Dry Early Week; Then LOTS of Rain

7pm Sunday…

Today sure felt like December…we only reached 44 in Portland under mainly cloudy (but dry!) skies.  That’s about normal for this time of year but the coolest day in two weeks.

These next three weeks are (on average) the coldest of the year in Portland.  The average high temperature is just 45 degrees from December 14th through January 5th.  It goes uphill after that time; reaching 49 by the end of January.  Our “winter” occurs earlier than other parts of the USA.  The darkest/coldest time of the year is right around the solstice.  I’ve always found it interesting that in our climate we go from summer to winter much more quickly than the reverse.  Springs are LONG here but we cool down quickly from late summer to December.

What’s ahead?  Two dry days for most of the region Monday and Tuesday; that’s due to high pressure temporarily overhead

ecm_tuesdaypm

But then for about three days we’ll be under the influence of a strong jet stream coming at us from the southwest.  This chart shows windspeed up around 18,000′ late Thursday night.  Notice the strong jet aimed right at the Pacific Northwest.

gfs_500_friam

And an “atmospheric river” is transporting a tremendous surge of moisture from the tropics into our area.  Precipitable water map for Thursday evening shows values up around 1.00″ or so.  I’ve seen higher, but this is the “juiciest” setup so far this wet season.

gfs_precipwater_Thursdayevening

Models are all showing several surges of rain from Wednesday night through Saturday.  Each is a bit different, but notice the operational versions of the GFS/GEM/ECMWF all give a huge soaking to the northern half of western Oregon and southern part of western Washington.  Click on each for a closer view of rain forecast now through next Sunday.

So the million dollar question is whether this will just be a “very wet period” or will this be a flooding setup for some of us late in the week?  We don’t know yet, but we’re watching it closely.  Check a couple of model “ensemble forecasts”.  Both say that SOME PART of the region will get a lot of rain.  The ECMWF ensembles show widespread 2-4″ in valleys and more in the Coast Range by midday Saturday.

ecmwf_ensemble_precip_saturday

The GEFS ensembles are interesting because they are running as a separate model now from the operational model GFS-FV3.  It was upgraded this summer, but the ensembles continue to use the old model.  In this case they are both showing the same heavy rainfall.

gfs-ensemble-all-precipsaturday

To summarize, confidence is high that we’ll make up a lot of our November/December rainfall deficit in just 3-4 days later this week. 

We could easily see 2-4″ rain in the valleys; luckily reservoirs are at the lowest of winter and creeks/rivers are very low.

I’ll keep a close eye on it this week; otherwise enjoy the dry weather these next two days.

WHAT ABOUT CHRISTMAS SNOW?

I’m still seeing nothing for the lowlands the next 7-10 days.  We dry out around Sunday and then turn cool & drier heading deeper into Christmas Week.  It’s the same splitty upper-level flow we’ve been seeing since around Halloween.  As of now I don’t see a single model showing anything close to lowland snow through Christmas Eve or Day.  Check out the 51 ECMWF ensemble members.  Only 3 of 51 produce some sort of lowland snow between now and Sunday the 29th.   Sorry kids!

ecmwf-ensemble-KPDX-indiv_snow_24-6411200

36 Responses to Dry Early Week; Then LOTS of Rain

  1. W7ENK says:

    Red sky at morning…

  2. Andrew says:

    my prediction based on latest model runs is around 3 inches of rain wed-sat. looks like the initial bullseye is to our north. we’ll still get plenty of rain but doesn’t look like anything “historic” or frankly all that unusual. it just feels that way based on boring weather we’ve been having. disappointing that long range outlook continues to keep cold air at bay. not even a little eye candy! oh well.

  3. Joshua Lake Oswego says:

    Fizzle, fizzle, fizzle.

  4. JERAT416 says:

    I’ll take the 7″ of rain with a 2,000 ft snow level so idiot drivers don’t ruin the fun in Portland but the mountains get buried in snow.

  5. Evan -- Cedar Mill says:

    LMFAO. My weather app was showing a period of freezing rain Wednesday morning. What a joke! This is why you don’t use weather apps kids. 🤣🤣🤣🤣

  6. Jason Hougak says:

    Winter Storm Watch for 2’ of snow possible, that’s a nice surprise before the change over. Hopefully we get the mountain snow and mild heavy rain misses us.

  7. Joshua Lake Oswego says:

    NAM and GFS trending north into WA with bullseye. 18z ECMWF backed off too.

    • Joshua Lake Oswego says:

      WRF-GFS too. We’ll see how this shakes out. Looks dry for a long while after Saturday. We need all the precipitation we can get.

      • K says:

        It’s not too bad, actually– maybe not 7 inches as it was showing earlier, but maybe more like 2-4 as Mark has been saying.

  8. Jake in Gresham says:

    Another wild event is coming. I prefer snowstorms but this should be interesting. The bomb cyclone that set the record for California was pretty cool. I mean I could feel the air pressure drop here in PDX!

    Hopefully we don’t lose snow pack for at least the higher elevation resorts. I don’t think we serious issue in the valley unless we get 3 inches of rain for 2 or 3 days. We don’t have much water in the rivers as Mark stated and there’s no snowpack in the valleys like in 1995. The weather models also I noticed really like to exaggerate the pineapple express. Sure it’s a lot of moisture but unless it’s something insane? We should be good with the same ol’ same ol’ minor flood warnings.

    But for the resorts they don’t need bad news with climate change being affected by human air pollution so badly (looking at you China). One thing I’ve always noticed on the debate about climate change is people tend to leave out the scientists from the debates when they naturally already don’t want to the spotlight and would rather work. There’s very few that have the time or income to do so (and let’s face it – they get mocked by the general public).

    Makes for a dangerous combo that we’re seeing the full swing of now in politics and other sectors of society. I recently spoke to a family friend of mine that comes from an Eastern European country. I’ve never been although my family is mostly originally from there. Since he’s older I figured to prod’ him on how the weather is now compared to “back in the day.”

    Everyone likes to embellish their stories but his is truthful 100% because he was a plumber. He told me that back in the day some days were so cold you couldn’t stay more than 20 to 40 minutes outside before forstbite. And Winter was about from late September/October to mid April or so. Now he says it just snows a few times really good and melts in between rain down in the valleys.

    I asked, so the weather is kind of like here now? And he perked up and said, “Yes! Exactly like here!” I thought that was interesting considering the stories I heard from my dad as a kid of the “great” neighborhood snow battles they used to have in his neighborhood back across the pond. I didn’t go into how we used to get pretty decent snow too back in the day here too because I could tell he saw it as a positive.

    It’s stories like this (the firsthand accounts) that have me convinced that the climate is indeed changing due to human air pollution at a pretty dramatic rate. I personally find it frustrating that other countries seriously slack on this issue and our own politics has their head in the sand save a few. I mean it really doesn’t take a climate scientist. I majored in science back at college but went into computers. The data is there and it makes sense like anything else be it water, soil or the atmosphere. If left unregulated it can indeed be polluted.

    Anyways thought to share the pretty drastic story (I felt) considering the general populations “meh” nature on the matter.

  9. Grizzly Bear says:

    1/2 ft. of new snow in the Kamiah Valley yesterday the most this season, Surprising that it was heavy wet snow like western Oregon gets. Still most of it stuck around and today is below freezing with beautiful blue skies and the moon above.

  10. WEATHERDAN says:

    Probably more like 1-2 inches in the Valley Thursday-Saturday. The models are usually way overdone. Peace.

  11. Joshua Lake Oswego says:

    12z operational roundup through Saturday…

    ECMWF=5.5”
    GFS=4.5”
    GEM=4”

    • Andrew says:

      thanks for sharing. close to a month’s worth of rain in a few days. should be interesting. with the strong southerly flow i would think there’d be concerns about snow melt in addition to rain totals. but my sense is that there just isn’t much if any snowpack at 4,000-5,000 feet to raise concerns.

      between the late week deluge and at least the proximity of some colder air by end of month, i’m hopeful we’re transitioning out of boring mode and will have more to watch in the coming few weeks.

    • W7ENK says:

      We really need to pay closer attention to totals in the upslope side of the Cascades. They’re expecting 18-24+ inches of accumulating snow before a quick warm up and transition to rain late Thursday. Meanwhile, that’s all rain in the lowlands, which should saturate things up nicely before the snow level jumps to 12,000 ft and all that fresh snow melts off and comes washing down into the Valley. Depending on how low the snow level is supposed to get, the same thing could happen in the higher reaches of the Coast Range, but with much higher totals expected. By some estimates, the models are showing upwards of 16-20+ inches of rainfall in the Northern Oregon Coast Range.

      This could become a real mess.

  12. Roland derksen says:

    pretty cool (38F) with light rain conditions here this morning- glad I don’t work outside. We’re expecting quite a bit of rain this week as well, so I’m looking forward to the drier stuff in a few days.

  13. Mike says:

    Mark, it’s interesting that the time from latest sunset to earliest sunset is 5 months. This, however, is due to the equation of time and the shape of the analemma, which varies with latitude. It wouldn’t explain anything at the same latitude and is probably true-true not related.

    I have found the following site helpful for ARs.
    https://cw3e.ucsd.edu/iwv-and-ivt-forecasts/

  14. JJ78259 says:

    Beautiful weather in Austin Tx this weekend 75 and knocking on 80 degrees great weather to visit 6th street and listen to some great music!

  15. Mr Realist says:

    Very excited for the rain coming, hopefully it washes all that snow off the mountains and passes.

  16. W7ENK says:

    Oh goodie, maybe it’ll be enough rain to put a stop to all the whining we’ve had to endure over the last several months. 😁

    • K says:

      I will say that we’re quite behind on rainfall. So, I would suppose that some whining is warranted considering the deficit.

    • Joshua Lake Oswego says:

      I reserve the right to whine no matter how much rain we get.

      • Paul D says:

        And I’m going to whine when the temperatures go above normal 🙂

      • Garron near the Hillsboro airport says:

        Wow! That’s not looking good for local ski resorts. Maybe north of the firehose, but those south of it…Gonna have to travel to get some decent snow pack, or east if you want powder.

  17. Jason Hougak says:

    Pineapple Express is really going to deplete our meager snowpack at the resorts. Terrible start to the season. We need the rain but more importantly mountain snowpack.

  18. MasterNate says:

    No mention about snow levels which indicates it wasn’t good news. Might need to start over on our snow base after this.

  19. JERAT416 says:

    Rain catch up time is coming soon!

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