Western Oregon winter amid a stereotypic El-Nino pattern–although, as my wife reminds, it is WAY too early to make an all encompassing “call”.

    Like all of us, I just keep pulling for that season defining BIG EVENT! Even ONE would do it for me this year!

    One thing that DOES intrigue me is that anomalies can and generally DO occur in an El Nino year. We have already had one in the form of 8 days of arctic temperatures!

    Along with that AND the downslope and inversional cooling of this past week, I will be willing to bet that our temperature for December will end up being significanly BELOW average overall! So that is impressive too!

    I hope that the e. wind AT LEAST keeps going this season. I will take cold and dry over wet and mild anyday!

  29. Rob "Wrath" S.E. Portland says:

    I know it’s far more likely up in the Gorge. I do like seeing my DP at 22 and dropping… Temp rising very slowly and east wind relentless. Also could be a real good shot of clearing overnight maximizing radiational cooling. … East wind continues and precip falls = wet bulb effect? I know I’m in a way grasping at straws, but it seems possible especially I-205 east….. Sound familiar?

  30. Rob "Wrath" S.E. Portland says:

    I also see areas away from the Gorge aren’t warming at all… PDX to Salem to Hillsboro all 32 or below….

  31. Rob "Wrath" S.E. Portland says:

    I really would not rule out something for Tuesday. My temp is hardly rising at all stuck at 35.4 with cold east winds gusting 25-35mph. I cannot see PDX or the Gorge losing east winds as this initial low does not move inland thus the cold dome won’t be eroded or surface high weakened substantially. Then as this stronger system approaches I expect this will only serve to tighten the offshore gradient again. I’m not sure models are handling this very well.

  32. stevied (North Portland) says:

    boy, models have taken winter out of the mix for the forseeable future. Grrrr. Well, Tuesday afternoon may have an hour or two of interest as a transition event. We’ll see. It happens in the middle of the afternoon, though, which decreases chances significantly.

    MM5-NAM this morning shows something might be possible in PDX briefly Tuesday afternoon.

  33. Gidrons says:

    Nothing exciting on the 12z gfs for these parts

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