Unusually Heavy April Rain Leads To River Flooding

7pm Sunday…

Models have done a very good job forecasting a rare heavy rainfall event (for April) across western Oregon and far SW Washington this weekend.  There was a break midday Saturday, but otherwise it’s been a wet weekend.  PDX has seen about 1.30″ rain since early Saturday morning, and over 1/2″ just today

Rain Metro Today Databound

Farther south the rain has been much heavier.  Approaching 3.00″ at this hour!   When the strong westerly flow runs into the Cascades, air is forced to rise and cool, squeezing even more rain out of the airmass.  A few spots have seen over 5″ with another wet 24 hours to go.

Rain Heavy Totals In Cascades

Minor flooding is occurring or will happen in the next 36 hours on several rivers, mainly in the central/southern Willamette Valley and Eastern Oregon.  Moderate flooding is forecast along the Coast Fork Willamette River from Cottage Grove through Creswell and also along the John Day River.  Since less than 50% of the Willamette River basin is regulated through reservoirs (north of Eugene) it IS possible to get flooding without having those reservoirs full.  An example is the river forecast plot (modeled, not a forecast) for Albany.  At this point the river could rise 14 feet in the next 2 days.  That’s a lot of water!

albo3_hg

After one last wave of moisture moves through tonight, we’ll be back to showers & sunbreaks Monday (much brighter!).  I think there’s enough instability that a thunderstorm or two will pop up inland; especially since the atmosphere overhead will be relatively warm.  Highs should make it into the lower 60s west of the Cascades.

The one bright spot in all this rain is the storage of water for the upcoming dry season.  I see Detroit Lake is forecast to be full or nearly full in just a few days, having risen about 30 feet in just the past week!  Another 35 feet of filling is forecast in just the next four days.  THIS is the reason reservoirs are kept low all winter and only slowly allowed to fill in the spring.  Imagine if that lake was full right now…

Chief Meteorologist Mark Nelsen

10 Responses to Unusually Heavy April Rain Leads To River Flooding

  1. Mike says:

    According to records, this is the eighth highest crest recorded on the Willamette in Eugene and the only major crest event to occur after January. Currently, this is the fourth wettest April in Eugene. Still twelve inches below normal for the water year, to give an idea of how dry it has been. The lowland trails below 2000′ are a mess with blowdowns, and I’ve helped clear some: 8 of us with two chain saws got 800′ cleared in about 6 hours. I was out on Pisgah and the Ridgeline three times, and there were 300 year-old trees down. Oaks did well. Cedars got hammered. It’s brutal. Fire, snow, rain, and now waiting for locusts. Lookout Point Res is about 77% full taking in 33K cfs; Detroit is about the same with 26K cfs inflow.

  2. JERAT416 says:

    How is tillamook doing with the flooding?

  3. boydo3 says:

    The coast fork of the Willamette river below Dorena res. is flooding. That’s forcing mandatory evacuations in the Creswell area. Apparently the reservoir is releasing more water that it did back during the ’96 flood.
    Just a couple months ago that area was hit with 2′ of heavy snow causing power outages lasting a week or more. Been a forking bad winter for that area!

  4. Roland Derksen says:

    We avoided most of the rain up here- Other than occasional light showers and some gusty winds, I didn’t see half as much as I was excpecting. Sunday afternoon was really pleasant with mostly sunshine and a maximum of 59F.

  5. W7ENK says:

    “I think there’s enough instability that a thunderstorm or two will pop up inland; especially since the atmosphere overhead will be relatively warm.

    Isn’t that the opposite of what we need for thunderstorms?? Warm at the surface, and much cooler aloft…

  6. Jason Hougak says:

    Looks like a great week of fresh snow at Timberline after today’s rain.

  7. Andy says:

    Amazing how they were talking very low conditions at Detroit lake on the local news last week and how fast conditions change. This will be very good news for recreation on Detroit lake. It just shows how a weather pattern can change conditions so fast. It has been a soaker here in Albany today. Making up for the relatively dry March.

  8. Ken in Wood Village says:

    I went out this afternoon and hit one of those heavy showers on the freeway. I will admit, when those showers hit, it is very heavy and a lot of standing water is one the freeway were people need to slow down. It’s no fun…lol.

    One good thing about the upcoming wet weather, it will help with giving us drinking, snow (for skiing) and for recreational use. To bad we couldn’t get this much moisture during winter and when we had some cold air…lol

  9. JERAT416 says:

    Another full year for Detroit lake, nice!

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