Heavy Rain Wrap: Similar to 1996?

December 9, 2015

11:45pm Wednesday…

It’s been an incredibly busy 3 days.  Not only was the forecasting tough initially, but extra updates to the news people, a school visit, extra hits in the shows, more social media updates etc…

There have been several references to the last big flood…1996.  In some places it has definitely been similar or worse.  In a line from about Tillamook to White Pass (WA) and a bit north and south of that line I think it was very similar.  For the rest of us it wasn’t nearly as similar.

Here in Portland, a cursory look at rain records says we haven’t seen a 5 day total up around 6″ since the February 1996 flood.  I found 4 instances of 3.70-4.17″ in 5 days, but nothing higher.  In the Portland metro area we were incredibly lucky that line of heavy rain stayed about 30 miles north of us yesterday, or else we would have seen catastrophic flood issues by late evening with an additional 2-3 inches of rain.  That would have been after the 3″ the day before.

BMAC Rain Two Day Total

You think that’s wet?  Take a look at some of the wettest places I could find…these are 5 day totals ending at 10pm tonight:

MarkRain_MtHood_Totals

Those 15-18″ totals in a few isolated spots in the Coast Range and S. Washington Cascades are getting a bit closer to the 1996 values.  Notice the big totals are in that band that sat across the far NW tip of Oregon and into SW Washington yesterday.

The lack of snowpack in the mountains, low reservoir levels, and lighter rain from the metro area southward means no flooding issues for the Willamette River system too.  Take a look at Detroit Lake…up 27 feet in just 3 days, but still 80+ feet the summer level.  The outflow was almost zero…all water was being held back the past few days.

MarkDetroitLake_WillametteReservoirs_FloodInfo

I still expect another 1.0 to 1.5″ rain the next 3 days here in the lowlands, but that will not be enough to bring any rivers back to flood stage.

Tonight a very strong storm is moving by offshore and the associated front will move overhead in the next few hours.  Some nice wind gusts to 35 mph plus brief heavy rain too.

Chief Meteorologist Mark Nelsen