Snow In The Valley Friday Morning; Then Very Cold!

11am Wednesday…

I think there’s a good chance you will get a snow day Friday if you live in the central/southern Willamette Valley from Salem down to Eugene AND on the central Oregon Coast!  Models are in total agreement on the track of a cold low pressure system that will slide down the coastline Thursday night into Friday.  They haven’t changed much in the past 24 hours, slightly farther south on last night’s runs, slightly farther north on the snow this morning.  I’ve looked at all the info this morning, and nothing significantly different comes out between now and later this evening;  so a good time to post..

 

THE HIGHLIGHTS

  • Clear and cold again tonight, in fact a bit colder than last night.  Notice a few of the official stations made it down into the upper teens.  I expect about a 5 degree cooling for tonight.  That means PDX could drop below 20 for the first time since February 2011.
  • High clouds thicken up Thursday, as a result our coldest day so far, just creeping a few degrees above freezing
  • Snow will spread onto the beaches (yes, the coastline!) later tomorrow evening and inland before sunrise Friday.
  • At this point it appears accumulating snow will most likely stay SOUTH of a line from about Seaside to Newberg to Mt. Hood.  Yes, that means just flurries at best for the Portland metro area Thursday night and Friday morning.
  • 1-3″  is possible from Tillamook to Newport on the coast, and in the Valley from McMinnville to Salem and south during this time (Friday AM)
  • 2-4″ is possible Albany, Corvallis, and Eugene (south Valley)
  • Avoid travel south on I-5 during the day Friday between Salem and Eugene
  • Any northward movement of the whole system in future model runs would put accumulating snow into the Portland metro area.  There is still (fading) hope!
  • Gusty east wind pours out of the Gorge Friday, bringing a frigid arctic airmass west of the Cascades, the coldest we’ve seen in 4 years.  High temps probably won’t rise above freezing Saturday and Sunday; our coldest weekend we’ve seen in a long time…but sunny!

DETAILS

Amazing model agreement this morning on the big picture considering we’re 36-48 hours out.  Look at the Friday morning forecast from the GEM, GFS, NAM, & ECMWF.

can_18z
nam_18z
gfs_18z
ecm_18z_fri

All have the low pressure system sliding down the coast, and deepening (always good) as it moves into southcentral Oregon by Friday afternoon.  They all show a good shot of precipitation just to the south of the Portland area centered on sunrise Friday.  Looks like a very good time to be in Corvallis, Lebanon, Albany, and Eugene!

Now the problem is that we are right on the edge of the precipitation band here in Portland.  I tend to lean on the dry side too because the low-level atmosphere will be very dry in the metro area due to a strong and gusty east wind.  Take a look at the surface map off the UW WRF-GFS for 7am Friday.  That’s beautiful!  A classic snowstorm setup with the low pressure sliding down the coast pulling cold and dry arctic air through the Gorge.  Not quite easterly downslope windstorm material, but it’ll be a windy morning here.

wrf_slp_7am_fri

Here are the snowfall accumulation graphics from the UW’s models, the NAM-MM5 and WRF-GFS:

nam_mm5
wrf_snow

Technically the first one is just precipitation accumulation, but there is no snowfall accumulation graphic for that model.  Notice the WRF-GFS pushes the snowfall slightly farther north.  Also, to really send you geeks over the cliff, note the 2-4″+ snowfall out over the ocean offshore going to waste on the turtles and whales!  This really points out that you can have lots of cold air, but need moisture to get snow, and they often don’t line up correctly in our area.

In this setup, with an east/northeast wind over the Willamette Valley ahead of the low, there will be a upslope component on the west side of the valley.  Assuming the moisture makes it far enough north, I could see Gaston, Willamina, and Dallas getting better totals than in the valley itself.

Our RPM is still having issues, developing flurries and/or light snow even up in SW Washington as the low moves south Thursday evening.  Notice it’s snow total from the 12z run doesn’t show that, but the 15z does.  At least it got rid of all the precipitation farther north:

RPM_72_SNOW_12z

Remember that this is unusual territory for us, having a system drop out of Canada, spin up a surface low, throw moisture over the cold air and deposit snow in our area.  If models are off by just a bit, we could get snow here in Portland.  At least we still have the 00z models tonight and 12z tomorrow to look for any trends.

Here comes the cold air…all 12z models REALLY COLD with the airmass behind this thing.  Take a look at our 12z RPM text graphic.

web_RPM_12z_Text_PDX

I don’t think I’ve ever seen it show negative dewpoints like that.  And I haven’t seen it show such cold temps for this spot since 2009 either.  Wow.  Probably overdone a bit on those dewpoints, but this will definitely be the coldest since 2009.  When the wind goes calm Saturday night in the valley where snow cover is on the ground?  I think single digits are real likely down there.  Here in the metro area we’ll be in the 10-15 degree range…Brrr!

We removed any precipitation out of the forecast until at least Tuesday.  The general forecast pattern would get us out of the cold air quickly at that time with maybe only some ice in the Gorge…we’ll see.  That’s still 6 days away.

Chief Meteorologist Mark Nelsen

 

60 Responses to Snow In The Valley Friday Morning; Then Very Cold!

  1. 27.8 here. Running just barely cooler than last night at this time.

    Still have a wind of 1-2 mph…

  2. dharmabum says:

    Got most of my weatherizing done here on the farm, a beautiful midday walk with the wife and dogs down by the Clackamas a good load of firewood on the hearth and “Celebration Ale” in hand. Needless to say I am happy!!!!!!!!!! Oh ya I still have to go out to the garage and put together my snow making equipment. Snow tomorrow 120 % guaranteed!!!!!!!!!!

  3. Longview - 400 ft says:

    Currently 30.2

    Boy Saturday night is going to be cold!!!!!

    I am hoping for snow Early Friday morning.

  4. Let’s hope the high clouds stay away to allow us optimal radiational cooling tonight!

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

  5. WEATHERDAN says:

    18z looks good for some snow in NW Oregon. Got this off Mark’s weather links.

    • Ryan says:

      Yea, not sure if Mark trusts that model this time. It’s proved accurate in the past. I think KOIN may use this same model since Sussman had that same type of snow cover map on his forecast last night. He did say that the other models weren’t showing anything close to that, but I bet it’s a similar model to the RPM. Am I right, Mark?

    • Mark Nelsen says:

      We have the exact same weather system (that includes model grid data too)

    • Ryan says:

      That makes sense then, thanks. Well let’s root for the RPM!

    • Dave in South Salem (500') says:

      Wait, so I can watch KOIN instead?

    • Ryan says:

      You could for the modeling, but not for the individual insight. I prefer Mark over Bruce any day, even though Bruce seems like a good guy who likes snow too. And KOIN tends to overdue the “arctic blast” stuff for higher ratings.

  6. Josh Gardner says:

    18z RPM is umm interesting to say the least. Basically it indicates a similar track, because its heavier south still but spreads a wider swath of precip indicating a stronger system

  7. Paul D says:

    I hate to get too scientific on all of you, but I predict significant snow in the Portland area Friday morning. What do I base this on? I’m scheduled to drive from Hillsboro to Seattle Friday morning to take my daughter to visit a college. Mark my words 🙂

  8. Model Rider says:

    Everyone talking about the low going too far south now. Remember its the 18z. Hence why Mark said above, nothing significantly comes til the models tonight. I cant remember how many times there’s been a snowstorm in and around PDX being a surprise to all. Am I right?

  9. Brad says:

    Both NAM and GFS 18z look colder through 48 hr.

    • Brad says:

      18z GFS has us at -9C at 925mb at 72 hr and colder at 75hr! That’s about low 20s (maybe) for highs on Saturday.

    • Brad says:

      Rob’s going to freak out when he looks at the 18z GFS. Days 3-7 are definitely colder and are worth watching going forward.

  10. paulbeugene says:

    RPM must be broken. 18z RPM shows snow SW Wa to Eugene

    • Brad says:

      I expect GOLU to prove most accurate over the next 48 hours.

    • Joshua in Lake Oswego says:

      Keeping hope alive! Those other models are chumps compared to the RPM for local snowfall.

    • Ryan says:

      Or are all the other models broken and the RPM knows the secret? 😉 Highly doubtful but it seems to see something the others don’t.

    • Annoyed says:

      These lows never make it as far south as forecasted. How many times have they been forecasted to make it to Astoria in these situations only to hang up 100+ miles north?

    • Dave in South Salem (500') says:

      Two years ago the RPM showed snow sometime late in March and the other models didn’t… That’s when I learned to respect the RPM

  11. paulbeugene says:

    Both 18z GFS and NAM weaker with Fri AM low. No precip except SW OR

  12. Heatblizzard says:

    Here’s a thread about snowfall in San Francisco where they have had dustings to 1 inch a few times with 1976 the most recent year of 1 inch accumulation.

    http://www.city-data.com/forum/san-francisco-oakland/800033-has-there-ever-been-snow-san.html

    One of the posters posted a really good picture *for it’s day* of the 1976 snow that got up to 7 inches at Twin Peaks.

    One side of the Golden Gate Bridge tunnel was clear driving while the other side was snowing on the *Mountain side* with very icy roads and that part of the freeway has lots of turns.

  13. Heatblizzard says:

    The outlook shows California Central valley having snows below 1,000 feet and in some places could fall to sea level.

    It happened in March several years ago that San Francisco had a dusting of snow in the foothills above 500 feet and it accumulated over 1,000 elevation.

    The forecast was for snow flurries that night for Downtown SanFrancisco but the low pressure fell apart so they never got any but in the afternoon before they did get grapuel and hail mixed.

  14. David B. says:

    At least PDX has a chance this time; there’s not even that up here in Puget Sound country on this one. Maybe we’ll get some overrunning on Monday or Tuesday.

  15. Rob - Southeast Portland says:

    Amidst all the excitement of possible Snow flurries Friday, did anyone check out the 18z NAM? Coldest run yet
    PDX HR 508 thickness, 850mb -16c to -17c

  16. Taylor says:

    Well rat. I want to be happy for you guys in the Southern Willamette Valley but I just can’t. Who knows if this is our only shot at snow this year….

  17. WishingforSnow says:

    Does anyone think we will get any snow out here in Estacada?

  18. WEATHERDAN says:

    Salem looks to be getting maybe 2 or 3 inches of snow Friday. Then with the snow cover on the ground and the bitter cold airmas behind it I expect to easily see 5-10 degrees. Lows just off to our West in Dallas might drop to 0-5 degrees. Highs will have a hard time rising above the low 20,s. Looking ahead to Monday night and Tuesday I expect the precip to start out as a heavy snow. Then change to sleet and ZR on Tuesday night before maybe changing to just rain.

    • BoringOregon says:

      I’m going to lol if we get it here :).

    • Heatblizzard says:

      Is there any chance of schools having a 2 hour delay or will the snow plows and gritters clear things up in time since the snow is falling in the late evening vs the early morning hours around am.

      I hope the snow happens more towards 4AM.

  19. Brad says:

    18z NAM pushes moisture way south through 48hr

  20. TygrrQueen says:

    I’d be happy with flurries in eastside Vancouver…

  21. Dave in South Salem (500') says:

    Looks like a familiar moisture pattern that I saw 2 years ago. The snow line is roughly along highway 22…

  22. Andrew (Beaverton, OR) says:

    Dewpoints are dropping fast out there! Down to the mid-lower teens across the metro area now.

  23. WEATHERDAN says:

    Here in Salem I expect 2-4 inches of snow on Friday. Then with another blast of even colder Arctic air on Saturday I expect lows on Saturday and Sunday to be in the 5-10 range with jighs to be 19-23. I think that when the precip arrives Monday night we will get a good dumping of snow before we get som ZR and then just rain by next Thursday. Just like that monster TRW we had in Salem in September maybe the mid valley might be a good place to be. Peace.

  24. A new chart finally surfaced for the KPTV tower temps. This one was made by Jim Little. Looks better than the chart the NWS had. 🙂
    http://weather.wxnorthwest.com/kptv_tower_temps.htm

  25. Let’s bury Sweet Home! Would be a perfect day for kids (well maybe admin). We are on a four day week here with no school on Fridays.

  26. Ryan says:

    It’s close enough for us to hope! I’ll take an inch if it’s going to stick around all weekend. That would be fun. Come on low, head a little more north for us PDX’ers! Any chance of it being stronger than models show?

  27. W7ENK says:

    I’m hoping!!!

    • gidrons says:

      I expect another demonstration of the dome effect

    • W7ENK says:

      Oh, absolutely it will. Did you see this morning’s graphic from the NWS Portland office? Not even kidding, they practically drew the outline of The Dome on their snowfall prediction map!

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