12 Hours Away: Areas of Snow & Ice Pellets For A.M. Commute

7pm Thursday…

There are no watches, warnings, or advisories for late tonight and Friday morning, but anyone up and around in the late night and early morning hours may see either snow/sleet.  Either in the air or a dusting on the ground; this MAY end up just being a “conversational snow”, as we like to say, for a good chunk of us in the metro area.

Something should start falling out of the sky sometime between 3-7am.  It’ll start as snow; temps will be right around freezing, maybe slightly above.  Then right around sunrise warmer air moves in above, which means ice pellets (used to be called sleet)  are more likely.  That’s when snowflakes melt into raindrops up above and then refreeze into little chunks of ice before they hit the ground.  It has a “clinky” sound when it hits.

By 8am, the atmosphere will be too warm to support anything frozen since the freezing level will be jumping up to 8,000’.

The Highlights

  •  A brief “wintry” mix between 3-8am.  A dusting is possible anywhere from the metro area to Longview down to the valley floor.  But not everyone will get it.  It’s real light.
  • Snow to sleet, then probably straight to rain.  Freezing rain looks unlikely since temps won’t drop much below freezing (if they do).
  • Some areas may see sleet/snow on roads, depending on the temp.  Best chance would be West Hills, central/north Clark County, Scappoose/St. Helens, and Banks/Vernonia.  Those areas also have the best chance of seeing actual freezing rain at the end of the event around 7-9am.
  • It’s all over after 8am for just about all of us.
  • Gusty south wind tomorrow afternoon, maybe gusts 30-35 mph as temps climb into the 40s.

What We Don’t Expect

  •  A snowstorm; not enough moisture for more than 1-2” of snow even if it did that the whole time.
  • An ice storm; again, just not a whole lot of anything.
  • Widespread frozen roads and a hellish commute.  Probably not cold enough or enough moisture.  Different story up north as mentioned in the highlights
  • More than ½” for 90% of us in the metro area
  • Snow/ice pellets south of the metro area (Salem/Albany) or at the coast.

Here is the latest from this evening’s run of our RPM showing a changeover from snow to ice pellets already at 6am spreading west to east across the metro area

rpm_6am

Then at 9am all frozen precipitation is over in the lowlands unless freezing rain/ice pellets holds on up in northern Clark County.  And, actually it looks mainly dry at that time anyway.

rpm_9am

I’m getting the feeling that Amboy, Yacolt, and Battle Ground are the places to be for this event.  And finally the snow total graphic showing the main accumulation “action” in Clark County:

rpm_snow_9a

The evening NAM model has snow a bit farther south and west into the middle of the metro area.  This is snow accumulation from 7-10am.

nam_snow_10am

The sounding is definitely all snow through the 7am hour.

To wrap it up, here are the percentages I assigned to each of these events…

MarkSnow_PortlandOutlookPercentages2

By the way, for those of you that work the late shift and wake up around 9am like me?  You’ll miss the whole thing!  Go ahead and sleep in.

Chief Meteorologist Mark Nelsen

56 Responses to 12 Hours Away: Areas of Snow & Ice Pellets For A.M. Commute

  1. chiefWright (Marquam) says:

    Now mostly very light rain on top of a sparse speckling of sleet. Hovering around freezing on the ground, so it’s in that inbetween solid/liquid state. Roads aren’t too bad, but that can change in a heartbeat with this setup!

  2. Distinct back edge to the precip coming down. 32.3 with still an east wind.

    http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?rtx_ncr+/2h/

  3. Seahawks Fan - NE Vancouver says:

    100% snow and sticking to everything!

  4. runrain says:

    Been all fluffy snow here at 500′ in Happy Valley. Street looks ok but everything else lightly covered. Temp 30.9, snow appears to be floating from the east with a light easterly breeze.

  5. …switched to freezing rain here…

  6. Longview - 400 ft says:

    Currently 32.7

    All is white here. A nice dusting.

    Merry Christmas all!!!!!

  7. chiefWright (Marquam) says:

    Lightly precip here, just started in the last 10 minutes. 100% sleet.

  8. “Heaviest” snow of the day now in BG. Still nothing too heavy though.

  9. Temp holding at 32.4 here in BG with a wind due east, light, 2-4 mph

  10. GTS1K' says:

    Oh, I forgot: wind light and variable, but with a definite easterly component – say 42.685%…

  11. David B. says:

    Looks to be on the light side of forecast amounts up this way. About 1/2″ accumulation on Bainbridge Island so far. Looking at regional WSDOT cameras that’s about representative. Radar shows no intense showery activity, just a widespread shield of light/moderate snow, and it’s been getting lighter in the past hour. 31 degrees here.

    • David B. says:

      In fact, it’s really looking as if the party is over for those of us south or west of Seattle. Winds here are picking up, and from the radar it looks like shifting to westerly, which puts us smack-dab in the middle of the Olympic rain (or in this case snow) shadow.

      That was forecast to happen around midday. Looks to be happening on the early side. Oh, well. At least I got SOMEthing out of this one.

  12. GTS1K' says:

    Frozen precip the last 15 min. or so. Holding at 30.2.

    83.5 % sleet, 14.3% snow, 1.6% rain, .6% other.

    • W7ENK says:

      Wow, that’s quite the precision you’ve got there! Did you use a ruler to measure that? Hygrometer? Lasers? Supercollider?

      I just rough estimated, but I guess you’re better than me, so you win!!

  13. W7ENK says:

    Halfway to my bus and it just started raining with a little sleet mixed in. 34 degrees, road surfaces are becoming wet.

    70% rain, 30% sleet, 0% snow.

  14. pappoose in scappoose says:

    Started as sleet here, now light snow.

  15. Andrew (Beaverton, OR) says:

    Sleet coming down on my drive over sylvan and in downtown as well.

  16. Snow and sleet in Battle Ground. Temp 32.4.

  17. Muxpux (Castle Rock 175') says:

    Snowing pretty decently, according to the Langley radar should get a yellow band through here within the hour. Cars white, gravel driveway turning, road slushy.

  18. Marcustheweathernut says:

    Light snow in La Center….. And sticking!!!! 🙂

  19. David B. says:

    Falling harder. Sticking. Ground and pavements are now white.

  20. …sleet is starting to fall here…

  21. Longview - 400 ft says:

    Very light frozen precip is stating to fall.

    Currently 33.3

  22. David B. says:

    Light, sleety, slushy snow falling on Bainbridge. Hasn’t been falling for long. Pavements just wet. No accumulation yet.

  23. schmit44 says:

    12/19/2013 Oregon (All) Temperature Summary

    Warmest:
    High:52 at BROOKINGS( 79 ft)
    Low: 39 at BROOKINGS(79 ft)

    Coldest:
    High:15 at HOWARD Mt Howard(8150 ft)
    Low: 0 at KLAMATH NWR (4531 ft ) & ARNOLD CANAL NEA (3900 ft ) & MAZAMA (4596 ft ) & CHRISTMAS VALLEY (4360 ft )

    Largest Diurnal Change: 36 degrees
    MALHEUR RVR BLO (41/5 ) (3305 ft )

    Heaviest Rainfall:
    0.13″ at WANDERER’S PEAK(4350ft)

  24. Model Rider says:

    Alright, after the model runs tonight I’m taking a little winter break from the weather. I’ll see you guys after Xmas. And Merry Christmas everyone and may the models be in our favor after Christmas.

  25. MasterNate says:

    This from Dave at KATU
    “KATU has declared a Breaking Weather Alert.”

  26. justwatching says:

    Hey Mark,
    You said that the central/southern valley will probably escape the mess…BUT the NWS has a different forecast completely..
    This is from the Special Wx Statement “…WINTRY MIX OF SNOW…SLEET…OR FREEZING RAIN FOR THE FRIDAY
    MORNING COMMUTE IN SOUTHERN AND CENTRAL WILLAMETTE VALLEY…”
    They have us at 80% chance as of the 9pm update.

    We’ll see who is closest to being correct

  27. Marcustheweathernut says:

    My temp has warmed up to 32 from 30 last hour….. Cloud cover is putting a lid on temps!!!

  28. David B. says:

    The Dome is real! If you have any doubt, just look at the 8th and final graphic in Cliff Mass’s most recent post at http://cliffmass.blogspot.com/ .

  29. GTS1K' says:

    30.2 and counting…

  30. Marcustheweathernut says:

    I don’t see how we get snow….. Warm front coming in, I’m sure we see virga initially, warming the upper layers of the atmosphere… If anything we would get freezing rain but temps are not that cold for it to freeze…. Soo that leaves us with ice pellets then rain!!!!! Yay!!! I can hardy contain myself!!!!

  31. pappoose in scappoose says:

    Next post

  32. Don Troutdale 230ft says:

    31 in Troutdale.

  33. SnowedIn - North Plains says:

    Already down to 29F out here in North Plains…

  34. Andrew (Beaverton, OR) says:

    Temps are still dropping in the region, down to 31 here now, looks like hillsboro is the same. However, PDX is up to 35….

  35. Brian *Wilsonville says:

    first

  36. pappoose in scappoose says:

    Who’s on first?

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