September 17, 2021

A Potential Intense Feature Moving Through Tonight. My New Podcast. And Why are Northwest Summers so Dry.

A potentially VERY intense frontal feature will move through western Washington tonight, one that could produce intense rainfall and localized urban flooding.

A very strong front will move through this evening, crossing Puget Sound sometime between 8 PM and 11 PM.  This front will bring INTENSE, heavy rain for a short period (less than an hour) that will cause localized flooding and strong winds.  There could be a thunderstorm with it.   

To illustrate this threat, here is a simulated radar image for 10 PM tonight.  Wow. The orange/red colors indicate very heavy rainfall.  The NOAA HRRR model is doing the same thing.  


This feature will pass through the coast a few hours earlier. 


I would not be driving during this event and if you live in a basement apartment with flooding issues, I would be watchful.  The City of Seattle used to have the RainWatch system that provided warning capabilities for such events, but since they dropped it a few years ago,  I am providing the heads-up manually. 

The total precipitation for the storm follows the previous guidance (the total through 5 AM Sunday is shown below).  Even eastern WA gets good rain, with over 5 inches in portions of the Olympics and Cas Cascades.

In western Washington, the rain will be very heavy tonight, with showers into Sunday.  Good chance of thunderstorms on Saturday and Sunday.

I talk about the forecast in-depth in my podcast.   

In the second section of the podcast, I explain why the Northwest has some of the driest summers in the nation.  In fact, the entire West Coast is very dry (the plot below shows you the average July precipitation).  By the end of the podcast, you will know the reason.
 




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22 comments:

  1. What are the chances of thunderstorms in and around Seattle? Also will they stick around till Saturday night?

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  2. What are the predicted rain fall amounts for Southwest Oregon?

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  3. Interesting that your July precipitation map does not have smooth iso-lines, but rather, rough blocky edges. Note in particular the transition from southern Wyoming to NW Colorado. Since Nature does not work this way, generally, I suggest that these are county average rainfall values.

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  4. I good guess, but there are many more counties in the US than what is shown.

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  5. So far (2:40pm Friday) this rain event has been a complete BUST. The ground underneath large trees in north Seattle is not even wet. We are are getting a full rain shadow here so far. Disappointing.

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    1. Be patient.....the real action is tonight. Puget Sound has been rainshadowed today....

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    2. I see the front approaching on the radar but what an overhyped event for today. We've been hearing all week how today was going to be "very, very wet" and windy. I'm in Tacoma, we had a little light rain earlier, then everything dried right out and no wind at all. Been outside this afternoon and it was very pleasant. Weak.

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    3. Isn't this always the case? Seattle, especially North Seattle, is always severely rain-shadowed. I grew up in Tacoma and remember winter days where it rained all day and night, and into the next day. Almost a different climate from Seattle. Driving north, it clears up and no rain.

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    4. Rain shadows are what it's all about. At my place near Sequim, we got 0.53" against a 0.58" forecast for the day. Very good forecast and a good rain for us in any month. We had some significant shadowing the whole day, and the really ugly stuff (looked a bit like a squall line) on the radar around 10pm or so mostly went north into southern Vancouver Island. We got the southern tail of it given it was moving east-northeast as usual, but it kept disappearing off the radar as it moved east of Port Angeles. Typical for us. Our Blue Hole was eating it, or so we say (actually, downslope effect).

      But in the end, a great soaking rain that my trees are very thankful for. Hopefully we'll get another tenth or two from convective stuff this weekend, if any cloud happens to wander over us.

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    5. Tacoma got hit by torrential rain about 45 minutes after Tim’s post.

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  6. It appears on the radar that Two small low pressure clusters are forming off of Vancouver Island. Might this portend a more intense wind event?

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  7. Orcas Island: 1.25 inches today as of 9:20pm with something big and nasty coming our way down the Strait of Juan de Fuca...should be here in a few hours....

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  8. 10pm. S. Everett...moderate rain falling, moderate winds...I am ready for more action!...Hope it shows up.

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  9. That intense ribbon is right on time, for Olympia-Cathlamet at least. Pretty good modeling, again!

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  10. Just as predicted...nice work! Wish I could paste in UW radar right now...had to sweep off rain from our veranda.

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  11. No joke!! Right on time. That was crazy

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  12. 10:51pm and hardly any rain in North Seattle. I knew it.

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  13. That was one very strong front! First the temp rose from 64 to 71 between 1830ish to 2200. At 2230 all hell broke loose! Wind, heavy rain, wind, sideways rain, and did I mention winds...temp took a nose dive, down 12 degrees (70 to 58)in 40 minutes here in Puyallup. We did loose power shortly after. Great forecast! The UW models did a great job forecasting the front, almost to the minute. Looking at actual radar vs the predicted!

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  14. The real action is fascinating and never perfect to the predictions. That's why we all love weather or at least me. It's beautiful chaos. Thank you so much for everything you do. You make weather beautiful and beneficial cliff. Forever a following.

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  15. Orcas Island Update at 6am: big event late last night just missed us to the north, total event rainfall 1.88 inches

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  16. I did a 4 mile run/walk at 3pm, light rain to medium but otherwise pleasant outside. Anxious to hear how it went over there on the east side of the Sound. Us on the west side seem to have had the expected quiet night.

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  17. Hi Cliff, great podcast this week, I can tell you are excited about fall and back to active weather! :) I noticed from around 6pm (9/17) in N. Bend the wind became very warm, almost like someone turned on a hair dryer and I could smell faint smoke in the air. I looked on Windy.com I can see the winds are blowing from the SE and converging with SW winds over Tanner, can you explain what is happening here? I'm assuming that there is a pressure gradient that's causing air east of the Cascades to make its way easterly and pulling in wildfire smoke from Yakima?

    Separately I was in the mountains on Thursday 9/16 and the fire east of Glacier Peak seemed to really rev up after 1pm after as winds started to increase, hopefully the rain deluge has dampened things down this weekend.

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