December 20, 2019

Torrential Rains Bring More Serious Flooding Threat

A potent and nearly stationary atmospheric river is bringing the threat of flooding and landslides to western Washington and Oregon, with the situation more serious than earlier forecast.

Water vapor satellite imagery shows the plume of atmospheric moisture extending from the subtropics into our region

Urban  and street flooding is already occurring around the region and several rivers are going to crest at major flood stage during the next day.

First, take a look at the rainfall totals over the past 24 hr (below(.  Over 8 inches above the Willapa Hills of SW Washington.  More than 6 inches over the south side of the Olympics.  4-6 inches on the western slopes of the Cascades.  And over 3 inches from SeaTac to Olympia. And this is nowhere near over.


The contrasts over Puget Sound are stunning.  A little over an inch near Everett to 3+ inches over the south Sound.


Really want to be impressed?  Here are the radar-based totals over the past few days.   Almost nothing over north Whidbey Island, but 3.5-5 inches in a band stretching from the Hood Canal across Tacoma and to the east.  Lots of rain in the Cascade foothills.


And thanks to Senator Cantwell, we have the coastal radar at Langley Hill that shows an extraordinary storm total on the western side of the Olympics and coastal mountain (below)--reaching 6-7 inches.



The latest forecast model predictions though 4AM Sunday predicts another 2-5 inches over the south Sound.  This is vert unusual.   Seattle is going to end up with the wettest day in decades (not just a daily record).


As noted, streets are flooding.   We used to have Seattle RainWatch to help in this kind of situation, but that is no longer available, but my drive in showed many Seattle streets are under water, at least partially. 

The NOAA/NWS River Forecast Center is predicting major flooding on several local rivers (see graphic below).  Blue dots indicate major flooding. There will be a lot of water over the roads in Snoqulamie drainage and near the Chehalis River.


One reason that the lowlands are going to experience a particularly bad day is because the atmospheric river is rotating to a more southerly direction (as suggested by the latest radar image).   Thus, Puget Sound will experience LESS rainshadowing from the Olympics, which means heavier precipitation.

The precipitation should continue all day, but back off on Saturday after approximately 8-9 AM.  Stay safe and don't drive through standing water.

29 comments:

  1. Until the blob vanishes I have predicted warmer then average nights with cooler highs and so far it's panning out. Airmasses can't overcome it as the 'blob' is a higher pressure then the surrounding area which lows take the path of least resistance. Strong enough lows may temporary override it but the thing is unlike natural highs this little one is permanent as long as whatever is heating up the ocean remains.

    The models do not factor this and assume old school patterns will work

    ReplyDelete
    Replies
    1. There is no "Blob," as I've seen Cliff define it, you can see here: https://www.ospo.noaa.gov/data/sst/anomaly/2019/anomnight.12.19.2019.gif
      (In fact, the water is getting even cooler off WA coast).

      Surface temp reading: https://www.ospo.noaa.gov/data/sst/contour/namerica.cf.gif

      Delete
  2. Wow. What is the snow forecast for the mountains?

    ReplyDelete
    Replies
    1. Rained today at both Summit and Stevens, don't know about elsewhere. Lots of holes and streams running on the slopes. It was snowing by the time I quit skiing at Summit but it was wet and wasn't accumulating.

      Delete
    2. For BC some areas in the mountains got several feet of snow.In fact on Thursday, all highways east of Vancouver including the infamous "Highway thru Hell",the Coquihalla, were closed due to heavy snowfall and treacherous conditions. BC was far enough north to avoid the warm surge of air but still got copious amounts of precip.

      Delete
  3. This comment has been removed by the author.

    ReplyDelete
  4. My rain gauge registered exactly 5.0" for the 24 hours ending at noon today 12/20. That's the max amount calibrated on the gauge! We are located in Olympia just NE of downtown overlooking Budd Inlet. Typically we receive ~30% more precip than the Olympia airport (KOLM) does.
    Gary

    ReplyDelete
  5. Wunderground indicates there was a tornado near Gig Harbor today. Is this valid? I can't seem to attach a photo, but here's the details:

    Tornado
    Gig Harbor, WA
    Station ID: KLGX.R8
    Lat: 47.38
    Lon: -122.80
    Time: 12:47 PM
    Movement: NE 13.8 mph

    ReplyDelete
  6. Almost to the day one year ago the Port Orchard tornado hit. What we initially observed here on the west side of Sinclair Inlet was it became dark enough to need to turn on indoor lights (two solid walls of windows, always enough daylight), a few minutes later we heard about the tornado. The eerie thing is it has stayed almost as dark all day today as when last year's storm cloud went through.

    ReplyDelete
  7. Cliff. On a hill in bellevue right now, 3:43 pm, there is fog AND rain. I thought this like never happens?!

    ReplyDelete
  8. "Do you think it will rain tomorrow?"
    "I don't know, but I'll ask my friend Rudolph."
    "But will he know if it will rain?"
    "Absolutely. He used to be the official weather forecaster for Pravda. Rudolph the Red knows rain, dear."

    ReplyDelete
  9. Snow level currently at 5000 feet. Probably not what skiers and snowboarders envisioned as this event turned out to be an unfavorable outcome compared to if it hit Oregon, stayed colder with less moisture as the forecast a few days ago suggested. Instead we got the full blast. Yes, the rain deficit is a thing but this might not do much for the overall snow pack. Gains at higher elevations but significant losses at lower = net loss. There isn't much surface area to collect snow above 5000 feet compared to if the snow level was at 2000 feet. Flood and avalanche warnings are not where we want to be.

    ReplyDelete
  10. Snow level currently at 5,000 ft? Where?? I've just seen a string of cars coming down from Mt Baker ski area with inches of fresh snow on them.

    ReplyDelete
    Replies
    1. Pretty much everywhere one can ski. Those folks probably parked up at Heather Meadows, was a nice rain/snow mix today. Such a shame the cold air lost out and we went from fresh powder to Cascade concrete quite literally "overnight". Now, back to waxing my goretex ...

      Delete
    2. Literally everywhere south of Baker, sadly. Rain even ataParadise on Rainier. I predict that Baker will be swamped with skiiers this weekend since all other resorts are in such poor shape!

      Delete
    3. mount baker is at about a little higher than that but just becasue is 5,000 feet doesnt mean its not going to snw

      Delete
  11. Snow report at Heather meadows last 24 hrs,3500' elevation 24" snow.

    ReplyDelete
    Replies
    1. The Heather Meadows weather station is at 4210' ASL, not 3500'. That's an awfully big difference in the PNW.

      Delete
    2. I am simply reporting what I saw in the mount Baker ski area report.

      Delete
  12. Cliff, the first picture - the plume of atmospheric moisture - is a strange-looking formation. Is it unusual? It looks like there's an area of relatively low moisture around the "tongue." Could you talk a bit more about this formation? Thank you.

    ReplyDelete
  13. So the local media here immediately pivoted from their past narrative of "OMG no rain in November we're this close to a catastrophic drought for next year"to "OMG the rain isn't falling as snow we're this close to a catastrophic drought for next year due to lack of snow depth!" Total clown shoes for all of them.

    ReplyDelete
    Replies
    1. Local Media: "EVERYTHING IS CATASTROPHIC CLIMATE CHANGE! RUN FOR THE HILLS!"

      LOL

      Delete
  14. Their job is to have you glued to your TV/laptop/device, scared S-less. That is while being enticed by their adverts for shiny things.

    There are several drought types, so the newsies are not completely off base.

    1) Low Precip winter (High Pressure Ridging)
    2) Abnormally warm Precip winter(Pine Apple Express/AR)
    3) Exceptionally warm dry(or wet but suddenly very warm) spring/hot dry summer. (Heat wave with AR in spring, Ridging/BLOB etc)

    The first two can hurt salmon and skiing but if the summer months receive some rain and temps stay within reason, then its not dire. Unless you enjoy winter recreation or are an Orca.

    A year that is all high pressure ridge (1 and 3) is pretty much all around bad. There is a forth drought variant but it might just be a combo of the others.

    So far this winter has been a blend of both 1 and 2.

    ReplyDelete
    Replies
    1. We have never had a year where it's "all high pressure". You could argue we have had summers where its all high pressure and certain extended dry spells in fall and winter where it's all high pressure. However even in the driest years with more high pressure than normal, there are still wet periods and troughs and low pressure when the high pressure weakens or retrogrades. This year we had a dry November which isn't winter, it's fall, and so far in this first month of meteorological winter it has been wet. We have had much drier than normal fall/winter periods such as 76-77 and 00-01 where the overall precip amount was much below normal but we still had rain at times and it wasn't a dire drought due to the fact it really wasn't that dry in the whole scheme of things. Just drier as compared to normal with normal being super wet. The times when we can actually say that we are in a drought is when we get extended ridging into September and October following a dry summer that could have followed a drier than normal fall and winter. However these "Indian summer" patterns are much more rare now as compared to 30 years ago. A delay in the fall rains after a typically dry summer is when we can actually say the "drought" word because it's only in this scenario where water levels could hypothetically become dire and this is when it will hurt salmon and water supply.

      Delete
  15. just imagine if this jetstream went right were a huge mass of cold air like im talking -10 and picked that air all up and went into us and and the amount of rain we got was just snow we probably would have welover 4+feet if anything 1 inch of rain is equal to 13 inches of snow remember anything is possible

    ReplyDelete
  16. Suggestion to call this event the "2019 Atmospheric River Solstice Event" - or 2019 ARSE for short. Who's with me?

    ReplyDelete

Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

A Record Storm and the Power Outages Begin

This morning, the offshore storm rapidly intensified and a chieved record status, with the central pressure dropping to at least 943 hPa (t...