Long Range Outlook: First Wet & Cold Pattern In 2 Months?

February 16, 2015

We are now in our 7th week of upper-level ridging and/or split flow giving us warmer than normal weather.  In fact most of the past three months we’ve seen ridging over the West Coast or just a little bit to the east or west of us.  The only significant breakdown of the ridge was around Christmas when several cold and wet storms moved through the region.

It appears that this pattern will persist another 8-10 days, but all long-range models show a change in the last few days of February.  Models have been showing this for the past 4-5 days too.  To highlight:

  • Mild and dry weather continues for about one more week across the Pacific Northwest
  • Wetter and cooler weather arrives the last couple of days of February…plan to finish dry weather projects by that time.
  • Ski areas may see their best snow conditions since Christmas NEXT weekend (Feb 28/Mar 1).  But nothing will change for this coming weekend; lots of thin spots down low still.
  • It’s possible some closed ski areas could open up again by the first full weekend of March

Today was great, tomorrow looks the same, and then a mix of clouds and sun coming up the last few days of this week as the ridge breaks down a little.  Then the ridge pops back up quite strong to our west over the weekend.  Look at Sunday:


With the ridge slightly to our west, we get a cooler push of air out of southwest Canada Sunday and Monday.  Not an arctic blast by any means, but we likely won’t see 60 degree days.  More typical low-mid 50s instead with the gusty east wind.  I noticed both the GEM and ECMWF (12z runs) had a very strong pressure gradient on Sunday, but the 00z GFS does not.  The 00z GEM on the other hand has a significantly colder push of air, one that would give us high temps in the 40s with more of a winter feel Sunday/Monday.

Beyond that, the upper-level ridge then takes a few days to flatten, then redevelop much farther west.  Here’s the 00z GFS for Saturday the 28th, and the following Wednesday the 4th of March.  gfs_sat28

gfs_wed_4 Wow…quite a change from what we’ve seen in January and February!  This can be a great pattern for mountain snow, the GFS would give us snow levels 2,000-4,000′ through period.

Is there much confidence in this pattern change?  I think so…take a look at the 00z GFS, 00z GEM, and 12z ECMWF ensembles.  It’s 500mb height and anomaly:  gfs_mar3 gem_mar3 ecm_mar3

They are all in almost perfect agreement by Tuesday, March 3rd…two weeks from now.  At least the ensemble averages are…this leads to high confidence of a pattern change towards colder and somewhat wetter as we head into March.  The first significant rain and mountain snow arrives a week from Thursday, the 26th.

A huge question is whether it’s a temporary change…like back at Christmas.  Or is it the classic switch to wet/cool as meteorological spring arrives?  Good question.  The monthly run of the ECMWF from last night implies it’s going to last longer than a week.  Here is the map for week 3, March 1st-8th…pattern is the same.


Then week 4 which takes us into mid-March:


Still the same pattern with the upper level high out over the Aleutian islands.

Chief Meteorologist Mark Nelsen

Record Highs Today…Feels Like Spring!

February 16, 2015

What a string of warm days…4 out of the past 5 days we’ve seen temps above 60 in Portland.

Today the dry east wind pushed Salem up to 66 degrees, your warmest February day since 2005!  Here are the other records in the Willamette Valley:


Tomorrow should be exactly the same as the east wind keeps the fog away.  There will be a dramatic change Wednesday though…a marine push in February!  It’ll be coupled with a weakening front dragging through in the afternoon.  The combo of the two means cloudy skies, maybe a sprinkle, and temps 10 degrees colder. Check out our RPM model showing the clouds surging up from the south and inland:




Beyond that, no dramatic changes for the next 8-10 days.  The upper-level ridge pops up just to our west again late this weekend and early next week.  That means more east wind, although it’ll be cooler since we’ll have chilly Canadian air seeping south.  The GEM and ECMWF both show about a 20 millibar pressure difference from Spokane to North Bend Sunday afternoon as this cooler air arrives.  This could lead to a decent downslope wind event Sunday/Monday.  Either way, expect dry weather and sunny skies.

More on the long-term forecast later…the new ECMWF monthly maps are in and still show a big change in the pattern late next week…

Chief Meteorologist Mark Nelsen

“False Spring” Is Here! Two Sunny Weekends in February Likely

February 13, 2015

Yep, this weekend is sure looking nice and signs are pointing to another one NEXT weekend too.

First, we’ve got a very weak weather system moving overhead tonight that could give us a few sprinkles and lots of clouds.  Behind it I see drier northerly winds tomorrow to gradually clear us out.  The 2nd half of Saturday looks sunniest with just about our entire viewing area mainly clear by late afternoon.  Here’s your weekend forecast for both the Cascades and Coast:

MarkCoast_WeekendFcst2 MarkSkiWeekend_3Days

Then from Sunday through Tuesday a gusty and dry offshore (easterly) wind flow develops through the Gorge and over the Cascades.  That’s from high pressure settling in east of the Cascades.  As a result, fog should be non-existent in the metro area for a few days under clear skies at night and blue skies during the daytime.

Temperature forecasts are a bit tough since we’ll have gusty easterly wind.  Typically in winter that means cool temps, but we’re nearing the end of inversion season and very warm air above should mix down a bit.  This pattern in March would give us 65-70 degree temps.  I think we’ll most likely end up around 60 or so this time around though.

We have a very warm atmosphere overhead for at least the next week.  Take a look at the big upper-level ridge by Monday:


Cool air is flowing south to the east of the Rockies, but the West Coast is quite warm.  Then NEXT Saturday…looks the same doesn’t it?  Warm ridge in the West and cooler than normal to the east.


This means more “False Spring” weather.  That’s a period in February around here when we think winter is done and spring is here.  Often it’s followed by a return to cold and rainy weather soon after.  This year though it appears the warmer than normal weather and dry conditions will stick around for at least the next 10 days.  So enjoy the “early spring”.

By the way, The Oregon Cascades climate zone was the warmest part of the USA relative to normal in January. january  It was the warmest January on record up there and the warm weather is sticking around in February.  As of today snowpack is around 10% of normal up there, with no snow below about 5,000′.  Timberline, Meadows, and Bachelor are open, but with some lifts shut down and bare spots in the lower parts of the ski areas.  Skibowl has the tubing hill and restaurants open.  If you plan on skiing, best conditions and quite deep snow (5 feet or more) are up around the timberline and higher.  Otherwise, a great couple of weekends for hiking are on the way with all the lower Cascades snow-free.

Chief Meteorologist Mark Nelsen

ECMWF Monthly Run…A Bit Cooler

February 12, 2015

Last night was another monthly run of the ECMWF.  Here are the 4 500mb height anomaly charts.

Week 1:  Another dry one with ridging staying close to us over the next week, although just far enough west to keep offshore flow going at the surface.


Week 2:  Same thing, although ridge is slightly farther west.  Looks like February will finish off with the same pattern; drier than normal with temps near to a little above normal due to offshore flow.  Strong sunshine the last few days of February means even a “coolish” offshore flow gives us normal to above normal temps.


Week 3:  First week of March, ridging has pushed farther west and it looks near to below normal temperature-wise.  Drier than normal weather continues, at least to start.


Week 4:  This implies a possible significant pattern change with lower than normal heights over us…What do you know, it turns cool and likely wetter by mid-March…spring REALLY begins!


You can sure see the move towards cooler the last few days of February on today’s ensemble anomalies from the GEM & ECMWF 12z runs.  We may yet get a late season “backdoor blast” to finish off the season like we started in mid-November.

m500za_f360_bg_NA (1) m500za_f360_bg_NA

Chief Meteorologist Mark Nelsen

Vacation Time

February 7, 2015

No new posts until Thursday the 12th…taking a few days off…Mark


Is the Ski Season Over? Weekend Rain Update Too

February 5, 2015

Let’s get that first question out-of-the-way.  NO, it’s unlikely the ski season is over.   Especially since it’s only February 5th!  But it appears the worst conditions (thinnest snow pack) we’ve seen since the season opened around December 22nd are on the way over the next 10 days.

Where We Are Now:

  • Little or no snow is on the ground below 5,000′ on Mt. Hood
  • Lower ski areas were only open for 10-14 days this season around the New Year and have been shutdown for almost a month.
  • Only 3 ski areas are operating in the Oregon Cascades, all with limited lifts & terrain.  Just yesterday Mt. Bachelor announced two of its lifts (Outback and NW Express) are shut down until new snow arrives.  Two main lifts at Timberline are unusable for the same reason (Molly’s & Flood).  It appears Mt. Hood Meadows can’t use the Stadium, Hood River Meadows, or Heather Canyon lifts.  I see Nordic skiing has closed at Meadows too.  Skibowl is now just operating its tubing area on man-made snow from the cold spell in early January.  But hey…the Alpine Slide could open early at this rate!

What’s Ahead?

  • More rain with snow levels above 6,000′ Friday, Sunday, & most of Monday = More melting
  • Snow levels lower to around 5,500′ Saturday with a few inches possible above that elevation
  • 2-4″ possible as cooler air arrives later Monday and early Tuesday
  • Warm ridging with temps into 40s again, along with sunshine, Wednesday and beyond next week = More melting

Depending on exactly how the next 5 days play out, it’s possible we see even more cutbacks in terrain/lifts after this event.

I see no pattern change in the next 2+ weeks, and that puts us into the last week of February.  There won’t be a “February Miracle” for the ski resorts this year.  And of course we have no idea what’s coming in March, although there aren’t any indications the pattern is going to break down.  It’s always possible the best skiing this year will be later in March or April.

Traditionally Spring Break is considered the end of the ski season, for obvious reasons…skiing is a winter sport.  But the Cascades almost always have more snow on the ground in April than December.  The problem is that interest drops dramatically because spring is here in the lowlands and attention turns to warm-season pursuits.

Alright, enough of that.  Let’s talk rain and wind this weekend.

There are no big wind storms or flooding coming up the next few days, but we’ll see plenty of rain and breezy conditions at times.

I see two systems that give us a surge of wind at the Coast and into the valley.  One early Saturday and another early Monday.  Both of those could produce gusts 50-70 mph at the Coast and 25-35 mph in the valleys.  Nothing we haven’t seen already this season but we also haven’t seen active weather since around the New Year.

Our RPM rain totals (which often run a little high) show 2-3″ the next 3 days, so 2″ or so seems like a good forecast for most of us in the lowlands.  RPM_12KM_Precip_NWOR  That won’t produce flooding, but creeks and rivers will rise quite a bit.  Your yard may become a pond for a while!

Chief Meteorologist Mark Nelsen

ECMWF Monthly Run: At Least 2 More Warm Weeks Ahead

February 5, 2015

Last night’s monthly run of the ECMWF didn’t contain any surprises.  Ridging holds over us the next two weeks, then shifts slightly west and north the last week of the month and first week of March.  Looks like ensembles are not pushing it as far west/north as they did 3 days ago (previous post)

I’ll post later on all the rain and possibly (possibly) stormy weather the next 4 days.  Don’t get too excited, there’s no flood or windstorm on the way, but we’ll take what we can get this winter…





Chief Meteorologist Mark Nelsen