Christmas Weekend Outlook: Who Gets The Snow?

December 22, 2017

9am Friday

Now that the threat for freezing rain has ended since the lowest elevations are near/above freezing, let’s talk snow.

BIG PICTURE:  This weekend we are in a “battleground” between 1) a cold arctic airmass over the Rockies and east of the Cascades and 2) Pacific moisture coming in from the west and southwest.  Models always struggle with what goes on in this battleground or major clash between airmasses even though they are much better than 20+ years ago.   This is always a tough forecast; but I’ve been through LOTS of these events!  This is my 27th winter forecasting in the Portland area…wow.  This setup is the #1 way we get significant (or sometimes major) ice/snow events in the metro area.  Sure it’s the SETUP, but everything has to be just right (or wrong if you don’t like winter) to get a snow or ice storm here.  And it’s even more rare to get this setup right at Christmas!

HIGHLIGHTS

  • It’s unlikely anything frozen falls the next few days on the Oregon Coast…a bit too mild this time around.
  • We only expect some snowflakes mixed in with the showers TODAY in the lowlands.  No sticking snow in the lowest elevations in the Portland/Vancouver metro area.
  • Hills at/above 1,500′ could see an inch or two, but that’s way up in northern Clark county or other foothills of Cascades/Coast Range.
  • Saturday will be a dry or mainly dry day as cold/dry east wind arrives, bringing chilly air out of the Gorge.  Highs up around 40 as we’ve been forecasting.
  • Sunday is the #1 question for nowI see the possibility of either brief freezing rain early in the day and/or a real snowfall in at least parts of the metro area by afternoon/evening.  Yes, as of now a White Christmas is a possibility in the Portland metro area.
  • Sunday south of the metro area (Woodburn to Eugene) and on the coast should be uneventful.  Likely too “warm” for either freezing rain or snow.
  • Christmas Day:  All models agree we dry out Christmas, it’ll just be a matter of whether we have leftover snow/ice on roads that day or we don’t get any to start with.

GORGE HIGHLIGHTS

  • The central/eastern Gorge turns white tonight with 1-4″ fresh snowfall as cooler air filters in from the east.  That’s east of Bonneville Dam; west of there I think it’ll be pretty quiet, although a dusting is possible by sunrise IF enough cold air shows up.
  • Saturday will be a dry day.  Cold east wind gets going, eventually reaching full-on winter strength by Sunday AM…brrr!  Peak gusts 55-70 mph Sunday…ouch.
  • Sunday turns snowy by midday, expect difficult I-84 travel by Sunday afternoon through Christmas morning.  Another 2-5″ is likely
  • Enjoy your White Christmas!  3-8″ should be on the ground Christmas morning.

 

Today’s forecast is relatively straightforward:  a boundary between a “mild” Pacific airmass and modified cold arctic air is sitting right over the middle of Washington state.  We are on the “mild” side of that through 6-9pm tonight.   The lowest elevations still have some cool air trapped from yesterday’s inversion/fog, but they will gradually “mix out” today and temperatures will rise into the 35-40 degree range.  We aren’t getting a significant onshore flow, but it’s enough to raise the sticking snow level to above 1,500′ by midday/afternoon.

Tonight the showers continue but sticking snow levels remain above 1,000′.  Temperatures remain in the mid 30s in the metro area (above freezing).  Easterly wind arrives in the Gorge and that means a switch to all snow out there.  You can see the forecast snow totals now through Saturday PM.  A nice 8-12″ on the way for Mt. Hood too!  That may help the ski areas open a few more lifts:

 

By Sunday morning we have cold modified arctic air pouring out of the Gorge on strong east wind into the metro area.  At the same time a juicy low pressure area and approaching frontal system is offshore, heading toward the Pacific Northwest.  You can see the cold surface high pressure eastside and the approaching system on the 7am Sunday map:

 

The forecast is a mess at this point (Sunday) because the GFS model (and Canadian GEM) continue to insist that surface low heads NORTH of us and into Western Washington. Note the liquid rain forecast for 10pm Christmas Eve:

That brings mild southerly flow over us, ending the frozen precip threat everywhere except in the Gorge by Christmas Eve evening.  As of now the GFS suggests there will be no interesting snow/ice episode this weekend except MAYBE patchy freezing rain early Sunday AM before we wake up.  But it would only take a slightly southern move of this system to bring snow into the metro area on Sunday.

On the other hand the NAM and ECMWF models bring the surface low either right over us or to the SOUTH of us Sunday and into Christmas Morning.  That’s quite a bit different!  If this is the case, we could easily get a real snow storm Christmas Eve and into Christmas Morning.  These models imply a rare White Christmas for the metro area and only the 3rd in Portland’s history!  Note the total snowfall product from the ECMWF for 4am Christmas Morning.  You can ignore the heavier stuff in the NW metro area, that’s partly due to terrain.  But you see a general snowfall across much of the central/north metro area due to cold air pouring out of the Gorge getting overrun by Pacific moisture; our classic snow/ice storm setup.

A good 75% of the time eventually models seems to settle on the more northern approach (and warmer) solution for Sunday and Christmas morning.  But my inner child wants a snowstorm Christmas Eve and 2-4″ snow sitting on the ground Christmas morning.

By Saturday morning we should have a much better idea what’s going to happen Sunday.  I’m home through the weekend, not in some tropical location, so I’ll keep on top of it through Christmas.

Chief Meteorologist Mark Nelsen


No Freezing Rain Today

December 22, 2017

7am Friday…

freezing rain

Good morning!  There’s some good news in the forecast.  Temperatures are not cold enough to support freezing rain in the metro area this morning; you don’t need to worry about that west of the Cascades.  We didn’t really think that was a big concern, as my coworkers have been saying on-air the past 24 hours and I didn’t even mention it on a blog post a few days ago for that reason.

web_temperature_ORWA

ODOT road temperature sensors are all well above freezing as well.

That said, at this moment we have a cold enough airmass overhead to support incoming showers being of the “white” variety.  Shower action is starting to pick up on radar and much of that will fall as a rain/snow mix in the lowlands, or all snow today for the hills.  I’m looking at that closely and will post within the next two hours.  Lots to talk about between now and Christmas Day!

Chief Meteorologist Mark Nelsen


Cascade Snowstorm & What’s Up With Freezing Rain On 7 Day Forecast?

December 19, 2017

6:30pm Tuesday

Today’s cold front sure delivered the advertised goods!  Heavy rain & a gusty southerly wind from daybreak through early afternoon.  The cold front is moving through the Blue Mountains of NE Oregon right now.  This is the leading edge of a much cooler airmass.  No more 50s until further notice!  It appears 6-8″ snow has fallen in the Cascades and we expect more tonight and Wednesday AM:

Sticking snow could fall as low as 1,500′ to 2,000′ tonight.

We now enter a cooler weather pattern that eventually turns very chilly this weekend.  The highlights:

A modified “arctic” or polar front drops south out of Canada on Friday.  Moisture appears to be very limited and snow levels will be above the valley floor anyway so I’m ignoring that.  Then a massive area of high pressure sets up over the Western USA, check out the 1050 millibar surface high sitting over the northern Rockies

That gives us a widespread and strong/cold east wind over the weekend.  Not just in the Gorge but ALL of us in the metro area will feel the cold wind as the air sloshes right over the top of the Cascades too.  This setup could give us 30-45 mph gusts just about anywhere both Saturday and Sunday.  On a side note, the anemometer has already been replaced at Vista House in the Gorge, the Oregon State Parks people replaced it Monday.  You can find it here:  http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=pqr&sid=D6193

So then we get to Christmas Eve where problems COULD show up.  This morning’s run of the ECMWF & GEM both show a weakening system punching right through the upper-level ridge along the coastline.  It’s the southern part of the jet stream attemping to sneak in beneath the ridge…note the ECMWF rain/snow/cloud forecast for 7pm Christmas Eve:

Green means the snow level is well above the surface.  Probably around 4,000′ or so in this case.  There will be  cold air pouring through the Gorge at that time (the one part of the forecast with high confidence).  Assuming moisture shows up (a big assumption 5 days ahead of time), this would be a setup for freezing rain in the metro area/west Gorge and snow farther into the Gorge.  The ECMWF shows this with the ice accumulation product

The GFS has the system much farther west at the same time Christmas Eve, slower to break through the ridge:

Thus the uncertainty in the forecast!  It could be anything from a dry Christmas to an ice storm Christmas Eve & Day in the metro area.  Regardless it’ll be the coldest/windiest Christmas we’ve seen in awhile.

I’ll be on Christmas vacation (theoretically) tomorrow through Christmas Day.  I’ll be around the area so if some weather happens I’ll be hopping online of course.  Stay tuned!

Chief Meteorologist Mark Nelsen


One Rainy Day, Then a Cold Christmas Weekend

December 17, 2017

9pm Sunday

Today was a mild one and the next two days will be mild too.  High temps will make it up around 50; a typical high is 45 now that we are in our coldest month of the year.

This has been an incredibly dry December so far, less than 1/2″ of rain has fallen in the first 17 days of the month

Driest Decembers Ever Graph 2017

THAT is the one consistent story through the next 7-10 days.  Our dry December is going to continue.   Let’s go over the…

HIGHLIGHTS

  • There is only one rainy/windy weather system in sight for the next 7-10 days.  That’s Tuesday.  Pretty weird to see this happen twice in December.
  • Expect mild temperatures tomorrow and Tuesday, then back around normal Wednesday & Thursday
  • Another blast of east wind arrives Saturday and continues for quite a few days.  That means it’ll be a windy Christmas for the usual east wind locations.  At first ALL of us in the metro area will get the wind Saturday/Sunday.
  • That east wind will be at least somewhat colder than the last event, but could be a bitter cold “arctic blast”.  Models aren’t agreeing how much cold air makes it into the Pacific Northwest
  • Regardless, it’s likely the coldest weather so far this season is on the way for Christmas weekend and into sometime next week.
  • SOME models produce light showers Friday & Friday evening as the first colder air arrives.  This CAN be a setup for mixed rain/snow showers in the lowlands…or we just stay dry.  That’s TBD.  I haven’t even bothered to change to snow tires on my car yet; obviously I’m not freaking out so no need for you to either.
  • Since the airmass coming in is colder than last time, it’s time to wrap your pipes & cover your faucets.

Right now we are in a mild westerly flow since the big upper-level ridge broke down late last week.  But that big ridge is going to rise again.  Check out the Saturday 500mb forecast from this morning’s GFS model…a full-latitude ridge from offshore California into Alaska & Yukon.

Jet Stream Forecast 2017

ALL models show that big ridge this weekend and beyond.  It’s just that some have the pool of cold air closer to us than others; this evening’s GEM model is especially cold. Probably highs around 20 degrees in Portland; that’s at one extreme.  Others just shove a little cool air over us with highs maybe 40 or so over the weekend.  They ALL push a massive blast of polar air into the west-central USA.  I’d hate to be in Denver, Salt Lake, Billings, or Minneapolis for Christmas…brrr!    Check out the ECMWF model meteogram for Denver.  Near 60 Wednesday and then a HIGH around 10 by Saturday:

KDEN_2017121712_ecmwf_min_max_10

So to summarize:  Don’t get too excited about snow for now.  In general a very dry weather pattern is going to persist for another week or more and it’s going to turn colder.

Looking farther out, of course once the cold air gets in here there’s always the threat for Pacific moisture to return and ride over the chilly air.  That’s how we get snow/ice storms (as we all know from last year).  There are hints of that on the ECMWF.  21 of 51 ensemble members from the morning run show at least some sort of sticking snow somewhere in the 15 day period after the 26th.  I’ll be keeping an eye on that of course.

The great news is that the first dumping of snow since Thanksgiving is coming to the ski resorts Tuesday afternoon through Wednesday midday:

RPM Snow Accumulation

Those totals might be a little high, but I expect a solid 10-15″ to freshen things up.  A foot should fall at Government Camp.  This should help salvage a terrible start to the Christmas Break.

Chief Meteorologist Mark Nelsen


No Freezing Rain This Morning

December 15, 2017

8:30am Friday

I’m not working today, but figured I should check in and let you know that we’re in the clear now.  NO FREEZING RAIN THIS FRIDAY AM, or at least nothing that will freeze on roads. There have been a few reports of a windshield or deck getting a brief icing, but that’s it.  We knew today was going to be a close call: a clear night with temps below freezing followed by rain arriving at sunrise.

web_metrotemps (1)

The good news is that clouds arrived a few hours ago and temperatures have risen to or above freezing. ALL METRO ROAD SENSORS SHOW PAVEMENT TEMPS WELL ABOVE FREEZING. East wind has also ended so no new “supply” of chilly air is on the way. Enjoy the return to cool & showery weather without the wind!

Speaking of wind…it’s gone!  As forecast the easterly gradient is down to almost nothing this morning after 11 days of strong east wind.  Relax and enjoy the quiet if you live in/near the western Gorge.  But don’t worry, our old friend (East Wind) will likely be back for Christmas Weekend.

Chief Meteorologist Mark Nelsen

 


Evening Earthquake, East Wind, & The Next 10 Days

December 13, 2017

10pm Wednesday

Did you feel the quake last night?  The largest earthquake in our area in the past 2 years hit just a mile or so east of Scotts Mills.  That’s near Silverton.

A 4.0 sure doesn’t generally cause damage, except we did get one photo of a Christmas ornament fallen off a tree, and a tree fell off a bookshelf.  For some of us it was the first quake we’ve felt since that Spring Break Quake in March 1993.  This quake was centered within a mile of that one!  Check out all the 4.0 or larger quakes (over land) in our area since 1990

Let’s talk weather…

The easterly wind has spread back across more of the metro area this evening and gusts within the Gorge increased a bit too after a lull yesterday afternoon/evening.  Check out the past 9 days…ridiculous and the longest/windiest period we’ve seen since January 2009.

The very good news is that the airmass coming in with Friday’s cold front is MUCH colder overhead which will kill the inversion and kill the high pressure in Eastern OR/WA.  In fact by Friday afternoon I expect a breezy WEST wind through the other end of the Gorge.  Yes, Friday afternoon it should be calm at Vista House for the first time in 11 days!

The upper-level ridge over us will weaken a bit over the weekend, then strengthen again, but a bit farther west as we go through the next 7-10 days.  You can see the change from tonight’s 500mb map…

to 10 days out…Saturday of Christmas Weekend

During this time one or two cool systems will drop in over us from the north or northwest.  First will be Tuesday/Wednesday and possibly a 2nd late next week.   Neither will be all that wet, but bring showers and some mountain snow.  This setup will likely turn us a bit cooler as we head toward/into Christmas Weekend.  But models are in disagreement on exact placement of the ridge.  If it’s close to us we’ll just have sunshine and easterly wind again.  If it sets up farther offshore we’ll be significantly colder (arctic air) and that brings up the possibility of snow.  I’m leaning toward the first option for now.  It’s still a mainly dry pattern as I pointed out on my 12 Day Trend graphic this evening:

This is bad for ski resorts; we need new snow, and no significant snow is in sight for the next 6 days.  Christmas Break skiing/snowboarding will be limited, at least to start.  Hopefully that midweek system will produce at least a foot of snow.  We’ll see.

Chief Meteorologist Mark Nelsen


What Happened to “The Coho Wind”?

December 12, 2017

We’re going through what will likely end up as the strongest east wind event of the cold season…so let’s take a look back.  Do you remember the one winter when that wind had a name?

It was 20 years ago this month…

In 1997 the Oregon Chapter of the American Meteorological Society undertook an ambitious attempt to give the seasonal wind a name.  Why not? The dry east wind is called a “Santa Ana” in southern California.  Reno has the “Washoe Zephyr”.  Northern California gets a “Diablo” wind.  The Great Plains have a “Chinook” (although originally assigned to our warming southwest wind here).  But all through written history in our area the easterly winter wind has always just been referred to as “The East Wind”.  Local Native American tribes just called it an east wind in their distinct language.  And of course they were likely smarter than us, not camping near the west end of the Gorge in the winter.

A group of us figured it deserved a special name and ran a contest through the Autumn of 1997 to find a new name.  It was a huge collaborative endeavor with all local radio and TV stations getting involved.  Dozens of local and Pacific Northwest newspapers ran the contest or at least ran stories about it.  It was even mentioned by The Weather Channel.  You couldn’t avoid hearing about it at the time.

The volume of entries was far greater than expected; nearly 7,000! Pat & Sara Timm opened/sorted compiled the entries into a database.  Some were duplicates and the final 54 page listing contained 2,424 unique names.  We’re talking some really good names, but some real strange one too.  “Big Bad Momma”, “A Real Nipple Popper”, and “Devastating Doozy” come to mind as I peruse the book of names I still have in my file cabinet.

  • coho-alaska-salmon

Finally a group of maybe 10 AMS members got together and voted on the top 3, then a final one.  COHO was picked for a couple of reasons:  1) it’s the opposite of a CHINOOK wind (easterly vs. westerly), and 2) the COHO is known as a fierce and tough fish.  There may be other reasons but that was 20 years, 2 jobs, and 2 kids back in time for me.

For that first winter all of us regularly used the name and all seemed okay, but then the name fell out of use somewhat quickly.  As I recall by the following winter (1998-1999) the name was barely used.  I know I didn’t use it the 2nd or 3rd winter.  Why?  I found the people most affected by the wind seemed to hate it most and the people not affected much at all thought it was just fine.  As I recall (again, 20 years ago), I thought if people hate it and want to keep the current “name”, why should I be pushing it on them?  The Portland NWS and all other media stopped using the name as well.  It more  or less went into the history books.  Pat Timm used the name regularly in his weather column (The Columbian) for many years.  I just asked him about it yesterday, he said “I think it was a great name for a number of reasons…Just not enough support I think by the media to promote it. I think with social media now days and the Weather Channel naming almost every storm etc it would make it.”  Pat also says he would be interested in reigniting the name with a new generation of weather watchers.

In the past 24 hours I got an earful on a local (Corbett) FB group when I asked about the naming 20 years ago:  Jeanette- I never accepted Coho, it just was too polished or almost phony sounding. The wind is cold, harsh, and destructive and the only words that seem right are “The East Wind” .  Patrick– Those of us who live in the heart of it know it as The East Wind, a proper noun; not a common noun with a directional modifier.  Jeanie- They tried to force that name on us when we were so proud to live in “Corbett, Corbett home of the East Wind” (a song taught to all local school kids) . The music teacher had made a song about it which the grade school kids had performed many times. There were even T shirts printed with the East Wind blowing.  Catherine- One of the main reasons was that it was folks who didn’t live here or had ever experienced the East Wind who were trying to change the name!!  I think the best was from long-time resident Nev Scott.  She told me 15 years ago “It has always been The East Wind and always will be.  That’s it”  She wasn’t the type of person I wanted to argue with either!

Looking back 20 years, I think the problem may be that you can’t just force a new name onto an existing weather pattern with a known name.  Yes, it does have a name for those most affected; The East Wind.  Those other regional wind names likely came on gradually over many years as settlers move into an area.  Just my best guess on that.

What do you think?  Leave it as it is or try again in the age of social media?

Chief Meteorologist Mark Nelsen