Tuesday is “Transition Day”; briefly icy weather ahead!

6pm Sunday…

In the Portland metro area we sometimes get a great (or horrendous) transition from a cold arctic airmass back to our usual wet and mild weather.

This won’t be one of those times.  That said, most of us in the western valleys north of Salem are going to get a little snow and/or freezing rain/drizzle Monday night and Tuesday morning.

First, the bitter and historic cold temps this morning for some parts of our region

In the metro area, in general, today saw the coldest weather since December 2009.  We had a low of 12 and high of 28 at PDX.  We haven’t seen temps that cold in 4 years.  For a few spots around town it hasn’t been this cold since 1998.

Down in the southern Willamette Valley and in some areas east of the Cascades this has been a truly historic event:

  • Eugene hit -10, 2nd coldest temperature of all time
  • Redmond hit -27, 2nd coldest temp of all time.
  • Lakeview had an all-time low of -27.
  • Burns also had an all-time low of -30.
  • 850mb temperature at Salem was -14.1 degrees Saturday morning, which makes this the coldest mid-level air mass that has moved over us since 1998.  It just barely squeaked past 2009.  Thanks to Chris Callais for that info.

Here are the highlights for those just wanting the basic forecast info:

  • Most areas will be dry tonight, not as extremely cold, but still cold
  • Mainly or all dry Monday west of the Cascades.  Skies will cloud up and a flurry is possible, but nothing that would affect traffic from Longview to Eugene through sunset.
  • Increasing areas of light snow OR freezing rain/drizzle after sunset Monday night through midday Tuesday
  • Temperatures won’t rise above freezing until midday Tuesday, so whatever falls during that time will be frozen.
  • Not much moisture, so just a Trace to 1″ snow, or light glazing of freezing rain/drizzle.  Many areas from the middle of the metro area south to Salem may see little or nothing, we’re talking real light stuff.
  • Issues on roads, where frozen precip falls, will be sometime after sunset Monday to midday Tuesday.  Before and after that time it looks clear.
  • There is little or no chance this turns into a prolonged or heavy freezing rain or snow event.  We get very little of anything, then we’ll be dry from midday Tuesday through Wednesday night, and temps warm well above freezing.

DETAILS

It’s funny that the perception continues to be that each time we plunge into an arctic air mass  “there’s no way we’re getting out of this without an epic event“.  Or something along those lines.  I think it’s because we remember the “epic” events for good reason!  January 5-8, 2004, December 21, 2008, February 1996, December 25, 1983.  But what about more recent arctic blast events.

  • November 24, 2010:  Just some spots of light freezing drizzle here and there and then a warm up after a high of only 30 degrees on a sunny day.
  • December 12, 2009:  Trace of freezing rain, then 41 the next day
  • December 17, 2008:  Gusty south wind took us from 23 in the morning to 38 in the afternoon with little/no snow accumulation, then mixed showers.   The big snowstorm was after the 2nd surge of arctic air 3 days later.
  • December 24, 1998:  2″ snow in the morning, then wet roads by sunset

I think this will be one of those times too for these two  reasons

  1. This is the big one, no cold east wind pouring out of the Gorge.  All of our significant transition events involve cold and dry air getting reinforced by the freezer door at Troutdale.  Not this time.  Atmosphere can easily (but slowly) warm up with light onshore flow, especially once cloud cover brings nighttime lows up closer to freezing.  That’ll happen Monday night.
  2. Extremely light precipitation to moisten up the air mass, once that happens forget about evaporational cooling helping us beyond Tuesday.

There is no “storm” or even organized weather disturbance moving through our area later Monday through Tuesday, just mid-level flow turning onshore, moistening things up and riding over the cold low-level air mass.   Notice how light the precipitation will be:

precip_wrf

Very little in the middle of the metro area and almost nothing south of us.  Snowfall off that same model is about as pathetic.

snow_wrf

No more than 1″ anywhere except maybe in some foothill locations.  Clark and Cowlitz counties are probably the place to see.  You may notice there is more precipitation than the snowfall coverage shows even though temps are below freezing.   Check out the WRF-GFS sounding, hinting that it may rise slightly above freezing around 2,000-3,000′.  Good setup for freezing rain or drizzle.  Our RPM is hinting at this, showing an area of freezing rain (pink) on the south side of the light precipitation.

rpm_ice

Here’s a great explainer from the Seattle NWS from today’s discussion:

HERE IS A QUICK WEATHER LESSON. IT IS POSSIBLE TO GET LIQUID FALLING FROM THE SKY…EVEN WHEN THE ENTIRE ATMOSPHERIC SOUNDING IS BELOW FREEZING. THE KEY IS THAT PRECIP HAS TO BE GENERATED IN A LAYER THAT IS -5C OR WARMER…IN WHICH CASE SUPERCOOLED WATER DROPLETS ARE FORMED… RATHER THAN SNOWFLAKES. WHEN THESE CONTACT A SURFACE THAT IS BELOW FREEZING…IT WILL FREEZE UPON CONTACT AND BE OBSERVED AS FREEZING DRIZZLE OR FREEZING RAIN. THIS BECOMES A CONCERN IN A SETUP LIKE MON AND TUE…WHERE PRECIP IS BEING GENERATED AT FAIRLY LOW AND RELATIVELY WARM LAYERS OF THE ATMOSPHERE…EVEN IF THOSE LAYERS ARE A LITTLE BELOW FREEZING.

Gotta love those All Caps!

Beyond Tuesday, we’re in the clear here in the metro area as temps warm. There could be a 2nd transition event possibly in the Gorge Wednesday night or Thursday as real moisture arrives with a much stronger front. By that time we’ll be in the 35-45 degree range here in the valleys so ice/snow won’t be an issue.

To wrap it up: We’re going to see a little frozen precipitation at some point tomorrow evening through Tuesday morning that could impact travel during that time, then the weather gets boring for awhile.

Chief Meteorologist Mark Nelsen

86 Responses to Tuesday is “Transition Day”; briefly icy weather ahead!

  1. paulbeugene says:

    It did not occur to me until this morning that I have not seen a SINGLE snowman in all of Eugene since the snow fell. That just never happens around here. Too cold…snowmen migrated to Redding CA in search of warmth. (Snow too dry/cold).

    Average LOW temperature in Eugene in the past 20 days has been 20.5 degrees

    That is the third coldest 20 day stretch behind only Dec 1990-Jan 1991(19.6) and Jan 1949 (18.3)

    I am concerned about persistent trend for ridging overhead or offshore. We could be headed for a period of persistent sub freezing nights (fake cold) before perhaps real cold again after Christmas. This will be my worst heating bill ever

  2. Marcustheweathernut says:

    Gobble gobble gobble goes the coast range!!!!! Going to take all of our snow blahhhhh :/

    • JohnD says:

      Maybe not all! Will be looking all day for
      that vagrant snowflake to make it through!
      “We must be relentless in our watch!”hehe

  3. Mark says:

    La la land on the EURO 00Z shows some promise (talking 240hr out). Although, I can’t read the progression and whether the high is a blocking omega-style setup, or not… Yah, already onto the next! Looking for that fabled white Christmas…

  4. chris s says:

    So nobody wants to comment on the models showing blah the next 10+ days ? At some point some snowpack in the mountains would be nice, especially for the ski resorts.

  5. Longview 400 ft says:

    Snowing here in Clatskanie. All is white.

  6. Danny says:

    The dome has become very cloudy now very quickly after sunrise, which was minimal cloud cover here, hoping for the best maybe a better shot at snow this time in the dome. Either way it’s ok winter hasn’t even begun yet!

  7. Traci-Gresham says:

    My mother in-law says it is snowing in Astoria. What time might we begin to see something?

  8. W7ENK says:

    Repost from previous:

    Sunday morning low temperature at my location in Milwaukie:
    9.0F degrees at 6:45am.

    Monday morning low temperature (so far) at my location in Milwaukie:
    10.8F degrees at 6:15am. I will know what the final low was when I get home from work.

    Had an amazing time with friends (most of which from here or the Facebook counterpart to here, actually) in the hills East of Silverton on Saturday night. 0 degrees with about an inch of squeaky snowcover, but we did our best to warm it up…

    There’s nothing quite like a bunch of crazy weather geeks playing in the snow during a historically COLD night!!

    • weathernate says:

      Does anyone know if the roads will be impacted in the vancouver wa area tonite. Iam leaving at 830pm to take same food to the food banks and would like to know what it may be like. Local weatherman afraid to pull the trigger and dont really want to be caught offgaurd.

    • Garron near Washington Square says:

      I love a good nuclear insta-fire!!!! NICE JOB, Maybe next one, you could use some dramatic concert style music, pour a trail of gasoline to the fire, maybe some fireworks involved???? Just a future suggestion for a bottom of the cliff style bonfire….Hoping you do an Eric-log “no” storm comic relief to our transition event?

    • Mark Nelsen says:

      Could start seeing some road issues anytime after sunset I think. Not due to cool temps, but timing looks about like that. Flurries before that time though.

    • Ryan says:

      That would line up with the 4pm winter weather advisory.

    • weathernate says:

      Thanks guys. Would love to see it stack up after 11 when i get home. Wont happen but would be fun. Lets hope the ice stays away.

  9. Garron near Washington Square says:

    I always love Shawn Weagle’s commentary on the NWS Area Forecast Discussions…Today’s feature was: I HOPE THIS DOES NOT
    COME BACK TO HAUNT ME…BUT AM CONTEMPLATING TO REMOVING THE CENTRAL
    WILLAMETTE VALLEY FROM THE WINTER WX ADVISORY…

    The rest of the AFD as follows…http://forecast.weather.gov/product.php?site=NWS&issuedby=PQR&product=AFD&format=CI&version=1&glossary=1

  10. Joe Schmoe says:

    What are the chances that we see school canceled Tuesday in the Portland Metro area?

  11. MasterNate says:

    8.5 degrees so far this morning just outside Molalla. Just as cold as the night before.

  12. Josh Gardner says:

    Here’s my thoughts. I believe we will see a period of snow for all areas. Trace to 2″ with the higher amounts in Clark and Cowlitz counties. Freezing rain is also very possible, IMO this will be a threat not only today, but Wednesday and Thursday.

    • Sapo says:

      Yeah, I think that most areas will at least see a trace before we transition to freezing rain, possibly even more snow.

  13. Darlene in Boring says:

    What’s this I see? Precip. already moving into the Astoria area and it is only 0630. Hmmm…

    • Sapo says:

      The precipitation will move in slowly, probably arriving 6-9pm.

    • Darlene in Boring says:

      I would be very happy with a 6-7 pm arrival time. After that, it can do whatever it wants out there. :) It sure clouded over quickly out here. I just came in from morning chores and it feels like snow to me. (not wishcasting…just that feel and smell that is present before snowfall)

    • JohnD says:

      Concur–feels/smells like snow to me too! You
      would sure think that it will stay cold with
      the cloud cover today. No south wind stir up
      today either.

  14. Rob - Southeast Portland says:

    **** EUGENE BACK-TO-BACK CONSECUTIVE NIGHTS BELOW ZERO ****
    They did it again! Eugene for the 2nd consecutive night in a row has plunged below zero! Now currently sitting at -2. The dewpoint of -6 and CLR skies suggests further cooling is possible.

  15. Muxpux (Castle Rock 175') says:

    Up to 23 at 10k feet at camp Muir

    • Josh Gardner says:

      Yeah, we’re setting up for a lower level COLD inversion. These small systems won’t moderate the atmosphere

  16. Josh Gardner says:

    NWS not favoring a quick warmup..

    NO DOUBT THIS IS AN HISTORIC COLD AIR MASS. WHICH BRINGS US TO OUR
    NEXT FORECAST CHALLENGE…THE PRECIPITATION TYPE EXPECTED FROM OUR
    NEXT TWO EVENTS. CONSIDERING THE MAGNITUDE OF COLD ASSOCIATED WITH
    THIS AIR MASS…IT IS VERY HARD TO BELIEVE WEAK CLIPPER SYSTEMS WILL
    BE SUFFICIENT TO ERODE THE COLD AIR ENTRENCHED OVER THE PACIFIC
    NORTHWEST. WE CONTINUE TO DISAGREE WITH MODEL GUIDANCE THAT SUGGESTS
    THE COLD AIR WILL SCOUR OUT QUICKLY…AND OUR TEMPERATURE AND
    PRECIPITATION TYPE FORECAST REFLECTS THAT ALL THE WAY INTO THURSDAY.

  17. EY (Oak Grove) says:

    Could get close to the record low in Portland tonight… But I highly doubt we’re going to pull it off.

    Down where I live, readings as low as 11 and as high as 15 abound. Could have another sub-10 moment around here if those temps are accurate.

    Cold as heck regardless.

  18. PeteCJ says:

    That developing disturbance off the northern Washington coast looks to me like it could provide us with earlier and more moisture than forecast.

    http://www.atmos.washington.edu/~ovens/wxloop.cgi?ir4km_enhanced+12

    Moisture already showing echoes off the coast

    http://weather.cod.edu/satrad/nexrad/index.php?type=LGX-N0Q-1-48

    I’m optimistic for measurable snow

    • Jake at the Lake says:

      What, another bust forecast? Imagine that. :)

    • well, NWS was calling for flurries after 4am here, lol i see now they took that wording out and instead are saying, “before 10am” instead of “after 4am”

      also, whats with this?

      Wednesday: A chance of rain, snow, freezing rain, and sleet before 10am, then a chance of rain. Mostly cloudy, with a high near 39. Chance of precipitation is 30%. Little or no snow accumulation expected.

      Wednesday Night: Freezing rain and sleet likely, possibly mixed with rain, mainly after 4am. Mostly cloudy, with a low around 31. Chance of precipitation is 60%. Little or no snow accumulation expected.

      Thursday: Rain, freezing rain, and sleet likely. Cloudy, with a high near 40.

  19. Louis says:

    Would appreciate more info on timing of changes in gorge at times like this coming up since I live in the middle of it. (Hood River) 7 degrees at 12:18 a.m.

  20. schmit44 says:

    12/8/2013 Oregon (All) Temperature Summary

    Warmest:
    High:45 at Gold Beach (US 1( 60 ft)
    Low: 28 at BROOKINGS(79 ft)

    Coldest:
    High:2 at HARL BUTTE(6071 ft) & Lakeview (US 395(4780 ft)
    Low: -41 at Horse Ridge (US (4160 ft )

    Largest Diurnal Change: 56 degrees
    Horse Ridge (US (15/-41 ) (4160 ft )

  21. Jason Hougak says:

    Record weekend of people who had well systems that froze up and quite working. We had nearly 100 phone calls,I could not put the phone down! We got alot going over the phone but had to actually service many who had wellheads freeze solid. When are people going to take warning and plan ahead! All it takes is some heat and keep your system above 32F. I went out and there would be a light on at the ceiling and no other heat source. Holes in the building and cold air being drawn right in. The water in the pipes is a magnet for ice formation. Please next time can we order three feet of snow for good insulation! Jason
    Steve’s Pump Service
    Here’s to a busy day tomorrow as “WELL!”

    • David B. says:

      Already saw one house here with a burst hose cock. Not smart to leave it uncovered with a hose still attached when freezing weather is forecast.

    • DELXV says:

      What is your location Jason?

    • Mark Nelsen says:

      Luckily you recommended I put mine underground. Well, technically YOU put it underground. Although I didn’t do anything about my outside faucets…oops. We’ll see. Jason put in a new casing, pump, and buried the pipe a bit below ground to avoid the issues apparently lots of people are having.

  22. While the major metro areas had little snow (PDX) or none (SEA), this arctic outbreak is clearly impressive, if for no other reason than the coldest 850mb sounding at Salem since 1998. Micro scale events like the south willamette valley snow or historic Eugene cold are memorable. But if one is simply trying to gauge the “strength” of an arctic outbreak, I think the Salem sounding is the best yardstick. So, with that said, may I raise a glass to the big cold of December 2013. Here’s to a short marine interlude, till the euro tees up the next arctic reload (and may we up north get the snow this time)

  23. BoringOregon says:

    I thank it would be funny if we had another weather bust, I mean it did happen. Its 16 out here. And we still have January, for some good weather events!!

  24. Taylor says:

    Yup officially in the teens again here in Clackamas. 18.9 degrees right now.

  25. Longview - 400 ft says:

    Just came over the wire:

    TUESDAY FOR THE LOWER COLUMBIA RIVER AND THE I-5 CORRIDOR IN COWLITZ COUNTY
    UNTIL 4:00AM PST
    Urgent – Winter Weather Message
    National Weather Service Portland OR
    212 PM PST Sun Dec 8 2013

    Lower Columbia-I-5 Corridor In Cowlitz County-
    Including The Cities Of… St. Helens… Longview… Kelso

    … Winter Weather Advisory In Effect From 10 AM Monday To 10 Am
    Pst Tuesday For The Lower Columbia River And The I-5 Corridor In
    Cowlitz County…

    The National Weather Service In Portland Has Issued A Winter
    Weather Advisory For Snow… Which Is In Effect From 10 AM Monday
    To 10 AM PST Tuesday.

    * Timing… Light Snow Flurries Around Sunrise Monday With Snow
    Becoming More Steady Mid Morning And Persisting Through Tuesday
    Morning.

    * Snow Levels… Near The Surface.

    * Accumulation… 1 To 3 Inches.

    * Impacts… Roads Will Likely Become Snow Covered And Icy.

  26. Drow says:

    I’m sorry people but I have a gut feeling we’ll get more than has been forecasted as well. So far NWS and Accuweather have been accurately forecasting. Mark, your a great weather man but you did busy Friday morning along with all the other mets. Just sayin

    • Mark Nelsen says:

      Hey, a bust for Clark County up to Longview and Scappoose. Otherwise a perfect forecast for the rest of the viewing area west of the Cascades, the Coast, and 2/3rds of the metro area. Give me some credit!

    • Model Rider says:

      Mark, you were right on. Especially with the temps. The only miss was the “1″ inch of snow slightly to the north. Wow, what a bust. Give me a break, Mark is by far best forecaster in the west. Bet he’s right this time too.

    • EY (Oak Grove) says:

      The NWS also forecast Portland to hit 6 degrees for a low Sunday morning, thus tying the all-time December record low set back in 1964.

      Then we hit 12.

      Not a huge miss, but neither was Mark’s snow forecast.

  27. Taylor says:

    Temperature will probably get to the teens one last time tonight here in Clackamas, OR temperature right now is at 20.5 just a little bit warmer right now than it was yesterday at this time. Probably won’t be as cold tonight, but still very frigid for this area.

  28. MasterNate says:

    Another cold one. 12 degrees at 8:15 just outside Molalla. Walked across our pond today, approx. 200′ across. Not even a crack.

  29. Ryan says:

    I’ll take anything at this point. At least it feels like winter.

    • pappoose in scappoose says:

      +1

    • JohnD says:

      Yep, we take what we can get–even if few and far between– including near misses translating to bullseyes for our brother-sisters a mere hour drive to the south. We live in a solid 45th parallel Marine! climate where low elevation winter weather events are few and far between. Sooooooo maybe either time to move to Duluth–or forget the whole thing and move to San Diego!

    • David B. says:

      Seconded. Have an ice day!

  30. Ben T says:

    Hang on cold air, it’s not time for you to go home!

  31. snodaze says:

    Nah… (this one is easy blog-boys)… It may just be a light dusting of freezing drizzle “FZFG”… (of course it’s frozen before it bounces off the pavement)… So ice pellets… — Very little snow — Maybe some periods of “tweeners”… — There’s just not any energy to draw cold air out of the basin up into the column.

    Nothing to write home about. — Next? (see you in a couple of weeks)… lol…

    • snodaze says:

      What I really mean is… — This is nothing. — zip / zero / nada… :-) — See you in two weeks.

    • JohnD says:

      I concur. Just the way it is. As well as ironically frustrating in light of those in the nearby surround, who experienced an epic–or near epic–event.

  32. Seahawks Fan - NE Vancouver says:

    I see that Crown Point made it up to 38 degrees today.

  33. Roman~Snow-Zone-Monmouth, Elv. 223' says:

    7:00pm observation at Eugene 3F!!! They could very possibly have the coldest night on record holy toledo!

  34. Timmy_Supercell (Klamath Falls @ 4200') says:

    7:00pm. It’s already -9.0!! BRRR….

  35. chris s says:

    Mark with all due respect, i think you may be doing another forecast bust posting come tuesday morning, maybe even monday night. At least i hope so, lol. :-) Seriously though, you forgot to mention Jan 2004 down here in salem, as we tuned into the news everyday and heard “we were going to moderate today” !! I just have that gut feeling that its not gonna go as advertised. :-).

    • chuck on mt scott says:

      I get the slightest bit of East Winds up here, when the rest of town is not. Not a lot of wind today and tonight. And I suspect not much tomorrow either. That seems to be the fuel to keep the cold air trapped in our area. When I start to get the slightest Southern Wind, its all over. I have seen snow turn to rain very quick once the winds shift up here. I just hope what ever happens, people are wise and not take chances.

    • JohnD says:

      Yeah Mark sometimes is doggone annoying because he is mostly right all the time and while most of we “wish casters” hope for the contrary. Whatever.

    • Benjamin (West Salem) says:

      I think in January 04 we had north and east winds blowing, where as this time there is no east wind being forecast.

      With that said I do remember watching the local weather mets saying every day during that transition event that we would finally get above freezing. They copied and pasted the same forecast for 4 or 5 days before we finally moderated above 32. It was truly EPIC!!!

    • Mark Nelsen says:

      East wind was raging the first 3 days of that event. Sure did screw up the Salem forecast that time AND in December 2008! Remember snow to freezing rain, then back to some snow?

    • Benjamin (West Salem) says:

      Yes, in 2008 that Sunday night after the big storm I remember we were starting the “silver thaw” with the temp around 34 or so. Than I woke up Monday morning and was blown away to see a temp of 28 and 4 inches of new snow on the ground with more snow falling later that day. I wish I knew more about that event. How weird was that? A transition event from snow to freezing rain followed by more snow… :)

      I’m just glad I’m not a forecaster like you, even this upcoming forecast is going to be a hard one to nail down until it happens. Being in Salem it looks like we are right on the bubble of snow/no snow for Mon night/Tue morning. I agree, the biggest difference this time is that there wont be a cold east wind blowing like 04 and 08.

      Thanks for all you do on this blog!!

      Also thanks for putting together this page: http://www.cascadeaccess.com/~mnelsen/markswxlinks.html it is one of the most interesting and helpful pages I have ever used.

  36. Josh Gardner says:

    Monday wintery precip event.

    WHAT WE KNOW

    -We’re under a WWA from 4pm Monday, to 4am Tuesday.
    -Some kind of wintery precip will fall between midday Monday and Midday Tuesday

    WHAT WE DON’T KNOW

    -Timing or amount of precip
    -When we moderate, or if we immediately moderate

    X FACTORS

    -Strength of the system (ideally weak enough to bring precip and possibly develop easterly flow, but not too strong as to moderate too much)
    -The aforementioned easterly flow, this could keep areas specifically east of I-5/205 cooler and messier
    -Snow cover to our South and its impact on moderation

    FORECAST TOOLS TO WATCH (links)

    4km WRF Time Heights http://www.atmos.washington.edu/mm5rt/rt/timeheights_d3.cgi?current_gfs

    MM5 NAM 12km 1 hour Precip
    http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d2_e_or_pcp1+%2F%2F72%2F1

    WRF GFS 4km 1 hour precip
    http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d3_or_pcp1+%2F%2F%2F1

    HRRR hourly model runs (This is what I used to forecast the surprise snow on Friday, was the only consistent model showing this, and it nailed amounts as well)
    http://rapidrefresh.noaa.gov/HRRR/Welcome.cgi?dsKey=hrrr_dev1_zeus&domain=t1&run_time=08+Dec+2013+-+23Z

    • Roman~Snow-Zone-Monmouth, Elv. 223' says:

      Thanks for the links very helpful.. I feel like tonight would be colder than last night if we didn’t light cloud cover guess ill see where we end up in the morning. Currently 19.6F

  37. Paul D says:

    Time warp! I’m reading the 6pm update at 5:41pm! :-)

  38. Taylor says:

    Mark how come the National Weather Service has issued a Winter Weather Advisory for snow starting as soon as Monday afternoon? But your calling for a transition event beginning Monday evening to Tuesday? And lots of meteorologists are not forecasting anything for tomorrow.

  39. Roman~Snow-Zone-Monmouth, Elv. 223' says:

    1!! Thanks Mark, hope the transition is more epic than anyone expects.. But dang it’s already 9F down at Eugene for the 5pm update!

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