Showery End To November; Dry December Start

November 29, 2020

9pm Sunday…

The long Thanksgiving weekend is coming to a close this evening. We’ve had some pretty good weather! A dry Thanksgiving Day, then lots of sunshine in the metro area Friday. A weak system gave us a drippy day Saturday, with about 0.10″ total in Portland, then bright sunshine again today. Of course it’s been a different story south of town. Two of those days the fog & low clouds just wouldn’t go away. In fact today the southern edge of the metro area could be seen sitting in fog/clouds from our Skyline camera

Next spring when I look back for a winter recap, it’s obvious November will go down as a boring month. Sure, we had a couple of windstorms at the coastline, but no gusts above 37 mph in Portland. Temperatures ran near normal across most of Oregon and Washington

Rainfall ends up near normal as well…

…although slightly below in Portland

What’s Ahead?

A weak system moves into the region tonight, bringing a quick shot of valley rain and mountain snow, you can see the dip in the upper-level flow over us tomorrow

By Wednesday a strong upper-level ridge will have developed overhead

And it sticks around through the end of the week. 8 days from now the ridge is still there, although weakening quite a bit

It looks most likely that we won’t see significant rain again until about the middle of NEXT week; 9-10 days away. So it’s clear December will start quite dry. Notice lots of ensemble members from this morning’s ECMWF model show rain around next Tuesday/Wednesday.

Models have been consistently advertising that change about 10 days out for several days now. Will the upper-level ridge back to the west and allow some cold air to come down from the north, or do we go back into some sort of wet westerly flow? Too soon to know, but I’ll be watching that closely

In the meantime, the strong ridging means a classic “gap wind” event is on the way for the Columbia River Gorge. High pressure pops up east of the Cascades behind tomorrow’s system. For the first time this season a cold surface high develops late Tuesday and into Wednesday over the Columbia Basin of Eastern WA/OR. The WRF-GFS has been showing about 10 millibars worth of pressure gradient through the Gorge by sunrise Wednesday. That’s the only one sea-level gap through the Cascades and all the wind is headed there.

At the same time, temperatures at 850mb overhead reach around +10 or so, that will be quite an inversion! It’s a classic setup for extra-strong east wind in the western end of the Gorge plus out into the east Portland/Vancouver metro area. Check out the thin layer of easterlies in the WRF sounding from Wednesday afternoon to Saturday.

When the east wind layer is “squished” relatively low to the ground by the strong inversion, two things happen:

1) We don’t get a widespread wind event like Labor Day, but most wind remains confined to central/east metro and the West Hills.

2) The wind is even stronger IN THOSE AREAS as opposed to when it’s widespread over the entire metro area. Same volume of air is forced into a smaller “channel” = stronger wind.

Expect wind gusts 35-50 mph east metro and 60-80 mph in the west end of the Gorge Wednesday-Friday. Yes, this setup should produce 100 mph gusts on the steps of Vista House. If not Wednesday, then Thursday or Friday. The wind sensor there is offline, but the new part should arrive this week, hopefully it’ll start working again.

TO SUMMARIZE

  • There’s no sign of a stormy weather pattern and/or lowland snow/ice in the next 10 days. That’s through December 9th
  • Other than light rain tonight and Monday morning, we should be mainly or all dry for the next week
  • Expect lots of sunshine most areas west of the Cascades Tuesday afternoon through the rest of the week
  • Prepare for a very strong “winter-strength” east wind episode for at least 4 days starting Tuesday afternoon in east metro and western Columbia River Gorge

That’s it for this evening, I’ll be back on TV at 10pm. Enjoy the rain later tonight and bright sunbreaks following the showers tomorrow afternoon.


Thanksgiving Week Outlook; Partly Wet

November 22, 2020

8pm Sunday…

We had our first taste of the cold season “fog inversion” this weekend. That means cool air remained in the valleys while the atmosphere overhead warmed. Yesterday Portland only made it up to 41 degrees…quite a taste of a typical winter day around here

Which brings up a good point…from a meteorological point of view we’ve pretty much entered “winter” west of the Cascades. I suppose it seems like a ridiculous thing to say, with a week left to go in November? Nope, once we hit mid/late November, we’ve entered the busy three months of the year in our area. “Winter” tends to come early and melt away a bit quicker than in colder continental climates. No, I don’t mean just snowfall. I’m referring to what we tend to see in winter here

It’s EXTREMELY rare to see a real arctic blast outside of this window. And if we’re going to have an “all-day” snow event in the lowlands, the type where roads stay frozen, it happens during this time. Remember the past few years? When we’ve seen snow from mid-February onward, the effects on lowland roadways are minimal mid-late day. That’s because of increasing sun angle. If we get significant flooding this year, most likely it’ll be within the next three months.

What’s Ahead?

I took a few extra days off this past week; still have a few leftovers from our summer furlough days. When I came back in to the station today I noticed three specific items while perusing all the models/maps:

  1. I don’t see a stormy weather pattern in the next 10 days
  2. After a wet Tuesday/Wednesday, we’re headed into a drier weather pattern through at least the first few days of December
  3. There’s no sign of lowland snow/ice or an arctic blast in the next two weeks. That means most likely we won’t be seeing an early freeze this year (November or early December).

Basically the weather looks a bit on the slow side over the next 1-2 weeks. In the short term I see a couple weak systems moving inland tonight, then a stronger cold front and chilly airmass Tuesday/Wednesday. We should see another 1/2″ rain early this week out of these systems.

Beyond Wednesday, upper-level ridging wants to be the dominant weather feature over the western USA for awhile. Take a look at 500mb height map from Canadian ensembles for this Friday

and then 10 days from now…Wednesday the 2nd

I think the ridging may be overdone on this model. Other models show above average heights but not so extreme.

Weak (and wet) systems will probably still be coming through the ridge during this time; I don’t think it’ll be one of those “completely dry for 10 days” setups. But this eliminates the chance for any significant cold spell and/or snow in the lowlands for the next 10+ days.

Ski Area Weather

We’ve got a fantastic early season snowpack on the ground in the Cascades above about 3,500′. These numbers a bit deceiving since the average snowpack is very low this time of year; anything significant is way above the average. But you get the idea…

Both Timberline and Mt. Hood Meadows have about a 3 foot (or more) settled snow pack on the ground now. Even Government Camp has somewhere between 4-10″. In other years those first two ski areas would already be open, but of course COVID is throwing things off. Regardless, the slopes are just about ready! Timberline is opening this Wednesday the 25th and Meadows is opening for the season Monday the 30th! I don’t see anything that would stop either from happening. Another foot or so should fall above Government Camp by Thanksgiving morning. At least according to the ECMWF model

The only possible rainy weather at the ski resorts would be Friday night or early Saturday as a weak system moves through the warm upper-ridge. So we should remain in good shape for an early start to the ski season through at least early next week. We’ll see what happens beyond.

Enjoy the showers early this week; I’m focused on the dry weather later in the week. After Thanksgiving Day it’s the Christmas season…good weather for hanging some lights Friday-Sunday!

Chief Meteorologist Mark Nelsen


Cascade Snow Season Starts Early!

November 13, 2020

7pm Friday…

Last night was fun…strong wind arrived right on schedule. The first wind storm of the season produced widespread 50-65 mph gusts along the coastline. Of course the usual high wind spots recorded much higher speeds.

In the inland areas peak speeds were a bit lighter than models were forecasting, although close enough to our 35-50 mph forecast. PDX hit 37 mph. Around 7,000 PGE customers lost power in the northern Willamette Valley.

We picked up a LOT of rain, you probably noticed!

If there were any doubts this would be a dry November…that’s disappearing quickly.

We have November snowstorm #2 in progress in the Cascades. The live view from our Upper Bowl camera at Mt. Hood Skibowl shows at least 20″ on the ground up there. Last year we had trouble getting that much all the way through late December!

About a foot and a half of new snow has fallen above 5,000′!

Both Timberline and Meadows now have a base around 30″…ON NOVEMBER 13TH. This is way ahead of last year when ski areas had less snow on the ground the third week of December! Excellent news.

So what’s ahead? Lots more rain in the valleys, and snow in the mountains. Another system moves inland tomorrow afternoon/evening; snow sticks above about the 3,500′ elevation. That snow level does go as high as 4,500′ early Sunday, then drops by midday. The result should be another 8-12″ in the Cascades by Sunday evening when things dry out. I do expect a “warm” system in the mountains Monday and early Tuesday, but then we’re back to cooler systems the 2nd half of next week.

To summarize:

  1. Cascade ski resorts appear to be in excellent shape for early openings this year. In the past few years ski areas have opened with limited operations with only 20″ on the ground.
  2. There WILL be a 2 day spell of rain/warm conditions, but not really a pineapple express. I expect the snowpack to consolidate a bit and we’ll lose quite a few inches. But more snow fill follow the 2nd half of next week.
  3. There’s no sign of a warm spell or series of warm storms that would melt most of the snowpack. Good news!

This is quite a change from the past two years. Check out snow depth at the bottom of Pucci Lift. This is for November 19th (next Thursday). Last year there was nothing on the ground at this point…big improvement.

By the way, we’ll see at least another inch of rain in the lowlands this weekend. Keep in mind this is precipitation; much of that falls in the form of snow in the Cascades.

Expect a soaker the 2nd half of tomorrow, plus gusty southerly wind. Then it’s back to a showers/sunbreaks mix Sunday…like what we’ve seen today.

Enjoy your weekend!


A Wet & Windy Night Ahead

November 12, 2020

9:15pm Thursday…

A very quick update this evening, I’m busy on-air until 11:30pm, you can find me there!

Everything is still on track for a gusty south wind tonight west of the Cascades as I posted about last night. Notice graphics are about the same

Several of today’s models continued to show strong wind gusts spreading onto the coastline. I think the 00z HRRR surface pattern shows what’s going on. As a strong cold front moves inland, a “wave” or open low pressure area tracks northeast, making landfall around Astoria in the early morning hours. You can see the small circle in the isobars (equal pressure lines) over the mouth of the Columbia River around 3am.

This tightens the southerly pressure gradient nicely during the wee hours of the morning.

Others were a bit weaker (GFS), but now they have come into line with the stronger solutions. The ECMWF and IBM’s GRAF model have been most aggressive, sending gusts up to 70 mph along the coastline and 50 mph in the valleys

Once the front passes and that wave moves north we go to a much more reasonable southwesterly breeze.

We’ll see how it goes…again, not a big windstorm, but many of you will wake up to rain pelting your south-facing windows. We recorded a podcast discussing the overnight setup early this evening as well. You can find it already dropped into your Apple Podcasts

Or listen at this link: https://www.kptv.com/podcasts/weather/

We’ll see how it goes!

Chief Meteorologist Mark Nelsen


Lots of Rain & Wind Ahead Plus Another Winter Storm In Cascades

November 11, 2020

8pm Wednesday…

I’ve got a quick update this evening on our incoming weather the next two days, I’ll be on-air on FOX12 Plus 8-10pm and then on FOX12 10-11:30pm

HIGHLIGHTS FOR PORTLAND/VANCOUVER METRO AREA

  1. All quiet tonight and tomorrow morning, then light picks up tomorrow afternoon. Expect breezy southerly wind west of the Cascades. Maybe 25-35 mph gusts in the evening. A typical mid-November day.
  2. Tomorrow night and Friday morning rain turns heavy at times. We should pick up at least an inch of rain. Southerly wind gusts could reach 35-45 mph during this time. Not a big storm, but enough to drop a few limbs onto powerlines = a few power outages.
  3. Lots of showers & sun mix Friday afternoon through Saturday. Typical breezy southerly wind at 10-20 mph

A High Wind Watch is up for the Oregon and southern Washington coastline. In the Coast Range too. This is tomorrow night and early Friday.

Remember a WATCH means a weather event MIGHT be on the way, a WARNING says that event is imminent.

There are no watches/warnings/advisories for now in the interior valleys where about 85% of KPTV’s viewers live. At this point I’m thinking 35-45 mph gusts tomorrow night and early Friday is the best forecast.

A strong westerly jet stream is punching across the northern Pacific ocean right now. By tomorrow evening it’ll be at our doorstep. Check out the 220 mph windspeed!

All models agree that an area of low pressure (or two) will “spin up” underneath the “exit region” of this jet stream. That’s the northern edge where the wind slows down. But each model has it’s own idea where/when that happens and how deep the low pressure will be. Of course a deeper low is associated with stronger wind. Movement of the low is important too. Over the past three days SOME models were showing a very deep low pressure center traveling west to east just north of Portland, or up across Puget Sound. That could possibly give us a windstorm. But the screaming message this evening is that almost no models are giving us a significant wind storm. Take a look at the 30 ensemble member low pressure locations for 10am Friday. You get the idea. Some stronger, some weaker, some have the low going in SOUTH of Portland. In that case we wouldn’t get any sort of strong wind.

The latest operational ECMWF model gives us gusts 35-50 mph late tomorrow night, then Friday it’s back to showers/sunbreaks/breezy

In general what I’m seeing is not the setup for a windstorm, but lots of rain and some wind in spots. Maybe just a warmup for the storm season ahead.

The Cascades picked up around a foot of snow in the first storm of the season. Now we expect another 5-10″ at pass elevations and 20-30″ up above 5,000′. That’s tomorrow afternoon through Saturday afternoon. Maybe some pre-Thanksgiving skiing? We’ll see

That’s it for now, time for dinner. See you on TV!

Chief Meteorologist Mark Nelsen


Cool November Weather Is Here To Stay; Valley Rain & Mountain Snow

November 8, 2020

10pm Sunday…

Well, that’s been an exciting 5 days since the election started eh? Since I love numbers and politics I’ve watched everything closely. Now that things are settling down I figure we should talk about weather. And what a change we’ve seen!

For the first time this season we’ve seen sticking snow down below 3,000′. I took a run today, midday, with a temp in the upper 30s. It felt like December under a gray sky (east side of metro). Portland saw it’s coldest day of the fall, just 47 degrees

You know winter is close when at 8pm we’ve already got parts of the metro area below freezing.

Expect widespread mid-upper 20s tonight for another hard freeze. Whatever survived frosts a couple weeks ago probably won’t make it through tonight. We’ve seen a few inches of snow at Government Camp, maybe 4-5″ higher up at the ski resorts. Here’s the 8:45pm view from the top of Upper Bowl at SkiBowl

The rainy season has arrived; that’s the screaming message on maps/models this evening. In fact if you’re looking for a 3 day period of dry weather? Extremely unlikely…

Summary of What’s Ahead

  1. Expect steady rain or showers just about every day for at least the next week to 10 days west of the Cascades. IF we somehow squeeze in a mostly dry day, consider that a bonus! Somewhere between 2-4″ rain could fall in the next 10 days…
  2. Temperatures will remain between 40-50 degrees most of the next week too. A mild Pacific airmass will be in control of our weather most of that time.
  3. I don’t see a setup for low elevation snow OR ice/snow in the Gorge for at least a week, probably much longer. There’s no sign of cold Canadian air surging south in the next 7-10 days either
  4. Snowpack will be building in the Cascades over the next week. IF we don’t get a set of warmer systems NEXT week, I could see ski areas trying to open up at least a few runs!

Details

As expected we’ve seen a surge of cool/dry air drop south into the Pacific Northwest, thus the cold temps tonight. But starting tomorrow afternoon our weather will be dominated by a succession of cool-ish weather systems coming in off the Pacific. For at least the next week, none of these are forecast to be “warm” or related to atmospheric rivers. For example check out the ECMWF 850mb ensemble chart. Each thin line represents one of the 51 ensemble members. That’s for the next two weeks. It’s temperature (C) at around 4,000′. So the “zero” line means freezing around Government Camp.

Notice there is general agreement that there won’t be any extra-warm ridging or cold spells. In fact there’s only one or two of those members showing anything really “cold”, at the end of the run. Otherwise it’s generally just a little below average (green line) for this time of year; excellent for mountain snowpack.

Then check out precipitation from the GFS ensembles. Tomorrow through a couple of days before Thanksgiving (2 weeks out). Wet!

It shows six hourly rain totals for each of the 31 ensemble members. Each horizontal line (upper part of chart) is one member. You don’t see many gaps do you? This says it’ll be hard to find much dry weather the next two weeks. Other models are similar. The reason? A typical November Pacific jet stream aimed at the West Coast. Six days out, this coming Saturday

Models are telling us somewhere between 2-4″ rain could fall in the next 10 days west of the Cascades. Very wet, but…it IS November. And precipitation in Cascades maybe around 8-12″. Get ready for an overdue soaking, it’s time.

Snow levels linger between 3-5,000′ over the next week.

Snow at 4,000′ will come and go, but it’ll be ALL snow up above 5,000′. The ECMWF model shown here would imply 2-3 feet may fall at the top of Skibowl, and the upper parts of Mt. Hood Meadows and Timberline ski areas too. Ignore the Gorge, that’s a contouring issue with the terrain.

This COULD be enough to jump-start the ski season a bit early! What we don’t want to see this early is a warm/wet storm following next week to melt the snow. That’s not unusual in November. Last year there was some very basic skiing for Thanksgiving, but then things lagged until we got to mid-January. But this upcoming pattern looks great!

Again, there’s absolutely no sign of lower elevation snow. This is a mild westerly-flow setup, just a bit cooler than normal. Take a look at the stable temperature regime from the ECMWF, actually that’s weirdly stable.

Maybe this will be a 2007-2008 type La Nina winter? That’s when it hardly snowed in Portland, but multiple systems came down in WNW flow pummeling the Cascades AND the foothills with feet of snow. We will see. It’s still very early…kind of like looking at those first few hours of election results and making an assumption of how things were going to play out.

So remember, you’ve got a mainly dry day tomorrow to get outdoor projects done (I have a few), and then it’s on to wet, wet, wet…

Chief Meteorologist Mark Nelsen


Warm November Start; But Cooler Weather Ahead

November 4, 2020

9:30pm Wednesday…

What a warm day! Temperatures clipped the 70 degree mark in the metro area today; on November 4th. Portland was just one degree shy of the 69 degree record, and Troutdale broke it at 69 degrees. Even warmer temps to our south and east. It was the warmest day in the past three weeks in Portland

I see The Dalles, Meacham, and Yakima all broke record highs for the date. Of course it was just two days ago that Redmond broke their all-time November high temperature record of 76…reaching 80 degrees!

In fact it’s a bit strange that our temperatures have gone uphill in the time of year they typically go down. Remember that 48 degree sunny day with a gusty east wind? That was the coldest so far this season

I’ve been negligent in posting the past week or so. Slow weather, working on new weather graphics, and election drama has distracted me. But as we move deeper into November the weather action usually picks up. Although this year things are looking quite benign through mid-month.

Right now a very warm upper-level ridge is fading away, weak systems are pushing into the PACNW

A Pacific frontal system is getting organized offshore as cold air drops into the Gulf of Alaska under a developing upper-level low. Look at the change by Friday! That cold low has dropped down the central California coastline.

This gives us the “big rain event” of the week. Now through Friday afternoon, the GRAF model is showing up to an inch of rain in western valleys of OR/SW WA. Thursday is definitely an “indoor” day.

A secondary upper trough drops straight south out of Canada Saturday; it helps carve out a huge trough over the western USA. Las Vegas was in the mid 80s today, but only 50s by Sunday…

There won’t be much rain with that secondary system so this weekend will be mainly dry; most likely some afternoon showers popping up Saturday though. In the Portland area, temperatures cool off from 60s today to upper 40s Saturday/Sunday. Back to normal and then below. The pattern remains cooler than normal through the middle of next week, here comes another upper-level trough dropping down along the BC coastline Tuesday. This typically isn’t an especially wet setup, but cool

I expect at least a bit of snow in the Cascades the next few days as temps cool, but not a huge dump around Mt. Hood since snow levels will be relatively high through most of the precipitation.

At least it’ll be a start, but I sure don’t see skiing by November 10th.

So enjoy the rain tomorrow and refreshing/chilly weather over the weekend. Those leaves should be turning crunchy again by later Sunday/Monday as we dry out.

Don’t forget to subscribe to our FOX12 WEATHER podcast. Lots of weather geek talk every week or so. We’re on episode #9 and another should drop next week. Subscribe on Apple Podcasts or just go directly to the weather page on www.kptv.com

Chief Meteorologist Mark Nelsen