Still On Track For Drying Halloween Evening

October 29, 2015

10pm Thursday…

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:

web_RPM_Rain_NWOregon

wrf_throughsundayam

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:

RPM_Cloud_Rain_Fcst

Whew!  That’s intense…not a good time to be having an outside party.

Then check out the 5pm image:

RPM_Cloud_Rain_Fcst2

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.

MarkSnow_MtHoodFcst_2013

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