Snow & Freezing Rain Tonight For Some of Us

4:30pm Saturday…

It’s a cold afternoon in Portland; temperatures are right around 40 degrees and the chilly east wind is back.  That wind will be very strong the next 12 hours, blasting in a supply of cold eastern Oregon air while milder Pacific air with moisture rides over the top.  This IS the classic setup for a snow or ice storm in the Portland Metro area.  But in tonight’s case, temperatures are a bit too “warm” for that to happen, plus we don’t have much precipitation on the way.

In the metro area, and through much of the Willamette Valley, we’re going to see at least an hour or two of mainly snow as precipitation arrives.  As early as 9pm around Albany to maybe midnight up in Clark County and near the Gorge.  But very soon after it starts falling, the air a couple thousand feet up goes above freezing.  That means snowflakes melt to liquid rain drops.  Of course anyone that is near freezing those first hours could see some snow accumulation; probably less than 1″.  That’s most likely out closer to the Coast Range (Forest Grove, Hillsboro, Yamhill, Banks) and hills throughout the Willamette Valley (West Hills, Eola Hills, South Salem hills etc…).  But ANYONE could see a quick dusting.  Nothing has changed with models today; none showing any significant snowfall.  The latest ECMWF model agrees, although I think it’s a bit too dry in general.

Once we go to liquid rain, the remaining “threat” is freezing rain.  That cold wind screaming out of the Gorge means most areas east of I-205, and metro hills above 500′ or so (West Hills, Mt. Scott etc…) will drop to freezing.  Expect an icy glazing on any outdoor objects in those areas.  Although for roads to freeze up, air temps need to drop down to around 30 degrees.  That’ll be tough to do except right around Troutdale/Camas and the top of West Hills or Mt. Scott.

 

All the rest of the Willamette Valley should escape freezing rain and/or more than a dusting of snow.  95% of us won’t see any effect on our daily lives tonight or Sunday.

The cold east wind continues Sunday, but temperatures rise to around 40 degrees in the metro area.  Any icy roads near the Gorge should slowly thaw by midday, and the rest of us will just see bare and wet or dry roads.  Your life can continue as planned Sunday in MOST of the metro area.  For sure after 10am even in those colder icy spots.

In the Columbia River Gorge, expect snow at first, then warmer air overhead west of the Cascades (around Multnomah Falls westward) changes that snow to freezing rain.  Late tonight and tomorrow morning I-84 may be very icy from Troutdale to mid-Gorge, then snow-packed roadway beyond that point

With easterly flow continuing tomorrow, temperatures will only crawl a few degrees above freezing so I-84 ice/snow will be slow to melt off the roadway.  Keep a close eye on ODOT cameras and TripCheck.  Plus FOX12 will be on the air with Good Day Oregon at 6am.  Monday would be a much better day to travel through the Gorge; or consider going over Hwy 26 around Mt. Hood.  No freezing rain and snow level near 4,000′ means not much snow/ice once you get below the summit on the west side of the passes.

For the weather geeks

As you can see, no big changes to my thinking.  I’m watching those temperatures/dewpoints closely this afternoon.  A good guess for how much the temperature will fall with evaporative cooling tonight is to take 1/3 of the temp/dewpoint difference and subtract it from the current temp.  For example, right now Troutdale is 39/17.  That’s a 22 degree difference.  1/3 of that is about 7.  Take 7 off the 39 and you get about 32 degrees once evaporative cooling has kicked in.  Subtract another 2 degrees since it’ll probably be around 34-35 when precip starts in Troutdale; so maybe we bottom out around 30 at Troutdale later tonight?  That’s why I’m thinking there may be some icy roads that close in to the metro area.  Same temperature setup up on the West Hills and Mt. Scott.  Farther south in the valley dewpoints are higher so it will be tougher to get down to freezing.

WRF-GFS soundings continue to show quite a warm layer surging in overhead right after precipitation begins.  It’s almost a perfect “snow sounding” at 10pm over Portland

Then a sharp warmup around 2,000′ overhead by 1am (near freezing at the surface though with cold Gorge outflow).  This is a freezing rain setup, if your neighborhood is at/below freezing.  Otherwise a real nice 35 degree rainy night…

ECMWF and GFS both show the warming up around 925 mb as well.  That’s why I’ve been leaning more toward liquid precipitation instead of snow since yesterday.

The latest WRF snow forecast confirms little/no accumulating snow west of the Cascades, best chance for an inch would be in those previously mentioned communities right up against the Coast Range east slopes.  That shows up on this graphic.  Dallas, Willamina, maybe Yamhill?

That’s it for now.  I’ll be on the air at 8 & 9pm on FOX12PLUS, then 10pm on FOX12.

Chief Meteorologist Mark Nelsen

A Few Snowflakes While You Sleep Saturday Night; But Snowy & Icy in the Gorge

6pm Friday…

A quick blog post this evening; busy on evening newscasts.  You can find me there.

THREE IMPORTANT POINTS

1. Saturday will be just like today, although clouds thicken a bit in the afternoon and a strong east wind starts blowing out of the Gorge by sunset
2. If you live west of the Cascades in the lowlands, I don’t expect snow/ice to have any effect on your life this weekend.  95% of us will see bare roads
3. The Columbia River Gorge could be a real mess late tomorrow night through at least midday Sunday. 1-4″ new snow, followed possibly by some light freezing rain.  That’s most likely (freezing rain) at the western end

 

Friday was a nice day once again…after a very chilly start!  It was the coldest morning so far this “winter”; only 26 in Portland.  The cold east wind has backed off as well.  Tonight will be similar with coldest metro spots down into the upper teens again and mid-upper 20s in the city.

Saturday starts sunny, but then clouds show up the 2^nd part of the day.  The only other change will be a noticeable (chilly) east wind strengthening in the late afternoon through the evening.  Highs top out in the low-mid 40s once again.

Tomorrow night a very weak weather system passes overhead, dropping light precipitation sometime after 10pm and that continues through early Sunday.  The first few hours it could fall as snow, but I doubt temperatures will drop down to freezing in most of the metro area.  That means a dusting at best for a few spots while we sleep.   After 1am or so, warming air overhead would change most snow to rain.  BUT, near and in the Gorge that cold wind could lead to light freezing rain on top of a few inches of snow .

Regardless, roads in the metro area should be fine during this little event for 95% of us.  SUNDAY DRIVING WEST OF THE CASCADES WILL FEATURE BARE PAVEMENT ONLY

FOR THE GEEKS

A few points:

• WRF-GFS soundings don’t inspire much confidence for snow.  See the “warm layer” develop sometime after midnight on a southeast wind.  The three soundings are 10pm, 1am, & 7am

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• No model is showing any significant accumulations (beyond a dusting in spots.  Check out the WRF-GFS snow forecast

A closer view…

Hot off the presses…the 18z ECMWF, maybe a little in the Eola Hills west of Salem?  And cold air pushed up against the east slopes of the Coast Range could give a little snow to Yamhill, Forest Grove, & Banks…if everything works just right:

The pressure gradient through the Gorge jumps to around 10 millibars by Sunday morning.  It’ll probably be a 70 mph east wind night in Corbett and around Mt. Pleasant.  The airmass is cold enough that when the west end of the Gorge goes to liquid rain during the night, it’ll likely be freezing rain as far west as Troutdale or Camas.  This may be one of those situations with icing on objects but not pavement…we’ll see.

This is the only interesting weather I see in the next week, very mild weather continues with no sign of a long wet spell…yet.

I’ll have a fresh blog post up late tomorrow afternoon or early evening.

Chief Meteorologist Mark Nelsen

Rumors of Snow Fly Again; But Don’t Plan On Building A Snowman

9pm Thursday…

It’s a long evening here at FOX12 with only one 10pm show; good time to clean the weather center!  Now I see rumors of snow are flying around again this evening, so here’s a quick post to summarize.  Maybe more important…would some of you stay off those online shopping sites so I can get my shopping done here at work?  I can’t even get through to the one that sells large pallets of toilet paper and roast chickens, what is the world coming to…

WHAT’S THE STORY?

A weak weather disturbance moves overhead Saturday night, passing north across the region quickly.  It’ll likely be gone by sunrise or so Sunday.  There will be some light rain showers with this as it passes by

• Models imply there will be little or no snow or freezing rain west of the Cascades; I agree.
• That’s because there’s a good chance westside temperatures will be a bit too warm (just barely). OR, a few thousand feet overhead it’ll be above freezing, which means flakes would make it down to us as liquid rain drops.  If so, it would need to be down around 31 degrees or lower for those drops to freeze on contact (freezing rain).  That seems even more unlikely than snow since we may not make it down to freezing Saturday night.
• There’s no chance this turns into one of those all-day snow or freezing rain episodes; it just isn’t that cold to start with.

The evening WRF-GFS gives no snow to lowest elevations west of the Cascades.

The latest ECMWF tries to give us just a little snow Saturday night, although temps stay above freezing the whole time…hmmm

The GFS & GEM models are like the WRF and say “nope, not this time PDX”

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It WILL be cold enough for snow or freezing rain in the Gorge, at least east of Multnomah Falls.  I’ll keep a close eye on it and have a more detailed blog post tomorrow

Chief Meteorologist Mark Nelsen

A Quiet Thursday-Saturday Across the Pacific Northwest

6pm Wednesday…

Yesterday’s storm was exciting, but now it has fizzled over in Eastern Oregon.  There are still areas of snow falling across the Cascades, Eastern Gorge, and Eastern Oregon.  But in general we’ll be drying out region-wide by midday Thursday.  The strong northeasterly “upslope” flow into the Cascades dumped a huge amount of very dry snow on Mt. Hood ski resorts.  Even though that snow will compress a bit, it’s enough to allow Timberline, Mt. Hood Meadows, & Mt. Bachelor to offer some lift-served skiing this weekend.  Skibowl is opening their tubing runs Friday.

I don’t see much more snow in the next week.  First it’ll be dry, then mainly dry but warmer next week

Have travel plans?  Tough over the Cascades right now, but things should gradually improve through the weekend

All other Cascade and Siskiyou mountain highways are open this evening.  Here’s what you can expect elsewhere

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Offshore (easterly) flow continues through Saturday.  At that time an approaching upper-level low and surface low tighten things up a bit.  Expect much stronger easterly wind near/in the western Gorge Saturday PM and night.  At the same time all models agree a very weak band of precipitation moves north across Oregon and southern Washington.  This CAN be a classic setup for a brief freezing rain or snow event in the metro area.  At this point I’m thinking many areas west of the Cascades will be too warm for frozen precipitation.  The 18z ECMWF model ensembles think it could be a minimal or “non-event”.  Only 7 of 51 members give us an inch of snow or more during that time.  The rest are either too warm at the surface, too warm overhead (possible freezing rain), or mainly dry.   This would explain my lack of enthusiasm for some real wintry weather in the metro area this weekend.  We’ll see how it looks in 24-48 hours.

Our headlines graphic captures the general plan for this four-day weekend well

I’ll be working through next Monday, keeping a close eye on things through the holiday weekend.  Check back again Friday for a weekend update on this weather blog.

Enjoy your Thanksgiving!  Chief Meteorologist Mark Nelsen

 

Storm Moves Across Southern/Eastern Oregon Tonight…Lots of Snow!

3pm Tuesday…

A quick blog post to let you know everything is proceeding according to plan.  Take a look at that cyclone!  A gust over 100 mph at Cape Blanco

This is the water vapor image.  NOAA has a mesoscale floating sector over the storm right now.  That means a pic every one minute.  Check it out here, you can switch to different viewing “channels” to.  For example TRUE COLOR is the typical visible view we show on TV:  https://weather.cod.edu/satrad/?parms=meso-meso3-10-96-0-50-1&checked=map&colorbar=undefined

We’ve dried out in the metro area and we expect a gusty east wind tonight as the low moves onshore.  Then the wind dies down toward sunrise.  Here’s the latest ECMWF snow forecast for the next 48 hours:

PORTLAND METRO AREA:  All quiet now except for that breezy east wind tonight.  Dry weather through at least Saturday and chilly, although not “arctic cold”.

CASCADES:  Big snow storm tonight.  Timberline/Meadows have picked up at least 15″ snow and they can expect another 10-15″ the next 24 hours.

SW OREGON:  Lots of snow above the 1,500′ elevation down there.  Looks a bit too warm for significant accumulation in Eugene or Roseburg.  Maybe a brief wet inch this evening?  Travel looks terrible south of Ashland on I-5.  Wait until Thursday

CENTRAL/EASTERN OREGON:  Lots of snow, plenty of winter storm warnings out over there

GORGE:  Gorge should be mainly dry, but some light snow is possible at times now through Thursday AM east of Cascade Locks.  I’d be surprised to see more than 1″ at river level.  Much better snow accumulations in the middle/upper Hood River Valley.

That’s it for now…busy tonight on the 4pm, 5pm, 8pm, 9pm, 10pm, & 11pm shows.  You can find me there.

Chief Meteorologist Mark Nelsen

Southern Oregon Storm Tomorrow, But Quiet Weather Ahead Metro Area

6:30pm Monday…

As mentioned in last night’s post, a strong storm is headed for the California/Oregon border tomorrow afternoon.  Not much has changed and I’m in six evening newscasts tonight, so this will be a bit briefer.

Highlights

• Low elevation sticking snow is very unlikely west of the Cascades north of Eugene tomorrow and tomorrow night.  That includes Longview, Vancouver, Portland, Salem etc…  No, it’s not going to snow & stick in Portland.
• Weather will be uneventful the next few days in these areas (including metro) as well
• Expect another 12-15″ snow in the Cascades before it dries out Thanksgiving morning.  Most of that falls Wednesday.
• I-5 south of Roseburg to Redding could easily shut down tomorrow night and/or Wednesday, especially south of Ashland.  Plan accordingly!
• Thanksgiving Weekend will be chilly, although not an “arctic blast”.  Highs 40-45 in the western lowlands and lows 20-25 degrees.

The “explosive cyclogenesis” is still forecast to occur off the Oregon coastline the next 24 hours.  That’s sometimes called “bombogenesis“, a “meteorological bomb”, or even a “bomb cyclone”.  The 18z ECMWF model takes a 1010 mb low down to 970 mb as it moves onto the coastline somewhere around Brookings.  That’s 40 millibars in less than 24 hours!  Luckily the track means most of the big wind is offshore and the southerly movement “takes away” from the southerly wind gusts over land.

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As of early this evening, all models except the ECMWF totally dry us out within 24 hours north of Salem.  Even the new 18z ECMWF just gives us a few sprinkles tomorrow evening/night.  Thus it’s very unlikely the lowest elevations will see snow, even just in the air.  Notice the 10″ plus over Siskiyou Summit south of Ashland on I-5?  That’s going to cause plenty of trouble tomorrow evening and Wednesday

The rest of the forecast is easy…dry and chilly Thursday through Saturday.  Snow-covered areas east of the Cascades turn VERY cold.

See you tonight at 8pm/9pm on FOX12PLUS (usually channel 49 or 13), then 10pm/11pm on FOX12.

Chief Meteorologist Mark Nelsen

A Bomb Cyclone, Southern Oregon Snow Storm, & Coldest Thanksgiving Weekend In Years

6pm Sunday…

It’s been a real boring November for weather nerds like me; no storms, little/no mountain snow, mild temps etc…  But it’s been GREAT for anything outside.  I just took a bike ride yesterday with only a light jacket on.

That’s about to change; November is going to go out with some weather action plus cold wintry temps are arriving early this year.  Get your pipes wrapped!  Remember in my previous post I figured that “something was up”?  Sure enough, it appears we’re going to see the coldest Thanksgiving Weekend in at least a decade or two.  And snow may fall to sea level before we finish out the day Tuesday in at least part of the state.

If you’re just looking for a summary, skip to the bottom…

First, there isn’t much of anything interesting happening through Monday, just a little cooler with showers/sun mix all day tomorrow.  I expect 3-5″ snow in Cascades as the sticking snow level drops to around 2,000′.  This is the leading edge of colder air tomorrow.  Take a look at the change in the atmosphere overhead from right now to Thanksgiving

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TUESDAY’S “BOMB CYCLONE”

The real action is Tuesday.  In a span of just 12 hours, a weak area of low pressure well offshore deepens 42 millibars! (Based on ECMWF)  That’s a stunning rate of deepening.  Anything over 24 millibars in 24 hours is considered a “meteorological bomb cyclone”.  No, it’s not a made-up media phrase.  Meteorologists have been watching these storms develop in the north Pacific/Atlantic for decades and that’s the term we’ve always used.  Somehow national media stumbled upon the term a few winters back and decided it was appropriate for the public to hear.  Generally (for good reason) I have kept the word “bomb” out of my on-air forecasts, but apparently it’s okay now.  Here’s what the Euro model looks like Tuesday, click for a more clear view

And the wind forecast showing calculated gusts 80-110 mph mainly offshore near that low pressure center!

SOUTHERN & EASTERN OREGON SNOW STORM

Green/blue on that previous graphic represents rain/snow. Notice the storm is far enough south that NW Oregon sees only light showers Tuesday.  With such a rapidly deepening storm, it’s possible to get intense precipitation just north of the low center.  That means snow could fall to sea level just north of landfall.  Yep, it’s quite possible Florence or Yachats gets a brief wet snowfall Tuesday and Portland stays dry.  More likely snow will fall along parts of I-5 south of Eugene Tuesday afternoon/night.  Headed to California for Thanksgiving?  Traveling through the Siskiyous Tuesday night could be very rough.

That storm will move through Southern Oregon and into SE Oregon by Wednesday morning.  Depending on the exact track, this could be a big snow storm for parts of central & eastern Oregon.  The ECMWF snow forecast

WRF-GFS model is similar

In the Portland metro area we will see a strong easterly wind develop Tuesday evening as that storm approaches.  I doubt it’ll be a damaging wind, but should make for a chilly and windy evening.  It’ll also dry us out nicely too, which leads me to…

A DRY & COLD THANKSGIVING

The cold air settles in Wednesday through Saturday.  I don’t expect a crazy strong east wind Wednesday/Thursday in the Gorge and east metro, but as high pressure settles east of the Cascades Friday-Sunday it’ll turn into the strongest/coldest of the season so far.  Expect some ice on Gorge waterfalls by Friday.   The long period of cold easterly flow and dry atmosphere shows up nicely on the WRF-GFS cross-section.  That’s Wednesday PM through Sunday PM.

How chilly?  High temperatures will struggle to get above 40 degrees in the metro area, and 30-35 will be more common in the Gorge.  West of the Cascades, overnight lows in calm areas should end up in the 15-25 degree range.  Brrr!

SUMMARY

1. Winter (cold for all + snow for some) is arriving early this year.  An extended period of cold weather arrives Wednesday.
2. Avoid traveling through SW Oregon (south of Eugene/Roseburg) Tuesday
3. Avoid traveling south of Ashland on I-5 Tuesday and at least the first half of Wednesday
4. Expect snowy roads at times anywhere in Eastern Oregon from Tuesday evening through Wednesday
5. Cascade passes and ski resorts should pick up 10-20″ snow Monday-Wednesday
6. Sticking snow is unlikely in the metro area below 1,000′ this week

I’m working through the Thanksgiving Weekend so I’ll be keeping a close eye on the weather for you!

Chief Meteorologist Mark Nelsen