September 05, 2013

11 AM Heavy Rain NOWCAST

Many of the media outlets (e.g., KUOW) are giving very poor weather information, saying it is going to rain all day.  It is not.  The big rain is coming in TONIGHT.

So let's try some NOWCASTING for this event as an illustration of the future of forecasting.   

Right now, it is pretty much dry over Puget Sound and much of eastern Washington, with the line of showers/thundershowers that hit this morning moving over NW Washington (see radar).

The next few hours should be dry for much of the state (except for those poor folks on the N. Olympic Peninsula and southern Vancouver Is.)

The NOAA/NWS High Resolution Rapid Refresh modeling systems shows dry conditions for much of the state over the next 6 hours.  Here is the simulated composite radar imagery for noon (1900 UTC), 4 PM (2300 UTC), and 9 PM (0400 UTC).   Note that a band of strong showers will be moving northward late in the afternoon (very wet in Portland then) and pushing northward into Washington State during the early evening.  THAT is the big rain threat.

The latest run of the UW high-res model still shows very heavy rain tonight and Friday AM over much of the region.  Below is the 24h total ending 5 PM Friday.  The mountains are going to get hit very hard--expect rapid rises on most rivers.   You want to be dry tomorrow?...head to Tatoosh Island!  Eastern Washington will be getting a lot of rain.

Next NOWCAST UPDATE at 4 PM on this blog.

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 the NOWCAST - what I was seeing on the radar didn't match up with what I was hearing. Now I can plan my day better!

  2. Cliff:

    While the circulation (shown in a recent Langley Hills radar composite loop) seems to be SE to NW why are we not getting more precip in Eastern WA as the clouds move up the east facing slope of the Cascades?

    Thanks for the blog.

  3. I was wondering why the news sites kept reporting rain in the afternoon.

    I woke up this morning in the middle of the thunderstorms and pouring rain, but one glance at the radar and other maps clearly showed a drying trend for most of the day.

    Turns out I was right, but I still urged my Wife to get home early today since she has our 6 month old daughter with her.

    The lightning/thunder/rain storm early this morning was pretty awesome. I hope we get a lot more of that tonight.

  4. I saw the morning forecast and glanced at the radar, but I still got soaked in a cloud burst.


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