No Evening Snow; Forecast Goes Off Track Into Ravine

February 5, 2017

11:30pm Sunday…

Things were working out just fine through about 7pm tonight.

  1. Lots of rain, mixed with snow at times in parts of the metro area with cold enough temps at the surface for snow (low-mid 30s)
  2. Heavy snow just west and north of the metro area.  3-5″ in Astoria, 8″ Clatskanie, 3-8″ Longview, & 18″ at Sunset Summit Rest Area.
  3. No issues traveling around most areas in the lowlands
  4. The low-level cool air actually moved FARTHER south than expected this afternoon; Eugene’s wind was north for a while.

Then things went wrong as that snow forecast train jumped the tracks…BUST!  It’s painfully obvious (from my point of view) that models totally missed the above freezing air that remained overhead all the way through the evening.  In the end things are turning out almost exactly like last night’s GFS and ECMWF model snow forecasts; little or nothing in the lowest elevations from the metro area south to Salem.  Yeah, this one stings, like the lack of ice back in early December or was it early January?  This is the 2nd event that has turned into at least a partial bust.  But out of 7 difficult winter forecasts, maybe that’s not so bad in our climate.

We’ll be lucky to get a trace of snow in the next two hours as the back edge of the steady precipitation moves overhead.  Most of us just stay wet between now and 5am.

If you want to see snow, pretty much your only hope is several bands of snow showers that move through the region around daybreak Monday.  This will be similar to the very first snow shower event we saw on Monday, February 5th.  Exciting to see, but won’t have much affect on the morning commute:

markheadlines_coldwx

The rest of this week should be uneventful and we MIGHT get several days of dry weather starting next weekend.  It’s still a week or so too early to break out of the winter inversion and see 55-65 degree weather, but we’re getting closer to that first stretch of “false spring”.

Chief Meteorologist Mark Nelsen

 


Forecast On Track; Cold Rain Metro Area Through 7pm, Snowy North & West

February 5, 2017

2:45pm…

It’s nice to see a forecast end up correct…so far.  There is a very clear line that runs from around Gaston to Forest Grove and then over to Scappoose and Woodland, WA.  North and west of that line it’s snowing bucketloads.  South and east (95% of the metro area) it’s generally all rain or a rain/snow mix.  You can see it with all the surface observations plotted…it’s not pretty but it tells the story.  The numbers are current temperatures; 33-34 means it’s probably snowing and sticking.

capture

Radar also shows the snow/rain line well:

kptv_default_world_borders

This setup should continue through the Super Bowl and probably through 7-8pm.  That means roads for just about all of us in the metro area remain clear.  Of course that doesn’t include water flowing over some roads due to the heavy rain.  Speaking of heavy rain, it has been really dumping from the metro area south the past 6 hours, although it has let up south of Wilsonville which is good news…approaching 2″ today in Salem.  Lighter rain (snow) has been to the north and west of the metro area.  The band has shifted a bit north, but there will still be minor flooding in spots the rest of the day.  Watch for water over roads…but at least we’re used to that!

plot_rain_metro_autoplot

I still think we’ll get that Trace-3″ in the lowest elevations of the metro area late this evening and into the overnight hours.  Stay tuned…

Chief Meteorologist Mark Nelsen


Forecast on Track…So Far

February 5, 2017

10:30am Sunday…

The forecast is still on track for a Trace-3″ across the lowest elevations of the Portland metro area by Monday morning, with almost all of that sticking AFTER 7pm tonight.  BUT, the chance for someone to get really dumped on far west metro or up north toward Longview seems to have increased from what I saw at midnight.  Here’s the latest snow accumulation forecast from HRRR model.  A pretty good representation of what I think is most likely to happen between now and the Monday AM commute:

hrrr_snow_portland_19

Notice the heavier totals west and north metro and far less south and east where we’ll stay as rain or rain/snow mix before a late evening switchover.

As expected the airmass over us has cooled off and many are seeing a rain/snow mix in the lowlands.  Here at 1,000′ I’ve had mainly snow the past 2 hours, but it was sticking better an hour ago and now I’m getting more rain than snow.  I do see the warmer air is moving in aloft in the SE metro area with the sticking snow level up around 4,000′ just SE of Estacada on Wanderer’s Peak.  Yet at 1,000′ in the Coast Range it’s snowing like crazy.  That’s the effect of a stationary front sitting over our region; warmer south and east and colder north and west.

We’ve now seen the last of the model runs before this event.  The last-minute “wrinkle” is that they are all slightly farther south with the surface low pressure that tracks through the region this evening.  The ECMWF decided to move the low much farther south and now brings it just south of PDX around 10pm.   This is what I mentioned in the posting yesterday evening that “could go wrong”.  In this case that opens up the possibility that some locations in the far west or north metro (Forest Grove, Banks, Vernonia, St. Helens, Woodland) could get totally dumped on with snow this evening.  The ECMWF itself shows that possibility, although a bit extreme…a foot+ snow out near the Coast Range and north:

ecmwf_totalsnow

The resolution of the model leads to some contouring issues here, but you get the idea…loads of snow possible far west and north metro.  We’ll see how this plays out, is it really going to be a “Trace-15” in the metro area?  That sounds familiar…but could happen.

Flooding may be in issue this afternoon/evening as well with the heavy rain sitting directly over the Portland metro area.  Assuming it all falls as rain south and east metro through the evening, check out the forecast from the HRRR!

hrrr_precip

That will cause some urban flooding and creeks surge out of their banks.  I’ll be keeping a close eye on that this afternoon too.

I’ll be doing some live Facebook videos later once I get settled in and the Super Bowl is on, then we’ll be on the air much of the time from 8:30-11pm tonight on FOX12.

Chief Meteorologist Mark Nelsen