Last Blast of Winter?

March 20, 2008

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These pictures were sent by Amanda out in Sandy and Kathleen in the hills above Amity.  Tonight’s cold front was able to briefly push snow levels down below 1,000′ in spots.  Once again precipitation intensity really matters.  We know it stuck down below 500′ just east of Neskowin and below that elevation in the Tillamook Valley.  Then the east side of the metro area up around/above 1,000′ picked up a half inch or so of snow before 9pm.  We had a wind gust to 32 mph on our roof, and I see McMinnville and Aurora had gusts around 40 mph.  Pretty good for the first day of spring!

More active weather is on the way for Oregon’s Spring Break.  A quick switch to offshore flow, warmer 850mb temps, and abundant sunshine in late March means a dramatic warming Saturday.  According to the temperature "magic chart", we could see as warm as 64 on Saturday.  Of course I’m getting old and conservative, so 60 seems like a safe bet.

Tonight’s AMS meeting had a heck of a turnout…almost 30.  A bit tight in the KPTV conference room, but Tyree Wilde and Andy Bryant from the National Weather service gave a great wrap-up of the windstorm and flooding the first few days of December.  Hopefully in the Fall the Oregon Chapter AMS will put together a detailed look at the Vancouver Tornado too.  I got to meet a few more of the regular readers of this blog as well.  It’s always nice to put faces together with names.

Rainy weather and westerly flow resumes Sunday and ALL of next week.  The 00z GFS is quite cold at times again…showing 850mb temps down around -6 or -7 deg C.  That’s pretty cold for the last week of March.  A 75 degree sunny day can’t be too far away right?  We’ll see…Mark Nelsen


Nice Cold Front Today

March 18, 2008

SnapshotI noticed a quick change in wind direction and drop in dewpoint behind today’s cold front.  In fact you could track the front over about a 9 hour period from Portland all the way east on I-84 to Ontario.  I feel sorry for those who were driving into the strong post-frontal westerly wind surging east of the Cascades.  Mileage must have been REALLY bad from Pendleton to Hood River don’t you think?  Check out the speeds on the graphic.

Another wave moves inland by morning, it’s somewhat obvious on the satellite imagery this evening.  Models continue to say most of the moisture will go in to the south, then we just get leftover convective-type showers in the afternoon up here in Northwest Oregon.

The colder airmass seen behind (speckly clouds on satellite) arrives on Thursday.  Looks like snow levels with steady precipitation drop to 2,000′ during the day Thursday.  Then Thursday night and Friday morning it may go slightly lower.  This IS the sort of setup where a sustained period of heavy precip could drop the snow level down to 1,500′ or less.  You may remember 1998 when several inches of snow fell above 1,000′  in the first few days of April…unlikely, but possible.  I also see that all record highs from here on out are in the 70’s…come on ridging!  Unfortunately, there is no sign of any sort of that in the long range maps.  Oregon’s spring break is looking quite wet next week…Mark Nelsen


More Rain!

March 17, 2008

SnapshotThis 6-10 day average 500mb height forecast gives you the general idea as we head through the last 1/2 of the month….Cool & Wet.  You can click on image for a better look

A weak front and surface trough/low is passing through tonight as it heads off to the south and east.  That accounts for the absolutely annoying drizzle and low ceiling in spots.  At least we have a mild night on the way with the south wind.

Nothing too dramatic in the next 2 days…just showers and sunbreaks, not all that much in the way of precipitation in general.

Thursday-Sunday a cool upper-level trough sags south and brings quite chilly air to the region.  The new 00z GFS gives us a break from the cold showers Saturday…before a stronger system moves in Easter morning.  So obviously the holiday weekend (and start to Oregon’s Spring Break) is a bit up in the air weatherwise.

Sorry for the lack of posts lately…but just not a whole lot to talk about.  It’s clear the weather geeks are a bit bored too since some days we’ve only seen 10 comments!  Mark Nelsen


Cold Showers

March 13, 2008

SnapshotThe cold airmass along with it’s showers definitely has arrived.  A shortwave moving through this evening gave us some healthy downpours here in the metro area.  A 2nd wave is sitting (actually it’s moving quickly) right over 130W here at 11:15pm.  It will be here soon after daybreak.  Then I’m planning on more sunbreaks midday-afternoon tomorrow to give us a better chance of convection.  We didn’t get any lightning strikes west of the Cascades.  There were several strikes between Pendleton and Walla Walla around sunset, but that’s it here in the Northwest. 

Snowfall is coming down like it should in March too.  NW Avalanche center sensors indicate about 18" since yesterday evening up at Timberline.  The image up above (or left or right or below depending on your browser and window size), shows the snowfall so far each winter up to February 28th.  I think we’ll add a few feet to this winter’s total over the next week as well.  I notice that evey single long range model has consistently wet weather over the next 7-10 days…Make up time for the warm and sunny weather is definitely here!  The 2nd half of March will be wet….Mark Nelsen


Cold Showers On The Way

March 11, 2008

SnapshotI found this old graphic in the archives and decided to use it at 11pm tonight since I have little to nothing else to talk about.

It does appear that a much colder airmass (especially in the upper levels) will move over the Northwest later Thursday-Sunday.  With surface temps just a few degrees cooler than today’s, the atmosphere should destabilize nicely each afternoon.  I notice the Lifted Index for Thursday and Friday is forecast to be right around zero, which is good for spring hail and thundershowers.  Not a severe weather situation for sure, but we usually get active weather this time of year (March-June) with cold troughs.

I don’t really have any other great thoughts on my mind at this hour.  We are inbetween the February and May ratings period here in TV land, so that always means it’s a bit more mellow in the newsroom.  The start of Season #4 BSG is still 3 weeks away, so not too much to get wound up about there yet either…Mark Nelsen


Slogging Through March

March 10, 2008

SnapshotAs I was coming in to work today thinking how slow the weather has been.  We really haven’t had any sort of significant system/storm since February 7th!  So basically it’s been really quiet in the First Live Local Weather Center.  I think I mentioned this a few posts back, but during the What Will the Winter Be Like meeting in early November, most forecasters expected the 2nd half of the winter to be very active with plentiful mountain snow.  Instead after amazing snowfall totals (especially in the lower elevations), we’ve see little additional accumulation over the last month.  I still don’t see a big "dump" coming up in the Cascades either.  So it’s a good thing that we got all that snow.

With the warm weather today, I was out planting my first spinach and lettuce (under a warming plastic hoop in anticipation of cold/wet weather ahead).  It made me think of that spring 3 years back.  Remember all those days in early March that felt more like May?  Then around mid-March, cold westerly flow returned and we went through a wet period that lasted for MANY weeks.  Weather patterns can change quickly in spring, and then linger for a long time too.  I don’t have the numbers, but I enjoyed last spring…no long periods of rain OR sunny/warm weather.  It was a good mix of some dry weather and then wet periods.  We’ll see how this spring turns out.

Short term, a nice cold front moved through this evening, but wimpy with rainfall totals (again).  Showers resume in the next few hours as the westerly flow pushes in behind the front.  Then 2 more quiet weather days tomorrow and Wednesday.

A colder trough drops in towards us Thursday for steadier rain, then moves directly overhead Friday and Saturday for cold showers and maybe hail or thunder?  If the airmass is cold enough, we may see snow below 2,000′ at some point between Friday AM and Sunday AM. 

The trough moves east Sunday, and model solutions vary after that time.  Some show more troughiness, others a milder southwest wet flow…Mark Nelsen


La Nina & Spring

March 6, 2008

SnapshotI had some free time tonight between shows (remember we do a 4-5pm show now), so I looked up some La Nina stats.  I heard somewhere, either on TV or in print, that we tend to have cool & wet springs in La Nina years.
The data doesn’t support that for the Portland area for moderate to strong La Nina events.  There are 13 of these events since 1950.  6 of those springs had normal rainfall, 4 were wetter than average, 6 below average.  I don’t see any significant trend there.  A closer inspection shows only 2 really wet springs out of the 13.  What I really notice is that in the wetter than average springs, most of the time the wet conditions were in March or April, mainly March.  Maybe it’s the "left-over" of the active winter storm track that lingers into the beginning of spring? 

Something else I noticed…a wet May seems to be quite rare.  Only 2 of the 13 years produced above average rainfall in May….NONE more than 3"!  That’s a bit strange…because every few years we have a very wet May and you would think one of those would have occurred during a La Nina year. 

Well, I really messed up the forecast today…too little (or no) offshore flow, and a thick shield of high clouds until 3pm or so.  Ah, at least in meteorology you get another "stab at the weather pin~ata" every day!  Mark Nelsen