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Friday, July 30th, 3:50 P.M. 

Happy Friday!

Clouds and a smoky haze kept today a bit cooler than expected, but it was still very warm with highs making it into the mid 90s around the metro area. We are seeing some showers on the radar, but most of the rain is very light and evaporating before it hits the ground. A chance of thunderstorms or light showers will linger tonight, especially over the Cascades.

Saturday brings more high clouds and a smoky haze above with highs in the low 90s. Expect that smoke to stick around on Sunday, but it should have little to no impact on our air quality.

After a couple more 90 degree days on Monday and Tuesday, things cool off midweek. Thursday and Friday bring our first decent chance of showers in over a month and a half!

  • Posted

11:00pm Thursday…

We’ve had a nice spell of summer weather lately. Today was the 5th warm and dry day in Portland

We’ve only seen rain one day out of the past nine.

I finally hooked up my drip irrigation system in the garden the past two days; it’s pretty clear the summer dry spell has begun and we’re into a stable temperature regime. No long period of cold/wet weather is in sight.

THE BIG PICTURE

  1. There won’t be much rain the next 10 days or so. Showers are likely Sunday and MAYBE a shower the middle of next week, but that’s about it. You should now be watering everything in your yard and garden.
  2. Temperatures cool over the weekend, then bounce back to around normal through next week. There is NO SIGN of a hot spell or heat wave in the next 10+ days. If you want to hit the river or lake with your boat, you won’t find roasting hot temperatures to go with it.

In case you are headed to the northern Oregon or southern Washington coastline this weekend:

Take a look at the morning ECMWF ensemble model forecast of 24 hour rainfall. Each horizontal line on the upper half of the chart represents one “member”. Basically the model is run 50 times at a lower resolution with slightly different initial conditions.

Most ensemble members produce light showers overhead Sunday as an upper-level trough passes. But notice only about half of those give us .10″ or more. Not exactly a soaker! Then there are hints of a shower possibly Tuesday or Wednesday but that’s about it; mainly dry the next 15 days. The GFS model is similar

The cool weather coming for Saturday and Sunday is due to a cool upper-level trough dropping south out of Canada. If it was January we’d be talking about low elevation snow and modified arctic air moving south. The center of that low moves over Eastern Oregon and Idaho and that’s where the much heavier rain will fall. That low lingers through Monday and Tuesday over there. A very unusual late June soaker is on the way for northeast Oregon (which has been plenty wet this year). ECMWF thinks 1-2″ by Tuesday afternoon!

The Canadian model (GEM) brings an inch of rain all the down into the Ochoco mountains by this time.

This general pattern (without much rain) continues the rest of next week and likely beyond the 4th of July. Notice the below average heights across the West next week

Then just a bit below average heights for the 2nd week of July. This is from last night’s run of the ECMWF, but the GFS and GEM models are similar.

That’s it for this evening…I’ll be back at work Sunday.

  • Posted

8pm Wednesday 

It’s been a very slow couple of weeks weather-wise; hard to find inspirational blog post material.

Putting that fork in winter was definitely the right thing to do two weeks back.  We have slipped back into a weather pattern similar to December with weather weather systems occasionally sliding into the Pacific Northwest.  Precipitation has been well below average across almost the entire western USA the past two weeks.  Portland has only seen .27″ in those two weeks!

hrap-all-nw-14day_percent_anom-3323200

February ended with near normal temps for us…nothing unusual there.  We’ve had a ridge of high pressure over us or just to our west the past couple of days.  Some nice weather has been the result!  By tomorrow that ridge is moving east and you can see a cold upper-level trough approaching.  This is the 500mb GEM (Canadian) ensemble average.  That’s the average of 21 difference ensemble members.

m500za_f024_bg_NA

One would think we have a cold/showery few days ahead (beyond tomorrow) with lots of mountain snow.  But all models show that trough splitting/stretching as it moves over the Western USA.  By Sunday a cold trough is well west of California and what’s left is moving over the Pacific Northwest.

gem_sundayam

That splitting means we get a weak cold front tomorrow night, then a few light showers Friday and Saturday.  Even though snow levels plummet down below 2,000′ by Saturday, there just isn’t much moisture to go around.  Expect only a few inches of snow in the Cascades and higher parts of the Coast range.  Yes, more slow weather.  Although on the bright side we MIGHT see some convection (brief heavy showers) Saturday…maybe.

That cold trough shifts east early next week, likely leaving us with mainly dry weather Sunday through Wednesday.  The same GEM ensembles for Wednesday the 11th

gem_wednesday11th

This gives us some pleasant, but not overly warm early/mid March weather.  All models then are in pretty good agreement another cold troughing “episode” shows up in about 10 days…the following weekend.  Saturday the 14th:

gem_saturday14th

Notice with ridging now, plus the first half of next week, that rainfall will remain below normal through the next 7-9 days.  The ensemble average rainfall from the ECMWF shows a half inch or so for the next week, and less than 2″ in the next two weeks.  That’s a bit drier than average, although clearly looking wetter that 2nd week.  The big story here is that I don’t see a long wet period ahead.

ecmwf-ensemble-KUAO-indiv_qpf-3323200

Temperatures will remain near (or even a bit below) average for early-mid March.  There’s no sign of a real intrusion of cold air in the ensemble averages.  But I don’t see any models going for extra-warm upper-level ridging either.  That means no 65-75 degree weather; which can happen this time of year.

To summarize

  1. Other than showers tomorrow night through Saturday evening, there isn’t much rain in the next 7 days.
  2. Near normal temps today/tomorrow turn cooler Friday through Sunday, then warm again early-middle of next week
  3. No sign of widespread frost west of the Cascades until at least Sunday night
  4. The increasing sun angle means even a 55-58 degree partly cloudy day feels warm for a few hours midday through afternoon!
  5. There’s no sign of a stormy March weather pattern ahead

By the way, are still hoping for snow?  I’m sayin’ there’s a chance!

Remember late March 2012?  A stalled front dropped steady/heavy precipitation right over the Willamette Valley.  4-6″ fell in the central/south Willamette Valley and even a few inches fell in the hilly areas around the metro area.  But measurable snow at the lowest elevations west of the Cascades in March IS rare.  Last year was exceptionally cold the first 10 days of the month.  That was mainly due to extensive snow cover left to our north and east from the record cold February.

Portland Snow Last Few Times In March2

Portland Snow Last Few Times In March2

More likely is a temperature getting close to 70 at some point this month!

March Warmest Temp

Chief Meteorologist Mark Nelsen

  • 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

Well that was fun; if you were out driving in the metro area around midnight it was a brief snowstorm with the east wind blowing/drifting the snow on the freeways.  That was the “snowiest” I had seen since last February.  The rest of the night was relatively quiet and accumulations have “behaved” according to the forecast so far.  That means a bunch of snow south of Portland metro again, but not much here.  It was a good night to be in Salem, Albany, & Eugene if you want snow.  The TRACE TO 1″ forecast in the metro area was good.

It appears little/no snow fell in Vancouver so far

I-5_29th_pid767

and less than 1″ in the rest of the metro area up to this point.  The big difference this time is the frozen roads; a dry snow due to that cold east wind.  OFFICIALLY 0.1″ FELL AT THE PORTLAND NWS OFFICE (SO FAR).  That makes this the 4th measurable snowfall of the season, all in the past few weeks of course.

Farther south, several inches have fallen in the Willamette Valley.  I see an official 2″ measurement in Albany, then 5″ in Eugene followed by freezing rain (ice glazing) during the night.  Yuck.

WHAT HAPPENS THE REST OF TODAY?

  • Snow showers should taper off, but they will continue off/on the rest of the day.  In the next hour or two anyone could still see some additional accumulation.  But after 10am it sure won’t be sticking to roads as temps gradually warm
  • Expect a few sunbreaks later this afternoon with a cold high around 37 degrees.  That annoying & cold east wind will continue to back off as well
  • EVENING COMMUTE WILL BE CLEAR

TONIGHT & TOMORROW

Light showers will continue to rotate inland through the area with breaks between.  The cold airmass will gradually modify the next two days.  That means IF temperatures drop below freezing tonight and IF showers show up between 11pm and 9am, anyone could get a skiff of snow on the ground again.  But don’t count on another snow or delay-day for the kids Thursday.

 

Chief Meteorologist Mark Nelsen