Some Snow?

February 24, 2009

Snapshot Ahh, the good times are back this evening with some good heavy rain showers in spots (right over Steve Pierce's home).  And now we have the possibility of snow to low elevations tomorrow night and Thursday.  I just had the studs taken off my
"snow car", luckily it's a 4 wheel drive that'll do fine in a few inches of snow!  For tonight…more showers.  For tomorrow…more showers.  A nice slug of moisture to our southwest keeps the showers going overnight.  It still looks like the heaviest precipitation will be from the Columbia River south. 

     Then a sharp cold front moves into Northwest Oregon tomorrow afternoon.  This is the leading edge of a very cold maritime polar airmass.  Arctic air is already beginning to spill out of British Columbia between Vancouver Island and the Queen Charlotte Islands.  So we get an upper-level low and a surface low spinning up near Northern Vancouver Island later tomorrow.  These both pass overhead Thursday.  00z models all seem to be in agreement now on the movement.  The surface low comes inland around Astoria as it fills Thursday morning.  It's a really cold airmass!  850mb temps are somewhere around -8 to -9 deg. C.  That's usually cold enough to get snow to sea level if you can get rid of a mixing wind.  We still have a light southerly flow up the Willamette Valley tomorrow evening and Thursday because the low is staying farther north, but it's not exactly a raging south wind.  Heavy precipitation intensity always helps in these situations, or is sometimes the key factor to getting snow to low elevations.  With the westerly flow, the areas west of I-5 may have lighter precip.  In general I don't see a ton of heavy showers.  The steadiest precipitation should be in that 4am-10am time period Thursday…then we dry out in the afternoon (and warm up of course). 

Put these all together and this is what I get:  I think it'll be tough to get significant snow (>1") here in the lowest elevations of Portland, but all of us should see at least a dusting in the morning Thursday.  I'd say 1-3"+ snow is a done deal at/above 1,000' anywhere in our region, and anywhere in SW Washington north of Vancouver.  The Coast is a big question mark…there's no reason we shouldn't be able to get snow to the beaches, unless the southerly breezy from Astoria south kills it for you folks.  We have 24 more hours to keep digesting information for this little event too.

Beyond Thursday, pretty quiet.  A new upper level trough develops offshore Saturday through Monday.  There are some deep surface lows that linger way out over the Pacific, but they aren't really going anywhere in a hurry, so they aren't a high wind threat for us…Mark Nelsen


A Wet Week

February 23, 2009

Lightning1 It appears that I've chosen the right week to pack my schedule full of work, school visits, and other things.  Not much chance to enjoy the outdoors this week unless you are a skier or like to hike in the rain (great for waterfalls).  It appears to be payback time for all the dry weather the 2nd half of winter.

The NWS has a high wind warning for the Coast again tonight, probably a bit overdone, but gusts to 50 mph in the cities seem reasonable.  A nice little low pressure area is heading quickly up the coastline this evening.  It is filling (becoming weaker), but the quick movement will probably help keep windspeeds up as the southerly wind rushes in on the south side of the low.  I see there have been a few lightning strikes offshore with the low as well…good times keep rolling along.

Not much to talk about tomorrow or even the first part of Wednesday.  Then it gets a bit more interesting late Wednesday through Thursday morning.  Cold arctic air spilling out of British Columbia forms a surface low off of Vancouver Island.  It then moves south either right over us or offshore, making the closest approach to Portland early Thursday.  The 12z WRF-GFS and our 12/18z RPM model both showed snow levels down close to sea level at that time.  However, there wasn't much moisture either.  IF the 12z WRF-GFS panned out, we could see another coastal snow event for daybreak Thursday as the wind goes calm and waves of snow showers move onshore.  It's something to keep an eye on the next 36 hours.  Another reason to sit here panting at the computer waiting for the 00z runs to come out.  Those of you laughing, don't pretend you haven't done that!

Of course March is now in our seven day forecast and it looks wet for Sunday and beyond.  As I said at the beginning, it's payback time for all the sunshine and dry weather so far this month…Mark Nelsen


Rain Returns

February 20, 2009

Snapshot  I borrowed this info from Jesse (the one in Orchards).  He found that we haven't had this many 32 degree nights at PDX so far this decade.  Drew and I were a bit surprised, since we had lots of split flow and clear skies for a couple winters in the early 2000s.  BUT, the big cold spell in December really helped the numbers add up this year.  By the way, I credited you each time I used the info Jesse.

The big change is the return of rain this weekend.  Freezing levels are going to be quite high through early Monday due to the mild southerly flow…forget skiing for Sunday.

I'm about out of time this evening due to keeping my eyes on another tv show (BSG) right now.  A change towards cooler and wetter weahter is on the way for later Monday through next Friday.  There seems to be very little moisture Wednesday through Friday until another trough digs in by Saturday.  Earlier GFS runs were wildly cold from that point forward into the first week of March.  I notice the 00z is more reasonable with occasional low snow levels during that time, but no big snow events for the lowlands.  As we all know (especially after last year) it's quite possible to get snow to low elevations in March, but sticking snow IN THE CITY only seems to happen maybe once every 5-10 years.  I think I've only seen it 3 times in my entire career which goes back to 1991.  I'm sure someone can correct me if I'm wrong, but it was only 1999, 2006, and 2008 when we had widespread low elevation snow here in the metro area in March.  Each of those times I think only a trace of snow was recorded at PDX…Mark Nelsen


A Quiet Evening

February 18, 2009

IMG_3236  A very nice picture sent in today by Bobby Corser.  It's an early flower…a crocus.  They show up just before the daffodils…the earliest harbinger of Spring.  I don't know if today felt like spring…at 55 degrees, but highs closer to 60 the next few days should give us more of a spring-like feel.

Not much to say tonight, except that models are pretty clear on a change to some wetter weather starting Sunday.  Once again, I see the 00z GFS has a split in the jet still clearly visible all the way through NEXT Thursday.  Sure it's wetter and cooler early next week, but the 00z looks more split than the earlier 12/18z models the 2nd half of next week.  At this point I don't see a significant change back towards stormy or very wet weather.

I couldn't make it to the AMS meeting tonight…too far from work.  Go ahead and post comments below to let us know how it went!  Mark Nelsen


A Quiet Evening

February 18, 2009

IMG_3236  A very nice picture sent in today by Bobby Corser.  It's an early flower…a crocus.  They show up just before the daffodils…the earliest harbinger of Spring.  I don't know if today felt like spring…at 55 degrees, but highs closer to 60 the next few days should give us more of a spring-like feel.

Not much to say tonight, except that models are pretty clear on a change to some wetter weather starting Sunday.  Once again, I see the 00z GFS has a split in the jet still clearly visible all the way through NEXT Thursday.  Sure it's wetter and cooler early next week, but the 00z looks more split than the earlier 12/18z models the 2nd half of next week.  At this point I don't see a significant change back towards stormy or very wet weather.

I couldn't make it to the AMS meeting tonight…too far from work.  Go ahead and post comments below to let us know how it went!  Mark Nelsen


ECMWF, ECMWF, ECMWF

February 17, 2009

Snapshot As all of us who watch the weather closely know…it's been a very dry month so far.  And now California has been getting a soaking in this split-flow pattern.  Take a look at the numbers:  SFO has had about 10 times the rainfall Portland has seen.  Even LAX has beat us handily.  They are going to dry out the next few days as the Pacific Northwest get's it's first taste of Spring. 

Skies have cleared out this evening, which should lead to some morning fog.  Luckily we're getting towards the time of year where all-day long fog becomes unlikely.  The strengthening late February sunshine should punch through quickly in the morning and push our highs into the mid 50s by afternoon.  Then on Thursday and Friday upper level heights build over us in advance of a deepening low offshore.  Later in the spring this pattern would really warm us up.  This time of year 65 degrees is about the maximum I could see Friday or Saturday.  East wind returns Thursday through Saturday and that may temper the "heat" possibility.  I bet PDX makes it to 62-63 one of those days, but for today I'll leave it at 60.

ONCE AGAIN, the 00z GFS has made a swing towards drier and split flow this weekend and beyond.  Maybe more important is the fact that it looks more like the ECMWF did earlier today.  Seems to be a pretty common occurrence over the last month or so.  The ECMWF has been doing a much better job staying with drier flow and higher heights.  Exhibit A: Has anyone out there noticed that the GFS has had some sort of snowy or cold weather pattern around 200-360 hours for the last 4 weeks???  That would be 4 runs a day times 28 days…hmmm, we've probably seen about 100 runs of the GFS in the last 4 weeks that showed "the big pattern change" coming up.  My point is the ECMWF is doing a much better job.

In the short term, I'm looking forward to our first taste of spring the 2nd half of this week.  Remember that in 2005 we started a 3 week stretch about now that included many days 55-65 degrees.  That culminated with 4 days in the lower 70s in the first week or so of March.  THAT was real sweet.  Mark Nelsen

REMINDER FROM STEVE PIERCE…AMS COUNCILOR —

OREGON AMS MEETING THIS WEDNESDAY AT 6:30PM IN PORTLAND!

Hope to see you all this Wednesday at the "Mid-Winter Weather Sampler." This is an open AMS meeting / gathering with no formal agenda. The floor is open and anyone can present on any weather related topic. Yes, there could even be talk of the next cold wave that could be headed for the Pacific Northwest. This month's meeting is being held at the ever popular Stark Street Pizza Company in Portland. I can personally attest to their great pizza and warm atmosphere. This meeting is open to all ages! Please spread the word.

We hope to see you all there TOMORROW at 6:30pm!

Here is a link to the official meeting flier as well as a map with driving directions —

http://www.ametsoc.org/chapters/oregon/meetings.html


ECMWF, ECMWF, ECMWF

February 17, 2009

Snapshot As all of us who watch the weather closely know…it's been a very dry month so far.  And now California has been getting a soaking in this split-flow pattern.  Take a look at the numbers:  SFO has had about 10 times the rainfall Portland has seen.  Even LAX has beat us handily.  They are going to dry out the next few days as the Pacific Northwest get's it's first taste of Spring. 

Skies have cleared out this evening, which should lead to some morning fog.  Luckily we're getting towards the time of year where all-day long fog becomes unlikely.  The strengthening late February sunshine should punch through quickly in the morning and push our highs into the mid 50s by afternoon.  Then on Thursday and Friday upper level heights build over us in advance of a deepening low offshore.  Later in the spring this pattern would really warm us up.  This time of year 65 degrees is about the maximum I could see Friday or Saturday.  East wind returns Thursday through Saturday and that may temper the "heat" possibility.  I bet PDX makes it to 62-63 one of those days, but for today I'll leave it at 60.

ONCE AGAIN, the 00z GFS has made a swing towards drier and split flow this weekend and beyond.  Maybe more important is the fact that it looks more like the ECMWF did earlier today.  Seems to be a pretty common occurrence over the last month or so.  The ECMWF has been doing a much better job staying with drier flow and higher heights.  Exhibit A: Has anyone out there noticed that the GFS has had some sort of snowy or cold weather pattern around 200-360 hours for the last 4 weeks???  That would be 4 runs a day times 28 days…hmmm, we've probably seen about 100 runs of the GFS in the last 4 weeks that showed "the big pattern change" coming up.  My point is the ECMWF is doing a much better job.

In the short term, I'm looking forward to our first taste of spring the 2nd half of this week.  Remember that in 2005 we started a 3 week stretch about now that included many days 55-65 degrees.  That culminated with 4 days in the lower 70s in the first week or so of March.  THAT was real sweet.  Mark Nelsen

REMINDER FROM STEVE PIERCE…AMS COUNCILOR —

OREGON AMS MEETING THIS WEDNESDAY AT 6:30PM IN PORTLAND!

Hope to see you all this Wednesday at the "Mid-Winter Weather Sampler." This is an open AMS meeting / gathering with no formal agenda. The floor is open and anyone can present on any weather related topic. Yes, there could even be talk of the next cold wave that could be headed for the Pacific Northwest. This month's meeting is being held at the ever popular Stark Street Pizza Company in Portland. I can personally attest to their great pizza and warm atmosphere. This meeting is open to all ages! Please spread the word.

We hope to see you all there TOMORROW at 6:30pm!

Here is a link to the official meeting flier as well as a map with driving directions —

http://www.ametsoc.org/chapters/oregon/meetings.html