October Will End Unusually Dry

6pm Wednesday…

Today was a great late October day; early fog/clouds then afternoon sunshine.  Temperatures peaked out around 60 in the metro area, perfectly normal for October 23rd.

Looking at all the maps/charts/models this afternoon, the most obvious feature is a persistent upper-level ridge near the West Coast of North America for at least the next 7-10 days.  One weak weather system slides through the ridge Friday for clouds and a few sprinkles/shower, but that’s about it.  Take a look at the current pattern at 500 millibars (around 18,000′)

Mark Jet Stream

Behind that weak system, the ridge pops up again but farther west.  This gives us cool northerly flow again; like we have seen twice so far this fall season.  Although this time the core of cold air is farther east.  The view Saturday…

Mark Jet Stream2

This setup in the cool season (we’re just about there) typically features very dry air coming down from the north or east.  Low relative humidity = not much cloud cover or valley fog.  So this weekend will feature abundant sunshine and a “cool-ish” feel.  That’s perfect pumpkin patch weather.  Our wet ground will be drying out nicely.

That ridge is probably going to remain near or just west of the West Coast through next week.   And it’s quite a block in the atmosphere.  Look at the high/warm anomalies stretching north to the Arctic Monday afternoon (red/pink colors).  On the backside see those low/cold anomalies from Hudson Bay all the way down to Baja California!


Jumping ahead to NEXT Friday (the 1st), the ridge is still there.  Maybe a bit farther west


These last two images are from the EPS (ECMWF ensembles), but other models are similar.  The screaming message here is that we’re going to be quite dry for the next 10 days.  We’ll probably see a gusty east wind develop after Saturday as well.  That plus dry air should keep fog to a minimum.  Take a look at the WRF-GFS cross-section that covers Saturday afternoon (right side) to next Wednesday afternoon.  Lots of easterly flow, especially early in the period.


This will be our first drier than average October in 6 years.

October Rain Stats

It’s interesting that during the Autumn of 2013 we saw a similar rainfall setup; a very wet September then a dry October.  That also happens to be the last time we were in ENSO-neutral conditions leading into the winter.  That refers to no El Nino or La Nina in the tropical Pacific.   Speaking of…I’m working on some winter thoughts this evening.  I should be able to get a post done for that by early next week.

Enjoy this last weekend of October!

Chief Meteorologist Mark Nelsen

28 Responses to October Will End Unusually Dry

  1. Roland Derksen says:

    A beautiful finish to October here: The sun shining on the colourful leaves, nice breeze, blue skies… October 2019 is going to end up slightly drier than normal as well.

  2. JohnD says:

    The OMSI weather conferenence Sat, was entertaining and interesting as always. Definite concensus that–amid a weakening blob and ENSO neutral conditions, low elevation snow is definitely possible this year!
    Great to experience a live presentation by Cliff Mass.
    And the synergy between Mark and Steve Pierce is excellent!
    KOIN Kelley Bayern’s presentation very impressive too!
    Here’s to,a great season ahead!

  3. Garron near the Hillsboro airport says:

    Interesting hike yesterday around Sherrard point/Larch mountain. Had no idea that I’d run into a heavy graupel and thunder storm at 4000 feet. It just started dumping that popcorn like snow up there. Turned the trees and some of the roads white. Really cool, literally. The temp fell from 52 to 36 in a matter of 20 minutes.

  4. runrain says:

    Heavy rain but no hail or lightning in Happy Valley. In the fading light, I can see a nice dusting of snow in the Cascade foothills, maybe down to around 2,500-3,000 feet.

  5. W7ENK says:

    So, it has a shelf cloud…

  6. brucie555 says:

    Heavy rain/Hail and frequent lightning here in Troutdale..

  7. Hal in Aims says:

    pretty good little thundershower here the last half hour or so……

  8. W7ENK says:

    Uhmm, yeah, hey guys? Anyone take a look at that wall of cells coming out of the hills and down the Gorge toward Portland? It’s got lightning in it, should be here in less than an hour…

  9. Jason Hougak says:

    Intense boom from thunderstorm and hail headed out of the NE toward foothills.

  10. WEATHERDAN says:

    So is Mark saying this October pattern similar to October 2013. Why in December of 2013 we had our last Arctic outbreak. Eugene dropped to -10F. Fascinating. Peace.

  11. Roland Derksen says:

    Well, the cold front passed through here pretty quickly: I’d say between 7:15-9:15 am. Some fairly heavy showers, especially around 8:55-9am. Skies have cleared quickly, and now the winds are blowing through.

  12. …here’s how you spell cold front for La Grande 😉
    LGD 67 34 46 26

  13. tim says:

    The latest enso 3.4 region is now plus 0.8 C and some models are showing continued warming till end of the year i think our neutral winter is a bust

    • W7ENK says:

      Current ENSO 3.4 SST shown +0.68C this week. And yes, while the temperature is currently rising, nearly all forecast models show an increase in Easterly tradewinds along the equatorial Pacific, which should lead to an upwelling of cooler water from below, and thus cooling in the 3.4 region. Only one ensemble member is projecting continued warming, which would be considered an outlier. In all fairness, one member is also showing a significant drop in SSTs of nearly 2C over the next few weeks, which would also be considered an outlier.

      This is from Australia’s BOM, the world’s leading authority on ENSO.

  14. Roland Derksen says:

    It’s rather ironic for that system tomorrow (Friday) to be described as “weak”. Forecasters here in BC are predicting some pretty intense (though brief) rainfall here in Vancouver, followed by strong NW winds and clearing skies.

  15. Paul D says:

    Quite pleasant!! Sunny and not hot.

  16. tim says:

    The blob is never gonna disappear now with that strong ridge offshore if anything it’s gonna get warmer more balmy nights on the way i guess.

  17. Mark Nelsen says:

    Not sure why post didn’t allow comments at first. Working now

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