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  • Updated

Friday, July 30th, 12:30 P.M. 

After a warm start to the day, temps will soar close to 100° in the Portland metro area this afternoon/early evening. We are keeping an eye on some clouds and showers over the Cascades this afternoon. I can't rule out the chance for a brief shower or thunderstorm in the metro area or central valley this afternoon and evening.

High pressure will slowly back off over the weekend, but we will still have a southerly wind overhead. Thin smoke and high elevation clouds will be possible at times, and isolated storms could fire up during the afternoons & evenings along the Cascades and east of the mountains. Highs should trend back into mid 90s to upper 80s Saturday and Sunday.

High pressure will continue to inch away from the Pacific Northwest next week, resulting in cooler temperatures. Afternoon highs will slowly trend back down into the 80s, with overnight lows in the upper 50s and low 60s. 

  • Posted

2pm Saturday…

It’s very nice to see the snow forecast turn out as close to perfect as it can get.  That’s rare.  Last night (see previous post) we forecast Zero to 2″ in the western valleys.  We expected little impact on lowest elevation roadways plus snow showers continuing through the day as temps rise to around 40 degrees or so. That’s pretty much what happened.  It appears most areas saw at least a dusting, and a few spots even in the lower elevations up in Clark County picked up 3″.  Areas around 1,000′ or so have see up to 4-5″.  Temps at 2pm…higher as sunbreaks pass over, lower under snow showers.

web_metrotemps (2)

Sure enough, a steady band of snowfall developed after midnight and temperatures dropped close to freezing, bringing sticking snow down to the valley floor in many spots.

Are you ready for the GRAND OFFICIAL TOTAL IN PORTLAND???

0.5″  < The Big Total

Yes, the NWS (in Parkrose) picked up 0.3″ leading up to 5am, a trace from 5am-11am, then 0.2″ just after that time.  That adds up to 0.5″, our only measurable snow of the “winter”.

Are you thinking March snow (even a little) doesn’t seem too unusual lately?  It isn’t.  Actually through the first 10-15 years of my career it was pretty much a no-show.  We’ve only seen measurable snow in March 6 times in the past 50 years!  Only once in the 30 years from mid-70s to mid-2000s.  Now we’ve seen it three times in 10 years.

Portland Snow Last Few Times In March

Today’s snowfall also ties for the 4th latest on record in Portland.  Official records go back to 1940 at PDX/NWS forecast office locations.

Portland Snow Latest 2

As mentioned numerous times the past few years, the latest is the 0.5″ on March 22, 2012.  There had been some “later snow events” (one in 1968), but the NWS cleaned those up and decided they were hail and not snow.  And the old downtown records show an April 1st snow back in the 1930s.

We have LOTS of sunshine ahead, after a couple of cold nights.  I’ll be back at work tomorrow afternoon

Chief Meteorologist Mark Nelsen

  • Posted

4:30pm Saturday…

It’s a cold afternoon in Portland; temperatures are right around 40 degrees and the chilly east wind is back.  That wind will be very strong the next 12 hours, blasting in a supply of cold eastern Oregon air while milder Pacific air with moisture rides over the top.  This IS the classic setup for a snow or ice storm in the Portland Metro area.  But in tonight’s case, temperatures are a bit too “warm” for that to happen, plus we don’t have much precipitation on the way.

In the metro area, and through much of the Willamette Valley, we’re going to see at least an hour or two of mainly snow as precipitation arrives.  As early as 9pm around Albany to maybe midnight up in Clark County and near the Gorge.  But very soon after it starts falling, the air a couple thousand feet up goes above freezing.  That means snowflakes melt to liquid rain drops.  Of course anyone that is near freezing those first hours could see some snow accumulation; probably less than 1″.  That’s most likely out closer to the Coast Range (Forest Grove, Hillsboro, Yamhill, Banks) and hills throughout the Willamette Valley (West Hills, Eola Hills, South Salem hills etc…).  But ANYONE could see a quick dusting.  Nothing has changed with models today; none showing any significant snowfall.  The latest ECMWF model agrees, although I think it’s a bit too dry in general.

ecm_18zsnow

Once we go to liquid rain, the remaining “threat” is freezing rain.  That cold wind screaming out of the Gorge means most areas east of I-205, and metro hills above 500′ or so (West Hills, Mt. Scott etc…) will drop to freezing.  Expect an icy glazing on any outdoor objects in those areas.  Although for roads to freeze up, air temps need to drop down to around 30 degrees.  That’ll be tough to do except right around Troutdale/Camas and the top of West Hills or Mt. Scott.

Freezing Rain Ice Accum Warnings Metro2

All the rest of the Willamette Valley should escape freezing rain and/or more than a dusting of snow.  95% of us won’t see any effect on our daily lives tonight or Sunday.

The cold east wind continues Sunday, but temperatures rise to around 40 degrees in the metro area.  Any icy roads near the Gorge should slowly thaw by midday, and the rest of us will just see bare and wet or dry roads.  Your life can continue as planned Sunday in MOST of the metro area.  For sure after 10am even in those colder icy spots.

In the Columbia River Gorge, expect snow at first, then warmer air overhead west of the Cascades (around Multnomah Falls westward) changes that snow to freezing rain.  Late tonight and tomorrow morning I-84 may be very icy from Troutdale to mid-Gorge, then snow-packed roadway beyond that point

Gorge Wintry Weather Text 1aGorge Wintry Weather Text 1b

With easterly flow continuing tomorrow, temperatures will only crawl a few degrees above freezing so I-84 ice/snow will be slow to melt off the roadway.  Keep a close eye on ODOT cameras and TripCheck.  Plus FOX12 will be on the air with Good Day Oregon at 6am.  Monday would be a much better day to travel through the Gorge; or consider going over Hwy 26 around Mt. Hood.  No freezing rain and snow level near 4,000′ means not much snow/ice once you get below the summit on the west side of the passes.

For the weather geeks

As you can see, no big changes to my thinking.  I’m watching those temperatures/dewpoints closely this afternoon.  A good guess for how much the temperature will fall with evaporative cooling tonight is to take 1/3 of the temp/dewpoint difference and subtract it from the current temp.  For example, right now Troutdale is 39/17.  That’s a 22 degree difference.  1/3 of that is about 7.  Take 7 off the 39 and you get about 32 degrees once evaporative cooling has kicked in.  Subtract another 2 degrees since it’ll probably be around 34-35 when precip starts in Troutdale; so maybe we bottom out around 30 at Troutdale later tonight?  That’s why I’m thinking there may be some icy roads that close in to the metro area.  Same temperature setup up on the West Hills and Mt. Scott.  Farther south in the valley dewpoints are higher so it will be tougher to get down to freezing.

WRF-GFS soundings continue to show quite a warm layer surging in overhead right after precipitation begins.  It’s almost a perfect “snow sounding” at 10pm over Portland

kpdx.18.0000.snd

Then a sharp warmup around 2,000′ overhead by 1am (near freezing at the surface though with cold Gorge outflow).  This is a freezing rain setup, if your neighborhood is at/below freezing.  Otherwise a real nice 35 degree rainy night…

kpdx.21.0000.snd

ECMWF and GFS both show the warming up around 925 mb as well.  That’s why I’ve been leaning more toward liquid precipitation instead of snow since yesterday.

The latest WRF snow forecast confirms little/no accumulating snow west of the Cascades, best chance for an inch would be in those previously mentioned communities right up against the Coast Range east slopes.  That shows up on this graphic.  Dallas, Willamina, maybe Yamhill?

wrf_oregonsnow_model

That’s it for now.  I’ll be on the air at 8 & 9pm on FOX12PLUS, then 10pm on FOX12.

Chief Meteorologist Mark Nelsen

  • Posted

All evening models are in at 10pm.  They are all drier, which of course means less snow for the Portland metro area.  I’ve lowered the forecast a bit because of this

Snow Tonight Forecast 1

What does this mean?

  1. I think Portland will pretty much operate “as normal” tomorrow after a light morning dusting.
  2. As mentioned in the previous posting, if we really only get 1″ of snow roads will be just plain wet most of the time or for sure by noon
  3. Afternoon commute will be fine

All the other forecasts remain unchanged, a snowstorm just about everywhere south and east of the metro area.  Click on each for a closer view.

The final holdout (ECMWF) model came in just before 10pm and looks like this.  Seems pretty reasonable to me.

ECMWF Snow Accumulation

See you on the other side!  That would be the other side of the snow event, I’ll post sometime tomorrow morning

Chief Meteorologist Mark Nelsen