Sticking Snow Unlikely Metro Area Tonight

It’s one of those weird nights, in which we are forecasting little to no snow (less than today) in the metro area yet the NWS is forecasting 1-3″ (more than today) for the morning commute tomorrow and has a Winter Weather Advisory up.  We’ll see how it turns out by daybreak tomorrow.

For those just tuning in for the basics, here is our graphical overnight forecast, read the details below:

MarkSnow_PDX_2Elevations

  • Steady rain/snow returns to western Oregon and Washington by midnight.  For most of us, especially north of Salem, it’ll be mainly snow falling, not rain.
  • However, it’ll be just 3-5 degrees too warm (35-38) in the Eugene to Vancouver corridor (lowlands) for the snow to stick. 
  • The morning commute should just be wet in the majority of the metro area.
  • Better chance for sticking snow 1am-4am in Columbia County (Vernonia, St. Helens, Scappoose, & Rainier).  Also northern Clark County (possibly Battle Ground, Amboy, La Center).  We could see a trace to 2″ in all these spots.
  • Tomorrow looks very windy and very wet with south wind gusts 30-40 mph and heavy midday-evening rain.

So why am I so “anti-snow” this evening, especially considering the NWS is forecasting a bigger event than last night?

1. Upper levels are plenty cold to start, but even at 1800′ right now (top of TV tower), it’s 30 degrees.  In a well-mixed atmosphere, one would expect 37-38 down at sea level.  That atmosphere does not cool in the next 8 hours, in fact it warms dramatically after 4am.

2. Precipitation rate on models is very light through 4am.  If we’re going to drag the snow level down to the surface, the precipitation had better be at least moderate, preferably heavy.

3. No dry air coming in from the Gorge; actually no real cool air coming out of the Gorge anyway.  Gradients are flat right now and will go to maybe 3 millibars easterly by 4am when it goes calm again.  Either way, the Gorge is not a factor and will not help get us the usual evaporative cooling.

4.  Southerly wind just above the surface will be increasing through the night, with temps holding steady through 3am, then a big jump after that time.  No matter what happens down at the surface, the 1,000-2,000′ temps go well above freezing before sunrise.  Model soundings, cross sections, and meteograms show temps at the surface holding steady or rising the next 6 hours.

Our 00z RPM is pathetic generating very light snow totals as a result of these points:

RPM_SNOWACCUM_METRO

Wait, there’s more to talk about…

Strong Wind

…in the warm sector tomorrow, quite a strong and gusty south wind up the Valley.  I could easily see gusts 40-50 mph down at Salem during the day, and maybe 30-40 mph here in the Portland area.  That should be fun.

Heavy Rain

We’re really going to get soaked tomorrow.  Models showing a cold front just about stalled over us in the evening and early overnight hours Wednesday.  Our RPM is showing a good 1″ through 8pm, then another 1″ in the following 6 hours.  The WRF-GFS is similar with very heavy rain 7-10pm.

Post Front Heavy Snow Tomorrow Night?

This one has been hinted at by several mesoscale models the past 36 hours.  Immediately behind the stalled cold front tomorrow evening, the atmosphere suddenly cools with the very heavy and steady precipitation.  There is an area of snow levels just about down to sea level as a result.  Last night our RPM was hinting this would occur on the east side of the metro area.  Tonight the WRF-GFS paints heavy snow from 10pm-4am along the east slopes of the Coast Range (Gaston to Banks to Vernonia area).  Note the foot to 18″ forecast by that model over the N. Coast Range?  This will be a very interesting feature to watch.  In fact if you look at the WRF-GFS meteogram for Portland, it drops temps down into the 30s under the heavy precipitation, although it doesn’t generate sticking snow.  Tonight may not be our last brush with snow!

or_snow24_36_0000

Beyond that…I don’t see a setup for snow as we just have weaker and cool weather systems through Christmas Day.

By the way, Andrew from Silverton pointed out this disparity in forecasts has occurred before.  I had forgotten about the big snowstorm forecast 2 days after Christmas 2007 that never happened.  Some fun old reading on the blog there.  And of course the big event the day the blog started back in 2005.  A winter storm warning was up for a big snowstorm, but I was forecasting no snow, that was a very stressful night.  In both cases it hardly snowed or none at all.

Chief Meteorologist Mark Nelsen

324 Responses to Sticking Snow Unlikely Metro Area Tonight

  1. Ray Mongrain says:

    In Camas Washington it started to snow at 4:30 P.M. and still falling, currently have 2.25 inches and more coming. Just got rid of most of the last Sunday’s snow. Winter wonderland

  2. Jordan (Raleigh Hills, 420') says:

    Rather cold and rainy outside this morning. Only 38 here outside of beaverton. Temps have been dropping most of the morning — i think the cold front is slowly pushing east. Tower temps are also finally dropping significantly. Still awaiting the 1215 update for 10am-11am, but readings at 10am were already 33.3F at 1043′

    http://www.wrh.noaa.gov/pqr/tower_temps/tower_temps.php?&units=F

    If some heavier precipitation were to develop, I see no reason why snow would not try to mix in with the rain at least down to 500ft or so…. Although it appears the cold front is slowly exiting the coastal range. I see clear skies just offshore.

  3. LurkinginFG says:

    Quite the disparity between both cams for Hwy 26. Elevation nearly the same, yet it looks like a shot from the coast and cascade ranges. Wonder if that is where the line is?

  4. W7ENK says:

    Areal Flood Advisory
    Issued 7:36am

    http://inws.wrh.noaa.gov/weather/alertinfo/8344052

    Areal Flood Advisory
    Canceled 7:41am

    http://inws.wrh.noaa.gov/weather/alertinfo/8344299

    What the hell are those guys doing over at the NWS office this morning?? o_O

    • Ben T says:

      Marijuana morning at the office?

    • pappoose in scappoose says:

      Looks like they expanded the area.
      NEW FLOOD ADVISORY ISSUED TO EXPAND THE AREA THAT INCLUDES COLUMBIA AND CLATSOP COUNTIES….IN ADDITION TO LINCOLN…WESTERN BENTON…WESTERN POLK…WESTERN YAMHILL…WESTERN
      WASHINGTON…TILLAMOOK AND NORTHWESTERN LANE COUNTIES…
      * until 130 PM PST Thursday.
      * At 730 am PST the rain gage network indicated 3 to 4 inches of rain has fell over the coast and Coast Range of northwest Oregon. Department of Transportation cameras show water over the Road on Highway 101 south of seaside. Some landslides have also been reported in Tillamook and Columbia counties. The heavy rain will cause sharp rises on streams and creeks today which may spill over their banks and cause minor flooding.

  5. 38 at my house, 37.9 at Newport That’s pretty chilly for them during a rain storm.
    Oh, somebody mentioned flooding? ;)

    http://www.tripcheck.com/RoadCams/cams/Seaside_pid652.jpg?1355988842

  6. cgavic says:

    It’s raining in sandy. You can drop the winter storm warning for us.

  7. pappoose in scappoose says:

    National Weather Service Portland or
    310 am PST Thursday Dec 20 2012

    Short term…broad upper and surface low centered over the southern Gulf of Alaska near 140w. The strong front associated with this low as weakened early this morning as far as wind is concerned and all wind warnings have ended. Rain and snowfall are the major issues as the front is nearly stalled over the Coast Range. Rain rates around 0.25 to 0.35 inches per hour are occurring over the Coast Range and could have higher rates in the favored south-southwest facing slopes where orographics are greatest. This is concern enough for small stream and flooding advisory for the next 6 hours or so.

  8. LurkinginFG says:

    Getting cool at the coast. Tillamook – 36 and Rockaway – 38. The snow is falling just up from my house. Aunt’s house is at 36 and snowing. She lives along the coast range outside of Forest Grove el. 850ft. Just south of Gales Peak.

  9. Siletz resident says:

    Its snowing in Siletz, Oregon. We have about a half inch and its still coming down, Pretty large flakes.

  10. shawnpippin says:

    Whew what a stormy night out here in Cornelius gusts at 40mph from 10pm to 4am with rain rates .2/hr. winds are dropping, but the temp is also 4degrees in 2hrs. (41, dp 39).

  11. Ben T says:

    Rob, are you an actual meteorologist or do you just love the weather?

  12. bgb41 says:

    12/19/2012 Oregon (All) Temperature Summary

    Warmest:
    High:54 at DW9524 Lebanon( 354 ft)
    Low: 45 at CW9314 Florence(23 ft)

    Coldest:
    High:18 at HOWARD Mt Howard(8150 ft) & CALIMUS(6629 ft) & WOLF CREEK(5700 ft)
    Low: -9 at Burns Municipal (4144 ft )

    Largest Diurnal Change: 35 degrees
    GERBER RESERVOIR (29/-6 ) (4850 ft )

    Heaviest Rainfall:
    2.64″ at DW0237 Lees Camp(699ft)
    2.60″ at Astoria Regional(10ft)
    2.55″ at W7KKE-3 Road’s E(89ft)
    2.48″ at MEARES Cape Mear(1421ft)

  13. Mule-Estacada says:

    Boring!!! 

  14. geo says:

    I was hoping for a good old fashion ice storm here in east mult. cty. so it can trim my birch trees.

  15. geo says:

    What’s your interpretation of the ECMWF

  16. Traci says:

    So are we close enough to Christmas to know that it won’t be white this year, or is there any hope?

  17. longbeachrob says:

    3.14 inches of rain now today, and still some time left to go!
    38 degrees out, but no wind really anymore here at the house.

  18. Why oh why is the snow not falling?
    Is it because it cannot hear me calling?
    It’s cold as ice, some snow would be nice.
    Those Cascade Mountains, have got me poutin.
    Oh how I wish these clouds were spoutin!

  19. thomyee says:

    Huge arctic event on tonights GFS. Hope the ECMWF follows suit.

  20. Jeez McMinnville G 47, and Newberg G 56 !

  21. alohabb says:

    South wind picking up big with heavy rain. No snow for you

  22. germantownsummit1000' says:

    Weirdness is right – suddenly dead calm and 40.4.

    Power out at 9:10; the generator symphony has begun (again)…

    …sing along, if you’d like.

  23. Enjoy the somewhat chilly rain…. Back to you in the studios

  24. shawnpippin says:

    Out here in Cornelius between 6-8pm my wind died to calm / east or Northwest. Right at 9pm Huge South wind gusts, temp went from 40 up to almost 45 now.

  25. germantownsummit1000' says:

    Been 40.1 here for the last 4 – 5 hours – wind is kickin’…

  26. alohabb says:

    Not feeling the snow idea tonight. May just be cool and rainy. I thought we were supposes to get a ton of rain?

  27. KPTV Tower Temps
    As of 7 PM(1 hour lag. Updates every :15 after the hour)
    Upper Sensor(1818′) 38.3 (Was 40.8 at 6:00 PM)
    Middle Sensor(1473′) 38.8 (Was 41.4 at 6:00 PM)
    Lower Sensor(1043′) 39.7 (Was 43.0 at 6:00 PM)

  28. Jclack says:

    Still at 45 degrees in clackamas at 340 ft.. no signs of any cooling here..

  29. alohabb says:

    S wind still blowing good here.

    • That’s weird…. seems east of I-5 are seeing the wind go calm or shifting, but Mesowest map shows westside yeah S wind continues. Strange mesoscale situation.

    • AlohaWeather says:

      It is SSE near Cooper Mountain, and gradually dying down…

    • Ben T says:

      What’s your wind at? According to weatherbug it’s like SE 6 here in Longview.

    • AlohaWeather says:

      *SE

    • Mark says:

      Mesowest also shows some low-mid 30’s temps in the gorge, but on the east-side it is much warmer than that. So tapping any gorge influence – I should think – would be short lived to produce anything near freezing. It’s more like a “plug” of cool air between cascade locks and Hood River and that’s about it.

      With the low north of the Columbia – and way off shore – I don’t see how any deep easterlies are going to show up, where the cold air is, and how a warm flow out of the south is going to manifest into snow below 2k or so.

      Just seems far, far too many items would need to line up perfectly for anything to happen tonight.

      Anyone, feel free to fill me (and probably others) on what we are missing here. Or if we aren’t. Thanks.

    • Sounds about right and is more than reasonable. Just nothing showed a wind shift… I guess we’ll see how things play out.

  30. vernonia1 says:

    man..i do not get this…temp is inching up ever so slowly. Is there still a S wind component showing up on the maps??

  31. I’m not trying to get anyone’s hopes up, and I’m not saying “Yes, it is going to snow”, but if this wind shift continues and precip rates can increase.. I rule out nothing past midnight now….Models seem to be doing awful with this dynamic mesoscale situation unfolding….

    In fact, looking closer at 00z MM5-NAM 925/SLP model, Cross Section, and Sounding shows no wind shift with southerly flow continuing. That’s obviously not correct as many people are reporting either that they have lost the south wind, it has gone calm, or a wind shift to the N or E.

  32. longbeachrob says:

    2.65 inches of rain and a gust of 35 mph (and lots of gust to 30 mph). I only lost a few strings of Christmas lights… the LED ones don’t seem to like rain and salt air! Darn steal leads on the LEDs like to rust… On the other hand a little butter ball duck likes all the water in the pasture.

  33. Don Troutdale 230ft says:

    Went from 40 to 37. East wind now 5-10mph. Troutdale about 230ft. Hope we get a suprise tonight.

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