Sunny Sunday to Heavy Rain??? How Did THAT happen?

5pm Saturday…

No one has asked me yet, but lots of you must wondering…

How in the heck does the forecast of mostly sunny and low-mid 70s on Sunday go to rain, possibly heavy at times, and a high around 60???

TOTALLY REASONABLE QUESTION!

Here’s what happened:

  1. The “plan” for this weekend has been for a few leftover showers this morning to lift north and then an “atmospheric river” of moisture sets up the rest of the weekend over northern Washington and British Columbia.  We’ve known for days that a big wet weekend event was setting up just to our north in the northern half of Washington.
  2. In the past 24 hours it has become increasingly obvious that Sunday is going to be wet, and as of last night’s models…very wet, because…
  3. The whole band of rain is shifting about 200 miles farther south than expected.  That’s due to a stronger northerly jet stream pushing the whole event south.  It’s all getting pushed south right over us and ruining our Sunday.
  4. What’s 200 miles among friends…right?

RAIN HIGHLIGHTS FOR REGULAR FOLKS WITHOUT THE TECHNICAL INFO:

  1. It will likely rain all day Sunday in NW Oregon and SW Washington.  A steady rain much of the day.
  2. Wind is not an issue.  It will be LIGHT after 8am or so from the north
  3. Heavy rain is possible at times from midday through the evening from the metro area south into the Willamette Valley.  Total rain should be in the 1.00-2.00″ range.  Wettest since January!
  4. There COULD be areas of localized flooding if the rain is heavy enough for several hours.  At this point the event looks less intense than the one last October that flooded MAX.
  5. Some models are giving us .20″ to .30″ for a few hours somewhere between Portland and Albany during that time.  With leaves blocking drainage, that could contribute to flooding issues IF the rain is heavy enough…it may not be.
  6. The front moves south and we’ll be all dry Monday.  With dry east wind Tuesday looks spectacular with blue skies and leaves changing color under the bright October sun.

 

For the geeks…

Check out the precipitable water forecast for midday tomorrow:

gfs_pwat_west3_5

Looks juicy with 1.5″ or higher!  Lots of subtropical moisture to work with as a cold front drags south across our area Sunday.  The problem with forecasting tomorrow is that each model is a bit different on where the heaviest rain falls and final totals too.  Of course we all know the heaviest rain will be in the Coast Range and Cascades, but I mean north and south.  Does the Salem to Wilsonville area get a heavy rain band early afternoon as the WRF-GFS shows?  That’s .60″ in 3 hours.  I’ve noticed we start having urban flooding issues with several hours of .30″ so even this is at the lower end.

wrf_2pmsun_3hrprecip

The WRF-GFS has these totals for the entire event…which are pretty reasonable.  That’s maybe an inch to two inches for many of us in the valley, but less for others:

wrf_rain_tuesam

But the RPM (definitely not always a stellar performer) has it right over PDX with several hours of .30″ intensity in the evening hours:

rpm_rainhighlighted

After almost an inch during the day, it then dumps another 1″ in the next 4 hours!  I bet that is overdone.  But the GFS is extremely wet too, showing 2-3″ over the metro area.gfs_precip_mondayam

The ECMWF is more reasonable than the GFS…

ecmwf_precip_monam

Giving us 1 to 2″ in the metro area but lighter totals (more like 1/2″) down around Salem.

I feel confident saying somebody SOMEWHERE in the lowlands is going to really get dumped on tomorrow, but we don’t know exactly where.  Stay Tuned.

By the way, have you hardcore weather folks noticed this is a pattern that would give us a surprise modified arctic blast in winter followed by freezing rain or snow?  Check out the 48 hour old forecast of 500mb for Sunday PM:

ecmwf_500mbthuram

I’ve added the yellow line to show the main flow.  A cool upper-level trough was forecast to stay just to our north (thus the rain forecast up in northern Washington).  Now check out the forecast for tomorrow afternoon but made this morning:

ecmwf_current500mb

Much better!  In January we’d be real excited about a push of arctic air coming in, or at least just scraping by to the north.  In this October case, that means much drier air for clearing Monday afternoon and then a breezy “coolish” east wind Tuesday for a spectacular sunny fall day.  Then moisture returns with brief offshore flow later Wednesday and Thursday.

As for late next week, it looks rainy and windy…our first real stormy pattern of the season and it’s arriving early.  More on that tomorrow when I’m back to work.

Chief Meteorologist Mark Nelsen

 

 

 

21 Responses to Sunny Sunday to Heavy Rain??? How Did THAT happen?

  1. James maass says:

    I was planning on getting a lot of fall yard work done Sunday based on the Thursday forecast!

    • JJ78259 says:

      Yes it looks like the annual river of constant rain is starting up. What happened to the blocking blob???

  2. runrain says:

    Would be nice to get some kind of exciting weather towards the end of the week, perhaps in the form of a decent wind event? Wednesday is the 54th anniversary of the Columbus Day Storm, you know. I see there is a special marine statement out for some potential offshore storm force winds there later this week.

  3. W7ENK says:

    1.82″ today.

    2.02″ since it started raining last evening.

    It’s still raining.

  4. Boydo3 N. Albany says:

    zero rain so far today in the mid valley…

  5. SortingHat says:

    Well if you call 0.03 heavy rain then one man’s garbage is another……….

    • Josh "The Snowman" from Gladstone, OR says:

      Or you guys can learn to watch the radar and realize it slid south later than was advertised. These bariclonic zones are hard to forecast. Pouring right now everywhere in the metro area.

  6. JJ78259 says:

    Weather Dan Weather 85 to 90 degrees for the next 15 days here in San Antonio. Great weather for Austin City Limits! My kids are attending having a great music fest!

  7. Lee Wilson says:

    Toutle lost power 4 days ago due to high winds.
    And I looked at intellicast and it was showing regions with 34 to 45 mile per hour winds.

    I kinda feel let down by the forecasters and failure to see weather alerts for high winds being posted.

    Now I don’t know what is going on with you technologies but something needs to be tuned.

    That day I posted “Shakes Mark and said Wake up! We have High Winds!” Was hopefully ng to cue you in to what was happening.

    And when my wind turbine pegs 500 watts, well that is some very serious winds as the thing produces 400 watts of power at 28 miles per hour.

    I enjoy these storms
    As it give us free power. But, people need to know as well about dangerous conditions and I feel that the forecasts of late have been rather….inaccurate.

    What I could foresee is if something doesn’t get working right, we could be faced with a surprise snow storm stranding people.

    I felt that the older way of forecasting was much more accurate today.

    Maybe you need to go and thump on that super computer crunching the data..

    Or..get it to fucuss on the Pacific Northwest.

    May be, all the.forecasters been preoccupied with Mathew.

    If that is the case, we really need to.focus here locally.
    Don’t get me wrong..I know Mathew was almost a super storm,
    But when forecasters fail to.predict deadly conditions occurring or even failing to recognize that we have high winds occurring, well that then becomes an issue.

    I know your Job isn’t easy Mark.
    I know there are now 2 models you are working with .
    But something is off and it could potentially be fatal.

    Or has our weather been come “Unpredictable”?
    If that is the case , then we are in a mess of trouble.

    If this is the way it is going to be, then I will toss in my forecast.

    I for see snow coming soon possibly by Halloween.

    I definitely see snow in November just before or just after thanks giving.

    And for Christmas., no snow….but…in January, I for see a deep freeze of an arctic blast complete with blizzard like conditions and high winds. I will say 400 with out power.

    So there is my forecast..

    But what are the chances of that happening?

    This is how I feel the forecasts have been going lately.
    Just post it and hope its accurate.

    Take note: if the forecast I forecasted comes true..I will run and hide.
    I hope that does not happen..

    • Scooter says:

      No one is truly free (even your “free” Femtowatt) , they are a slave to wealth, fortune, the law, or other people restraining them from acting according to their will. ~Euripides~

    • W7ENK says:

      Lee, you really need to let it go, man. We get it, you had some windy wind at your house there in Longview…

  8. Longview 400 ft says:

    I decided not to watch the radar this morning and through the day because I was expecting high pressure to push any chance of rain and clouds to our north. Then late afternoon a a fine mist was falling. After that I opened the windows because it was warmer out side then in my house. Then in the 3rd qtr of the the Husky/Duck game I heard cars going by as if they were driving on a wet surface. What? So I had to look outside between Husky touchdowns to see if my ears were deceiving me. They were not. :ike all of you I was prepared for all of that to go north. Well, bring it on, my trees could use more water.

    So the rainy season is upon us, we’ll plan that way!!!!

  9. pappoose in scappoose says:

    Right!

  10. As of today I am officially rooting for some kind of cold Canadian airmass to come into the Columbia Basin in late October this year. Let’s say a high of only 45 for two or three days at The Dalles with lows down in the 20-25 range.

    • Yes, of course, that’s the spirit!! Instead of always blaming us!!
      Anyway, I received 0.94 inches yesterday, with most of that coming before noon. Today, we’ll see mainly cloudy skies but little or no precipitation.

  11. Scooter says:

    Time will tell. This time of year the “crystal ball” gets a little foggy!

  12. Paul D says:

    Bring it on!

  13. Ann says:

    I came to check the blog because I was thinking this very question. Thanks for answering. I was looking forward to the nice day, but I guess a good book and hot chocolate will work, too.

    • Paul D says:

      Now that’s a good attitude to have – like making lemonade from lemons 🙂 Stay inside, keep warm, and enjoy it.

  14. Amazing turn around. The seasons storms are beginning.

    • Craig says:

      Hey Mark, I kayak and am doing so tomorrow and follow the rain river flow. so when is all this happening Sunday? Not sure to go north to the Lewis drainage or south to the Santiam.

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