A Stormy Saturday Ahead

April 5, 2018

5pm Thursday

One year ago, on April 7th, the strongest April windstorm since the 1950s hit the valleys of NW Oregon and SW Washington.   Peak gusts looked like this across the metro area:

It was PGE’s biggest power outage event since the December 2006 storm and it took over 3 days to get the last few customers back online.  That said, most customers were back within 24 hours due to those hard-working crews.

Mark PGE PowerOutages LengthOfTimeOut

So of course it’s VERY interesting that we have another wind “event” coming up exactly one year later…Saturday April 7th.  Luckily, this one does not appear as strong, but will likely cause some inconvenience for many of us during the daylight hours Saturday.

Just like all of our wind storms/events, a deep surface low pressure center will be tracking up the coastline Friday night and Saturday morning.  It ends up around 972-980 millibars depth somewhere around central/southern Vancouver Island Saturday afternoon.  Note the 2pm location from the WRF-GFS model.  Also see the tight packing of isobars, indicating large pressure change over relatively short distance.  The tightest packing is generally associated with the strongest wind as air rushes from high to low pressure.  Looks windy on the coast!

Each model is slightly different in the low location by midday/afternoon which makes for differing wind speed/gust forecasts.  Check the intense NAM-WRF 3km wind gust forecast showing 50-60 mph gusts inland

and the ECMWF, although it’s a bit weaker.

The WRF-GFS around 11am Saturday

Here’s our current forecast:

 

 

A few important points:

  1. The National Weather Service has issued a High Wind Watch for the western valleys, the only one of this entire “storm season”!  That’s due to an abundance of caution even though it’s unlikely we see widespread gusts above the 58 mph criteria required for a High Wind Warning.   Remember it’s a WATCH, not a WARNING.  The NWS may upgrade to a warning tomorrow or convert to a Wind Advisory…we’ll see.
  2. When comparing current models to last year’s storm, they are all a bit weaker, by maybe 10 mph.  That plus the low placement/depth leads me to believe that instead of 45-60 mph gusts in the valleys (last year) it’ll be more like 40-55mph for the vast majority of us.
  3. Coastal wind gusts were “weak” last year; the main action was inland.  We’ll see how that plays out this year.  In the springtime the strong upper-level winds mix down easily in the “warm” valleys so we can get as windy as the Coast.
  4. 42 mph is the peak southerly wind gust we’ve seen in the past 6 months.  Very weak.  That means it’ll be relatively easy to topple a few trees here and there.  Expect plenty of power outages, even if we only see gusts 40-45 mph.

 

To summarize…

We have a bunch of wind coming up this weekend, not a MAJOR storm, but pretty darn windy for April!

Chief Meteorologist Mark Nelsen