A Cold March Day

March 9, 2009

The picture here is one I took for my school visit Powerpoint presentation.Picture1 It's the form I start with each day when I get to work.  It's one of two that Drew and I fill in.  I started doing this back in the Jim Little – KOIN days.  I have found that part of the forecasting process is to write down much of the information.  If you click on the picture you can see some of what I look for.  Now this may seem old-school to those of you under 30, but I just like having things written down.

Today Drew did all the forecasting, filling out the sheet, making the graphics etc…  That's because I spent the day visiting 3 schools down in Woodburn and Salem, plus I had lunch with Jim Little and Pete Parsons.  We were like old men reliving the glory days of 1990s forecasting at KOIN.  Ahh, the pleasures of no internet and waiting for the 12z ECMWF to come across the 1980s era fax printer once a day.  Okay, maybe those weren't the glory days for data, but good times.  Of course it's always good to catch up with former co-workers and friends too.  They both work for the state down in Salem nowdays.

So my point about the forecast sheet is that I walked in 20 minutes before the 4pm show without having looked at all the model data, just trusting Drew's forecast and what I had looked at last night.  Luckily the weather pattern is slowing down and the basic point was simple:  snow showers end tonight, but we stay cold for another day and a half.  Then it's on to spring-like weather Wednesday afternoon through Friday.  More rain this weekend.  By the way, I only worked until 6pm today, so Drew should be on in about…10 minutes.  I'm at home ready to go to bed.

I'm happy with the weekend/Monday forecast.  Models did well with the cold.  High temps both days made it to 43 at PDX…pretty close to our forecast.  I thought there might be slightly more snow, but I said Trace-1" each morning, at least most lower elevation sites saw the trace.  This was a classic situation like we saw last winter with respect to elevation vs. snow depth.  I came up the hill from I-84 on the way home and didn't see a trace of snow until right in Corbett at 700' or so.  Then it gradually increased to 4" on the ground at my home just over 1,000'.  A friend up Larch Mtn. road about 5 miles farther has 11" (all from Saturday evening to now) on the ground at 1800'.  Those of you in the hills had a nice March snowfall.

I'll blog about the warmer weather and changing long range models tomorrow night…Mark Nelsen

Snow Totals: March Edition

March 8, 2009

The snow is back…winter is going out in style, but a few of you got more than 1/2".  If you did get that much, put the info here.

1.  Snow Depth

2.  Location (elevation if you know it too).


I Hate Daylight Saving Time

March 6, 2009

Snapshot  A sad evening…I realize that when I come back in on Monday all the weather maps and data will be showing up one hour later.  Of course that's due to Daylight Saving Time.  UTC or "World" time doesn't change, but here in the USA we have this bright idea that twice a year we should change our clocks.  Of course that's only 4 months of the year nowdays, and it is nice to get most of the 00z data in by 9pm.  Starting Monday it'll be 10pm.  I just think the whole shifting time thing is really dumb.

 We have lots of weather to talk about this evening.  Clear skies right now aren't going to last long.  A cold front is approaching quickly from the northwest.  This is the leading edge of a much colder airmass coming down the British Columbia coastline.  The front itself isn't going to produce much precipitation and then there is going to be a break in the morning hours behind it.  I have a feeling that sunbreaks the first part of the day combined with a +2 lifted index in the afternoon along with much colder air arriving up above means some convection.  We could see active showers tomorrow afternoon…maybe some hail or a rumble of thunder?Snapshot2 

The real fun stuff is tomorrow night through midday Monday.  Still looks plenty cold for sticking snow anytime late Saturday night through early Monday.  So how much moisture arrives at the right time?  I notice 00z models are a bit drier again.  Our RPM and the WRF-GFS from the UW are not impressive if you want more than an 1" of snow in the lowest elevations.  I also notice that the chance for significant precipitation seems to end Sunday evening.  Not much other than light showers or flurries through Monday morning.  In fact our model is dry midday-afternoon Monday as the big cold trough begins to head east.  So the two graphics here are my forecast for the weekend.  The time period is Saturday night through Monday.  My gut feeling is that we will all see some white, and probably mostly Sunday morning.  If you want 2" or more, you probably need to be up around 1,000' or so to capture the heavier showers as snow Saturday evening and Sunday midday-afternoon to get that total.

My favorite part of the forecast maps isn't this weekend or early next week…it's next Thursday and beyond.  ECMWF and now the 00z GFS agree on a pattern change with the first ridging of the season showing up over the interior West the 2nd half of the week.  It's finally going to feel like Spring by Wednesday or Thursday!  Mark Nelsen

Snow Thoughts

March 5, 2009

Snapshot I've looked at maps pretty closely this evening and have a few thoughts about possible snow this weekend.  There isn't much happening in the next 48 hours…just a partly cloudy day tomorrow and then a sharp cold front Saturday.  There has been one surprise tonight; the snow level has dipped to 1,000' in a persistent line of showers centered on Highway 26 from Sandy east to Zigzag.  Looks like all of the Hoodland area is getting at least a dusting.

Okay, now on to Saturday night and Sunday.  First…this is not like 1951.  As I mentioned yesterday, the upper level low was far deeper back then and 850mb temps were significantly colder.  So I sure don't see those 8" of snow at PDX.  Here are my thoughts:

1.  The chance for low elevation snow (let's say below 500') is late Saturday night and Sunday morning before 10am.  Then late Sunday night too if moisture keeps coming in.

2.  IF we get some good precipitation during the correct times, any area could get significant snow (1"+).  But the pattern looks pretty showery to me.  I do notice that there is more moisture forecast with this period than what we saw last Thursday.

3.  Those of you (us) at/above 1,000' are going to see several inches of snow (maybe up to 4" or so?) again.  Ugh! It would be nice to work outside this weekend now that March is here, but apparently that won't be the case. 

4.  WRF-GFS says no good sticking snow at the appropriate times in the lowest elevations, but WRF-NAM does.  Our RPM model says nothing through Sunday afternoon in the city.  I'll trust the GFS and our RPM for now considering how well they have done this winter.  But it's still not time to forecast amounts yet…I've got another 24 hours for that.

5.  Forecast Temps:  I see some of you think our highs in the 40s are too warm for the cold airmass coming in.  Drew and I are assuming there will be some sunbreaks and at least some brief periods of decent clearing between showers Sunday.  That's how we get 43.  Keep in mind that the extremely cold atmosphere the last week of March last spring saw us get to 46-50 when we had a dusting of snow on the ground in the morning.

The Tuesday night pattern sure grabs my attention as well.  On the GFS, a system approaches from the west while cold and dry air is pulled down into the Columbia Basin.  That gives us a classic set up for a snow storm in winter, and maybe some snow in March too.  Depends on the track of the offshore system, how much moisture comes in, and how cold the air is eastside.

This all adds up to an interesting weather period for us to watch from late Saturday through the first few days of next week.  Thankfully that appears to be it for cold weather with warmer temps coming up Wednesday-Friday of next week…Mark Nelsen

A Short Post

March 4, 2009

DSCF0013  This picture has absolutely nothing to do with weather…just a couple of friends smiling for the camera during a commercial break.  I spent a bunch of time this evening cleaning up my school presentation and taking some new pictures in the studio…this would be one of them.  So I didn't have much time to blog.

I don't see any major changes in forecast thinking for this weekend.  It appears to be cold enough to get lowland snow from sometime Saturday night through early Monday morning.  The limiting factor will be moisture showing up at the proper time.  I have a gut feeling that with westerly onshore flow (rain shadow), we have another Dusting to 1" event coming up in the lowlands for Sunday morning…maybe again Sunday night if the moisture holds out.

For fun I checked out the March 1951 maps, when we had 4-10" in the metro area.  500mb heights dipped to about 507 over Portland!!!  An incredibly deep upper level low dropped down and sat just to our north for about 3 days, circulating very cold showers onshore.  I noticed at one point 850mb temps were well below -10.  That must have been fun…Mark Nelsen

Meeting in the Middle

March 3, 2009

MtHoodSunrise_LarryFilz  Now THIS is a nice viewer picture.  Larry Filz took this picture last week on a cold morning up at Mt. Tabor.  Looks like the sky was on fire over Mt. Hood doesn't it?  Well, he says it was very chilly.

The title of this post is a reference to the Diamond Rio song from the mid 1990s.  I listened to a lot of country music back then…not so much now.  Maybe I've become a hermit recluse that doesn't pay attention to pop culture.  Anyway, the lyrics we're about two people coming together to "meet in the middle", specifically in a relationship.  I was thinking today though that this is more or less what the ECMWF and GFS have done over the last 24 hours.  Remember yesterday the GFS was very cold with two separate and cold closed lows dropping down over us both Thursday night and Sunday.  Now the GFS is more open with the waves (especially Thursday's) and the main energy heads farther east.  But the ECMWF has gone from a wave moving by well to east each time to a much sharper trough, and even a bit of a closed low dropping in on us Sunday.  So they both agree on a "close to sea level" snow possibility late Saturday and early Sunday…time to pull out the lonely little snowflake for the 7 Day forecast.

That's it for tonight…by the way, the Oregon AMS Meeting will be here at KPTV NEXT Thursday, the 12th at 7pm.  Anyone is welcome to attend.  Steve Pierce will be presenting about this past winter's weather.  Should be right up our alley don't you think?   Mark Nelsen

Spring Showers?

March 2, 2009

003 I've been real busy today with a midday school visit in SW Portland and then a 2 hour visit to a PCC Meteorology class this evening.  Lots of fun talking to the adults about the pros/cons of the business.  Today definitely felt like the start of the "springtime" convective season.  As I came out of the first school around 1pm, a very nice CB had developed over the middle of the area with a dark base and hail/big rain drops…big stuff for March 2nd in Portland.  Just a sign of things to come in April and May, hopefully.

Of course we really just care about the cold upper-level troughs forecast to drop down over us (or just to the east) later Thursday-Friday and again on Sunday.  There was a dramatic difference between the 12z ECMWF and 12z GFS.  GFS was cold and showery with a good chance for snow to low elevations both periods.  ECMWF pushed the trough much farther east with mild springlike weather.  Drew and I (we collaborate on the forecast) went for a middle of the road approach.  That leaves snowflakes out of the 7 Day forecast, but chilly weather from Thursday forward through early next week.  The 00z GFS seems to have confirmed that now; a slight shift eastward with the Thursday trough and slightly warmer 850mb temps.  I see it barely touches -7, about the time preciptation ends.  So I'm glad we made that move.   Sunday is still in play, but I wouldn't be surprised if/when the GFS backs off on cold air.

I could really use a nice big ridge with a few 70 degree days, but that's probably a bit much to ask in early March, especially in a La Nina year.  One thing is still certain about the 7-10 day outlook;  it's going to remain drier than average in this first half of March.  A ridge well offshore with troughs dropping south along the coastline is not a very wet pattern…just some light rain at times…Mark Nelsen