Icy Roads Continue Through Tuesday AM plus Freezing Rain Possible

January 15, 2017

9pm Sunday…

The past 5 days have been quite a ride with the snowstorm, then raging east wind, and very cold temps.  In fact today was the coldest day in Portland in 3 years; we only made it to 28 degrees under full sunshine.

plot_highs_metro

THAT is a cold low-level airmass and it isn’t going anywhere until sometime Tuesday when southerly wind arrives.  Check out the warming in the Cascades today:

markinversion_timberlinevsbrightwood

So we now have a trapped cold airmass below about 1,500′ and cold air still pouring through the Gorge.  In fact the flow from the east has increased again this evening.  Wind gusts over 70 mph have returned at Corbett…like the relative that left and is back at the front door.  Easterly gradient through the Gorge is back above 8 millibars.

Models don’t handle the lowest part of the atmosphere well in this case.  The WRF-GFS thinks it’ll be about 45 tomorrow, our RPM says about 45 as well, so…30 seems like a good number to me.  At least we know humans are still needed in certain weather patterns.

A very wet and warm weather southwesterly flow of air arrives overhead Tuesday and continues through Wednesday.  This means lots of rain, but not historic, Noah-like totals.  We’re NOT in for some sort of 1996 flood.  In fact we’ll likely just have localized flooding/ponding of water due to the snowmelt Tuesday night and Wednesday.  By Thursday we’re back to light showers.  Here’s the WRF-GFS, showing 3″+ in the mountains and 1.50-3.00″ in the valleys.  The snow on the ground is probably worth about 1″ as well once it’s melted

wrf_rain_thursam

I see two big issues in the next 48 hours:

1. Roads & Commuting

  • Those roads with solid packed ice, ruts, & snow will be exactly the same Monday morning and almost the same Tuesday AM.  The current rough conditions continue through the Tuesday AM commute.
  • I don’t see how schools can have widespread openings Tuesday with all the snow/ice on the ground in a good chunk of the metro area.
  • Finally by Tuesday evening after some rain and temps above freezing the solid ice should soften up, but then you have deep slush all over…what a mess!
  • Wednesday morning’s commute will likely be the first in a week that is pretty close to normal.

2. Freezing Rain Tuesday

Rain arrives soon after sunrise Tuesday west of the Cascades.  With temperatures below freezing, this is a perfect setup for a freezing rain event in at least part of the metro area and an ice storm in the Columbia River Gorge.  There is no sudden warming southerly wind in the metro area during the daytime Tuesday.  Lighter easterly flow continues through the Gorge through even early Wednesday.  The very cold airmass will only slowly modify Tuesday and Wednesday in the Gorge.  Since temps are starting very low in this cold airmass, I think there is a very good chance temps in the Gorge remain at/below freezing through at least morning/midday Wednesday!

  • Assuming temps are below freezing in the metro area Tuesday morning, prepare for freezing rain (liquid rain freezing on contact) for at least a few hours in the morning for at least a part of the metro area.  We’ll have a better idea of the coverage by tomorrow afternoon/evening.
  • By afternoon temps should be above freezing in most of the metro area and most of us should be in the clear.
  • Roads may become “freshly iced” for many of us Tuesday
  • The Columbia River Gorge has a major ice storm coming Tuesday and at least early Wednesday.  Very heavy rain is on the way this time…possible 2-3″ liquid in the central Gorge through midday Wednesday.  IF temperatures remain below freezing this will be a crippling event east of Multnomah Falls.

By the way, this ongoing snow/ice fiasco on metro (mainly Oregon) highways and arterials (5 days after the storm)  is well covered by Cliff Mass in his blog post today:  http://cliffmass.blogspot.com/2017/01/portland-fails-to-clear-snow-and-ice.html.  I call him the “Godfather of NW Weather” and of course he has his own opinions.  I won’t rehash all his points, but it’s definitely worth a read.  It’s too bad there isn’t some better alternative (than salting), but a metro area of  almost 2 million people shouldn’t need to shut down for day after day after day when we have an event like this every 4-8 years.    It last happened in 2008, and 2004 before that.  I really like his idea of sharing snow removal equipment too since the two metro areas usually don’t have snow/ice storms at the same time!  Seems like it probably wouldn’t work logistically, but interesting.

Chief Meteorologist Mark Nelsen

 


A Frigid Night & A Cold Winter

January 12, 2017

10:30pm Thursday…

It’s been a long and disruptive week for many of us.  Lots of you have missed days of work and the kids have been out of school.  Meanwhile transportation/utility/emergency/police/media folks have been working overtime.  Today is day #12 for me.  But I actually have two days off!  Looking forward to sitting around doing nothing important for at least that 1st day…

Tonight we have perfect conditions for the coldest night in at least 3 years, and possibly much longer.  Here is my forecast for the metro area:

fcst_tonight_metro

If low clouds or thick fog develops in any one spot, that could keep the temperature 5-8 degrees warmer.  As a result the low temperature forecast is tough in a situation like this.  PDX is right at the edge of the “well-mixed” east wind zone.  Near the Gorge the wind keeps the air mixed up all night, which keeps low temps up around 20 degrees.  Away from that area temps can really drop off (as you see in the map above).  IF we hit 12, that will tie the low during the 2013 cold snap.  IF we get down to 11, it’ll be the coldest temp since the December 1998 arctic blast.  If we somehow get down to 10, it’ll be the coldest in 28 years…since the February 1989 arctic blast.  Hillsboro has already hit 9 as of 10pm!  If Hillsboro gets below 9, that will be the coldest since 2009, and a 6 would be the coldest since 1998.

The next few days we are heading into a cold version of our typical wintertime inversion pattern with the mountains warming up and valleys remaining cold.  We may see increased low/clouds fog since we have a bit of a moisture source too (melting/sublimating snow).  But there won’t be any dramatic change through Sunday/Monday

It turns a bit tricky briefly later Monday as we go into a mild/wet period for three days.  Tuesday-Thursday next week feature a series of warmer than normal systems (first time in many weeks!) flying across the Pacific Northwest.  As we transition into that pattern, there is the possibility of brief freezing rain later Monday or Monday night. All models show the south wind quickly overwhelming the low-level cold air in a situation just like Monday, December 18th.  But the ECMWF gives us some freezing rain Monday night and holds the cold air in the Gorge longer due to south wind holding off until Tuesday AM.  If this is the case, we would have an ice storm in parts of the metro area Monday night and a big ice storm in the Gorge…we’ll sure be keeping a close eye on this one.  Note the ice accumulation forecast from that model:

ecmwf_frz_rain_portland_20

I just checked some temperature numbers this evening and they were surprisingly cold.  Check out the first 12 days of 2017:

marktemp_last13days

The first 12 days of January have been the coldest since 1979…yes, that’s the coldest start to January in 38 years!  For those of you that were around then, what you probably notice is that it hasn’t been EXTREMELY cold this time, but it has been consistently cold.

coldjanuarystart

Combine the chilly December with this, and Portland is enduring the 3rd coldest start (first 43 days) of winter!  Winter would be December 1st-February 28th of course. What a HUGE change from the past few winters.

Looking ahead, we have a mild and rainy week ahead starting Tuesday.  I’m confident we will see at least localized flooding Tuesday/Wednesday with the sudden low-elevation snow melt plus heavy rain.  The ECMWF has been showing 2-3″ in the valleys Tuesday-Thursday which isn’t a big flood by any means, but we’re definitely going to see some issues.  I bet we get some mudslides too due to all that rain on frozen/thawing ground.

Enjoy another snow day kids, and for you parents, we’ll try to get those kids out of the house on Tuesday…

Chief Meteorologist Mark Nelsen

 

 

 


Biggest Snow Storm Since 2008 In Portland

January 11, 2017

4pm Wednesday…

It appears the final numbers are in now since we’ve only seen flurries since 10am or so.

The big question…

How does this storm compare to previous snow storms in Portland???

It was the biggest snowstorm since December 2008, just over 8 years



The official total at the Portland National Weather Service office in Parkrose was 7.9″ 8.0″

marksnow_portlandwintertotal

Here are lots of other totals from around the metro area:

marksnowtotals_metro_onemap

Most interesting about last night’s storm was the convective nature of the precipitation.  Very heavy bands of rain/snow moved north right along I-5 from 7-11pm.  So the big dumping was straight south to north from Lake Oswego through the middle of the city (that’s rare!) north through Vancouver and Hazel Dell.

West of Hwy 217 and east of I-205 it was more of a “typical” Portland snow storm.  By that I mean 4-8″ for most of us away from that big dumping in the middle of the metro area.

Here’s a look at the past few storms…these numbers are the official numbers from the NWS Office:

marksnow_paststorms

So what happens now?  We have thick snow cover, clearing skies Thursday, and a cool/dry airmass overhead.  That means cold nights and cool, but sunnier days.  It’s pretty obvious that we have the potential for single digits in the coldest outlying areas Friday and Saturday mornings, assuming skies remain clear.  We will likely not get down below 10 degrees here in the city.

To summarize…the snow on the ground isn’t going to suddenly melt, it will compress the next few days and gradually melt off roads.  Another snow day for the kids tomorrow, and possibly Friday too!

Chief Meteorologist Mark Nelsen


What a Snow Storm!

January 11, 2017

I’m just getting going at 10am after the craziest night in my 23 years of doing this.  We forecast a snow storm (1-4″).  But, sorry, I missed a digit on the upper end.  Instead we got 1-14″!!!  Parts of the south metro at the edge of the cold air only saw very light snow at the end of the event.

The OFFICIAL total (as of 10am) at the NWS office in Parkrose is 7.9″  I don’t know yet if that one-day total is greater than the 2008 snow storm.  So officially it’s our greatest one day snow since at least 2008, but possibly back to 1993 or earlier.

At the airport (which is no longer the official observing site), through midnight 6.5″ fell, making it the 7th biggest one day snowfall in P-Town.  If you read that at face value, this was our snowiest day since 1977.  BUT, big issue, 2008 doesn’t show up in the records because the airport location has seen observations come and go the past 20 years.  Without 2008 in there we don’t know how this one ranks at the airport.

historicsnow

Regardless,  this event is winding down and we’ll just see flurries the rest of the day and then go clear and cold for a few days.

The center of the metro area got the most snow with less to the east and west.  When I got home (at 1:30am), there were only 3″ of fresh snow…so sad.

Here are the totals as of 6am:

snowtotals

Chief Meteorologist Mark Nelsen


A Historic Snowstorm

January 10, 2017

11:30pm Tuesday…

I’m heading home now; what a crazy night!  It’s still snowing and some spots in the Portland/Vancouver area have 9″ of snow on the ground!  It’s our biggest storm since the December 2008 event.

There won’t be a commute tomorrow morning since the city is pretty much shut down

More tomorrow…

Chief Meteorologist Mark Nelsen


Snow Totals: How Much Do You Have?

January 10, 2017

8:30pm…

It’s really coming down in a strip right through the middle of the area.  Reports of 1.5″ to 2″ from SE Portland all the way up through Vancouver and Hazel Dell.

Put in your totals,

TOTAL
LOCATION

We can forget elevation for this event since it’s not really elevation dependent.

REMEMBER TO MEASURE ON A HARD SURFACE, NOT ON THE GRASS.  That’s what Derrick from Dallas did in this pic of the 3″ snow he sent to us.

photo_dallas

 


Snow Storm Beginning

January 10, 2017

6:30pm…

Two obvious changes this evening:

  1. There is FAR more moisture available than models were showing, at least this evening.  There is very heavy rain moving through the central valley right now.
  2. Our snowstorm has begun a good 3-4 hours ahead of schedule, this is clipping the end of the evening commute.

We’ll be on most of the evening on FOX12 with snow coverage…I’ll see you there!

sylvan