Warmest January in 67 Years In Portland; Cooler Temps Ahead

January 31, 2020

8:30pm Friday…

I hope you enjoyed a bit of “Apr-uary” today.  As predicted, a warm southerly wind plus most rain shifting north of us lead to some record high temps.  PDX reached a record high of 62, tying for warmest of the month.  Troutdale also broke a daily record

Record Highs Cities

Three other cities tied record highs.

Record Highs Cities2

Salem, Eugene, Roseburg, & Pendleton made it to within one degree of their record highs.

This final push of warmth makes January 2020 the 2nd warmest on record in Portland; the warmest since 1953.  Interesting that 4/5 warmest Januarys have been in the past 15 years isn’t it?

Record Warm Month Top Five

What’s ahead?  A sharp cold front arrives early tomorrow morning with some steady rain.  Then it’s on to light showers (more dry than wet) this weekend.  Showers come to an end sometime after the Super Bowl ends Sunday evening.  Most likely we’ll be dry from late Sunday evening through at least midday Tuesday.

During these next three days the snow level takes a big plunge.  We use this graphic on-air to give our viewers a general idea of upcoming snow levels.  This uses 850mb temps as a proxy for that snow level.

ECMWF Snow Level From 850mb Temps LONG TERM

You can see the story.  A big drop down to around 3,000′ tomorrow afternoon, then down around 1,500′ Sunday.  A bit lower both Sunday morning and Sunday evening during the cooler parts of the day too.

Any of us may see snow/rain or even all snow showers Sunday afternoon.  That’s why we’ve had “MIXED SHOWERS” in our forecast for Sunday…for at least 6 days.  Some models are hinting at some brief heavy showers during the Super Bowl.  If so, a quick dump of snow could come all the way down to sea level under one of those showers.  I’ll be watching the radar closely Sunday afternoon!  In general models are going for little/no accumulating snow at the lowest elevations during this period.  The ECMWF

ECMWF Snow Accumulation Hourly

And the WRF-GFS (UW) 24 hour snowfall forecast Sunday morning to Monday morning

or_snow24.60.0000

Let’s assume we get plenty of showers Sunday afternoon/evening.  As skies clear Monday morning temperatures should drop.  There’s a decent possibility we’ll see areas of icy roads for the Monday morning commute.  Otherwise a cool and at least partly sunny day is on tap.

Beginning late Tuesday we enter another period of mild temps and rain that should last through the rest of next week.   The ECMWF ensemble forecast high/low temps show the cool period Sunday-Tuesday, then close to normal or a bit below as we head into mid-February

ecmwf-ensemble-KPDX-daily_tmin_tmax_ecmwf-0472000 (1)

Chief Meteorologist Mark Nelsen

 

 

 

 

 

 


Warm January turns into a Chilly February Start

January 29, 2020

9pm Wednesday…

I feel like we’ve done this before.  Oh yes, it was last year.  A very mild and boring winter, then suddenly it cools off starting Super Bowl Sunday.  Yep, it happened last year.  Although this year we don’t see a lowland snow event in the days following Sunday.

First, the warm weather.  January has been very warm compared to the 30 year average.  The only cool period was mid-month when we flirted with low elevation snow and a cold Gorge wind was blowing.

Almanac Monthly Temps So Far

As of this evening, with two days left to go, we’re running 5th warmest January on record.  But with two warm days ahead, including a 60 degree day Friday (assuming rain shifts north), we could end up at #2

Record Warm Month Top Five

And of course it’s been wet!  It’s so nice to see solid rain for day after day; that’s after a very dry October through December.  January has been the wettest month in almost three years; the wettest since 10″+ fell in February 2017

Rain Record PDX

But don’t complain!  If you live in the foothills of, or in, the Coast/Cascade Ranges it has been a huge soaker.  Some spots are approaching four feet of rain!  Again, this isn’t record-setting, but it seems “crazy wet” because we’ve gone through two relatively dry winters

Rain Coast Cascade Range

What’s ahead?

Three more very mild days.  An upper-level ridge strengthens over us through Friday.

ecm_friday

That pushes just about all the rain north of the Columbia River by Friday midday or so.  There should be 12-18 hours dry later Friday through early Saturday.  And the temps should be amazing!  Highs Friday should reach 60 or above from the metro area south through western Oregon.  Even the lower elevations of Eastern Oregon will reach the 60s (Hermiston, Pendleton) and maybe central Oregon.

Then a sharp cold front moves across the region Saturday evening, dropping snow levels from around 9,000′ midday Saturday to 1,000′ by Sunday morning.   Check out the drop

ECMWF Snow Level From 850mb Temps LONG TERM

We’ve had “mixed showers” in our forecast for Sunday off/on the past four days for this reason.  It’s the “chilly onshore flow showers” snow setup that rarely produces sticking snow at the lowest elevations.  Expect some snow on the Coast Range summits Sunday morning, and well down into the Cascade foothills.  Skiing will be MUCH better Sunday too, fresh snow!

Could it snow in the lowlands Saturday night or Sunday? 

Yes, in the air, or at least mixed with rain, but sticking snow on the ground is very unlikely.  850mb temps are marginal, around -6 to -8 and we have onshore flow in progress.  Showers taper off Sunday night and we should be dry Monday.  Yes, totally dry for ONE DAY!

Rain returns at some point next Tuesday, and of course there’s always the possibility it starts as snow.  But what models are showing is a classic setup for a quick warmup.  Breezy southerly wind arrives at the same time as precipitation.  Maybe a brief mix in spots, then a snow level jump up to at least 3,000′.  The ECMWF model agrees with basically no lowland snow through next Wednesday.

ECMWF Snow Accumulation

By Wednesday of next week (February 5th), models show the pool of cold air has moved off to the east

ecm_wed_5th

But then three major models are hinting another pocket of cold air may drop down the West Coast about 10 days from now.  Check out the ECMWF, GEM, & GFS models for next Saturday the 8th…looks chilly!  I’ll be watching this closely

The ECMWF ensemble chart today showed a HUGE variety of solutions beyond the middle of next week.  Some ensemble members were VERY cold, others just remain mild.  It’s 8-10 days away so plenty of time to wait and see how modeling comes together.

For now, enjoy the warm three days ahead!  I’ll be back at work for the shows Sunday evening after the Super Bowl.

Chief Meteorologist Mark Nelsen


A Mild January; Lots of Rain, but No Lowland Snow Ahead

January 23, 2020

7pm Thursday…

Our cold season so far (November through February) has been warmer and drier than average.  November was near normal, but then very mild December through January.

Winter So Far Recap

Of course November was excessively dry, and drier than average conditions continued through December.  Now it’s makeup time.  Plenty of rain this month and lots more coming the last 8 days of January

Winter So Far Recap2

This winter (so far!) has been similar to last year for meteorologists…one of the most boring on record.  I do a winter recap presentation for our local Oregon AMS Chapter each fall; keeping a file of important weather pics or events.  I just checked that file; some pics of vehicles stuck in tumbleweeds, a bomb cyclone into southern Oregon, and low snowpack images.  Oh, a little EF-0 tornado in Manzanita too.  That’s it!   No real flooding, lowland snow, valley windstorms, and just barely a coastal windstorm.

Winter So Far Intro It’s also interesting that our coldest temperature of winter was in November this year…again so far.  26 degrees the last two mornings of November during that cold snap around Thanksgiving.  Salem hit 20 those mornings, and a 19 at Hillsboro.

Winter Coldest Day Each Year

You may remember through much of October through early January we saw either a weak jet stream, upper-level ridging, or a split flow with weather systems going into California.  But in the past week a more typical wet westerly jet stream has been sending weather systems into the Pacific Northwest.  It’s a mild westerly flow with occasional rain at the ski areas mixed with snowy periods.  Plenty of rain falls in the valleys too.  Take a look at the rain forecast from the ECMWF model for the next 6 days.  2-3″ in the valleys and up to 8″ in mountains (some of that will fall as snow).  You can see the below average upper-level heights over us next Monday…

500_monday

Then weak ridging with a possible atmospheric river setup around next Thursday

500_thursday
We’re looking at the ECMWF ensembles from last night; a compilation of many different runs of one model.

It appears there will be a change right around Superbowl Sunday.  All models show at least a brief colder period with an upper-level trough dropping through the region.  Here’s that Sunday…this is 10 days out in time

500_sunday

Just for fun; you can see four days later the ridging pops back up closer to us.  This is two weeks from now.

500_thu_6th

So based on this and other model info available right now:

  1. The last 8 days of January will feature the weather we have right now: Mild, wet, & occasionally windy
  2. There will not be any significant freezing the rest of the month
  3. Expect the Cascade snowpack to increase in depth; a mix of more rain + snow
  4. No sign of lowland snow or freezing rain through the end of the month, but maybe a brief flirtation with low elevation “onshore flow” type snow in 11-13 days?  Just a small possibility now.

What about that cold trough in early February around Superbowl Sunday and the following Monday/Tuesday?  A few of the ECMWF ensemble members think it could be a “wet snow showers” setup.  I chose Aurora as a location since the PDX site tends to have resolution issues with SW Washington Cascades so close.

ecmwf-ensemble-KUAO-indiv_snow_24-9780800

CMC (Canadian) ensembles have fewer members with a wet snow chance

cmc-ensemble-all-KUAO-indiv_snow-9780800

That’s it for now…enjoy the rain and stay dry!

Chief Meteorologist Mark Nelsen


A Tornado on the Oregon Coast Today; In the Coastal Radar Gap

January 21, 2020

3pm Tuesday…

It appears we got lucky again today; a weak (likely) tornado seems to have moved onshore in the northern part of Manzanita, very close to the October 2016 tornado location.  No one was injured and not much damage either…Mark

THE FOLLOWING IS A RE-POST AND UPDATE FROM AN OCTOBER 2016 BLOG POST

The Oregon Coast has the WORST coastal radar coverage anywhere in the lower 48 states and it’s time to change that.  In fact there is no radar located along our coastline.  Local forecasters (private/public/media) have known about it for years.  I’ve blogged about it numerous times and Professor Cliff Mass up at the UW in Seattle has been pushing it for years too.

Important points:

  1. The central and southern Oregon coastline has no radar coverage below 10,000′;  almost all cool-season weather happens below that elevation.
  2. How is it possible Oregon’s 2nd largest city (Eugene) has no coverage below 10,000′???
  3. A tornado or squall line can roar ashore in Lincoln City, Newport, Florence, or Coos Bay with no warning.
  4. A tornado or squall line with damaging winds could move through the Eugene or Roseburg areas with very little indication on radar.
  5. NOAA’s Pacific Fleet is based in a location (Newport) with no good radar coverage…that’s a huge surprise.

#3 happened in the mid 1990s at Lincoln City, and #4 just happened January 16th this year in Lane County (near Eugene).

What Is The Problem?

The National Weather Service completed a major modernization in the 1990s, a central component being the installation of powerful Doppler weather radars across the country.   Such units, known as WSR-88Ds or NEXRADs, describe precipitation and winds in their environs and have revolutionized forecasting and meteorological research.
The range of useful radar coverage is controlled by a number of factors.  Terrain blockage is important in mountainous regions like the Northwest.  Furthermore,  the height of the radar beam increases with distance from the radar–resulting in an inability to see important low-level features at distances from the radar.  Under perfect conditions, the maximum range of the WSR-88D for wind information is 230 km (138 miles) and for precipitation sensing roughly twice as far.
An official National Weather Service map of national weather radar coverage (for precipitation) is shown below.  A second image with a blow-up of the Northwest section is also provided.  These radar coverage maps are valid at 10,000 ft ABOVE THE RADAR SITES (many of which are already thousands of feet above the surface!), not at the surface.  Radar coverage near the surface is far poorer, particularly over the western U.S. where blockage by terrain is significant.  Even for the optimistic 10,000 ft coverage, the Oregon coastal zone is poorly served compared to the California, Gulf of Mexico, and Atlantic coastal regions. Click for a better view:

wsr-88dconuscoverage2011

Note there IS a radar on the Washington Coast.  That was just put in 4 years ago after a years-long lobbying effort by a group up there.  A closer view shows the situation here in Oregon:

markradar_neworegoncoast3

The “partial coverage” refers to some blocking by mountains in the Coast Range.  The lowest beam from the Portland radar (located on Dixie Mtn. southwest of Scappoose) is intercepted in a few spots by the Coast Range.  We were extremely lucky that Manzanita was not behind one of those “blockages”.  But in general coverage is sketchy on the north coastline south of about Cannon Beach.

What about farther south?  It gets worse.   The Medford radar is even more problematic:  it is located at a very high (7500 ft) elevation to minimize blockage, causing it to miss most coastal and valley precipitation.  The Medford radar is also too far inland to provide useful information over the coast.  One has to go as far south as California (the Eureka radar) to get proper coastal radar coverage!  

capture2

You can see the issue here from the image above created by folks up at the UW before the Washington coastal radar was installed.  Very little useful information comes from that Medford radar in the cool season.  Dr. Mass has suggested moving the Medford radar down to the coastline around Coos Bay or Brookings.  However that would leave the largest southwest Oregon population (the Rogue Valley) with very little severe thunderstorm coverage in the summertime.  That’s not going to happen.

Where Would A New Radar Go?

The ideal location would be somewhere between Coos Bay and Newport.  Seems like Florence is a good location, up at a high enough elevation to get a clear path to watch Eugene, but not too high.  Coverage would look about like this:

markradar_neworegoncoast2

Much better don’t you think?  How much would it cost?  Maybe $5 million dollars to install and then regular maintenance and operational costs of course.  Is it worth it?  Yes, even one big event could erase some of that cost.  Consider the South Valley Surprise windstorm of February 7, 2002.

trees

A much deeper than expected low pressure center moved onshore just south of Florence, then raced northeast into the Columbia Basin.  The strongest wind gusts in that area since the Columbus Day Storm of 1962 peaked between 70-80 mph.  There was NO WARNING until the wind had already arrived.

markradar_neworegoncoast

Since there was no warning, local utility crews were caught completely off guard.  Nowadays utilities prepare for these storms days ahead of time by positioning their crews/supplies and having extra workers ready to go.  With some warning (even just a few hours) they may have been able to restore power more quickly thus saving a million or two worth of damage?  Just a guess, but you get the point.  That storm cost $10-$12 million dollars damage.  By the way, there was no strong wind in the Portland metro area or Salem because the low pressure passed by to the south.  We just had a breezy westerly wind.  This is just one example of what we’re missing.  A squall line moved into the southern Willamette Valley just this past January 16th, barely detectable (if at all) on Portland’s radar.  Check out the storm report, click for a better view.

capture

Where Do We Go From Here?

First, don’t bother calling the Portland or Medford National Weather Service offices and complaining.  Those folks do all sorts of good work forecasting and keeping on top of our wild winter weather…but they don’t control the money!  It’s a political solution, which means the U.S. Congress has to appropriate the money.

A coordinated effort has begun in our area; that’s why the story has now appeared on two TV stations (and hopefully soon on the other two!).  A group started by the Oregon AMS (American Meteorological Society) will have its first meeting in a couple of weeks.  It involves members of the local media, former television meteorologists, former NWS employees, educators, and many others.

I’ll keep you in the loop as we go through what will likely be a very long, but hopefully productive, journey.   I know there are lots of you on the Oregon Coast and down south in the Valley that want to help out.  The effort to get a Washington coastal radar included support from all sorts of community groups.

The Other Oregon Radar Gap

Of course there is one more huge hole in Oregon radar coverage.  There is no cool season coverage in Central Oregon either.  By that I mean we can’t see anything below 12,000′ or so in the area from Warm Springs to Redmond to Bend to La Pine.  Just before Thanksgiving 2015 a foot of snow fell in one evening in Bend and the Pendleton radar showed nothing.  At least the very tall thunderstorms in summer are detectable by surrounding radars, but at some point that area (where 200,000 people live!) needs a radar too.  There are many other gaps in the interior west, so that one might be a tougher sell.

UPDATE:  APRIL 2017

Good news…a study of radar gaps has been included in new legislation signed this month.  Now we’ll see what the NWS says about our radar gaps in Oregon.

Congressional Statements on Enactment of Weather Research and Forecasting Innovation Act
President Trump signs the first major piece of weather legislation adopted since the early 1990s into law

WASHINGTON – Leaders on the U.S. Senate Committee on Commerce, Science, and Transportation and the House Committee on Science, Space, and Technology which exercise legislative jurisdiction in their respective chambers over the National Weather Service (NWS) today, issued the following statements on the announcement last night that President Donald Trump has signed into law H.R. 353, the Weather Research and Forecasting Innovation Act of 2017. The bill includes sweeping reforms to federal forecasting to improve seasonal forecasting, monitoring and clearly communicating information about extreme weather events, the availability of aircraft systems for hurricane tracking, and the use of commercial data that have been collectively called “the first major piece of weather legislation adopted since the early 1990s.”

Radar study – Requires NOAA to identify areas where there are gaps in radar coverage and provide recommendations on the supplemental observations necessary to improve public safety.

UPDATE:  JANUARY 2020

Bad news…a study of radar gaps has not yet appeared in public.  It appears to be stuck somewhere in NOAA or Congress.  Too bad!

Chief Meteorologist Mark Nelsen

Thanks to Dr. Cliff Mass and his NW Radar Problem page for some descriptions used above.


Did You Expect A “Snowmageddon” This Week? What Went Wrong (Hint: It Wasn’t The Forecast)

January 16, 2020

8pm Thursday…

I’ve wanted to write about this issue for a couple years, but figure now that the weather has calmed down would be a good time.  That’s with memories of snow still fresh in our minds.

By the way, snow showers tonight will return, with ANYONE west of the Cascades possibly seeing something briefly stick.  More likely is a covering of snow on higher hills.  Yet it’s just showers so accumulations will be spotty.  A hill at 1,000′ in one part of town may be bare but 20 miles away at sea level there could be a dusting.  Scattered showers.

Snow Valley Salem Coast Forecast

After tomorrow midday, snow levels jump back up to around the passes.  This is quite possibly our “last chance” for snow this month.

So did you have the impression we had significant snow on the way this week?  Like a snowfall that could paralyze the metro area and give us a hellish commute?

Here’s the forecast timeline:

About 10 days ago we first put “mixed showers” in our 7 Day Forecast for this past Monday.  Yes, it’s a tough decision whether to throw a snowflake/rain mix into the forecast.  Because viewers and coworkers notice immediately.  Models clearly showed a cool/showery weather pattern, but not one that produces widespread snow.  So seven days ahead of time we forecast those mixed showers with a high of 40 for this past Monday.  For the following 6 days we had a high of 39 to 41 degrees for this past Monday and kept the same forecast.  That’s exactly what happened!

How about Tuesday?  We first forecast “mixed showers” six days ahead of time.  Then we changed it to “flurries and sun” five days ahead of time when it was obvious there wouldn’t be much moisture left that day.  Guess what?  We had flurries, sun, and a little graupel that day.  Highs were always forecast between 35-37.  We hit 40 with the sunbreaks.  Close enough, so for seven days we had a great forecast for Tuesday as well!  No problem so far…

How about Wednesday’s forecast?  This is where things got a bit more intense and we as forecasters were thinking could be the “real deal”.  Models were generally telling us we might have the perfect setup for large regional snow/ice event with cold east wind pouring out of the Gorge.  Or maybe just in the metro area, depending on the model.  Six days ahead of time we had “snow developing” and “snow or freezing rain” in the 7 day Forecast for Wednesday/Thursday forecast with highs at/below freezing.  That would definitely imply something big might be in the works.  For three days we kept that general wording, telling you something like this:

Snow Portland Preview

By Saturday, still four days ahead of time, I said this in the blog about Wednesday’s possible “big event”

Capture

By Sunday afternoon, the chance of a major event Wednesday was still alive, but on life support.  Some models were pushing the big low offshore farther north, ending our brief cold spell quickly. Our most reliable models (ECMWF & GEM) were saying there would be little or no snow…3 DAYS AHEAD OF TIME!  I wrote this on the blog Sunday evening:

sundaypm

Then by midday Monday it was very clear Wednesday could easily be a non-event.  From my post that day:

mondaymidday

TO SUMMARIZE OUR FORECASTING HERE AT FOX12

We nailed the Monday/Tuesday forecasts well ahead of time, calmly letting you know that your “life would continue as normal” through most of this period.  Expect to see snow in the air but not much on the ground at the lowest elevations.

We did indeed indicate Wednesday/Thursday could bring life-altering snow/ice to our area, but backed off drastically 2-3 days ahead of time.  We know that can be the case as we get closer to an event.  Would it have been better to ignore it and then suddenly spring a snowy/ice forecast on you just two days ahead of time?  I don’t think so.  Keep in mind we can’t just leave those last 2-3 days of the 7 Day Forecast blank!  We have to put SOMETHING in there.

WHY THE FEELING THAT A “SNOWMAGEDDON” WAS COMING?

I think it’s a combination of factors:

Today’s connected world:  There is a constant flow of information on TV, smartphones, & the Internet.   Rumors of snow, ice, cold move around in circles and pass through social media instantly.  The volume of information is staggering; we are exposed to far more “snow may be coming” posts/blogs/tweets than even 10 years ago.  Every news/media organization is promoting their brand or business. I think it’s perfectly natural for a person to think “wow, something big must be on the way” when they are seeing so much of this info.  Alert after alert, notifications promoting a newscast, web page, newspaper app, etc…   How could I not think a snowy/hellish commute is headed for Portland?

Government organizations prepare for the worst, as they should.  But that worst-case scenario can appear to be THE forecast.  Leading up to a snow event, city leaders, PBOT, ODOT, WADOT, & counties often put out media releases, tweets, hold live news conferences, show off their newest plows, compare sand/salt pile size, etc… It’s a constant feed of “WE’RE GETTING READY FOR SNOW”.  And of course they should always prepare for the worst.  After seeing all this info, it’s easy to think “something big is on the way“.  No one is doing anything wrong here, that’s just how it is.

Screenshot 2020-01-16 at 7.04.06 PM

Some people WANT to see a good snowstorm.  I think plenty of the recent complaints are from people genuinely disappointed we didn’t get a good 2-5″ snow event.  That’s fair, but a forecast of a dusting to 1″ up on the hills doesn’t mean we’re “forecasting snow for Portland” and missed it.

A final one, snow forecast maps from models passed around social media.  I actually didn’t see it much this time around.  It was an issue last February when one local news organization put out a snow map showing 15″ of snow in Portland.  These move around as fast as lightning!  Generally I don’t like to post images more than about 3 days ahead of time.  Notice I didn’t post any snow forecasts for the big Wednesday event here on my blog?  This is why.

What do you think?  What did I miss.  I’ve got a tough skin and would love to see your comments on my Facebook page:  @MarkNelsenWeather

 


Wednesday Evening Update: Snow into edge of metro area

January 15, 2020

8:45pm Wednesday…

Today turned out pretty much as expected, with a few last minute twists & turns.

  1. We saw a rain/snow mix which changed to mainly rain as the cold front moved through during the evening commute
  2. Clark county warmed up to around 40 as our “mesoscale” models showed; no snow for most of you up there.
  3. No measurable snow for almost all of us.

What was different than expected?

  1. Cold Gorge wind was very persistent (surprise!).  Although quite a bit more reasonable compared to a few hours ago, it is still transporting cold continental air westward into the eastern edges of the metro area.  Temperatures are hovering just above freezing in a narrow area along the Columbia River east of I-205
  2. Due to that, plus the cooling air overhead, snow has been falling for several hours in the western Gorge, all the way into Camas and Washougal.  Just got a report that two inches have fallen in Bridal Veil, that’s where we should have only seen freezing rain.

Take a look at current temps, only the numbers below 34 degrees plotted below. (click for a better view)

Capture

Areas to the right of the yellow line are generally seeing snow.  Mainly or all rain to the left.  Yet in general the snow level west of the Cascades is around 1,500 to 2,000′ right now.  Then how is it snowing down to the Columbia River in Clark and Multnomah counties?  What would typically be about a 1,500′ snow level right near the Gorge and into Camas/Washougal has become “sea level snow” since the last 1,000′ or so are near/below freezing due to that east wind; snowflakes are coming down much lower than one would expect in this pattern.   Due to this, and more precipitation on the way, the NWS has upgraded the western & central Columbia River Gorge to a Winter Storm Warning.  3-6″ likely in these areas.  The pressure difference through the Gorge does continue to weaken and it’s possible at some point Camas/Washougal/Troutdale lose the easterly wind.  If so temps will rise a few degrees.  They sure won’t go down any lower through tomorrow morning.

Mark Gorge Wintry Weather

Through the rest of tonight we’ll see waves of showers moving onshore behind this evening’s cold front.  In general the snow level will remain above 1,000′ through tomorrow morning.  But anyone at/above that elevation in the metro area could see a skiff of snow on the lawn/barkdust/car.  Same setup again tomorrow night and Friday morning.  Beyond that time we’re headed back to a milder weather pattern for the last 1/3 of January.

Chief Meteorologist Mark Nelsen


First Snow & Rain Moving Through At Midday

January 15, 2020

11am Wednesday…

So far things are going about as planned weatherwise.  Temps dropped to below freezing for most of us last night.  As of 11am all parts of the Willamette Valley up into Kelso/Longview are above freezing, a gusty east (cold) wind is blowing out of the Gorge, and a bit of “downsloping” southeasterly wind has arrived in the Cascade foothills, central Willamette Valley, and Clark county.

Now the first band of snow and rain is passing overhead.  I’ve seen reports of snow in St. Johns, McMinnville, but just rain in central Portland.  A mix in Beaverton too.  Looks like McMinnville was able to get a dusting as that passed overhead:

mcminnville

WHAT’S HAPPENING AS OF MIDDAY?

At 4am the balloon sounding over Salem said “all snow”; the air was below freezing all the way up through the atmosphere.  But that has changed; there is a huge storm that has developed off the coastline.

satellite

We are on the east side of that storm, which means strong south and southeast wind developing in the lowest few thousand feet of the atmosphere.  The air just above the surface up to around 3,000′ is warming quickly.  That continues until a cold front passes overhead around sunset (the sharp back edge to the cloud cover).  So for the next couple of hours it’ll be a rain/snow mix until temps get a bit warmer overhead.  As you can see the temperatures down here at ground level are too warm to allow snow to stick and we’ll remain above freezing through tonight.

web_metrotemps (1)

All the mesoscale models (with better terrain and resolution) say no sticking snow in metro area tonight, including Clark county.   The WRF-GFS model was perfect showing temperatures rising up to around 40 or higher in a weird sort of southeasterly “downslope” wind flow up there.  Here’s the snow forecast through 4am

wrf_snow4am

and the NAM-NEST model is similar, this is ending at 1am

namnest_1amsnow

The mixed precipitation should change to all rain as the main cold front band passes overhead 3-7pm.  After that it’s frequent showers tonight.

SUMMARY FOR LOWLANDS WEST OF THE CASCADES

  • Mixed rain/snow continues at times through early afternoon, changing to mainly rain.  Although a mix likely continues up in northern Clark County and maybe Columbia County around Scappoose and St. Helens.
  • Mainly rain showers tonight, although mixing with snow on hills.
  • Could see a trace to 1″ eastern metro hills up around 1,000′ and above.  1-3″ above 1,000′ possible any of the Cascade foothills (east of Battle Ground, Camas, Sandy, Silverton etc…)
  • Freezing is unlikely in metro area tonight.  But just like the last few nights, there could be spots where breaks in clouds allow some local freezing.  If it happens most likely it’ll be west metro areas.
  • Scattered light showers Thursday, still mixing with snow at/above 1,000′

 

COLUMBIA RIVER GORGE

A bit more complicated here because a shallow layer of cold air isn’t going anywhere.  This isn’t quite the typical situation since the real cold air is only about 2,000′ thick.  But since it’s not a real warm atmosphere overhead there should be no problem keeping precipitation type as snow from Bonneville Dam eastward.  There’s a very narrow area at the west end of Gorge that will see freezing rain late this afternoon/evening.  That’s from near Corbett/Cape Horn east to about Multnomah Falls.  Then back to a snow/rain mix later tonight in those areas.  So east of Multnomah Falls or Bonneville, expect a Trace to 4″ in the Gorge.  The trace would be out near The Dalles…just not that much precip to work with.