A Week of Wet Weather Ahead

7pm Tuesday…

Hopefully you’ve paid close attention to our forecasts the past few days.  If so, you’ve finished up any project that requires dry weather and are now ready for a week of rain.  No, it’s not going to rain for the next 168 hours non-stop.  Instead, we’ll see a succession of wet Pacific weather systems moving into the Pacific Northwest.

After a very wet September, the faucet has shut off this first half of October.  We’ve seen little/no rain the past 10 days in the Portland metro area

And of course it’s been a very cool 1st half of October; temperatures are running 5 degrees below average at PDX so far… THIS HAS BEEN THE COLDEST 1ST HALF OF OCTOBER IN PORTLAND IN MY LIFETIME!  Only two have started colder, October 1968 and October 1949.  Those were followed by some interesting winters…just throwing that out there.  I highly doubt what happens the first two weeks of October means anything about the upcoming winter.  Notice the last few Octobers have been wetter than average

A cool upper-level trough (dip in the jet stream) is sitting in the Eastern Pacific and moves a bit closer tomorrow

Tonight a weather system is sitting offshore; it’ll move inland Wednesday morning.  That system will be quickly overtaken by a cold front by tomorrow afternoon.  So we get two waves of rain tomorrow.  Behind that cold front, Thursday and Friday will feature the usual cold showers mixed with sunbreaks.  Friday night and Saturday a quick-moving trough spins up a surface low pressure system offshore.  Models are showing quite a slug of rain and gusty southerly wind with this one.

That said, I don’t see any hints that we’re entering a real stormy pattern with multiple areas of deep low pressure tracking along the coastline.  We’re just going to see a parade of wet and breezy  systems moving overhead.  In October, in this pattern, it’s possible to get those waterspouts or weak tornadoes too if the pattern is just right.  We’ll be on the lookout for that.

Now that you’ve finished planting your spring bulbs, garlic, or cover crops, you’re probably wondering how much rain is on the way?  Quite a bit!  The WRF-GFS from UW shows less than 2.50″ in the western valleys ending next Tuesday

ECMWF, GFS, & GEM models all show somewhere between 1.50″ and 3.00″ in the western valleys of Oregon and SW Washington.   Maybe 5-10″ wettest parts of Cascades and Coast Range.  This isn’t enough to cause flooding when spread out over a week, but it’ll help recharge groundwater I suppose

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This is the reason that I’ve been saying to “wrap up all your dry weather projects” by tonight.  It’s going to be quite wet over this upcoming week.

What about more dry days?  Models are suggesting we get some sort of upper-level ridging over the USA West Coast starting a week from now.  All three of the above models show a strong ridge right over us 8-10 days out.  Here’s Friday the 25th

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It’ll be interesting to see if we get a setup we’ve seen twice this autumn; a trough suddenly comes across the ridge, pushing it back to the west and putting us under cold northerly flow.  There are a few hints of that in the 12z ECMWF ensemble chart; some ensemble members take quite a dip in the 2nd week.

To wrap it up…enjoy your inside time this next week.  And enjoy the gentle Pacific Northwest rains splashing on your roof.

Chief Meteorologist Mark Nelsen

Coldest October Start in Almost 50 Years; But Mainly Dry Weekend Ahead

9:00pm Thursday…

These first 10 days of October have been the coldest in Portland since the early 1970s!  Not only did we see a record low temperature of 33 in Portland this morning; but it was the earliest 33 degree reading since 1985!  Take a look at some of the lows around the metro area

You’ll notice that some of us did not have a “first frost”.  Much of East Portland saw enough of an easterly breeze to keep temperatures up around 40 degrees.  A northerly breeze kept some Willamette Valley locations a bit on the “warm” side as well.  Now check out the frigid temps east of the Cascades…amazing for early October.  Single digits at Burns.

That 13 at La Grande is the coldest October temp in 13 years!  And it happened by the 10th of the month.  The last time Redmond was this cold (13) in the first half of October was 50 years ago!  Redmond has been all the way down to zero and even a little below in October, but it has always been in the last few days of the month.  This was a very rare event, and I think it’s VERY interesting that we’ve seen something similar occur twice now this fall.  The same weather setup a month from now would give us a blast of cold arctic air.

What’s ahead?  More of the same tomorrow, except a stronger east wind blowing through the west end of the Columbia River Gorge and east metro area.  Gusts have been in the 40-50 mph rage.  Expect those gusts to bump up to around 50-60 there tomorrow and 25-35 mph in east metro.  Of course we’ll see sunshine all day too.

This Weekend

Definitely a “meh” weekend ahead.  A very weak system dies overhead late Saturday and Sunday.  Lots of clouds but very little rain.  We lose the east wind Saturday.  At best we could see .10″ rainfall total by late Sunday.  Monday looks dry too.

There are strong hints that we’ll see our first soaking rain of October the 2nd half of next week.  See the ECMWF model forecast of 24 hour rainfall.  Each thin horizontal line is one of the 51 ensemble members on the top half.  The bottom half shows the average of all ensemble members.  Good agreement that next Wednesday-Saturday will be wet, maybe not excessively so, but back to normal.  Expect lots more cloud cover too.

All the more reason to enjoy this fantastic sunny/cool October weather.  Have a great weekend!

Chief Meteorologist Mark Nelsen

A typical October week ahead includes lots of sun and a bit of rain

7pm Sunday…

Today was spectacular wasn’t it?  Other than some spots of morning fog, wall-to-wall sunshine for the entire region.  I just caught the sun setting from our Shilo Inns Seaside camera out at the coast

Portland made it above 70 degrees today, the first time we’ve reached “normal” in 11 days!  It was quite a cool end to September and early October too.  I suppose that’s perfectly reasonable after months (years) of above average temps.  The warm temps were courtesy of a warmer atmosphere overhead plus a good amount of morning easterly wind.  Vista House gusted to 42 this morning; a small preview of the upcoming 5 months.

Tomorrow will be dry west of the Cascades from Longview to Eugene, at least up until around 5pm.  At some point after that (depending on location) the chance for showers picks up and your home may even get an hour or two of steady rain between 5-11pm Monday evening.  The rain will be along a strong cold front.  Freezing levels start at 11,000′ tomorrow at 5pm and within 12 hours plummet to 4,000′!  It’s another sharp upper-level trough dropping out of Alaska, headed for Washington and Idaho.  This one appears to be slightly colder than the one a week ago, for our area.  Not as cold for the northern Rockies.  But we’re also 8-10 days deeper into the autumn season; the same airmass overhead should be a bit cooler in the lowlands.   So even with partial clearing Tuesday afternoon plus a mainly sunny Wednesday, it’ll be tough to get out of the 50s.

I don’t see much rain out of this cold front tomorrow evening through Tuesday afternoon.  In fact much of the lowlands will see less than a tenth of an inch.  The flow will be strongly “orographic”, meaning the strong west/northwest wind overhead will squeeze a lot of precipitation out of the clouds in the Cascades and Coast Range.  About 10 times as much!

Much of this precip moves over the Cascades before snow levels drop much.  There should be enough precipitation left after a changeover to snow that Timberline sees 3-7″ snow and 1-2″ at Government Camp.  That’s from 5am Tuesday through evening.  Here’s the WRF-GFS snow forecasting ending Wednesday AM:

Weak upper-level ridging returns Wednesday through at least Friday, possibly through next Sunday.  Models disagree on whether a quick-moving disturbance late Saturday and Sunday gives us showers.  We’ll see if they get their act together the next few days.  This means that for about a week beyond this Tuesday we won’t get much rain.  Total rain for the next 10 days from both GFS & ECMWF show 1/2″ or less in the lowlands west of the Cascades.

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Other than the shot of cold air Tuesday with a bit of mountain snow, nothing all that interesting occurs between now and mid-month.  I don’t see a “stormy Eastern Pacific” pattern setting up through at least the middle of NEXT week.  It’s typically too early for that, but every few years we do get October storms.   There doesn’t appear to be a good pattern for the “October thunderstorms” either.

Summary

• We’re going to be dry far more often than wet the next 10 days, you will have many opportunities to participate in outdoor activities/recreation.
• There’s no sign of significant snow in the Cascades the next 10 days (that’s normal for October)
• Expect lots of sunshine Wednesday-Friday, maybe parts of next weekend too.

By the way, peak color on our leaves tends to occur within the next two weeks, often around the 20th of October.  Of course each tree species is different, but that seems to be the case just about every year.

Chief Meteorologist Mark Nelsen

 

 

 

 

Yes, Those Winter “Almanac Forecasts” Are Still Terrible

9am Wednesday…

It’s that time of year! Early October is here and everyone wants to know what Winter 2019-2020 will be like.  I haven’t put much thought into it yet since we just moved into fall, but a lot of you have probably seen these forecasts from the two different “Almanacs”.

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These come out in September each year.  Obviously their summary graphic doesn’t tell you much, but each almanac has some detailed forecasts for the upcoming winter.

But how accurate are they?  What follows is a large part of a 2013 blog post with a few updated graphics…enjoy!

Jan Null at Golden Gate Weather Services here has checked the almanac’s accuracy several times over the past 15 years, rarely does it do well.

Brian Macmillan and I put together a presentation based on 4 winters of Old Farmer’s Almanac forecasts.  By the way, the Old Farmer’s Almanac looks like this:

It has been in competition with another one for hundreds of years!  That of course would be the Farmers’ Almanac.

They both claim to have a “secret formula” for forecasting weather

 

Back in 2013 we looked at the past 4 winters, but didn’t analyze any sort of “snow/cold” forecasts. Just how the temp and precip forecasts compared to reality.

Here are the results…got it all?

The precipitation forecast was particularly abysmal that winter of 2012-2013.  They expected a dry start and a wetter end.  Instead the opposite occurred!   OFA (Old Farmer’s Almanac) was correct on precipitation anomaly (month-wise) only 50% of the time during the 16 months we analyzed.  As you can see the temperature forecasts below were even worse…OFA is wrong far more often than right.

The conclusion?

It’s terrible.  But the publications do have some stories that I enjoy reading.  Even a recipe for coconut cream pie this year!

Chief Meteorologist Mark Nelsen

Yep, it was cold! Coldest September day in at least 71 years in Portland

8:00pm Sunday…

No, you aren’t crazy; today felt like Thanksgiving Day outside.  Cloudy, rain showers at times, a breezy and chilly east wind blowing out of the Gorge etc…

Officially it appears Portland only hit 52 degrees at the airport.  That’s ties the all-time coldest September day.  It hit 52 on September 26th 1948 as well.  That’s an average high for the 3rd week of November around here.  For the first time a cold east wind was blowing through the Gorge too, gusts up around 35-40 mph.  This is due to a modified arctic airmass that has spilled south out of Canada.  Compare this to the coldest day each of the past few Septembers

We were probably complaining about those lower 60s too…

By the way, there is still an observing site in downtown Portland and the preliminary high there was only 49.  If that holds, that means it may have been the coldest September day in Portland in 145 years!  That said, the downtown temperatures records are a bit sketchier, sometimes on top of very tall buildings and they’ve been moved around quite a bit.   Regardless a high temp around 50 shows how rare it is to see an airmass this cold so early in the season.

Of course it’s been snowing in the mountains since Friday night and a LOT has fallen above 5,000′.  These are estimates, based on pics, ski area reports, and NW Avalanche Center telemetry.  There is

The next 7 days look uneventful…lots of sunshine and a couple cold mornings ahead.  A few outlying areas could see light frost tomorrow or Tuesday morning.  Just in case, bring in anything that shouldn’t freeze tonight.  No, not pipes/hoses etc…just plants.  We’re talking just a bit of frost touching the plants, not a freeze.

Alright, so the #1 question I keep getting is:

DOES EARLY MOUNTAIN SNOW & REGION-WIDE COLD MEAN ANYTHING FOR THIS COMING WINTER?

I think the short answer is NO.  What happens in September or October typically doesn’t have any positive correlation to the following winter that I’m aware of.   I’ve never noticed a weather pattern in these months that repeats through the following winter season.  But just for fun, let’s see.

Because this cold/snow event is so early in the fall season, there aren’t many winters to compare this one too.  For example, late September or very early October snow has only been recorded 4 autumn seasons at Government Camp.  3″-1984, 2″-1972, 2″-1971, and then October 4, 2009 when 3″ fell. Then let’s take 1948 as the other year we only hit 52 in Portland in September.  There were 3 very chilly days in late September that year.  So that gives us 5 years with very early season snow at Government Camp and/or very cold lowland temps.

What happened the following winters?

Winter 1948-49 

23″ snow in Portland that year, mainly January and February.  Extremely cold January 1949.  Nov, Dec, & Feb brought big snow to mountains.  466″ total for winter at Santiam Pass.  A very active winter with lots of lowland snow and extremely cold January

Winter 1971-72

Good snow year in Cascades, in fact 3rd snowiest winter at Government Camp.  But that wasn’t reflected down in Portland, 5″ snow for winter season.  An active winter with big mountain snow but nothing too unusual in lowlands.

Winter 1972-73

Extremely cold arctic blast early-mid December, 6″ snow fell in Portland that month, but little/no snow rest of winter.  A relatively dry winter with no real good Cascade snow until later in December (slow ski season start).  Crazy cold early, then a typical winter otherwise.

Winter 1984-85

Big October snow in Cascades and good ski season start.  Then NO snow with a massive ridge overhead all of January.  I remember that one.  Fog or east wind all month (depending on where you lived).  Then tons of February snow in mountains and even some lowland snow that month.  It was a relatively active winter, but with a weird “stoppage” in January.  8″ total in PDX.

Winter 2009-10

Other than a December freeze, a classic mild El Nino winter.  Only one 3 hour snow event (the December 29, 2009 commute debacle) in Portland.  This was the 2010 Whistler Olympics when it was very mild and they didn’t have enough snow at some of the venues.  Cascades didn’t have a very good snow year.  Only 9″ fell at Hood River all winter in the Gorge.  A mild & “boring” winter much of the time.

I suppose one could argue that in each of these “early cold” years at least SOME snow fell in Portland the following winter.  Maybe that’s because this big ridge offshore and cold trough dropping through Canada tends to repeat in the following months?  That’s a possibility.   As mentioned in previous posts, the current pattern is what gave us the record cold/snowy February this year.

One more thought…we’ve now seen three consecutive winters with 6″ or more snowfall at PDX.  The last time we’ve seen FOUR is way back in the mid 1950s.  We’ll see if it happens this year

Chief Meteorologist Mark Nelsen

 

 

Thunderstorms Pop Up Over Central & East Metro

4:25pm Saturday…

Today has been uneventful in the lowlands…until a line of thunderstorms formed over the southern Washington Cascades and dropped down into east Clark County.  These storms have slid south across the Columbia River and into East Portland, along and east of I-205.  Notice how nice it is Downtown right now, but dark skies and thunder to the right

Radar shows the heaviest action is over NE Portland & Parkrose right now, headed directly toward southeast Portland & Milwaukie.  It’s plenty cold for lots of hail too.

I see Clark Public Utilities has over 20,000 customers out…that’s a lot of lightning-related outages.

Showers have been powered by the very cold air overhead and relatively “warm” air down here at the ground.  A 60 degree high when it’s around freezing up at Timberline is an unstable atmosphere.  By the way, it appears Timberline has picked up 7-8″ of new snow so far.

So keep an eye to the sky the next 2 hours, storms are moving from north to south.  Showers and thunderstorms will die down as sunset approaches.

Chief Meteorologist Mark Nelsen

First Snow In Cascades This Weekend, Plus Cool Showers in Lowlands

7pm Thursday…

Get ready for a real taste of October weather this weekend!  Luckily that does NOT mean a ton of rain.  Let’s just say it’ll feel a bit more “refreshing”.

Summary

• Nothing dramatic is expected (weather-wise) below 4,000′ over the next few days
• Cooler showers arrive Friday afternoon in NW Oregon and SW Washington.  Then expect light showers off/on Saturday.  Sunday might be dry west of the Cascades.  There will be plenty of sunshine between showers the next few days, not gloomy at all.
• Coastal weather looks great!  Not many showers Saturday OR Sunday.
• Temperatures drop well below normal for late September, but frost is unlikely for 90% of us west of the Cascades
• Light snow is possible down to around 4,000′ or maybe a bit below both Saturday and Sunday mornings.  Trace-2″ at Government Camp, but possibly 6-10″ up at Timberline Lodge by Sunday afternoon when things dry out
• Passes should remain clear, although a brief morning dusting or icy spot is possible both Saturday and Sunday mornings.

This weather pattern has been forecast quite well by our weather models.  For the past week they’ve been showing a cold pool of air dropping south through western North America.  Sure enough, this evening a cold “upper-level trough” is right over Juneau, AK

By Friday afternoon it is right over Washington, this IS our “arctic outbreak” pattern in winter.

Then by Saturday afternoon it’s over NE Oregon.  A large upper-level ridge has developed in the eastern Pacific and cold northerly flow extends from the Yukon down to California!

We get a surge of showers ahead of it Friday afternoon and evening, then the majority of shower action Saturday evening and beyond moves south and east of us.  At the same time high pressure at the surface turns our wind flow “offshore” late Saturday.  That gives us an easterly wind Sunday and Monday, drying things out with plenty of clearing.

The WRF-GFS (from UW) cross section over Portland shows the big cool down in the airmass overhead.  Time goes from right to left, starting with this morning and ending on the left side with Sunday afternoon.    I’ve drawn the zero degree line (celsius) in blue.  The 850 horizontal line is around 4,000′.  You see it goes from around 50 degrees (F) at that elevation today to about 32 degrees late tomorrow night.  It remains within 5-10 degrees of that freezing mark through at least Monday morning.

That means it’s reasonable to say anything above that 4,000′ elevation will fall as snow beginning sometime after sunset Friday.  Models are showing plenty of mountain precipitation tomorrow night through Sunday morning.  I see the 18z ECMWF is giving the higher parts of Mt. Hood 6-10″+.  That seems reasonable.  Same thing in the central Cascades of Oregon and at least 2-6″ in higher parts of Eastern Oregon too.

Our RPM model thinks there will be spots over 10″ up around Timberline and higher.  Seems reasonable and goes with the Euro forecast

There are even hints that at least a dusting could fall down to Sisters, Bend, and Redmond by Sunday morning with a cold northerly wind blowing moisture “upslope” into that area.  This is a classic hallmark of an “arctic blast” in that area.  Northerly flow moves uphill from the Columbia River into Central Oregon, clouds form, and snow is squeezed out when the air rises.  We don’t get many situations with flow from that direction but it’ll probably happen over the weekend.

The big snow/cold event will be to our north and east.  Look at all the Winter Storm Watches and Warnings across Washington, Idaho, & Montana.  Some spots in the Rockies could see 3-4 feet of snow!  Very early, even for that area.

So how “cold” will we get in the lowlands west of the Cascades?  For most of us Sunday will probably be the coolest day.  Even with abundant sunshine we’ll barely make it to 60…maybe only upper 50s

If you’re a gardener like me you might be worried about frost.  I think that’s unlikely for most of us west of the Cascades.  Maybe either Monday or Tuesday morning around Tillamook, Vernonia, Banks, Battle Ground.  Just the very coldest outlying areas.  The rest of us remain above 35 degrees.  Your warm weather veggies won’t like it, but it’ll sure give them the hint the “end is near” for this growing season.

What you’ll notice most Saturday through early next week will be the refreshing air and bright sunshine and of course much cooler mornings.

Enjoy your weekend!  Chief Meteorologist Mark Nelsen