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  • Posted

7pm Sunday...

Today was sure a gloomy day!  It seems like it rained at least a third of the day, but we only ended up with a few hundredths of an inch in the metro area.  That’s a classic warm-front setup

Rain Metro Today Databound

The system changed snow to rain in the Cascades.  After a big dumping above 5,000′ Thursday night through Saturday, now it’ll be mainly rain through Tuesday up there.

Snow Mt Hood Totals

A warm but “flat” upper-level ridge is sitting over the NE Pacific Ocean.

Satellite Surface

That gives us lots of clouds, but not much rain.  Tomorrow another warm front sweeps mainly into Washington.  So we’ll see lots of clouds again but little rain.  On Tuesday a little “wiggle” moves over the top of the ridging and down over us.  At that point we should see at least a few hours of rain.  Then the ridge pops up again a bit stronger and closer to us.  Here’s Thursday, look at those 588 dm heights over Oregon!  ecmwf-namer-z500_anom-1940000

If it was early September we’d see 90s out of this pattern.  Instead, at the end of October, highs somewhere between 65-70 are more likely under dry offshore flow.   This means Wednesday and Thursday feature the best and warmest weather this week.

Then by this weekend the ridge pops up a bit farther west, allowing a cold upper-level trough to drop south out of Canada and into the western USA.  That looks chilly!

ecmwf-namer-z500_anom-2177600

These maps are the ECMWF ensemble forecasts, but other models are similar.  Notice the real cold air doesn’t drop right over us, but a bit farther east.  The Rockies and Intermountain region get nailed with cold snow showers next weekend.  This should give us a round of dry/chilly northerly/easterly wind Saturday through sometime early NEXT week.    The result for our area will be a sharp drop in temperatures between Thursday and Saturday/Sunday.  Overnight lows will go from near 50 Wednesday to around freezing once again next weekend.  But not a whole lot of rain.  Check out the change in airmass on the ECMWF 850mb ensemble chart, quite a drop isn’t it?  Just 5 days ago there was not hint this would occur.  That ECMWF wanted to put the ridge right over the top of us, but now wants to dump come cold air south over the West.  This is the 3rd time this fall season we’ve seen this happen.  Very interesting…

tseries_850t_000-360_Portland

Check out the ensemble runs from ECMWF, GFS, & GEM models.  All show 1″ or less rainfall in the Willamette Valley through these next two work weeks.  That’s through the first day or so of November.

It’s probably a bit premature to mention this, but why not…  It’s interesting that this is the type of pattern we can get during a weak El Nino winter.  Split flow can be common in those winters too.  We are on the warm side of ENSO neutral right now and it seems we’ll be right on the edge of weak El Nino conditions this year.  Just tossing that out there for fun.

Summary

  • I don’t see much soaking rain for these last 10 days of October, but it will rain here and there.
  • This work week features mild temps, Wednesday & Thursday should be the warmest!
  • Next weekend may feature a nice chill; perfect for the weekend leading to Halloween.
  • There’s absolutely no sign of a stormy weather pattern ahead.  I’m referring to our usual stormy setup with one area of low pressure after another giving us waves of strong wind and rain.
  • Snow in the Cascades will gradually melt over the upcoming week.  A few more inches could fall later Friday or Saturday.

Chief Meteorologist Mark Nelsen

  • Posted

6pm Monday...

Spring 2019 is in the record books now that May has ended.   Meteorologists consider spring to be March through May in the Northern Hemisphere.  How was it?

In a sentence… WARMER & DRIER THAN AVERAGE IN THE PORTLAND METRO AREA

You may remember the first 10 days of March were very chilly due to leftover snow cover over much of the Pacific Northwest.  But then April and May were significantly warmer than average.  May 2019 and 2018 rank as #4 and #2 warmest on record!   The result = Spring 2019 was #15 warmest out of 80 springs.

This COULD be one effect of a changing global circulation here in the Pacific Northwest (higher upper-level heights); but could be partly cyclical as well.  While speaking with local meteorologists at a Portland Water Bureau meeting last Thursday this subject came up.   It seems we are seeing more up/down movement of the jet stream and fewer stormy periods with strong westerly flow.  This would account for the extra cold/snowy February weather recently with persistent ridging offshore.  Or the shift to ridging directly overhead at times (warm and dry).  This is all anecdotal of course. One local meteorologist feels this has occurred in the past, mentioning similar setups in the 1980s.  Interesting eh?  Regardless, 4 of the top 10 warmest springs have occurred recently; in 2014, 2015, 2016, & 2018.

What about rain?  Of course it’s easy to remember the unusually dry three weeks in late April and early May.  But March was quite dry, and even with a little rain later in May it still ended up below average.

Most interesting is that this is NOT a trend in our area.  Looking back 50+ years the trend is slightly wetter, not drier.

I think these are the three most memorable weather events this spring:

  1. Record cold temps (but sunshine!) in early March.  A rare early March snow-cover east of the Cascades along with easterly wind allowed cold/dry Canadian air farther south than normal.  PDX hit 24 in early March!
  2. Rare (or unprecedented?) April flooding in Willamette Basin.  First time I’ve seen flooding this late in the season.  Did this expand the “flood season” in our area?  Time will tell.
  3. 2nd consecutive year with a long dry spell mid spring.  Around 25 days with little/no rain in our area from 3rd week of April to mid-May.

Looking ahead…

We have seen a series of warm June months as well.  We haven’t seen a “chilly” June since 2014 and looking ahead I wouldn’t be surprised if this happens again in 2019.  The warm May pattern continues into early June on models, but with a brief downturn the mid-late part of this week.  A cool upper-level trough drops into the Pacific Northwest just in time for Friday/Saturday Rose Festival events.  See the ECMWF ensemble 500 millibar heights for tomorrow AM

Then by Friday a cold trough is overhead.  Expect some June snow down to at least Timberline Lodge, could even get a dusting down to Government Camp and those Cascade lakes!

Behind this trough the strongest/warmest (hottest?) ridging of the season develops early NEXT week.  It’s possible we’ll see 90 degrees or higher around Monday-Wednesday next week if this pattern shows up

Rain?  Not a whole lot, but we’ll wet things down a bit Thursday-Saturday.  Possibly as little as .10″ in the driest parts of western valleys to 1″+ in Cascades

And the timing is VERY clear on the ECMWF ensembles.  This is 24 hour rainfall from each of the 51 ensemble members, then the average (in blue) down below.

They all agree on rain Friday/Saturday, then totally dry for several days following.  Obviously late this week isn’t a good time to plan a deck-staining, mowing the lawn, or painting a shed outside.