Ice Storm Ending: Snow Showers Monday AM

January 8, 2017

11pm Sunday…

It’s been a busy weather weekend.  First snow, then plenty of ice in the central/eastern metro area.  Now a new twist…

Tomorrow morning will feature a similar setup to our very first brush with winter back in early December…the dreaded “snow in the hills and a close call in the valleys” event.  By dreaded I mean that more often than not we don’t get anything significant out of these patterns, but they are a pain to forecast.  It IS possible to get a quick dusting of snow or even more in the hills and sometimes if you get a cluster of showers you can even get more than a dusting in the valleys.  Some models are showing this over the metro area or somewhere in the northern Willamette Valley.  This is what I showed during the 10pm show:

bmac-snow_textpanel

It is a plus (if you want snow) that the onshore flow is very weak so far; in fact we’re having trouble totally getting rid of the east wind but it IS slowly going away.  Due to this temps are still just a few degrees above freezing but they will rise the next 12 hours.  I don’t expect refreezing in the parts of the metro area that have thawed so far.

By the way, this is how things have turned out so far for the ice storm on the east side of the metro area…under 1″ of ice, abut some spots ended up with more than 1/2″ right near the Gorge.

kptv_default

 

A couple quick notes for myself in the future:

  1. The entire metro area never has a huge ice storm together.  I let myself forget that if the cold air is deep enough to keep it below freezing all the way out west of the West Hills and down into the south metro, then it’s too deep for freezing rain eastside.  In those cases it’ll be sleet or snow east metro area.  If it’s a thinner/milder cold airmass spilling out of the Gorge (like today), then it’s liquid enough for mainly freezing rain east metro.  In those cases though it’s going to be a bit too warm west and south metro.   In fact I made graphics to explain these situations just 2 years ago for a presentation to PGE line crews

markpge_storm_snow_ice_metroandgorge

 

markpge_storm_snow_ice_northvalley

More on the big snow storm coming for a good chunk of Oregon later Tuesday tomorrow.  Time to finish up for the night here…

Chief Meteorologist Mark Nelsen

 


Ice Storm Continues Eastside

January 8, 2017

3:30pm…

Here’s a note I just sent to the newsies here at FOX12.  I think it summarizes things well.

We will be on the air right after the football game around 5-6pm.


Our ice storm is continuing in about 1/3 of the metro area, the other 2/3rds are just a notch or two above freezing and should stay that way tonight.  We’re a metro area “divided” weatherwise.

As of 3pm the temperature is back down below freezing again at PDX and all areas east of I-205 are below freezing as well.  The West Hills are below freezing and Mt. Scott too.  These areas will continue to have ice glazing thicken up as the ice storm continues the next few hours.  After sunset it’s easier for ice to glaze objects too without the “daytime warming”.

We have been pegging 4pm as the general time we’d all go above freezing but (of course) the thaw is taking longer than anticipated and at this moment warming south wind hasn’t even reached Eugene yet.  It’s going to be a few hours before we get above freezing eastside.  Check out this nice map highlighting where the cold air was (as of 2pm)…it’s real clear where the ice storm is in progress.  Thanks to Brian Schmit for sharing:

freezing_2pm

HIGHLIGHTS

  • Ice Storm continues for at least another 2-3 hours eastside
  • Moderate to heavy rain means additional glazing = bad roads = more power outages and trees/limbs coming down
  • West of the west hills and south of Portland temps should remain warm enough to keep ice off roads (that isn’t already on them)
  • Central/eastern Gorge is seeing a big snowstorm, that continues through tonight. No significant thawing in the Gorge this week!
  • Cooling air above means snow mixes in with rain showers late tonight and early Monday.  Sticking snow falls down to 1,500′ at least.  Any of us could see snow in the air during the AM commute.  This is our typical wet snow shower pattern unrelated to the cold Gorge.

 

Monday AM Commute: All of the metro area should be above freezing with even the eastside slowly thawing out.  But probably lots of school closures/delays in those areas that have a lot of ice.

Tuesday afternoon/night another storm moves across primarily southern Oregon.  We will be on the far northern edge of that snow/rain.  So we may or may not get some sort of snow Tuesday night.  It’s possible we’re just mainly dry…stay tuned.

Chief Meteorologist Mark Nelsen


Ice Storm: Worst Conditions Central/East Metro & Hills

January 8, 2017

10am Sunday…

It’s pouring outside and for much of the metro area temperatures are below freezing.  Over the next few hours the areas that get heaviest ice accumulations will be where temps remain well below freezing (instead of 32-33) and exposed to the cold east wind blowing out of the Gorge.  That means lots of ice buildup in the West Hills, East Portland, and areas around the Gorge; not too much elsewhere.  Expect IMPROVING conditions in Clark county, south metro & west metro.  This is perfectly normal for an ice storm.  Biggest impacts are always in the city and closer to the gorge.

HIGHLIGHTS

  • Freezing rain continues through mid-afternoon, then turns to lighter showers for MOST of the metro area
  • A few spots that have gone above freezing (mainly IN Portland and eastside) will go back below freezing for a few hours
  • Areas ABOVE freezing (westside and south metro) will likely stay above freezing through the rest of this event.
  • 1/4 to 1/2″ is likely by sunset in the areas mentioned above
  • Roads west & south metro and up in Clark county should improve from this point forward.
  • Roads central/east metro turn a bit icier, but even they improve once the east wind stops
  • Temps in all areas, except east of Bridal Veil in the Gorge, warm above freezing this evening and ice slowly melts.

 

Our ice storm is transitioning into one in which the usual areas get hammered.  That includes the hills and all areas exposed to the sub-freezing air pouring out of the Gorge.  Away from those areas temperatures are gradually creeping above freezing.

A couple big meteorological notes this morning:

  1. The easterly strongest gradient I’ve ever seen in the Gorge (pressure difference from DLS to PDX) is occurring right now.  15.6 millibars!  The peak gust at the Corbett sensor hit 85 mph this morning before the freezing rain hit.  Of course now it’s slowing to a stop.  That’s the highest gust at that location since at least the January 2009 damaging wind event.
  2. Even more interesting is a mixing of some “warmer” downslope type wind with the colder Gorge wind the past few hours.  Wanderer’s Peak at 4,000′ SE of Estacada had warmed to 35 with southerly wind at midnight, but has dropped back to 21 with cold air coming right over the top of the Cascades again.  That would also explain why we’ve seen a few spots go back to snow near the Cascades.   PDX warmed up to 34 with a straight east wind gust over 40 mph.  The usual wind direction for the gorge outflow is ESE.  It’s some geekery, but the point is that downslope wind warmed some areas up a couple degrees and now it should be back below freezing the next few hours east of I-5 in the city.

The east wind and sub-freezing temps should suddenly disappear right around sunset as the cold front passes overhead.  Then we all thaw in the metro area.

Chief Meteorologist Mark Nelsen