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Monday, July 26th, 3:15 P.M. 

Good afternoon!

We managed to stay a bit sunnier than some of our computer models advertised, so temperatures are making a run at 90 degrees. Most of us will come up shy of 90, but it’s still plenty warm out there. Clouds are associated with a bit of a monsoonal surge coming out of the Southwest. East of the Cascades, we’ve been watching scattered showers and isolated storms. Expect to see mid and upper level clouds streaming in between this evening and Tuesday. Depending on cloud cover, high temps should range between the mid to upper 80s Tuesday afternoon.

A pretty impressive high pressure system is building over the Great Basin and the Intermountain West. This system will inch westward between mid to late week, causing temperatures to soar back into the 90s. We’ve trended our high temperature forecast up a tad, with the hottest days likely being Thursday-Saturday. Highs will range between the mid to upper 90s, with a few spots potentially hitting 100 on Friday. Overnight lows will only fall into the mid to upper 60s. The placement of the heat ridge will also cause our upper level wind to turn out of the south (instead of southwest). This will likely pull some smoke in from California, causing skies to turn hazy. Most smoke should be well above the surface, so air quality shouldn’t take a hit.

High pressure will back off by the end of the weekend, allowing onshore flow to strengthen and temperatures to dip back into the 80s. Overnight lows will turn cooler as well.

Home prices in the US hit another record, but sales are slowing down

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Single family homes line the streets of Clairemont on Tuesday, Oct. 27, 2020 in San Diego, CA.

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After experiencing our warmest Memorial Day Weekend since 1992, the weather scene REALLY heated up today. A very warm airmass + light offshore flow + all sunshine led to a record setting hot day. Portland hit 95 degrees, but look at all the other records!

Each of those numbers is a record for the date…not the month. The Dalles made it to 103. Surprisingly, Astoria hit 80 briefly, even with the weak/flat thermal trough centered inland, not on the beaches.

Of course last night marked the end of “meteorological spring”. That’s March/April/May in the Northern Hemisphere. You may be thinking spring doesn’t end until the summer solstice on June 20th right? That would be “traditional spring” like you see on a calendar. But official spring (according to NOAA) has just finished. And what a spring it has been. I’ve never seen such a dry spring here, and almost no one alive has seen it this way either.

It wasn’t about the temperature…Portland ended up just a bit above average. A cool March was balanced out by a warm April and slightly warm May

But check out the rain! Over 6″ less than normal…which is just above 9″. Not only was this the driest spring on record at PDX, but only about 1/2 of the previous record! This spring blows all the others out of the water. Grasses are drying quickly as if it’s early-mid July.

This was a historic spring with respect to rain…here are some other rankings:

  • #2 Driest DOWNTOWN PORTLAND: 3.83″ (driest was 1924 = 2.76″, #3 was 1939 = 3.92″)
  • #1 Driest PENDLETON: 1.01″
  • #2 Driest ASTORIA: 7.51″ Records go back into 1880s!
  • #3 Driest MEDFORD: 1.84″
  • #8 Driest SALEM: 4.54″ Records go back to 1870s!

Who would have expected a slightly warm and record dry spring in an La Niña year? A bit dry would have been normal, but not the combo of record dry and warm-ish.

WHAT’S AHEAD?

Just about out of time so I’ll make it quick. The hot ridging overhead weakens slowly the next 2 days. By this weekend and next Monday, we’re under a cool upper-level trough

Then the trough lingers/weakens through the rest of next week. This is the ECMWF ensemble average of 500mb height for June 10th (NEXT Thursday). A little bit of troughing, but it seems to be centered farther south.

Considering there will be upper-level troughing nearby from Saturday through next week, models sure aren’t producing much rainfall. The 15 day ECMWF forecast takes us through the first half of the month

Less than 1″ through the Willamette Valley with many areas seeing less than 1/2″. That’s not good. CMC (Canadian) ensemble is similar

Same general idea…less than 1″ for the first half of the month in the western valleys. It’s ALMOST time to panic rain-wise. Even I’m worried now about well water as we go into the 2nd half of summer. We have just about run out of time to see any real soaking rain. How much rain did we have form this point forward through June the past 10 years? Only 3 of those 10 saw significant rain (2″ or more)

I’ll dig a bit deeper into this when I get back next week. I just worked 13 of the last 14 days so I’ve got a bunch of days off.

Chief Meteorologist Mark Nelsen

That money you donated to a GoFundMe? It probably isn't tax deductible

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The money you donated to a GoFundMe campaign probably isn't tax deductible.

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Concerns about looming gun control legislation and rising crime continued to fuel gun sales in America throughout the month of April, according to industry observers.

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9pm Sunday…

Well, it rained a bit yesterday, but officially nothing in Portland today. Showers were widely scattered and mainly concentrated over the Coast Range and Cascades. Saturday’s showers showed up and were about what I expected, but not today.

Officially nothing measurable fell in Portland, which means it’s still the driest April on record with just five days left this month. I think there’s a very good chance it’ll remain the driest April we’ve seen…more on that below

WHAT’S AHEAD

A cool upper-level low (pool of cold air overhead) is sitting along the West Coast this evening. It’s going to stick around for one more day

But that trough leaves late tomorrow as strong and very warm high pressure builds in the upper atmosphere. By Thursday its hot anywhere south of southern Oregon and quite warm here. We could be close to 80 again Thursday

The ridge flattens for the first weekend of May, which may (or may not) lead to some decent showers

But there doesn’t appear to be another cold trough headed our way for at least 10 days! By Wednesday the 5th of May, weak ridging is overhead again

I’m only showing you one operational model, the ECMWF, but others are similar with upper level heights running higher than average the next 10 days…which takes us into the first week of May. It’s pretty clear that the much anticipated turn towards a wet spell is looking a bit weak. The GFS, ECMWF, & GEM models barely produce 1″ of rain in the lowlands of western Oregon & southwest Washington the next 10 days. And these numbers seem “irrationally exuberant” when compared with the upper-level maps.

To summarize:

  1. This record dry spring will continue into the first week of May.
  2. You will need to continue watering this week, since I don’t see any significant rain (0.25″ or more) until at least Friday evening
  3. It’s possible we still don’t get a soaking next weekend either, but we don’t know yet.
  4. We have three guaranteed dry days Tuesday through Thursday as the ridge builds overhead

RECORD DRY SPRING

I figured we could get at least 1/2″ of rain this weekend through tomorrow plus a bit more later next week. Not typically a tough feat in April. That’s why I was poo-pooing the idea of seeing our driest April on record. But as of tonight it’s looking quite likely once the clock strikes midnight this Friday. The last 7 years…

Notice last year was also in the top 5 driest Aprils… If we get more than .27″ rain before midnight Friday, it WON’T be the driest April on record at PDX. That may happen

Of course something we have been talking about for the past few weeks has been the record dry spring. It’s amazing to think we’ve seen less than 2″ rain in all of March and April! This year just 1.81″ at PDX so far. These records go back to 1940. I also checked the downtown location (records back to around 1880); there appear to be only two other springs so dry, 1885 & 1926. Its the driest spring in Salem since 1926 as well…so far

This is the 2nd spring with very dry March-April conditions. 2017 was a soaker eh?

WHAT DOES THIS MEAN FOR MAY/JUNE, OR SUMMER?

First, there’s no reason to freak out (yet) over the lack of spring rain.

IF we get deep into May with these conditions, I’ll start getting concerned. If the dry pattern continues into early-mid June then we have a serious problem. That’s only six weeks away.

We already know that we need at least normal rain from this point forward to fill reservoirs like Detroit and Green Peter. And we also know drought conditions continue to creep north through Oregon.

Lack of mountain snow and warm temperatures have caused a faster-than-normal melt in the Cascades. The snow melt season had been delayed due to a chilly March, but now snowpack is below average in most of Oregon

Does a dry March+April mean we’re headed for a serious drought? Possibly, I did a little bit of research this evening. I looked at the ten driest springs (up to this point) and then looked forward into May and June to see what happened. Here you go:

Yep, it was a divided verdict. In 2-3 years we saw a soaking in May, or June, or a combo of both in 4 of those years. But in 6 of those years, drier than normal conditions continued as we headed into early summer (June). It is interesting that only one May saw less than 1″ of rain. That shows you how unusual it is to have a sub 1″ rain month in spring in Portland. That’s what we’re seeing right now.

The following summers? I didn’t check rain since we don’t get much in July/August anyway, but I did check temperatures. Only 1 of the 10 summers could be considered a “cool” one. All the rest were average or hot. Does that mean we will see a 9th consecutive warm/hot summer? We don’t know, but this would imply a dry spring can lead to at least a normal/warm summer.

So…there’s a decent chance we continue with a dry-ish spring, but there’s no reason it can’t still turn around.

For now, keep watering! Chief Meteorologist Mark Nelsen

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9:30pm Thursday...

It's been nice waking up to sunshine every one of the past five days. And we'll do it for at least another five, but now it's getting a bit...weird. It's been nice, but we don't live in Sacramento. Most of our viewers live in western Oregon and Washington.

Take a look at those temperatures the past few days. We've gone from a high of 53 Saturday to 76 today in Portland...the warmest day of the year.

VERY DRY SPRING

We've only seen .09" rain so far this month and now we've reached the midpoint of meteorological spring. March-April-May is spring in the northern hemisphere (officially defined by NOAA). Take a look at the numbers...in the past 7 weeks we've seen less than 2" rain in Portland.

Assuming it doesn't rain by Sunday (it won't), this will be the driest March 1st - April 18th on record at PDX. Those numbers go back to 1940. I checked Salem, Astoria, & Olympia. Similar extremely dry numbers.

Last year was a bit dry, our 5th driest April. Luckily last year we had a wetter May and very wet June to make up for it.

I remember the flooded sports fields back in 2017 & 2018. Each year is different, but this spring (so far) is exceptionally dry.

The NWS has a Red Flag Warning out for much of western Oregon, also quite rare for April

WHAT'S AHEAD?

A strong ridge of high pressure in the upper atmosphere is centered in British Columbia with a cool low just to our southeast. It's been a chilly mid-week from Boise over to western Colorado, snow in spots

That warm ridge slides down right over us by Saturday...warmer atmosphere overhead

Then it weakens a bit by Monday, but at the same time another pocket of cool air is sliding down just to our east

The result will be offshore (easterly) flow and warming temps tomorrow & Saturday. 850 millibar temps to around +12 to +13 imply we could get as high as 84, but we're going slightly conservative with a high of 82 Saturday. That would be enough to break a record for the day

Then onshore flow arrives on the coast Saturday afternoon and tries to push a bit inland Sunday. I don't think that will drop our temperature more than a degree or two Sunday. The result is a very summerlike 3 days ahead. Then as the cool air drops in to our east Monday, that's high pressure which renews the easterly flow across the region. A cooler airmass Monday, but offshore flow returns quite strong. Looks like more sunshine for Monday and Tuesday. This all adds up to five more days of sunshine.

When does the rain return? Each operational model is different, but they all suggest a pattern change later next week. The ECMWF ensemble forecast suggests not much rain Wednesday/Thursday, but by Friday and into that last full weekend of April we could be back to a more typical wet/showery weather pattern

We can't do anything about the lack of rain, so enjoy the sunshine while we have it. And there's no reason to panic thinking that we're going to have a "terrible fire season"...remember last June we had soaking rains the first part of the month.

Chief Meteorologist Mark Nelsen

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9:30pm Sunday…

I’ve been on vacation the past 9 days, a bit of bike riding down in the Moab (Utah) area with my son. Sorry, not many pictures because I was having fun. Actually I was home part of that time as well; but I’m back at work this evening. Calling it “work” is a bit of a stretch meteorologically since we are in a VERY stable weather pattern for at least the next 7 days.

THE COLD

First, the record cold this morning. We’ve seen LOTS of late season frost the past month, because we’ve seen much drier than normal weather. Keep in mind we’ve seen less than 2″ of rain in six weeks in Portland! Drier air = less cloud cover = colder nights. Basically west of the Cascades we’ve been in more of a “continental climate” than usual. Right now dewpoints are down in the 20s in the metro area. Sometimes we don’t see them get that low all April long. Our spring in Portland (so far) is similar to a typical spring you would experience east of the Cascades. Wide temperature range; nights running cooler than average, but daytime slightly warmer. Last night we saw widespread cold readings. Look at the Portland metro lows:

Lots of upper 20s, even a few mid 20s…pretty cold for mid April! Portland airport dropped to 32 degrees, the first time we’ve seen frost beyond April 10th since 1982.

Quite an impressive reading considering the metro area is much larger than 40 years ago, more of an urban “heat island” now. Plus our climate has warmed a bit in general. We don’t see many record lows in Portland the last couple of decades. Record lows were also set in several other locations west of the Cascades

My peach tree is blooming and still LOOKS okay. Maybe it needed to be under 27 degrees to do significant damage, we will see within the next couple of weeks.

Tonight won’t be quite as chilly as the airmass has warmed a bit. Sure, some frost for outlying areas, but everyone should be at least 2-3 degrees warmer than last night.

AN AMAZING WEEK AHEAD

When I came in and looked at the maps/models today, it became obvious we are in for almost continuous sunshine for the next week for much of Oregon and SW Washington. That includes the coastline.

In the upper atmosphere, a ridge of high pressure and its sinking airmass is developing just to our west and north, keeping weather systems away. But a cold pool of air (upper-level trough) is coming down the back side of that out of Canada. By Tuesday it is centered over the Idaho/Nevada/Utah area.

It’s far enough south and east of us to keep cloud cover away. But we get a relatively strong northeast flow overhead. That’s offshore flow. Even though the air starts cool, this pattern under strong April sunshine will push our temperatures above normal. By Thursday the setup is strong high pressure to the north with a low south. This can be (and will be) a very stable weather pattern. It’s called a “Rex Block”.

Then between Thursday and Saturday the warm ridge expands south and east over us as the low moves away. A warming atmosphere means high temperatures climb from just above average to MUCH above normal. We’re headed from the lower 60s tomorrow to mid-upper 70s Saturday west of the Cascades. After tonight the widespread frosts west of the Cascades should disappear as well.

Meanwhile offshore wind flow appears to continue all week, although it may weaken briefly Wednesday/Thursday. Check out the WRF-GFS cross-section over Portland; Wednesday afternoon (right side) through Sunday afternoon (left side). Yellow line is around mountain pass elevation.

Offshore flow almost the entire time, plus a warming atmosphere. No cloud cover (maybe a few thin high clouds). It doesn’t get any better than this anytime April through June!

At this point we don’t appear to be setting up for record high temperatures…all in the 80s mid-April and beyond. But we’ll go from a perfectly average 60, to around 70 by Wednesday/Thursday, to upper 70s Saturday and possibly Sunday. For the weather geeks, 850mb temps need to make it to at least +10 over Salem this time of year to hit 80 in Portland with perfect conditions. That COULD happen Saturday, we will see. Regardless, this 7 Day forecast is something else for mid April!

When will it end? ECMWF ensemble precipitation forecasts imply the ridge breaks down somewhat next week, so it’s safe to assume showers will appear at some point after NEXT Monday

That’s it for now, enjoy the sunshine!

Chief Meteorologist Mark Nelsen