A New Year: Tough Forecasting Ahead!

January 1, 2017

9pm Sunday…

Who would have thought these 12 days of Christmas would be so challenging for forecasters?  Actually I suppose this is the busiest time of the year for meteorologists in the Pacific Northwest.  So lets just jump right into it.

The forecast for the metro area worked out just fine today, but the snow was heavier than expected up in Columbia County where several inches fell quite close to sea level.  Also we had a band of showers drop some heavy snow right over Clackamas and northern Marion counties this evening.  The official snow total in Portland?  Yes, once again it wasn’t measurable…just a trace at the NWS office.

marksnow_portlandwintertotal

But check out those totals in the hills around the metro area!

marksnowtotals_jan1st

If you live up around 1,500′ you really scored…after two winters of very little foothill snow it’s nice to see it back.

Showers will continue off/on tonight, although in general the airmass is drying out as modified arctic air filters down into the Pacific Northwest.  That dry/colder air has made it through the Gorge and the east wind has started blowing in the usual spots.  Already gusting over 30 mph at Vista House.  The wind will blow until further notice…sorry!  Tonight’s low temps won’t be too cold assuming we don’t get much clearing.  Probably just below 30 here in Portland.  I raised the forecast highs and lows the next few days since it’s obvious models have overdone the amount of cold air to our north, plus too much wind at night will likely keep PDX from dropping much below 22 the next few nights.  Still, high temps will likely just creep a bit above freezing tomorrow (32-34 metro area) even with mostly sunny skies.  Colder air will continue moving south through the region and then through the Gorge the rest of the week, but it definitely won’t be any sort of mega arctic-blast.  Just 2-3 days ago the northern stream of the jet was expected to dominate until further notice.  Instead we’ve seen models gradually allow more and more energy from the southern stream of the jet (milder and moist Pacific air) to move north over us the rest of this week.

My 7 Day Forecast this evening is mainly based on the ECMWF and its ensembles keeping the California system Wednesday to our south; thus the dry forecast.

Wednesday is a real challenge.  Most models other than the ECMWF are pushing some sort of moisture up north over Western Oregon Wednesday.  That’s right over the top of the cold air.  If they are correct, snow is likely coming for at least parts of the Willamette Valley Wednesday.  Here’s the WRF-GFS precipitation forecast ending Thursday AM, classy…nice dry hole over PDX:

or_pcp24-84-0000

 

Beyond Wednesday, all models agree on a “transition event” this coming weekend as we get rid of the lingering cold airmass.  Most likely a snow to freezing rain to rain event.  The ECMWF earlier today looked very similar to January 2004 with a low pressure system brushing up against the coastline but never really moving north of our latitude.  That’s a sort of “meteorological drive-by”.  It doesn’t dislodge the cold air, cold east wind continues, but a bunch of moisture arrives over the cold air.  What the ECMWF shows is a typical metro snow/ice storm Saturday & Sunday.    The GFS gradually warms us up Thursday-Saturday and we’d probably see little/no snow next weekend.  The evening GEM is more like the ECMWF showing a snow or ice event next weekend.

Chief Meteorologist Mark Nelsen


New Year’s Day Snow: How Much Did You Get?

January 1, 2017

photo_eric_charlton

This post is ONLY for putting in your snow totals, discuss the weather on the previous post.  All other discussion will be deleted.

  1. New Snow
  2. Location & Elevation (if you know it)

If you don’t know your elevation, this is a great tool.  You just input your address and it gives you the elevation:  http://www.whatismyelevation.com/##

IF YOU ARE NEW TO THE BLOG, THE COMMENT WILL NOT GO THROUGH UNTIL I HIT THE “OKAY” BUTTON.  IT MAY NOT SHOW UP FOR AWHILE.

The photo above is from Eric Charlton…7″ at 1,000′ near Yacolt!

Example:

2.5″
Corbett, 1050′

Thanks, that helps when making a snow map later!  …Mark

 


Snow Showers Die Down Today

January 1, 2017

9am Sunday…

It appears the weather has played out as expected with “Mr. South Wind” keeping us from getting an overnight snowstorm in the lowest elevations.  When we get that breeze keeping the lowest part of the airmass stirred up, we only get sticking snow to the valley floor during the heavy showers.  And the showers just haven’t been heavy enough all night to do the job (drop 1-2″).  I’ve seen it happen dozens of times in my 25 years forecasting in our area.  As with all the other snow events in the past month; most models (with some interpretation) have done very well again.  In fact this is the first winter that I’ve seen them do better some some human forecasts!

(9:24am:  The NWS just dropped the Winter Weather Advisory for most of us.  Now in effect only above 500′)

All lowest elevation airport observation sites from Salem to Scappoose are above freezing and will stay that way through the day.  Many of us are in the mid 30s, so it’s reasonable to expect high temperatures up around 40 once the showers back off.

For those of you that ARE getting snow up around 500-1,000′ and above, expect another 1″ or so before the showers turn to just flurries around 10am or so.  Farther south in the Willamette Valley towards Eugene the showers will continue through the afternoon.

HIGHLIGHTS

  • There won’t be any significant accumulation of snow in the lowest elevations north of Salem the rest of today.
  • But any area could get a dusting as showers pass over
  • Temperatures remain ABOVE freezing through at least 3-4pm
  • ROADS REMAIN CLEAR AT THE LOWEST ELEVATIONS
  • All wet roads freeze after sunset at some point as skies clear
  • We’ll be sunny, but cold the next 2 days

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