The next 45 or so hours are going to be a real soaker across the region. Models are in unusually good agreement that we’ll see a strongly “orographic” rain event. That means the mountains will be favored for the heaviest rain, even more so than normal. Take a look at our RPM rain forecast and then the UW WRF-GFS accumulated rain forecast:
In general the mountain totals will be around 3-5 times what we see in the lowlands!
By Sunday evening, I expect:
- 1.50-2.50″ rain in the western valleys of Oregon
- 2.00-3.50″ from Longview up through Olympia in the valleys
- 5-10″ in the Cascades and Coast Ranges. The usual very heavy rainfall areas in the southwest Washington Cascades could see 10-12″.
This shouldn’t produce any significant river flooding since reservoirs are pretty much empty and rivers are very low. I see Detroit Lake is lower than at any time last winter! The first few inches will be soaked up by the dry ground too.
There WILL be some local/urban flooding Saturday midday/afternoon as models are showing a very intense band of rain with the cold front.
Check out our RPM midday Saturday:
Whew! That’s intense…not a good time to be having an outside party.
Then check out the 5pm image:
This is even faster than model runs yesterday. The WRF-GFS is not quite as fast, showing the rain just leaving the metro area around 5pm.
Either way I think we’re still in good shape in the metro area for Halloween
Behind this system I see a colder airmass with some snow in the mountains. This isn’t a really cold airmass; at best we get a dusting or 1″ at Gov’t Camp by Monday morning. But higher up around 5-6,000′ we’ll get a good dumping, the first of the season. I could see a foot up around 7,000′. That’ll be it for another 5-7 days though.
Enjoy the weekend, I’ve been working a bunch of weekends this fall so I’m taking tomorrow off. No blog postings until Monday unless I get real inspired to do it from home.
Chief Meteorologist Mark Nelsen