Snowflakes on Your Weather App? Here’s What I’m Seeing For Thanksgiving Week

November 20, 2019

6pm Wednesday…

Am I getting old, or does it seem like a warm sunshine and temps in the 70s was just a few weeks ago?  Time is flying…

Forget about that warm stuff; it appears that winter is going to move in quickly over the next two weeks in the Pacific Northwest.

First, those weather apps.  This is what Brian MacMillan’s iPhone app showed today

iphone snow JPG

I use the FOX12 Oregon app which does not show lowland snow.  Keep in mind these apps are automated with no human intervention; although that isn’t as shocking as it was just five years ago.  I bet within 10 years most weather forecasting will be automated.  We’re not there yet but computer modeling is getting better.

Weather App Snow Forecasts

So what is going on next week?  I think SOMETHING is up with respect to cold and/or lowland frozen precipitation in the next 10+ days.  But it’s far too early to pin down any sort of details.  Our seven day forecast is snow-free right now, but it’s that time of year to start paying close attention to the forecast.

First, we have beautiful weather for three more days.  East wind keeps us mainly cloud/fog free through Saturday.  A warm upper-level ridge of high pressure keeps storms away and temperatures mild.

ECM_FRI22

By Sunday the flow overhead turns westerly and cools a bit.  Nothing too exciting, but we’ll likely get some light rain out of the first system.

ecm_sun24

But look at the change by next Wednesday!

ecm_wed27

A cold upper-level trough drops in over the western USA.  It’s still there the Saturday after Thanksgiving; the following is from the 18z GFS model.  A warm upper-level ridge into southern Alaska and a cold trough over the Pacific Northwest.  This is a very chilly weather pattern for us; historically a good setup for lowland snow west of the Cascades.

 

gfs_sat30

Look at the drop in temps the next 10+ days from the ECMWF model.  Forget highs near 60 like today.  Get used to 40s, which is typical mid-winter stuff for us.

ecmwf-operational-KPDX-daily_tmin_tmax_ecmwf-4251200

We have to see a specific placement of surface low pressure, wind direction, and precipitation; but snow CAN make it to sea-level with this setup.  Models have been all over the place the past few days on details.  On Sunday night the ECMWF model produced a snowstorm with 5-15″ snow in the metro area next Wednesday.  Last night the ECMWF brought a deep low into Central Oregon, dumping 2-6″ snow in the south Willamette Valley.  Today’s ECMWF (for example) doesn’t bring any snow west of the Cascades (other than flurries) because it’s much drier.  The latest 18z GFS brings snow into some of the lowlands on Black Friday and Saturday.    You get the idea…

Because of these wild run-to-run gyrations we use “ensemble forecasting”.  The ECMWF model is also run 51 times at a lower resolution.  A graphic showing each of those 51 members (horizontal lines) below shows about 6 of those 51 members produces notable snow (over 1″) in the metro area (Aurora) through Thanksgiving Weekend

ecmwf-ensemble-KUAO-indiv_snow_24-4251200

 

The GFS has 21 ensemble members, each going out two weeks.  Not much snow there, only 2 of those produce notable snow in the metro area through Thanksgiving Weekend

gfs-ensemble-all-KPDX-indiv_snow_24-4251200

To wrap it up…pay close attention to the forecast as we head toward Thanksgiving and beyond.  It’ll be turning colder.

One thing that’s also obvious, we sure aren’t heading into any sort of real wet/stormy pattern.   Just colder, and a little wetter.

I’m taking an extra day off this “weekend”, so probably no posts until Sunday.

Chief Meteorologist Mark Nelsen


Mild & Dry November; A Big Change Possible For Thanksgiving Week

November 18, 2019

7pm Monday…

What a November it has been, plenty of sunshine and warm temperatures at times.  The entire western USA has been VERY dry since late October; most areas west of the Rockies are under 50% of average.

anomimage

Of course temperatures have been mild/warm too.

conus_mtd_t2max_anom_2019

The only part of the Pacific Northwest a bit cooler than average is the Columbia Basin.  This November is tracking similar to one year ago.

Mark November Rain

Although last year the mild/dryish conditions continued through the end of January!  We’ll hope that’s not the case again this year.

A weak weather system is moving through tonight, we’ll probably end up with a quarter inch of rain or so.  A few inches snow fall up at the ski resorts too.  But this is a one-shot deal.  It’s back to dry tomorrow midday all the way through Saturday.  Expect a gusty east wind to return Wednesday PM and Thursday as well, but nothing crazy strong.

To summarize:  Not much happening weather-wise through at least Saturday.

Why so dry & mild?  Again we have persistent upper-level ridging in the atmosphere.  It’s either shredding storms apart as they move toward the West Coast, or shunting them to the north.  The result is mild temps and not much rain.  Here’s Thursday’s forecast from the ECMWF, showing the warm colors (above normal heights) again over our area.

ecm_thurs

Same thing Saturday, although the ridging is flattening quite a bit.  Something appears to be changing

ecm_sat

The upper-level ridging wants to push westward out over the eastern Pacific.  By Monday a chilly upper-level trough has dropped over us and into the central USA.  We should see a bit more mountain snow either Sunday or Monday.  Each model and model run is a bit different since we’re talking 7 days out.

ecm_mon_25th

Looking ahead to Day #9 (Thanksgiving Day!), all three main models show there has been a change to cool upper-level troughing over the Pacific Northwest.  That’s quite a change!  The ECMWF ensembles (images below are all ensemble averages, not a single model run) seem to be a bit hesitant making a big change.  Notice it wants to hang onto the ridging a bit more.  Not sure what to think about that.

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What does this mean?

  1. There may be a significant change in our weather beginning Sunday.  We may actually go back to normal!
  2. That would mean snow levels down below the passes, significant mountain snow, and valley rain at times
  3. Thanksgiving skiing is a possibility in this setup.  As I mentioned, each model run is different.  Check out snow forecast graphics from the Canadian, Euro, & American models.  They show total snow now through Thanksgiving Day.  All show at least a foot of snow, some much more.  Ignore the little bit of snow over the metro area.  That’s a graphical contouring issue.

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I did have a brief panic last night when the ECMWF showed a snowstorm over the Portland Metro area the day before Thanksgiving.  That’s another reason to stick to “ensemble forecasting”.  It was one of only a handful of the 51 members bringing snow showers into the lowlands.  It is gone in today’s run.  But it IS time to think about winter storms/snow/ice/wind/flooding. These three months from mid-November to mid-February are “action time” west of the Cascades.

Winter Months Explainer 2017

Here’s your Mt. Hood ski area forecast.  Expect some snow tomorrow, it’ll melt, but then a few more inches around Sunday/Monday.

7 Day Forecast GOVT CAMP

Chief Meteorologist Mark Nelsen


A Mild November Plus Ski Season Update

November 12, 2019

6pm Tuesday…

Quite a change out there today.  Yesterday we were 62 and mainly sunny, today we stayed around 50 degrees and remained under a thick gray blanket of cloud cover.

As expected, this first half of November is turning out to be mild and uneventful.  November is typically the start of the rainy season in the Pacific Northwest.  But in the lowlands we’ve seen much below normal rainfall.  So far, less than 1/2″ rain in P-Town and there won’t be much more by Friday the 15th.

Mark November Rain

Lowland Highlights

  • There’s no sign of a typical stormy November weather pattern for at least the next 10 days
  • Weak weather systems will bring rain at times Friday, next Monday, and again late next week
  • There’s no sign of cold/freezing weather like we saw back in late October
  • Weather shouldn’t impact your life too much for the next 7-10 days

Why so quiet and mild?  An area of higher-than-normal upper-level heights (also known as “ridging”) wants to remain near/over the West Coast.  This diverts storms to the north or weakens them as they move inland.  This was also a persistent feature for much of last winter (until February).

Satellite SurfaceNow take a look at the 500 millibar height map from the ECMWF model.  This is actually an average from 51 “ensemble” members.  The solid lines are contours, showing the height of that pressure surface.  Wind at this level (~18,000′) follows the lines.  So in the case of the map below you’re seeing westerly flow into far NW USA and western Canada.  The colors represent the anomaly.  Red = higher than average heights, blues/pinks = below average.  That’s quite a bit of ridging over the western USA!  This map is for Sunday.  So here we are at November 17th and the pattern continues.

ECM_SUN17

It appears the ridge will “back up” a little bit for NEXT week.  Check out Tuesday as a chilly upper-level trough has dropped into the PACNW.

ECM_TUE19

But for the rest of next week things remain the same, both on the ECMWF and GFS models.  Here’s Friday the 22nd, showing a bit of a “Rex Block”.  That’s an upper-level high north of an upper-level low.  It can sometimes be a stable pattern.  Definitely a drier than normal pattern for us.

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Up to this point I’m feeling pretty confident about the general trend…drier and milder than average for the next 10 days.  But right after, models diverge.  5 days later we’ve reached the two-week point of the operational forecast models.  The GEM and ECMWF both continuing ridging for this day before Thanksgiving (ECMWF below)

ECM_WED_27

But the GFS goes cool and wet, quite a pattern change…we’ll see.

GFS_WED27

So again, no big changes for at least the next 10 days.

What does this mean for the ski/snow season?

After a cold end to September and the coldest October in decades, some of us were getting excited.  Hard to believe there was two feet of snow on the ground at Timberline a couple weeks ago.  It’s all gone after many days in the 40s and even some 50s.  The view this morning before it rained…

Timelapse Timberline Lodge

So we’re starting from zero again.  No early start to the ski season this year.  Little or no snow on the ground through Sunday the 17th

Mark Ski Areas Not Open

We should see a little snow around Tuesday the 19th with the previously mentioned upper-level trough.  Then it’s mainly dry or mild/warm through the following weekend.  We use this graphic on our 6pm show during the cool season on FOX12.  Sometimes on other shows as well.

7 Day Forecast GOVT CAMP

 

Mark Ski Areas Not Open2

Cascade Ski/Snow Summary

  • No sign of a cold/snowy weather pattern
  • No skiing this weekend
  • Ski area openings unlikely the weekend of 23rd/24th, that’s the weekend before Thanksgiving
  • We can’t see beyond that point; models diverge on whether to maintain the mild/dryish pattern or go wetter/cooler
  • No reason to panic, this is normal!  But if it looks like this a month from now it’s a different story.

Enjoy the dry weather Wednesday & Thursday!

Chief Meteorologist Mark Nelsen


November Starts Dry & Mild

November 2, 2019

10pm Saturday…

I’m working this Saturday evening, but the weather is S-L-O-W.

October was a cold one across the Pacific Northwest.  But today with weak offshore flow we made it to 63 in Portland…a fantastic nice day!  I took a run mid-afternoon through Hoyt Arboretum and it was spectacular.  Warm sunshine, cool shade, NO MUD, and crunchy dead leaves on the ground.  We rarely see that combo in early November.

By the way, tomorrow we begin the “dark season” in the evenings.  For the next 2.5 months, sunsets in the metro area will be before 5pm.

Sunset Earlier

For at least the first week of this month and maybe well beyond we’ll see persistent upper-level high pressure (ridging) along the west coast of North America.  This is a “warm West, cold East” setup across the USA.

Satellite Surface

Take a look at the 500 millibar map for Thursday…the ridge is still there.  Red colors show above-average upper level heights

ecm_thur

Then NEXT Saturday.  Ridge weakens a little and allows a bit of rain to make it into the Pacific Northwest.

gfs_sat

But jump ahead ANOTHER week and the ridge is just as strong.  The GFS, ECMWF, and GEM models all show the same general setup all the way through mid-month

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If this is the case, the first half of November will be much drier than average and very mild too.

One BIG caveat.  More than once in the past 6 weeks we’ve seen models not clue in to a change in the ridge position westward.  Basically the ridge suddenly moves westward and a cold trough digs down through the Rockies.  That’s what just gave us record cold across portions of Eastern Oregon and Washington.   I’ll be keeping an eye out for that.

To summarize:

  1. Early November looks mainly dry.  Next real chance for rain is around Friday or Saturday the 9th/10th.  But even that may just be for a day or two
  2. Temperatures remain mild.  No sign of another freeze through at least the next week
  3. There’s no sign of a start to the traditional Pacific Northwest storm season.  Often November can be a stormy month

 

I’ll be on vacation during this upcoming week, back at work on the 11th.  If something really big shows up on the models I’ll likely “break silence” and make a posting.   Otherwise I’m disappearing for awhile.

Chief Meteorologist Mark Nelsen