Winter is Definitely Over, But Some Mountain Snow

February 26, 2015

11pm Thursday…

Snow has been very slow to show up in Cascades today, with only a dusting at Meadows and Skibowl.  As a result I lowered tomorrow’s forecast to 4-8″ as a cold surface low pressure center tracks right over us.

MarkSnow_MtHoodFcst

Beyond that, very little precipitation through the end of next week as upper-level ridging moves up close to the coastline.

Long range, the pattern is not very wet and models have gradually been moving towards some warmer upper-level ridging over us in the 8-12 day period.  Take a look at the 12z ECMWF ensemble chart, showing chilly air around Tuesday, then warming again.

tseries_850t_000-360_Portland

Same thing on the GFS, although not as cold early next week.

tseries_850t_000-384_Portland

This plus last night’s 32 day run of the ECMWF tell me that calling off winter 10 days ago was a good choice.  March weather is here and will continue.  Check out the 4 weekly maps from the monthly run:

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA

Looks like the 3rd week of March may be wettest/coolest, but otherwise heights are near or above normal the rest of the month.   That ridge to our west or northwest doesn’t want to give up.

I’ll be going to the annual Pacific Northwest Weather Workshop in Seattle tomorrow.  I haven’t gone for a few years and it’s time to catch up.

If there’s something really good I’ll recap in a posting early next week.

Chief Meteorologist Mark Nelsen


Snow Finally Arriving In Cascades

February 25, 2015

10pm Wednesday…

Finally, an inch or two of snow on Mt. Hood this evening as moisture arrives.   Can you believe this?

MarkSnow_GovtCampJanuaryFebruary

Government Camp, at 4,000′ has only seen 2″ of snow in TWO MONTHS! That’s just about unprecedented in mid-winter.

There’s a decent chance we have hit bottom for “snow water equivalent” (snowpack on the ground).  Most of the Cascades average around 10% of normal.

MarkSnowpack_Oregon_PlusFacts

MarkSnowpack_Oregon_PlusFacts2

Obviously it is too late now to make up for all that lost snow…the snow season will end up below normal even if we have lots of snow in March and April.  The question is just “how far below normal” will it end up.

I expect up to a foot of new snow at/above 5,000′ in the Cascades by Saturday morning when the snowfall ends:

MarkSnow_MtHoodFcst_2013

Spring break is only slightly over 3 weeks away and 10 day maps don’t show a real wet pattern.  Definitely a little bit wetter than what we’ve seen over the past two weeks, but not a huge snowy setup for the mountains.  The 00z GFS shows less than 1.50″ precip for us in the next 15 days.  The 12z ECMWF has about 1.30″ precip in the next 10 days.

So the good news…

  • Up to 12″ new snow the next two days at the ski resorts
  • Sunny skies and bluebird conditions BOTH Saturday & Sunday
  • Expect lots of people due to pent-up demand for good snow!
  • A little more snow Monday, then mainly dry next week

Chief Meteorologist Mark Nelsen


Cooler Weather Ahead: But Not Much Rain or Mountain Snow

February 23, 2015

What a spectacular run of February weather!  It’s been 20 years since we’ve seen so many 60+ days in Portland.  We hit 60 again today in Portland and with the very dry air mass it was crystal clear.  This was the 7th day at/above 60 degrees this month; the most since February 1995.  We’re in a “Central Oregon” climate for a few days with the low dewpoints, clear air, and chilly nights.  That will end after tomorrow.  By the way, we did a story on people suffering from allergies early this year.  Most likely the allergens are “ahead of schedule” along with our temps.  Notice it’s been warmer than normal for 3 months now:

Mark_PollenBackgroundCause

We finally have some snow on the way for the Cascades…The last time we saw significant snow at Government Camp (more than an inch or so) was two months ago!  Only 2″ has fallen there since January 1st.  Here’s our forecast for the next 8 days.

MarkSnow_MtHoodFcst_2013

Your next question is likely “…Hey, I thought we were entering a period of snowy mountain weather and rainy valleys?“.  Well, things have changed a bit in the past week since I posted those monthly ECMWF ensemble maps last Monday.

Instead of the big upper-level ridge pushing well off to the west, models have gradually decided to keep it much closer to us.  In a position quite close to where it was much of November.  Compare these two images.  ECMWF run a week ago for March 2nd-9th (next week):

old_week3_comparewithweek2

That was a “Week 3″ forecast.   Now look at the current “Week 2″ forecast, same time period:

500za_week2_bg_NA

The cool and wet trough is gone.  With the ridge much closer we just get some disturbances sliding down the coastline this Wednesday/Thursday and maybe another next Monday/Tuesday.  That’s it.

Now take a look at “Week 4″ from last week, followed by the new “Week 3″ this week.  Both are valid for March 9th-16th:

500za_week4_bg_NA

500za_week3_bg_NA

Much different, a weaker ridge off to the west, but the cold trough is gone on this latest run.  A bad sign if we want to build snowpack in the Cascades.

March has been the catch-up month for Cascade snow in most of the really bad years.  If it doesn’t change this month then it’s too late to have a recovery in the elevations below 5,000′ in the Cascades.  Take a look at 3 different SNOTEL sites at Red Hill (north of Mt. Hood), Mud Ridge (near Gov’t Camp), and McKenzie (McKenzie Pass).

redhill mckenzie mudridge

Thick blue line is current SWE (snow water equivalent on the ground) and light blue is the average.  These are all in the 4,000-5,500′ elevation.  All have little or nothing on the ground right now.  In an average winter/spring they max out in depth between late February and April 1st because rising spring temps and melting periods at these elevations are able to balance out the snowy periods.  Obviously in April then there is more melting than accumulation and the snow pack melts rapidly (in a normal year).

I know I’m making a bit of a leap here, but these maps imply the closed ski areas may NOT be able to open in the first half of March.  They need a good 3 feet of snow since they are starting from zero again.  And a week or so after that it’s mainly over for the lower elevation ski areas even in a normal year.  Most skiers lose interest after spring break because it’s…well…spring.  Yes, I know hard-core skiers continue in April or May, but most others move on to spring activities.

Here is Week 4 of the latest ECMWF monthly run (from last night):

500za_week4_bg_NA

There we go…just when Oregon’s Spring Break arrives, supposedly a cool trough centered just to our south.  Actually the ridge is still to our northwest with no sign of a wet westerly flow coming at us.  This could just be a slightly wetter pattern.

Just in, the 00z GFS is even more pitiful, showing ridging popping back up over us around days 8-13 and less than 1″  precipitation in the next 13 days!

Chief Meteorologist Mark Nelsen


Models Struggling With Big Ridge

February 21, 2015

I’ve noticed this for a few days and now it’s becoming a bit more obvious.  Models are having issues with what to do with our upper-level ridge.  For quite awhile it’s been looking like our ridge will be replaced by an upper-level trough later this upcoming week.  Now, over the past 5 days or so, models are keeping the ridge a bit closer to us and putting it off in time.  Here is the map of 500mb heights and anomaly for 15 days into the future.  I showed this on Monday.  It’s valid Tuesday the 3rd on the ECMWF:

ecm_mar3_old

Now (as of last night’s 00z run) the ECMWF looks like this:

emc_mar3

See the difference now that it’s an 11 day forecast?  Ridging is closer, although it supposedly will eventually pop back up a bit farther to the west eventually.  This is an interesting development I’ve been watching for a week.  Hmmm, not sure if it’s just a delay to the pattern change or if it means there won’t be all that much change in general for early March.  Check out the pathetic snow total from last night’s ECMWF out to 10 days…less than a foot around Mt. Hood!  ecmwf_tsnow_portland_41  That’s because weak systems coming around the top of the ridge don’t have much moisture when they come in from the north or north-northwest.  This will be a drier than normal pattern.

Enjoy the sunshine, I see it’s coming out and I’m headed outside for the weekend!

Chief Meteorologist Mark Nelsen


USA In February…Perfectly Normal? Sort Of…

February 20, 2015

Funny how things even out…

East of the Mississippi River and especially in the Northeast, 2015 has been brutally cold and snowy so far.  All the headlines would have you thinking the world has come to an end.  Part of that is because the big snowstorms have affected high population spots.  But the cold the past few days has been quite historic in the south.

That said, would you be surprised if I told you the USA was WARMER than normal in January and is running right at AVERAGE for February?  Hard to believe but it’s true!

January numbers show Oregon was the warmest state compared to normal and the nation saw it’s 24th warmest on record.

February has been more extreme, as you’ve seen on the news!   Capture  Very cold with the coldest relative to normal in the northeast and warmest in Utah/Nevada.

The whole country averaged together as of this evening is pretty much average.  It’ll probably end up a bit cooler than normal a week from now when the month ends since the upcoming week looks much cooler in the Rockies and Intermountain region.

Enjoy the weekend!  It looks bright and sunny after patchy clouds tomorrow morning.  Windy on Sunday but nothing we haven’t seen plenty of this winter.  East wind gusts should remain below 40 mph in the metro area and not much stronger in the Gorge since it’ll be a widespread downsloping event.  In those cases the Gorge wind typically isn’t much stronger.

Chief Meteorologist Mark Nelsen


February is Warmer Than Every March Since 2008!

February 19, 2015

Even though it’s been warm, I didn’t realize that it’s been THIS warm!  The average temperature so far this month is running at 49.4 degrees.  That’s warmer than an average March and warmer than any March back to 2008.  Of course we still have 9 days left this month and the cooler nights coming up next week mean in the end we’ll drop back down a bit.   MarkFebruary_TempsVsMarch

Still, this will be our 3rd very warm month.  December ran 4 degrees above normal, January 2 above, and now February about 6 above.  Quite a bitterly cold winter eh?  Wow…

Of course this is related to the warm upper-level ridging we’ve seen over and west of the west coast of North America most of the winter.  That leaves the eastern 1/2 of the USA in the freezer.  Check out the lows this morning in the South.  Cape Girardeau, Missouri had the lowest temperature ever recorded in that location this morning…-19 degrees.  Nashville only had a HIGH of 20 degrees.  Atlanta was colder last night than Anchorage, and many parts of Kentucky were colder than the interior AND arctic coast of Alaska!

PLOT_Lows_Florida_vs_Alaska2 PLOT_Lows_Florida_vs_Alaska

We had a few weak showers pop up from the metro area north into Washington this afternoon.  Possibly we see another one or two tomorrow, but I see a mainly dry forecast for the next week.  Next real chance for rain is Thursday or Friday a week from now.

By the way, we get a shot of chilly air and gusty northeast wind on Sunday.  Models aren’t as wild with the pressure gradient and wind as they were 4 or 5 days ago.  But you’ll notice the chill even under the totally sunny skies.  Hard to believe temps in the mid-upper 40s most of the afternoon are “chilly” in late February, but that’s only because it’s been so warm lately.

Chief Meteorologist Mark Nelsen


Winter Is Over: What Does That Mean?

February 17, 2015

MarkPromo_WinterOver1

I know what you’re thinking…one of 3 things:

“What Winter?  Please, tell me when this thing called winter happened?”

Or…

“Yeah, real tough forecast Nelsen…after 5 days in the 60s this month!”

Or…

“Are you nuts?  Winter doesn’t end until the 3rd week of March!”

We did actually have SOME winter this year.  You may remember the cold blast in mid-November was the earliest we’ve seen in years.  Remember the widespread Winter Storm Warnings on November 13th?  At that point I was thinking…”oh geez, it’s going to be a long winter in the weather center”.  But after that time the only other significant event was a somewhat localized windstorm in mid December that seemed to focus on the metro area up through parts of SW Washington.  That was a strange storm that didn’t do much on the Coast, central/south Willamette Valley, or Puget Sound.

Here in the lowest elevations of the Pacific Northwest, west of the Cascades, almost all our significant winter weather events happen between mid-November and mid-February.  Snowstorms, windstorms, ice storms, & flooding.  You get the idea…it’s rare to have these events (not so much with wind) outside of this time period.

But the past two months (mid-December to mid-February) have been Dullsville.  It has also been the warmest December-February on record here in Portland…so far.

Looking ahead to the next 11 days it appears the warm record may hold since we don’t see any really cold air before the end of the month.  We can see general weather patterns on our models a good 10-15 days in the future and no models are showing a stormy or unusually cold pattern through the first few days of March.  Just a return to what we should normally see this time of year (see previous post).  So…

WINTER IS OVER IN THE LOWLANDS OF WESTERN OREGON AND SOUTHWEST WASHINGTON

What does that mean?  This applies to anywhere west of the Cascades (including the Coast) below 1,000′.

1. You can take your snow tires off IF you plan to stay in the lowest elevations (below 1,500′) for the next few weeks.

2. You can unwrap your pipes, or any plants that need to be protected from temps below 25-28 degrees.

3.  We probably won’t see more school snow days or delays in these lowest elevations.

4.  Strong and cold east wind episodes are finished in the Gorge.  Still windy at times, but not the really cold stuff we saw in November and December.  The east wind always disappears in early March and then reappears in the fall.

5.  Dense and widespread valley fog is unlikely between now and October.  As we’ve seen the past week, inversion season is about over.

Here’s a good idea of what we won’t see again until next winter and what is still possible:

MarkWinter_Over1

Of course we all remember March of 2012 when wet snow fell several times in March.  That’s always possible, but we’ve only seen March snow in the lowest elevations 3 times in the past 19 years!  And each time it’s been the wet/slushy overnight and morning stuff in the metro area.

Chief Meteorologist Mark Nelsen


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