A Dry Weekend?

SnapshotSunshine all day long here in the western valleys…temperatures warmed nicely into the upper 70’s.  A weak push of northerly wind has been moving south through Eastern Washington tonight, much like an arctic front in winter.  Models show that turning flow easterly through the  Gorge by daybreak.  With a warm atmosphere still overhead, that should push high temperatures up a few degrees tomorrow.  My forecast could easily get screwed up by some high cloud cover keeping temps too low tomorrow.
Nice sharp trough swings through Saturday night through Sunday night.  This sets up a massive marine surge along with a cold upper-level atmosphere surging inland.  NAM showers showers in the chilly air Sunday afternoon, GFS does not.  I generally put more faith into the GFS, but a strong trough could give anyone a shower west of the Cascades.  I will be camping the first 2 days of the weekend in the Cascades…Sunday morning’s showers/drizzle at 40-45 degrees should be enough to chase me back home.
I’m much more confident on "the big warmup" beginning Tuesday.  All models (GFS, ECMWF, CANADIAN) have sharp ridging developing behind the cool trough.  A very nice thermal trough develops west of the Cascades Tuesday and continues at least through Wednesday.  East wind and 850mb. temps of +15 to +20 deg.C. will push temperatures up to or over 90 degrees in PDX-town in late May.  So IF the models don’t suddenly back off, we have quite a warm spell coming…Mark

58 Responses to A Dry Weekend?

  1. Derek-West Gresham says:

    thing* I hate how I always mess up the words think and thing and switch the “g” and “k”.

  2. Derek-West Gresham says:

    I absolutely agree. Zaffino is well..living in lala land. Its one thing to believe stupid long range GFS, but its another to just make stuff up that isnt even in the models! lol
    I also have been watching that thunderstorm threat. I havent said anything because its 6 days away but I will continue to watch.
    I would say the best we could do with this think is 90-92, 90 being my forecast on Wednesday.

  3. Justin says:

    94 won’t happen period, and Thursday looks to be the coolest day of the entire event. I don’t know what he’s thinking either….

  4. Justin says:

    Rob, if we can keep a southerly flow on Sunday evening, then I think we would get thunderstorms. A deep, digging trough will slide right into us Monday/Tuesday, with the vortmax going right over us. If you believe the longer range 18z GFS (never a good idea), then we’d get a chance for some evening/nocturnal convection Sunday followed by thundershowers on either Monday or Tuesday, with some steady rain in between.
    Its 6 days out but Sundya looks like a fairly classic late spring/early summer convection setup, with a collapsing heat ridge ahead of a dynamic front, and a southerly flow.
    Of course, it doesn’t surprise me that Rod Hill is already going for thunderstorms this far out. Remember when he was gung ho a few weeks ago about the chances for a strong thunderstorm outbreak, starting about 5-6 days out.

  5. winterhawk says:

    No offense to Matt Zaffino, but that forecast seems almost absurd.

  6. AtmosphericWrath -Southeast Portland- says:

    Rod hill mentioned t-storms Sunday afternoon through Sunday night temps in the 80’s… Hmmmm…….

  7. AtmosphericWrath -Southeast Portland- says:

    Hmmm well apparently Zaffino on KGW is seeing something. He’s got Tuesday: 88F, Wednesday: 92F, Thursday: 94F, Friday: 88F
    Any thoughts on that?
    Rob

  8. Derek-West Gresham says:

    Yeah its weird winterhawk. But I have been getting little bursts east wind all afternoon. Then it goes back westerly again.

  9. winterhawk says:

    Gradients are still solidly onshore, I’m not sure how any low level offshore winds are kicking in.
    Given the lack of teeth with this ridge, I still don’t see 90 being cracked unless the perfect wind/warming scenario occurs. It’s possible, but nowhere near a safe bet.
    As for next weekend, I agree that a lot of uncertainty exists. The models seem sold on the idea that some kind of onshore flow will reign supreme, so Wednesday should still be the high point for the week IMO.

  10. Derek-West Gresham says:

    I still say upper eighties tomorrow and low ninties on Wednesday. East wind is already trying to build in. I think the marine flow holds off because its so weak. By thursday we get some though. As for the weekend, yesterday there was a trough at that time so its anybodys guess.

  11. Jesse says:

    I actually noticed the same thing garron, the dome of really hot air seems to kind of slop over west of the Cascades on Sunday giving us our highest 850 mb temps of the period. That’s why I am predicting only 85-88 tomorrow and Wednesday with the best chance of 90 over the weekend. I think Saturday may manage to be warmer than Sunday though, despite Sunday’s high 850 mb temps, because at that point low level flow may be switching to onshore ahead of the approaching trough, cutting off heating early in the afternoon Sunday even though upper level temps are still in the +20 range. Our common Summer marine inversion.

  12. garron near washington square says:

    Well, I am wondering what to think of the “850MB” readings as I gaze into the future. We’re supposed to see our highest 850MB reading on Sunday of +21 degrees, yet only a high of 83 is predicted, but the +16/17 degree 850MB reading for Wed./Thurs is expected to make us reach near 90 here? Jusrt curious what indicator(s) I am missing? Thanks, an Happy Memorial Day!!!

  13. Jesse says:

    The 12Z runs are all out and looking at them I’m still gonna say we only make it into the upper 80s at best the next two days. Thursday and Friday will be slightly cooler in the low 80s with a bit of a marine influence. We have the best chance of seeing 90+ this weekend before we drop back into the 70s Monday and maybe even back to the 60s by Tuesday as a rather strong upper-level trough, our rose-festival low if you will, makes its presence known.

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