Weekend Flood Watch; Beautiful Fall Weather Follows

October 20, 2017

7pm Friday

We’ve made it to Friday and here we are sitting on the cusp of a soaker this weekend.

Nothing has changed from my thinking last night at this time (see previous post).  Steady rain associated with an atmospheric river arrives in western Oregon and SW Washington right after midnight.  That steady rain continues through tomorrow afternoon in the lowlands, then mainly shifts over/north of the Portland metro area tomorrow evening.  The cold front then slides back south during the morning hours Sunday.  So during the day Sunday rain will end first up around Kelso/Longview, then end by sunset down around Eugene.  Total rain?  1.5 to 3″ in the lowlands and 6-8″ additional in the wettest parts of the Cascades.  These totals will likely be enough (by Sunday morning) to bring localized ponding of water or flooded areas on roads.  This won’t be enough to give us any sort of widespread river flooding though; especially since we’re only looking at 24-30 hours of steady rain in the lowlands.

Wind is also an issue tomorrow; not a big windstorm but enough to bring us a few power outages.  That’s especially the case since leaves are still on the trees.  A high wind warning is up for the coastline…

and a wind advisory for the western valleys…

So to wrap things up…Saturday still looks to be a soaking wet day, with rain tapering off in the evening from Portland south.   Sunday starts wet, but then rain ends by midday, hopefully just in time for the 1pm Timbers match.

One would think this will be the beginning of the big wet season, but models say that isn’t the case.  Upper-level ridging wants to linger just to our west for the next 10+ days.  The result will be an extended period of mainly dry weather and beautiful fall weather.  Take a look at the ECMWF model ensemble forecast of 24 hour rainfall.  The big surge over the weekend and then just a few scattered showers here and there on the different ensemble members for the following 2 weeks.  Pretty good for the end of October and the first few days of November!

The blue line at the bottom is the ensemble average…quite dry.

Try to stay dry this weekend and hopefully we’ll avoid any big flooding issues.  But if you’re driving around tomorrow through midday Sunday, expect lots of water on the streets.

Chief Meteorologist Mark Nelsen