September 05, 2013

4 PM NOWCAST for the Heavy Precipitation Event

As predicted earlier today, this afternoon has been generally dry over most of the state.

Also, as per the HRRR and UW WRF modeling systems, heavy precipitation has exploded in northern Oregon this afternoon and is moving towards Washington. 

Here is the latest radar (3:54 PM) can see the strong echoes, with reds indicating torrential rain and hail.

What I am trying to expose you to is state-of-the-art forecasting in which information is frequently updated using modern rapid-update modeling systems.   So what does the NOAA HRRR system indicate for the next 12 hours?

At 6 PM, the heavy line of showers is crossing the border.

 Buy 11 PM heavy rain is over Puget Sound and SW Washington.  The rain had moved quickly into northeastern WA as well.
 At 3 AM it is still raining over Puget Sound and some of the precipitation has circled around down towards Portland.
Bottom line: wet night in Washington.  Total predicted rainfall for the 15 hours ending 3 AM is shown below.  1-3 inches over SW Washington and northwest Oregon.  And it is not over at that point.

This is not an end of the world event.  The ground is dry and can soak a lot up.  The rivers are low and can handle the precipitation.   But it is educational to see how far weather prediction has come and the great discrepancy between what meteorologists know and what many media outlets provide.

Announcement:  My Public Lecture Series on NW Weather

I am giving a five-lecture evening short course: "Reading the Northwest Sky: Understanding Our Weather and Climate"  

October 1, October 22, November 5, November 26, December 3  
Kane Hall: University of Washington  
Co-Presented by University of Washington Alumni Association   and Seattle Public Lectures.

If anyone is interested, more information here.


  1. Thanks for this! Your 11 pm heavy-rain prediction means I'll stay at work in Bellevue until 6:10, as usual. :-)

  2. Impressive modeling. Why are we getting such unusually intense thunderstorm activity for our area?
    Peter M

  3. I think you mean AM a few times you said PM

  4. Thanks for the update! Excited for some long awaited rain!

  5. Thanks for the update! I will be visiting the blog more often!

  6. Well, this is sure better than the NOAA forecast which has, and still is, a total bust for Anacortes and the San Juans. NOAA still showing 100% chance of rain, with 0.17 inches in the next six hours, at 5 PM. Meanwhile no rain since about 8:30 AM with a very nice partly sunny day. The rowing club enjoyed a pleasant dry row in Fidalgo Bay in the afternoon. Only so much planning you should do based on weather forecasts.

  7. Downtown Shelton just got pummeled by lightening strikes.. Several houses and an elementary school hit. One man near the school that got hit said his feet were "on fire" and there were burn marks on his knees.

    One strike caused a tree to fall into an apartment building and get embedded in the second floor. The fire department had to put out several structure and tree fires. A hay bale fire was reported on Skokomish Valley road.

    The fire department chased the high school football team off the field.

    It was VERY intense for about half an hour.

    The storm seemed to have moved north.. maybe up on the Hood Canal now.

    Oh yeah, there was some rain too, but nothing too bad by Shelton standards.. just the usual storm drains overflowing..

  8. I am watching the UW radar viewer in awe. I have never seen such a beautiful cyclonic rotating front. The way it is moving almost reminds me of a derecho. Can you speak to any similarities (or not) between this front and a derecho?

  9. What time do the lectures begin? How long are they? Thanks!

  10. Now this is some "pull up a chair" weather!

  11. Lightning and thunder in Newcastle started at 10pm with rain starting 5-10 minutes later. I hope my gutters can keep up!


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