Columbia River Flood Warning; What Does It Mean?

May 24, 2011

 

The NWS issued a long-awaited flood warning for the lower Columbia River this morning.  When I say “long-awaited”, I mean that we have been expecting minor spring flooding for a month or so now.  The river has been hovering around 16 feet at the Vancouver gauge, and will probably rise a foot to half a foot over the next few days.  Here’s a plot from the Northwest River Forecast Center, showing the flow over the past 10 days and the expected flow for the next 10 days:

Notice that there is no “surge” of water down into our area.  That’s because there is still lots of storage available higher up on the Columbia.  The largest dam, Grand Coulee, still has plenty of storage capability.  So the only event that would make the levels higher would be a sudden surge of higher water coming down the Willamette River.  I notice those reservoirs are all close to full.  We do have rain o the way later this week, but as of now none of it looks real heavy.

So what does a river level at 16-17 feet mean?  Not a whole lot.  No homes get flooded, but some paths, park benches, and farmland get inundated.  The river really needs to rise up to 20′ or so to start seeing “real” flooding.  Here’s part of the statement from the NWS:

EXPECT MINOR FLOODING OF SOME LOWLAND ACCESS ROADS NEAR THE RIVER ON SAUVIE ISLAND…AND ON THE WALKWAY NEAR DOWNTOWN VANCOUVER. THERE WILL BE SIGNIFICANT FLOODING ALONG  THE BANKS OF THE COLUMBIA RIVER THAT ARE COMMONLY USED FOR CAMPING SUCH AS ON GOVERNMENT ISLAND.

The last time this much water flowed through the Columbia River system was spring/early summer of 1997.  That year the river peaked twice around 19 feet at Vancouver…the first couple days of June and again the 3rd week of June.  I see there is high water even way up on the upper Snake River in eastern Idaho, and all that water has to work its way down the river system.  So you can plan on a very high river over the next 4 weeks but likely no big flooding unless we have an extraordinary rain event.  No camping on the Columbia River beaches this Memorial Day!

Chief Meteorologist Mark Nelsen


Red Sun = Alberta Fire Smoke Overhead

May 19, 2011

Did you see it last night and this morning?  A very reddish sun, similar to late summer and early fall when we see smoke from forest fires.  I first saw it during sunset last night, then happened to be briefly awake at 6:03am this morning when the sun came over the hill.  My wife mentioned the red color as well.

Check out the early morning visibile image (7:30am):

There is a fairly obvious swath of smoke from Southern British Columbia down into the Central Valley of California…do you see it?

We ran a story about “the worst forest fires ever” in Central Alberta the last few days.  And you can find more information online.  But how did the smoke move south?  Check out the ECMWF 500mb (about 18,000′) map from Tuesday, valid Tuesday night, about 36 hours previous to the smoke appearance overhead:

You can see the cool upper level low over us.  Note how the flow goes north through Wyoming, Montana, Alberta, then part of the flow swings back west into British Columbia, and some swings back south over the West Coast into the upper low again.  Basically you can just follow the lines.  Looking at this map it seems quite likely that some of that smoke was temporarily pulled down into the Pacific Northwest.

Chief Meteorologist Mark Nelsen


A Half Hour With Stephanie Kralevich!

May 19, 2011

Podcast #5 is hot off the press!   In this week’s episode, the guys welcome KPTV Meteorologist Stephanie Kralevich to the show. We get to learn about all sorts of things in the “Stephani-verse”.  Also, Eastern Oregon flooding, a nice warm up on the way, answer kids’ questions, and check out our cities of the week!

http://nwweatherpodcast.wordpress.com/


Three 70 degree days!

May 18, 2011

We haven’t seen that so far this year.  In fact today through Friday we’re doubling our seasonal total of 70 degree days to 6, but it’ll still be well below any other Spring lately.  Notice we’ve passed up (or fallen below) the cold spring of 2008.  That year we had an early hot spell in mid-May.

Most important, the brief warm spell, and reasonable temperatures next week, mean that we’ve broken out of the extremely chilly weather.  But that 7 Day forecast just looks “normal” for May with some above average temps and some below average.  There’s no long spell of warm weather in sight.  Long range models aren’t doing very well beyond the middle of next week either.

For tomorrow and Friday?  Two perfect May days with sunny skies all day tomorrow along with a warmer upper-level airmass means a few notches of warming.  High clouds arrive Friday afternoon, but my forecast assumes any thick cloud cover holds off until after peak heating time.  We do get very weak offshore flow Friday morning, but then it’s back to onshore flow by Friday night.  That’ll give us cooler temps Saturday.  But with no big surge of low clouds (probably) Saturday, we might just see partly cloudy skies that day.

Chief Meteorologist Mark Nelsen


Thunderstorms Developing Over Cascades

May 18, 2011

As expected this afternoon, the strong May sunshine and rising motions over the mountains are producing afternoon showers, and a few thunderstorms too.  They are moving from north to south, so it’s unlikely we’ll see any here over the lowlands close to I-5.  But if you live near or in the foothills, you might hear a rumble or get a shower the next few hours.  And you can see there is a storm at 2:30pm just north of Hood River, plus several getting organized over and just south/southeast of Mt. Hood.


Flooding Eases in Eastern Oregon

May 16, 2011

We mentioned a week ago that flooding was possible late this Spring with the heavy snowpack in the mountains.  Then heavy rain developed Saturday and Sunday in Washington and down into parts of Eastern Oregon.  Roughly a line from about Seattle down to Burns.  Very impressive rainfall amounts…one to two inches in the desert areas of southcentral Washington and northcentral Oregon. 

In our viewing area we still have two rivers under flood warnings:  the Grande Ronde in NE Oregon and Lower John Day in northcentral Oregon.  That river caused over a million dollars damage in Grant County around John Day.  The crest has moved down below the John Day Fossil Beds now with the crest at Service Creek just about now.  It’s the 4th highest level ever recorded at that location, within 2 feet of the big 1964 flood.  That’s going to be some muddy water pouring into the Columbia River!

Farther east, as you see in the graphic above, the Grande Ronde River (at Perry) near La Grande crested earlier today at it’s highest level on record.  That’s impressive, although I haven’t seen any reports of damage or widespread flooding in the Grande Ronde Valley yet.  If you have pics send them to photos@kptv.com

For the rest of this week, pretty quiet weather with just a chance for a shower tomorrow and then probably dry Wednesday-Friday.  Looking at the maps I’d say it’s pretty typical May weather, which of course is nicer than we are used to this season.

Farther ahead…it’s back to cool and wet next week, so I’m holding off on planting any warm weather veggies.

Chief Meteorologist Mark Nelsen


Podcast #4 Posted

May 13, 2011

On this episode, the guys (Mark Nelsen & Brian MacMillan) talk about the devastating flooding along the Mississippi River and the increased chance of flooding here in the Northwest.  Plus, the guys talk about a strange smell in the weather center, introduce a new segment (Cities of the Week), and the guys talk to special guest, Oregon AMS President Bobby Corser about the local chapter and how you can get involved.

http://nwweatherpodcast.wordpress.com/2011/05/13/episode-4-mississippi-nw-flooding-and-oregon-ams-president-bobby-corser/