Warm South Wind Has Arrived!

January 18, 2017

9:30pm Wednesday…

Portland suddenly jumped to 46 degrees this hour as a warming “Chinook” wind arrived.  The same thing happened in Troutdale and Corbett as a cold front passed by.  That front mixed out the cold air lingering at the far west end of the Gorge.  In fact Troutdale is the warmest location in the ENTIRE metro area this hour!

plot_temps_metro

By the way, the term “Chinook wind” was first used along the Pacific Coast, then the term was adapted to use in the Rockies and Great Plains to describe the warming west wind there in wintertime.  It refers to a sudden warming after a cold spell in winter.  That pretty much describes this evening.

But a south wind won’t make it far into the west-east oriented Columbia River Gorge.  Temperatures will only slowly moderate 3-5 degrees above freezing from Bonneville to The Dalles Thursday.  The cooler east wind does return on Friday and I don’t see a setup in the next 5 days that would push a warm wind all the way through the Gorge.

The NWS has dropped the Ice Storm Warning in the Gorge this evening due to precipitation tapering off quickly now that the cold front has moved by.

This ice storm is the most destructive I’ve seen in the central Gorge with 1-2″ solid ice accumulation from Troutdale to Stevenson/Cascade Locks area.  From what I hear the damage is especially extensive in Skamania county and around Cascade Locks to Dodson.  Hood River was spared the thickest glazing due to part of the storm seeing ice pellets instead of liquid rain.  I-84 has been closed now for about 30 hours and will remain that way until at least sunrise.  There is beauty in the ice though…take a look at some of the pics, which I’ve put into a gallery below:




I’m so glad we ended up slightly too warm in the east metro area or we could have seen something similar in Gresham, Fairview, & East Portland.

Tomorrow’s weather will be uneventful with scattered showers and maybe even a few sunbreaks.  Enjoy the slowdown.

Chief Meteorologist Mark Nelsen


Ice Storm Near & In Gorge Tonight

January 17, 2017

10:15pm…

At least the forecast ice thickness panned out, but just in a much smaller part of the metro area.  Check out how thick the ice is!

markfreezingrain_icetotalssofarpdx

…An inch of freezing rain in just about 8 hours in Troutdale.  There could easily be 1/2″ additional before temps rise much more by sunrise.

Farther into the Gorge the ice storm continues through Wednesday, likely going slightly above freezing at the west end though.

markfreezingrain_gorge

Chief Meteorologist Mark Nelsen

 


5pm: Most of Metro Dodges Ice Storm

January 17, 2017

It’s become clear the past two hours the very cold air pouring out of the Gorge is very shallow, more so than we expected.  The result?  Even most eastern metro locations will NOT be seeing a big ice storm tonight (Whew!) Sub-freezing air is mainly confined to right along the Columbia River and doesn’t extend more than 1-2 miles north and south.  You can see that in the latest temperature map, blue temps are below freezing.

plot_temps_nolabel_metro

Where the temperatures are below freezing, the ice accumulation has been very thick so far:

markfreezingrain_icetotalssofarpdx

That’s almost 1/2″ in Troutdale already.  If temps were 2-3 degrees colder eastside, this would have been the case for many more of you.

So only the areas right along the Columbia River will see additional icing tonight and of course it’s a big ice storm in the Gorge.

There will be no refreezing of roads tonight and the AM commute should be just fine (ice-wise) everywhere except right in downtown Troutdale and into the Gorge.

For the geeks like me…the Troutdale profiler shows us what’s going on.  The cold layer is VERY thin, less than 1,000′ deep over the west entrance to the Gorge!  Looks like abourn 50 degrees at the 2,000′ level.  Typically in a normal ice/snow event (even for east metro), the cold layer is around 1,500 to 2,000′ thick.  I thought it looked a bit strange this morning, but now we know what happened; something to remember for future storms.  A cold layer that thin, even with 10-11 millibars easterly flow,  will remained confined quite close to the Columbia River.  It is still 20-21 at Hood River and The Dalles, which typically would keep the entire east metro below freezing with the east wind.  This makes me think the current setup (cold air right along the river) could continue through the night and into midday Wednesday.  It’s still going to be a huge ice storm, but only in a very narrow ribbon along the Columbia River, both north and south.  I-84 will be close for a day or two I think.

capture

Chief Meteorologist Mark Nelsen


2pm: Heavy Rain is Here, Ice Storm East Metro

January 17, 2017

That accelerated quickly!  Moderate to heavy rain suddenly arrived in the metro area in the past hour and now ice is accumulating (technically accreting) where temps are below freezing.  I-84 immediately closed in the Gorge.  1/2 hour before that time I drove it westbound just as rain beginning and there were a LOT of semi-trucks flying through at 50-60 mph.  I’m guessing that didn’t go well once the heavy rain started at 25 degrees.  Where will the ice storm continue?  Take a look at the map:

plot_temps_nolabel_metro

Yep, in the areas exposed to the cold east wind coming out of the Gorge.  The cold air is only 1,000′ over Troutdale.

HIGHLIGHTS

Within the blue area above an ice storm has begun and will continue tonight.  Remember that temperatures have to be below 31 degrees for roads to turn icy, so in much of east Portland this will be a damaging event for trees/powerlines but not terrible on the roads.

ALL OTHER AREAS west of the Cascades are IN THE CLEAR for additional icing on roads.  This includes all of north/west/south metro areas.  Once you go south of the Multnomah County line in the east metro area you are mainly out of the freezing air.  You can resume your normal activities in those areas

markfreezingrain_icedetails3

markfreezingrain_icedetails3a

Chief Meteorologist Mark Nelsen

 

 


9am: Incoming Showers = More Spotty Freezing Rain

January 17, 2017

I hope most of you in the central/east part of Portland chose to skip work/school today!

That first band of freezing rain passed through the metro area before sunrise, but was light enough that most roads don’t appear to have been affected much.  Don’t be fooled, check out radar…

Here come more showers and they look quite wet this time!  They are sneaking in due to that ridiculous huge gap in the radar coverage off the Oregon Coast.

codnexlab-nexrad-rtx-n0q-20170117-1656-024ani

Except for the timing of the heavier rain speeding up, the rest of the forecast is still on track.  Let’s check current temps:

capture

I hope you enjoy my graphics talent…  The yellow shows the areas that are at risk of widespread road icing BEFORE NOON.  This is roughly the “blue area” I showed on-air last night and in the previous blog posting.  This is going to quickly become an event centered on those areas that typically see cold outflow from the Gorge.  I find it very interesting the top of Mt. Scott appears to be busting out of the cold air.  This tells me the cold layer is VERY shallow and will mix out easily anywhere in Clackamas/Washington/Clark counties.  I left Clark county in the “scary yellow box”, but even there after noon it should be warming above freezing.

To summarize

  1. In the next two hours a light glazing of ice is still possible anywhere in the metro area still below freezing.
  2. But for a large part of the metro area (outside of yellow area above+most of Clark County), you will be “in the clear” after the noon hour.
  3. Ice Storm is still on for central to eastside of metro area…roads likely turn very icy the next few hours there.
  4. Loading of ice on trees/powerlines will become a big issue this evening and tonight east of I-5 in Multnomah County, especially east of I-205

Chief Meteorologist Mark Nelsen

 

 

 


Ice Storm Warning Metro Area: Freezing Rain For A.M. Commute

January 16, 2017

8:30pm Monday…

Evening models are all in and they are all exactly the same, which gives us pretty good confidence on the forecast.

markwarnings_winter-wx-advisory

What has changed this evening?

  1. All models push a band of light rain (freezing rain) across the west side of Oregon right between 4-7am instead of waiting until mid-late morning.  TIMING HAS SPEEDED UP
  2. This means most roads will have a fresh glaze of ice on them for the morning commute from Longview to Eugene.  I’d forget the morning commute if you live in the I-5 corridor.
  3. I’m increasingly confident that most areas on the 3 maps down below will see gradual melting in the afternoon and be pretty much “out of the woods” for the evening commute.  If you’re not in the blue area BELOW, things look much better by afternoon/evening.  Click through those 3 for a closer look.
  4. East wind is even STRONGER this evening!  Peak gust this past hour 89 mph at Vista House and 83 mph at Corbett.  In the past 18 years I’ve never seen winds up in the 75-85 mph range in that 2nd location for more than a brief blip.  Crazy.

 

markfreezingrain_icedetails3

markfreezingrain_icedetails32

  1. A major and possibly crippling ice storm is BECOMING LIKELY in the central/east metro area similar to the 1996 event starting tomorrow afternoon and continuing through sometime Wednesday AM/midday
  2. The Columbia River Gorge (all of it) is LIKELY to see a major/crippling ice storm tomorrow through Wednesday.  This on top of heavy snow/ice already could lead to roof collapses in that area.

HIGHLIGHTS

  • The low-level airmass doesn’t change at all through Tuesday AM as frigid air keeps pouring out of the Gorge.  We remain below freezing in most of the Portland area.
  • A band of rain moves through most areas west of the Cascades between 6-9am, freezing on contact in almost all areas in the western valleys of Oregon/SW Washington
  • Roads in most of the metro area (that aren’t already icy) will turn icy within 15 minutes of the rain arrival
  • Then mainly dry for a few hours and temperatures everywhere except central/east Portland the Gorge rise to near or above freezing.
  • Temps remain in the 20s East Portland to around the Gorge entrance…solidly frozen all day there.
  • Heavy rain arrives around 3-4pm and it pours all night long into Wednesday AM as a brief “pineapple express” parks itself overhead
  • West and south metro plus Clark county should be slightly above freezing during this time, thus avoiding a big ice storm.
  • DURING THIS PERIOD, EAST PORTLAND OUT TO THE GORGE LIKELY REMAINS BELOW FREEZING
  • If models are correct, 1-2″ ice could form on all exposed surfaces, doing tremendous damage to trees/powerlines that we haven’t seen in 20 years.
  • Any precipitation through Wednesday midday/afternoon should be freezing rain in the Gorge.  1-2″+ is likely out there.

COMMUTERS/SCHOOL

  • I’d say both should be skipped tomorrow
  • Check right away in the morning when you get up to see how temperatures are doing and where the precipitation is of course.  Maybe I’ll be totally wrong this time and we’ll get lucky!

Chief Meteorologist Mark Nelsen

 


Winter Storm Watch: Major Ice Storm Possible Central/East Metro/Gorge

January 16, 2017

Noon Monday…

The Portland NWS has issued a Winter Storm Watch for many areas west of the Cascades for Tuesday.  A WATCH means conditions are set up for a certain event to occur.  These will likely be converted to Freezing Rain Advisories and Ice Storm Warnings (depending on ice accretion expected) this afternoon.

A few thoughts:

  1. A major and possibly crippling ice storm is POSSIBLE in the central/east metro area similar to the 1996 event starting tomorrow and continuing through sometime Wednesday AM/midday
  2. The Columbia River Gorge (all of it) is LIKELY to see a major/crippling ice storm tomorrow through Wednesday.  This on top of heavy snow/ice already could lead to roof collapses in that area.  Get roofs cleaned off today if you have the ability to do so.
  3. Most of the rest of the metro area will LIKELY see at least some freezing rain Tuesday before temps creep above freezing, not a big ice storm but enough to cancel schools and turn roads icy for a good chunk of the day.

HIGHLIGHTS

  • The low-level airmass doesn’t change at all through Tuesday AM as frigid air keeps pouring out of the Gorge.  We remain below freezing in most of the Portland area.
  • Rain arrives sometime between 7am-11am Tuesday, freezing on contact in almost all areas in the western valleys of Oregon/SW Washington
  • Roads in most of the metro area (that aren’t already icy) will turn icy within 15 minutes of the rain arrival
  • Light freezing rain continues through the afternoon as temperatures rise to near/above freezing south and west metro.
  • Temps remain in the 20s East Portland to around the Gorge entrance…solidly frozen all day there.
  • Heavy rain arrives around sunset and it pours all night long into Wednesday AM as a brief “pineapple express” parks itself overhead
  • West and south metro should be slightly above freezing during this time, thus avoiding a big ice storm.
  • DURING THIS PERIOD, EAST PORTLAND OUT TO THE GORGE LIKELY REMAINS BELOW FREEZING
  • If models are correct, 1-2″ ice could form on all exposed surfaces, doing tremendous damage to trees/powerlines that we haven’t seen in 20 years.
  • Any precipitation through Wednesday midday/afternoon should be freezing rain in the Gorge.  1-2″+ is likely out there.

COMMUTERS/SCHOOL

  • I’d say both should be skipped tomorrow
  • Check right away in the morning when you get up to see how temperatures are doing and where the precipitation is of course.  Maybe I’ll be totally wrong this time and we’ll get lucky!

The main reason for the forecast change in the past 24 hours isn’t just the usual “oh, the cold air is sticking around longer than expected”, it’s because models have backed off on bringing lower pressures to our north.  Surface low pressure centers are expected to stay much farther offshore now.  This only gives us weak southerly flow up the valley and not until Tuesday night for central/south valley.  Since we have the low-level cold air in place and it is VERY cold, that means a longer period of time spent below freezing central/east metro.  The preferred ECM

 

WF model shows the progression pretty well, 4am Tuesday wind…strong easterly gradient and we’re in the deep freeze

ecm_tuesam

Then 4pm Tuesday…still 7 millibars easterly gradient (cold east wind still sending cold air into metro area).  Only a very light southerly flow up central/south valley.  We’re still frozen most of metro area at this point.

ecm_tuespm

Wednesday 10am, southerly wind has taken over south of metro…easterly STILL going central/east metro.  This would keep central/east metro frozen through midday Wednesday!

ecm_wedmidday

And the really bad news.  Check out how much rain has fallen during that period, a solid inch to two inches glaze ice over the below-freezing areas.  There is no loss of precip in this case from the dry Gorge wind as we’ve seen in snowstorms because that dry air is very thin, in the lowest 1,500′ of the atmosphere:

ecm_precip_wed_midday

That’s a major ice storm that we haven’t seen in many years central/east metro and the Gorge.  The WRF-GFS model’s rain forecast is similar, showing 1-2″ rain in the metro area by Wednesday afternoon.

wrf_precip_wed_pm

Wednesday evening a cold front passes overhead and we change to a showery pattern.  Then temperatures even in the Gorge will gradually rise above freezing and in the metro area too.

Is there anything you can do to prepare?

  • Get plenty of gas for your generator if you have one of those and live in the ice storm area
  • Watch for falling trees/limbs Tuesday night and Wednesday AM.  I don’t expect significant icing until after dark Tuesday when the heavier rain arrives

Chief Meteorologist Mark Nelsen