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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

8pm Sunday…

Quite a soaker eh? A warm and humid southerly flow has given the metro area somewhere around an inch of rain since it started yesterday evening. PDX has officially picked up .86″ as of 7pm with more approaching. I’m guessing that by the end of today (as early as 9pm?) WE WILL SEE MORE RAIN OUT OF THIS THAN ALL OF APRIL + MAY COMBINED! In a typical spring we’d get something like this maybe every few weeks. Not this drought year. The numbers so far…

By the way, in Portland we’ve haven’t seen this much precipitation in two days since…wait for it…the big snowstorm day! That’s Friday, February 12th (and into Saturday the 13th). Of course, it was all frozen precipitation (mainly snow) that day for much of the metro area.

A few areas have picked up over 1.50″…notice all (so far) over/west of I-5. Models have done very well sending the heaviest rain over there. This map isn’t real pretty, but it shows any location that has picked up about 1.50″ or more as of 7pm. That’s a huge soaking around Salem and Corvallis.

Of course in a warm and humid airmass with southerly flow one can expect thunderstorms in the Pacific Northwest. We’ve seen quite a few fire up over north-central Oregon, even as far west as the eastern edges of the metro area. In fact at 7:30pm this soaker was right over the Hood River Valley. Luckily it’s moving fast so the heavy rain won’t last long. You don’t want a 3.50″ hourly rain rate to sit still…

Ahead of today’s system, it’s been HOT in Eastern Oregon. Check out the afternoon numbers…close to 100 in a few spots!

What’s ahead?

More humid and warm weather tonight as the main upper-level low continues to spin offshore.

But good lifting that would produce significant rain tonight and tomorrow seems to go away. So showers continue tonight, but then we get a break again tomorrow. Other than leftover morning showers (mainly east metro), it should be a MUCH brighter day and mainly dry. Sure, maybe a shower here and there, but widely scattered stuff. Lots of fresh rain-cleaned air too.

As the cool upper-level finally “kicks out” to the northeast and over us Tuesday, we get a round of showers. Maybe a thundershower midday too…maybe.

By midweek the hot upper-level ridge to our east has been pushed south & east. But then a new ridge is developing in this spring’s favored position; in the Gulf of Alaska. That leads to weak and warm westerly flow to our north.

This is a warmer than normal pattern for mid-June, but not hot. 850mb temps on our models are generally well under 20 degrees with no sign of significant offshore flow. So our forecast highs remain in the 80s for now. Weather systems will stay away Wednesday through at least next weekend.

Looking farther ahead (this map shows anomaly), the pattern remains the same through early NEXT week. This is NEXT Tuesday. We don’t have a hot ridge of high pressure overhead, but it’s close enough to cut off any rain chance. That’s what we’ve seen much of this past spring.

The ECMWF ensemble forecast for 24-hour rain is the driest I’ve seen in weeks. Very few members produce even light showers over the next two weeks (after Tuesday). So…this was a one-shot deal rain-wise.

Enjoy the rest of the rain this evening, and you can look forward to some warm sunshine later this week as a July-like weather pattern arrives.

Chief Meteorologist Mark Nelsen

  • Posted

What a weekend it has been! Both days in the 80s west of the Cascades, no rain, sunny from sunrise to sunset, and not much wind either. Must be mid-July right? No, just mid-April.

Portland ended up with these numbers the past three days…

A marine push of cooler air arrived on the central coast yesterday, but didn’t make it the Astoria and Long Beach until early today. So a few spots hit 80 yesterday up north, but ALL areas were much cooler today. Newport couldn’t even make it to 50. Keep in mind that in these situations proximity to the ocean determines how warm a location gets. Newport’s observations are taken at the airport, very close to the beaches. Yet Tillamook airport is quite a few miles inland = warmer when the marine layer is very shallow. Just a few miles inland at Toledo it was around 70 degrees today.

Typically I’d expect lots of that marine air to pour inland tonight. Then, since it’s so early in the season, we’d wake up to low clouds and afternoon highs only reaching to 65 or so tomorrow. But while we do have some marine air pushing inland this evening, a fresh round of “cool” and dry Canadian air is surging south through Eastern Washington. This is due to an upper-level disturbance moving down the back side of the warm ridge we are under. There was a gusty WEST wind in the Gorge today with the onshore flow, but by tomorrow morning models tell us we’ll be back to 3-5 millibars EASTERLY gradient. Expect gusts 30-50 mph at Vista House the first half of the day…quite a change. Spokane’s airport just reported blowing dust and a squall this hour as the late season “arctic front” passes by. Strong northeast wind is spreading south quickly this evening. So we’re back to a mild easterly wind tomorrow = no marine push and/or low clouds. Of course we’ll still be a bit cooler, but 10-12 degrees above normal instead of 20-22 above. To summarize, we have three more beautiful days, just some high clouds at times. That will give us 11 totally dry and mainly/all sunny days. Extremely rare in April! Check out that slow temperature rise since the cool/showery 53 degree day on Saturday the 10th

It’s back to onshore flow and a cooler atmosphere Thursday through next weekend…back to normal. We’re going for this right now. Typical late April weather for next weekend.

Of course, we badly need rain, it’s now officially the driest spring (at this point) we’ve seen in Portland since at least 1940. The ground is chalky dry in my garden; although I see the woods still have moisture an inch or so below.

How much rain is ahead? Enough to wet things down for sure, but we could use a nice 2-3″ over the next two weeks to start soaking the ground again. ECMWF ensembles say most likely it begins Saturday and continues off/on through the end of the month. So wrap up your deck-staining and other outdoor activities this Thursday/Friday and assume we’re headed into a wet period.

So is this very dry spring unusual? Yes, of course. But this isn’t a trend we’ve been seeing in springtime. In fact we’ve been turning just slightly WETTER west of the Cascades in springtime compared to 100 years ago. I just checked the entire NCDC Oregon Climate Zone #2 (western valleys) for March-April-May precipitation. This average ALL climate stations in the lower elevations westside. The last three years have been a bit on the dry side, but not excessively so.  One thing to keep in mind, we still have 6 weeks of “spring” left and a May soaker could make up for this very dry start.

What about temperatures? Here are spring temperatures for this same western lowlands climate zone. What really sticks out is the cyclical stuff; we go through several years of cool/wet springs (2008-2012), then warmer periods. The last 8-9 springs have been above average…we haven’t seen a “cold spring” since 2012. That’s good for gardening, but as we know, it can be bad for summer fire season. Also notice temperatures have NOT been rising dramatically at all during this spring period. Winters are warming, summers are warming, but not much with spring…so far. 

That’s it for now. Enjoy a few more bright days with more comfortable temps than we’ve see the past two days. Eventually the cool showers WILL return.

Chief Meteorologist Mark Nelsen

  • Posted

7:30pm Saturday...

The February 11th-13th 2021 snow/ice storm is going to be one for the record books. A few stats for you:

  1. PDX only made it to 30 degrees today; for the 2nd consecutive day. That's a rare event this late in the season. In fact only TWICE has PDX stayed at/below 30 degrees after the first week of February. In 1956 and 1960. We haven't seen such a cold day this late in the season during my lifetime...brrr!
  2. The Portland forecast office has picked up 8.0" snow so far, plus I wouldn't be surprised to see a bit more this next hour or two since it is snowing right now. That makes it the 4th snowiest February on record, or maybe it'll be #3 within a couple hours

3. At the peak earlier today, Portland General Electric was reporting about 220,000 outages due to the catastrophic ice storm in the northern and central Willamette Valley. That is a similar percentage of customers we've seen during previous big ice storm events. But those have generally been central/east metro closer to the Gorge. This time everything went wrong. A thin subfreezing layer of air at the surface plus heavy precipitation overhead.

Looking ahead...

KEY POINTS

Light mixed precipitation continues tonight through tomorrow morning throughout the region. In the Portland metro area it could be snow or freezing rain through sunrise. We are getting the typical showers between organized weather systems.

The entire metro area stays frozen tonight. Typically the showers putting down a fresh swath of light snow or a bit of freezing rain glazing would be a HUGE deal; but everything is covered in snow or ice already. Adding another inch or two of snow shouldn't change things much.

Another slug of steadier precipitation comes through midday/afternoon tomorrow. BUT, at this point it's warmed overhead so we're into liquid precipitation only. Temperatures rise into low-mid 30s metro area (away from Gorge) and that means we shouldn't see additional icing of roads tomorrow. In fact light rain showers will help melt things a bit. Tomorrow afternoon a southerly wind pushes up to the south edge of metro. Everyone in a line from Newberg to Wilsonville to Molalla and south should see temperatures jump into the 40s. We stay between 30-37 in the rest of metro.

Tomorrow night one last slug of steady rain comes inland. The last "holdout" of sub-freezing air will be east of I-205 and near the Columbia River from the airport to mouth of the Gorge. These areas (Troutdale, Gresham, East Portland) will see significant ice glazing tomorrow afternoon and night. Possibly up in the West Hills as well...maybe. I think the rest of the metro area will sit at 32-35 degrees tomorrow night which means no additional icing.

Finally, a mild southerly wind pushes through the ENTIRE metro area by sunrise Monday. We will immediately jump into the low-mid 40s at that point...MONDAY IS THE BIG MELT DAY. West wind pushes through the Gorge Monday as well, but midday/PM

TECHNICAL INFO

It was a somewhat poor choice to drive home last night; probably should have stayed at hotel one more night. 1-3 foot high snowdrifts...an experience like those Subaru commercials. I followed my son in his 4Runner through those drifts between Corbett and Vista House. That is the deepest snow I've driven through (separated by bare spots in the wind). Much better coming back to work today because Multnomah County and ODOT road crews have been working so hard. It was neat to be behind an ODOT plow blowing through those drifts today; an massive explosion of beautiful powdery white passing through each one.

This cold airmass is just about played out, we saw quite a bit of melting at 1,800' on our KPTV tower cam today. That means the cold layer is now that shallow overhead. Snow level from the Astoria profiler is around 2,300' or so right now, which means the cold air coming out of the Gorge is still thick enough to "fill the gap" and keep temps at/below freezing all the way down to the city. That's why we're seeing snow this evening.

That will change around sunrise tomorrow. WRF-GFS sounding for right now shows at/below freezing all the way down.

But by 10am tomorrow, a warmer layer has moved in (temp above zero C) = all liquid rain in the metro area from this point forward. The red line is temperature, blue is dewpoint

At 1pm tomorrow a weak front is moving onto the coastline, keeping easterly wind going through the Gorge. It's calm in the Willamette Valley.

But then a 2nd/stronger system sweeps toward the coast tomorrow night. This time the surface low is headed north of us. At 1am tomorrow night, east wind is screaming through the Gorge again, although it's a thin layer of cold air compared to yesterday. Warm southerly wind has reached up to about Salem.

Then at 7am the low is pushing across SW Washington. Gusty southerly wind has arrived in the metro area; temperatures suddenly pop into the mid 40s around sunrise...the melt is on.

Whatever falls from tomorrow morning through late tomorrow night will likely be freezing rain east of I-205 near and south of the Columbia River. Expect 1/4" to 3/4" glazing over there and into the western Gorge. Cold air will be deep enough for snow in the central and eastern Gorge until a warming west wind arrives Monday midday/PM. Seems unlikely that I-84 will reopen before Monday.

I'll be on TV tonight at 10pm, and of course tomorrow night at 5/10/11pm. Chief Meteorologist Mark Nelsen

  • Posted

Quick update to let you know what's going on as we are getting slammed by Round #2

  1. Heavy precipitation continues until around 5am Saturday, then it's just scattered showers. This event is going to be pretty much "over" by mid-morning tomorrow. By that I mean I don't expect significant accumulation of either snow/ice pellets/freezing rain after sunrise tomorrow.
  2. The entire metro area is now the coldest we've seen through the event. Low to mid 20s and in some areas it's pouring down liquid rain! That's not good.
  3. Portland officially recorded at least 4.7" snow today, possibly a bit more since 4pm

One relatively minor change, which makes a big difference for snow totals is here. This is what we've been expecting. Snow north metro, freezing rain far south for this event.

This is what has actually been occurring...do you see any difference?

Yep, that's about a 10 mile northward shift to the MIX and FREEZING RAIN AREA. Meteorologically pretty close, but it happens to lie right across the middle of a metro area containing 2.5 million people!

5-7" snow has fallen in the snowy area so far (as expected), but more glazing is happening farther north in the metro. Those places in the central metro that might have seen 4-8" instead are mostly done with snow.

So in the end we'll still end up with 2-12" total snowfall in the metro area, but the southern end of light snow shifts a bit farther north.

Models are hinting that we may see a southward shift of the snow line again late tonight as cooler air comes in with the front...before precipitation totally cuts off. SO IT'S STILL POSSIBLY ANYONE IN THAT MIX AREA PICKS UP 1-2" LATER

That's it for now...see you on TV at 10/11pm...Chief Meteorologist Mark Nelsen