Dry Weather Continues, But Cooler

Back in the “forecasting saddle” this evening and it feels good.  There’s nothing better than coming into the office, filling out the different forecast sheets, and checking out all the obs, maps, and numbers.  The big picture continues to be very easy at least.

1. Upper level ridging will hold strong near or just west of North America’s west coast for at least 7-9 more days.

2. A sharp (and chilly) upper-level trough will drop down the back side of the ridge Sunday, move through western Canada, and end up in southern Idaho by Monday.

3. Strong surface high pressure follows immediately Sunday night and Monday, bringing the first surge of cold/dry Canadian air so far this season into the Intermountain Region.

4. As a result, we’ll go from warm and sunny now to chilly and sunny Monday-Wednesday next week.

Today was our 3rd day at/above 70 degrees here in Portland, somewhat unusual (especially with all the sun) for the last week or so of October:


As I mentioned in a posting last week (before I was dispatched to Hawaii), temperature forecasting has been extremely difficult in this pattern.  Very warm air has been a constant in the mountains/foothills the whole time.  Larch Mountain, east of Battle Ground, has seen high temps between 70-85 degrees every day for the past week.  An amazing stretch of warm fall temps up there.  Meanwhile PDX has been between 63-73 degrees, averaging about 10 degrees cooler.  A stronger wind, likely either northerly or easterly, could have pushed the metro area up into the 70s to mid 80s any one of those days.  But once we lose the wind, the overnight inversion just doesn’t mix out this time of year.  An extreme example of that has been the persistent fog/clouds up in Puget Sound.  Poor Seattle has been stuck in the 50s for a week!  Yuck.  There’s plenty of time for that gray inversion stuff in November, December, January, and February;  glad we didn’t see the same thing happen here!

We do mostly lose the offshore (easterly) wind tomorrow and Friday, although it tries to make a comeback Saturday.  Then to strong onshore flow later Sunday.  As a result, even though upper level temps don’t change much through Sunday morning. our temps should drop here in the lowlands.  More fog and cloud cover is likely too.  I dropped Sunday’s high temp (down to 58) on our 7 Day Forecast assuming we will be stuck in fog/clouds most of the day.  We’ll see how that works out.

All models agree on the cold push of air and high pressure just to our east late Sunday through early Tuesday.  The only variation in solutions is how far west the trough digs and how cold.  The ECMWF at 12z was especially strong with offshore pressure gradients 15 millibars from Spokane to North Bend (OR) by Monday afternoon.  Here’s the map:


This is a setup for a gusty northeast wind all across the Pacific Northwest.   Dewpoints will plunge and we won’t have to worry about fog for a few days afterwards.  At first the wind will keep overnight temps up (Monday night), but then after that we should get our coldest nights of the season so far.

Take a look at the 12z ECMWF ensemble chart:


Then the 18z GFS chart:


Notice quite a disagreement on how cold the air will be as it heads south over us.  About 1/3rd of the ECMWF ensembles don’t bring any cold air south at all!  Or at least far enough to our east that 850mb temps only drop a few degrees!  The GFS on the other hand has much better consistency with itself, showing temps bottoming out around -2 on average.  In fahrenheit, that means 5,000′ elevations will drop from around 60 degrees Saturday to around 30 Monday.

No sign of rain through Halloween, so we’ll probably end up with .87″ rain for the month.  That still wont get us in the Top 5 though.

There are signs that the ridge breaks down around the END of next week, but no sign of wet westerly flow.  There will just be a better chance for some sort of light rain or showers towards the following weekend, the first weekend of November.

Chief Meteorologist Mark Nelsen



42 Responses to Dry Weather Continues, But Cooler

  1. BoringOregon says:

    439 PM EDT THU OCT 24 2013… .NOW…

  2. Rob - Southeast Portland says:

    18z ALERT!
    Most impressive run of the GFS yet. This is a bit further west and really carves out the trough nicely. Images posted below.

    Running the 500mb loop shows why. The contours are oriented slightly different from previous runs and thus the flow bends around just a tad soon allowing the shortwave to dig further west towards us.

    • Rob - Southeast Portland says:

      Sooner* rather…. quite chilly!

    • BoringOregon says:

      So does that mean it’s going to get colder out?

    • Rob - Southeast Portland says:

      Would be nice if 00z continued to pull the trough further west another 100 miles. This probably accounts for the wide ensemble spread seen after day 5. There is still wiggle room on how far west this digs.

    • Rob - Southeast Portland says:

      I meant in terms of 500mb and how much it carves the trough out. In that regard it is. Not as cold as a few runs the other day though. I should have clarified.

  3. WEATHERDAN says:

    Got this in an email from Steve Pierce. Sounds hopeful for Winter.

    I just got an advance copy of one of the winter weather forecasts slated for OMSI this Saturday morning. It is a top notch effort and I am confident you will all appreciate it. In fact, some of you may just “ooooze” over it. Remember, the hand stamp will be used if you want to cruise the halls of OMSI for free after the meeting. We will also be hosting the $300 Davis weather station raffle and the annual snowflake contest. Finally, we are raffling off a ton of other stuff such as the ever popular Tyler Mode weather calendars and some additional OMSI passes. Come pay your dues and help support the best AMS chapter in the country. YOUR CHAPTER!

    See you all at OMSI Saturday morning at 10am!

    • High Desert Mat says:

      I think we all got that yesterday. But sounds encouraging. Steve is an optimist though lol. I’ll be there on Saturday. Hope to see u all there

  4. Rob - Southeast Portland says:

    12z EURO is outstanding. A few days of northwesterly flow, then a positive tilting ridge develops near 150 W with a cut-off low nearing Hawaii. This is very similar to what the Euro Weeklies showed just the other day. Really want that cut-off low near southern California to be absorbed into the mean flow and beyond day 10 it may to do so. Also need to kick out that trough over the Great Lakes, but it is encouraging to see the block at 150 W.

    • BoringOregon says:

      What a beautiful morning out here, weird to see other spots shocked in with fog when it is so nice out here. It was about 43 this morning, starting to feel more like fall with these chilly temps. It’s amazing how fast the leafs are falling off the trees today!

    • High Desert Mat says:

      I agree Rob. We really just need to rid ourselves of these cut off lows since they are in effect causing weak split flows. And lets keep that high out there around 150w in future model runs.

  5. cgavic says:

    Last several days lows 43 hi 80 with no marine layer

    Starting out same today
    Sandy 1,100 ft

  6. paulbeugene says:

    Just so I get my long range thoughts out before the winter meeting:

    I think this winter will have enhanced blocking of westerlies, allowing for more intrusions of arctic air through much of the lower 48, more than we have seen lately.

    Have looked at CFSv2, Jamstec, but only via grapevine of Euro long range.

    Enhanced Siberian snow cover noted.

    Anomalously mild in Alaska past month, should flip in next 30 days.

    Greatest odds for arctic blast between Dec 1- Jan 10. Would not be surprised if we have 7-14 day period of very cold weather at some point. Kind of a one and done winter in terms of arctic stuff.

    Things will trend milder through Jan into Feb as cold weather heads E.

    This will not be a long cold winter with lots of precip.

    Wettest month relative to normal probably November. Dec-March overall drier than average. Won’t have the dreaded La Niña cold spring.

    Don’t think snowpack will be all that great this year but good enough.

    1919, 1924, 1932, 1972, 1985, 1990, 2013.
    2008 not in same league.

    • David B. says:

      1990 was epic in Seattle. Arctic front interacted with the PSCZ to dump a foot of snow as the cold air came in, then things stayed cold for most of a week so the snow that fell stayed around.

      I believe there was even one day with a HIGH temperature in the teens.

    • WEATHERDAN says:

      Funny you should mention 1972 Paul. It was a one and done, but oh that one. Four nights subzero in Salem in December. Two weeks almost subfreezing daytime highs. A foot of snow fell during one storm and 8 inches during another. Salem dropped to minus 12 for it’s alltime low temp. The rest of the Winter was mainly a dud although there was a smaller cold snap in early January. But mostly a one and done. But that one was enough. We shall see. Peace

    • oldwxwatcher says:

      (in)Accuweather also thinks November will be wet:


      13.6″ of rain in Portland, according to them. Where’s my ark?

  7. W7ENK says:

    628 AM PDT THU OCT 24 2013


    • David B. says:

      Nothing “overdue” about it here to the north, of course: yet another foggy morning. At least it cleared off for a few hours yesterday afternoon, and I am *very* pleased that all the models are staying on board for dry outflow winds early next week.

    • W7ENK says:

      Oh, I just found it funny that they waited until 6:30am to issue the advisory, when most areas down this way have been socked in thick since 11pm last night. Always a step behind…

    • So tired of this fog every single day foggy. Yawn Hope we get the cold north winds to get raid of this fog

    • David B. says:

      That’s what I call a “post-cast”.

  8. schmit44 says:

    10/23/2013 Oregon (All) Temperature Summary

    High:81 at ILLINOIS VALLEY(1389 ft)
    Low: 58 at ONION MOUNTAIN L(4438 ft) & SQUAW PEAK(4964 ft) & Mary’s Peak(4137 ft)

    High:50 at NERRS MET SITE A(10 ft) & YACHTS Yachats(82 ft)
    Low: 18 at Horse Ridge (US (4160 ft ) & CW0732 Seneca (4665 ft )

    Largest Diurnal Change: 55 degrees
    Lorella (74/19 ) (4160 ft )

  9. paulbeugene says:

    Looking at the 00z Euro…good call Mark. Euro with impressive closed low over Great Basin/SE Oregon. Lows could bottom out in 20-25 range in Eugene/Salem/Corvallis.

    Could be quite a bit of blowing dust in the Columbia Basin. A spooky October Haboob

    • Rob - Southeast Portland says:

      Yes indeed. EURO has trended further west. I was not expecting that. Quite significantly so too. Ridge positively tilts rather favorably. Then after this digging system departs we see some northwest flow aloft before things turn ridgy again. Beyond that looking further out in the Pacific reveals weak split flow. Interesting.

  10. paulbeugene says:

    Gutsy forecast of 28F next week Mark…you probably got Island Fever in Hawaii. Hope it verifies. Would like to see the teens again in Eugene but suspect will end up mid-upper 20s.

  11. Greg Carstens says:


    I’m glad I have great patience because the weather up here in the South Puget Sound area has been like looking like a broken record player that constantly skips over and over with short differentials in temperatures and anywhere from a trace to as much as 0.02 inches of moisture from dew overnight. Basically the grass has stayed wet all day every day. I sure was glad to see the sun in the afternoon eventually here the last couple of days. Some areas near the water didn’t even get that far.

    I am basically done with whatever yard work for the season. The only thing that is needed is a new door on the greenhouse because it is completely rotted out and falling off the hinges. I’m not going to run the heater in the greenhouse this winter because I no longer have lime, lemon, and grapefruit trees in there anymore. My step brother took those out to his house where he has a garden room inside the house that is good size. At any rate we don’t have the amount of plants we had in there anymore. I continue to grow 4 species of cacti in there which are doing pretty well. Otherwise there is a strawberry plant in there along with a few pots of geraniums. I monitor my cacti in there daily when I can otherwise I don’t worry to much about anything in there.

    As for the overall weather picture you mentioned here…

    I am not jumping for to much joy on hearing from the groups that cold air may be coming. I believe for one thing that it is to early for snow in the lowlands (just my thought here from watching weather in the PNW for 44 years) so some cool air maybe is surely all I see. I think we have a ways to go to break this stubborn stagnant weather pattern yet and don’t see it happening until sometime after the month is over. The position of the offshore high just has me shaking my head but I am glad that it is not happening in December, January, or February right now, More than anything as usual I see a gradual change back over to the normal showers for this time of year with temperatures overall being around normal and that is basically what the November forecast is also on the Climate Prediction Center website that they made back on the 17th of this month.

    • David B. says:

      I think there is a very good chance of an outflow event starting next week. Arctic cold? Not certainly, and an arctic outflow in October is not anywhere near as cold as one even a month later. And yes, it HAS happened before — I remember one October in the 1990s when we had such an event, daytime highs the mid-40s, lows well into the 20s, and even a bit of snow in Bellingham.

      “Reverse wishcasting” is every bit as nonscientific as wishcasting — the models ARE in agreement that something is about to happen.

    • Greg Carstens says:

      It snowed in the Puyallup Valley in October of 1984 on Halloween but it was not a wide scale snow event. The snow was the result of post frontal convection. I don’t remember seeing any lightning or hearing any thunder that day but the clouds surely looked convective earlier in the day. I had to work that evening washing dishes up at Federal Way but drove my truck down Levee Road on the north side of the Puyallup River and snow flurries were still taking place at the time. Once I got south of River Road (part of highway 167) the ground was white. A month or so ago I checked records from the old COOP weather station located at the WSU Experiment Station which has recorded 0.3 inches of snowfall for that day. It also shows up in monthly data kept on the Western Regional Climate Center website. I have not seen snow in October since. I should note the earliest snowfall I ever saw in my neighborhood here was mid December of 1971. About an inch fell in the neighborhood and I don’t remember it to well since I was only 9 years old at the time.

    • Greg Carstens says:

      UGH…I meant to say mid September of 71. Sorry Mark that is what happens when I try to type faster than I really am able to.

  12. “A stronger wind, likely either northerly or easterly, could have pushed the metro area up into the 70s to mid 80s any one of those days. ”

    Mid 80s in late October, Mark? Are you serious? Yes I realize we hit the low 80s in 2003, but that was a crazy fluke.

    Now, mid to upper 70s in the 2nd half of October ARE possible. And we had TWO days where there was decent warm easterly flow and temps well into the 70s across most of the Metro.

    I’m not going to complain about the temps not being warm enough though. This October dry stretch has been absolutely AMAZING!!!! And 3-5 sunny sharp days in the 70s this close to Halloween? Easily deserves an A+ grade!

  13. jason says:

    Mark, how strong of the winds from the N or NE do you think we will get and which time period? It looks like gust of 50 mph to me.

  14. Rob - Southeast Portland says:

    Nice update, Mark

    00z GFS was just a smidge further east kind of trending towards the EURO and the trough doesn’t dig as sharply southwestward over us. Still looks like cooler conditions and east winds. Otherwise no major pattern change, no wet pattern, just weak northwesterly flow or split flow.

    • BoringOregon says:

      So maybe a little rain by Halloween. And maybe some cold and foggy weather…Maybe it’s time to issue another “BoringWeatheralaert” for next week……?

  15. W7ENK says:

    Hasn’t rained in 15 days here, and the sun has been out for the vast majority of it!

    Best. October. EVAR!

  16. Lurkyloo says:

    Mahalo, bruddah Mark. Nice to see you’re back home.

  17. BoringOregon says:


%d bloggers like this: