May Turns Wet; Metro Downpours Tonight

9pm Monday…

Suddenly it feels like a normal May weather pattern is back, like an old friend.  All of us have seen at least a bit of rain the past few days, but some of us have seen tremendous gully-washers.  This is overdue, not just because we’ve been dry the past 9 months, but we’ve had quite a run of dry May weather.  We’ve seen 5 consecutive years with drier than average May rainfallRain May Recently

We’ve seen measurable rain in Portland each of the past 8 days.   Yesterday afternoon/evening thunderstorms moved over the Salem area and Colton/Estacada/Sandy.  There were some 1″ totals around Colton at that time.  Then a weak “deformation zone” sat over the area this morning and midday.  That dumped up to 1/2″ rain in some spots around the Portland metro area.  Finally, a batch of showers moved south through Clark county and central/eastern Multnomah county this evening.  It appears that the area from Troutdale to Happy Valley was nailed with the heaviest rain totals.    This was the radar view around 7:45pm

KPTV 2017 Default Earth

Daily totals at 9pm look like this; these are from official airport locations

Rain Metro Today Databound

But these small/intense showers have dumped even more in a few spots.

Rain Totals Metro Area

The good news is that these showers are making up for what has been a very dry spring.  The bad news is that we have a lot of cloudy/wet weather ahead.  The cool upper-level trough over the Pacific Northwest right now heads east tomorrow


But by Thursday/Friday another cool upper-level low is right over the region once again


In-between we get strong onshore flow both tomorrow and Wednesday.  This means almost solid cloud cover west of the Cascades, although not many showers.  Once we add in the showers Thursday and Friday from the new low, rain totals look something like this for the next four days

7Day Interactive 4

This will be a strongly “orographic” rain setup the rest of the week.  Areas just downwind from the Coast and Cascade ranges will be relatively dry (Hillsboro, McMinnville, The Dalles, Maupin).  But in the constant westerly flow the “upslope” areas will be wet…wet…wet.  If you live in the Cascade foothills or western Gorge, I hardly see any dry weather through Friday.  Yes, that sunshine in March, April and early May was nice, but it’s make up time now.

What about Memorial Day Weekend?  A weak ridge will be over us Saturday/Sunday then get “squished down” a bit toward Monday/Tuesday.  That means Saturday looks dry, but showers possible Sunday/Monday.  But that’s way out there in time.  We’ll nail down that weekend forecast as we get closer.

Enjoy the showers!


14 Responses to May Turns Wet; Metro Downpours Tonight

  1. Jason Hougak says:

    Each day the temps have been dropping in the extended forecast. Now there’s not one above 80 next week up here for the foothills.

    • Ken in Wood Village says:

      What I’m interested in is what could happen next weekend. If everything sets up right, we could see some very intense thunderstorms. It’s something to keep an eye on.

  2. Joshua Lake Oswego says:

    90 degree possibility for next week is disappearing fast. No complaints here.

  3. OMK says:

    Dry when it’s supposed to be wet, wet when it’s supposed to be dry, I’m glad I’m not a gamblin’ man.

  4. Tanis Leach says:

    Looking at the models in the mid-clown range (May 29th) and finding that it might be getting pretty warm. 10-90% range at 850 mb above Salem is between 57 and 74 degrees F (14-23C). Especially if we are on the upper end of that envelope, a 90 degree day is not out of the question.

    Note: Just looking at temps, not looking at convective possibilities.

    • Mike says:

      Has anyone looked at the full disk animated water vapor? Anyone think there is anything significant or unusual about the extremely well defined ‘heat low’ formed off the coast of southern Ca. and Mexico? I’ve never seen anything like it.

  5. Gene says:

    Many of you who have been pining for wet weather have finally gotten your wish — it’s been very rainy the past couple of weeks, especially this week. And we certainly need it after such a dry April. But I have to say I’m looking forward to the sunny, warm, dry weather that looks to be coming next week.

  6. paulbeugene says:

    Last weekend of May looks like a perfect setup for thunderstorms in the area. Of course that is 9-10 days away.

    • Ken in Wood Village says:

      I saw that too yesterday. With the warm to hot temps, that could give those storms a good chance to become strong. That’s if they show up.

      One a side note, some of the showers today are very intense. We had hail around 10am. Maybe that could give us a chance of thunderstorms later today 🙂

  7. runrain says:

    Lots of sunbreaks and shower activity. Sure looks like an opportunity for thunderstorms today. Also interesting to note: weather apps are indicating possible 90 deg weather at the end of next week 😮

  8. Joshua Lake Oswego says:

    When it’s all said and done, May will be yet another below-average precipitation month. Way warmer too.

  9. Ken in Wood Village says:

    The models are hinting at a possible dry and warm spell close to the end of the runs. What I do see on the Euro model is the possibility of a decent flow for thunderstorms around the 29th or 30th. It’s something to watch for in the coming days.

  10. Ken in Wood Village says:

    I believe that 1.27 inches in the Troutdale area. We had a lot of heavy rain today. Wondering how wet May will be compared to April!!!


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