The Big Winter Meeting

October 15, 2009

snapshotObviously it’s going to be really wet Saturday, so here’s something to do.  It’s time for the 17th annual What Will the Winter Be Like meeting at OMSI.  Hard to believe we’ve been doing this since the early 1990s!  It used to be held in a small conference room and maybe 15-20 people would show up.  Now we regularly see more than 100.  You are invited…the event is open to the public.  The meeting basically consists of 4­-5 forecasters getting up and giving their thoughts about what might happen during the upcoming winter.  A lot of times they are wrong, sometimes they are right, but there is always lots of good discussion.  Also lots of El Nino, MJO, QBO, and other big phrases.  The event is held in the auditorium and lasts about 2 hours.  I will be there, but I just give a review of the previous year’s weather.

Okay, let’s talk weather.  Rain is the big story.  00z models all give us quite a bit of rainfall, at least 1-2″ in the Valleys between midday tomorrow and Saturday evening.  Now our RPM shows 3.68″ rainfall, the GFS looks like 4″ or so as well.  The WRF-GFS doesn’t look quite as wet, and the NAM goes nuts with maybe 4″.  We’ll see, it’s quite a narrow line of rainfall along the cold front tomorrow evening.  We’ll see…

Chief Meteorologist Mark Nelsen

First Windstorm At Coast

October 14, 2009

snapshotLots of wind this morning at the Coast.  Definitely a bit more than expected.  Notice that even some of the coastal cities had gusts over 60 mph.  Even in winter that would a healthy storm.  Here in the Valley gusts generally remained below 35 mph.  All quiet now though as we are inbetween systems.  Tomorrow should be a very dead weather day as a weak warm front moves north…lots of clouds but not much rainfall.

Friday and Saturday are beginning to look quite a bit more interesting.  Some part of Northwest Oregon or Southwest Washington may really get soaked. Tons of moisture surges north and into the Pacific Northwest.  It’s definitely not a Pineapple Express, but not much different.  A narrow conveyor belt of moisture forms and sits generally overhead for about 24 hours.  Precipitable water forecast up around 1.40″ is juicy!  Add in a freezing level around 12,000′ (rain on the top of Mt. Hood), and we could have some early season flooding.  We’ll definitely keep an eye on it.

Chief Meteorologist Mark Nelsen

Snow & Wind: Wet Season Begins!

October 13, 2009

Snow briefly stuck on the side of the road near sea level.

GovernmentCamp_pid624Whew! Sure feels like early winter out there. Snow came down a little lower than I expected this morning. I mentioned some snow or freezing rain possible in North Central Oregon or the Hood River Valley on the broadcasts last night. But the evaporative cooling (with dewpoints starting in the teens!) really did the trick. Snow stuck all the way to sea level briefly in the Gorge! The main band of precipitation is now out of the Gorge, so that should be it for snow.

As for wind? A bit stronger than I expected as well. The PDX-DLS pressure gradient is up to 11 millibars! I suppose I did mention last night that the setup was quite similar to a snow/ice storm, so maybe I should have clued in to the wind a bit more. Sure enough, everything did pan out the same as one of those storms, except 15 degrees warmer! We’ve also had some downslope component to the wind, especially earlier this morning. I see a home weather station in Battle Ground had gusts to around 40 mph before that stopped. PDX gusted into the mid 40s, Glen Jackson bridge to 49 mph just this hour, and 62 mph so far in Corbett. I notice the wind chill is around 20 out there…pretty brutal for October 13th.

10:00 PM UPDATE: A real busy day in here making graphics and keeping the news people at bay.  Actually I think we covered the weather very well today.  Let’s be honest; it’s not like everyone’s life was trashed by the weather today.  BUT, everyone was talking about the weather with the wind and chilly temps.   That’s why we decided to talk about it right off the top of the show.  But we avoided the breathless reporter scraping the ground with his shoe and telling us not to drive in these high winds.  Don’t you hate that?

Seems to be one more wave coming through here in the next 3 hours.  After that we should see a southerly wind surge up the Valley and get rid of that east wind.  Much warmer temps on the way too.  In fact this chilly burst of weather will be history in a few days.  On Thursday and part of Friday we will be on the south side of the Jet Stream.  850mb temps surge up to +10 to +12 with southerly wind at the surface.  High temps might get back up to 65­­­­-70.  We’ll see about that.  In the meantime, plenty of rain showers.

By the way, I checked for the earliest measurable snowfall at Hood River.  It was 5″ on October 26th, 1919.  Parkdale’s earliest was October 20th, 1984…less than 1/2″ there.  Both of those towns MAY have set a new record for earliest snowfall!

Chief Meteorologist – Mark Nelsen

Turning Wet…

October 12, 2009
Now That's Windy!  We haven't seen wind like this in 47 years!

Now That's Windy! We haven't seen wind like this in 47 years!

A breezy and cool day again today.  I see only Vancouver made it to 60 degrees.  Once again for some reason that Pearson Airpark sensor seems to be 1 to 2 degrees too warm.  I’ve noticed that since last winter, then it seemed a bit too warm during the hot spell.  Anyway, a disappointing weekend with much warmer than expected low temps due to cloud cover both nights.

Dewpoints have been incredibly low the last 3 days…right now it’s 15 at PDX.  Gorge gradient is picking up now, approaching 6 millibars DLS to PDX.  This is due to an approaching surface low to the southwest.  Tomorrow is the “ice storm day” that we usually get after a cold outbreak.  Of course it’ll be about 20 degrees warmer than it is during the winter, but the sequence of events is the same.  Cool and dry offshore flow strengthens as the deep low approaches, then precipitation spreads over the cold air, giving us a very chilly day (54 at best tomorrow).  The east wind dies off and goes calm tomorrow evening/night, then southerly wind takes over by daybreak Wednesday.  That means rising temps tomorrow night.  I wouldn’t be surprised to see frozen precipitation in the upper Hood River Valley and southern Wasco County (Tygh Valley, Dufur etc…) as the precip. arrives tomorrow morning.

Lots of rain with good westerly or southwesterly flow begins tomorrow.  Models are very consistent showing at least 1-2″ in the driest parts of the Metro Area during the next week.  This is definitely the beginning of the wet season!

Chief Meteorologist – Mark Nelsen

Dry and Chilly Weekend

October 10, 2009

hoodriverChris Markes sent me another great photo he took this morning.  This definitely goes in the “Top Ten” viewer photos of all time here at FOX12.  You can’t get color like that out of my junky little camera.  Plus I don’t like to get up that early…possibly because I stay up late working and posting to a weather blog at 12:40 am???  It’s a picture take from the lower Hood River Valley, maybe Panorama Point, looking up towards Mt. Hood at sunrise.

A very short post since WordPress was down during my usual blogging time.  Cold and very dry air is arriving this evening and spreading across the Metro Area.  I see dewpoints are already headed down towards 20 degrees at Troutdale.  A couple hours ago the wind gusted to 40 mph at Corbett…it’s going to be a windy weekend out there.  I just ordered a new anemometer for that Davis Vantage Pro.  I saw it close up today;  that poor thing looks beaten up after 5-7 winters in the Gorge!

Rain moves in Tuesday as the east wind ends.  Enjoy the sunny, but real brisk weekend.  If you live anywhere outside the east wind zone I think your growing season ends tomorrow night.

Chief Meteorologist Mark Nelsen

Looking Colder…

October 8, 2009

snapshotLots of sunshine again today with temps finally reaching 70 degrees.  So I suppose if we actually would have seen offshore flow this week (remember that was the initial plan about 6 days ago), temps in the mid 70s should have been doable.  But the warm 70 temps will soon be a memory won’t they?

Not much has changed in the somewhat historic cold snap coming this weekend.  Arctic air is pouring west of the Continental Divide this evening…one would think it’s winter with temps in the Flathead Valley heading down into the teens overnight with snow.  This is the first surge of chilly air;  the leading edges of it come through the Columbia River Gorge tomorrow afternoon/evening.  Then a strong upper-level shortwave rotates south from west of Hudson’s Bay Saturday night and Sunday.  That one reinforces the chilly airmass.  So both Saturday and Sunday we’ll see gusty east wind in the Metro Area.  Nothing too crazy there, maybe gusts 50-55 mph.  Temp forecasts for Saturday and Sunday are tough.  If it was Halloween I’d say highs around 48-50 degrees, especially Sunday.  So I went with 55-60, coolest on Sunday with the 2nd push of colder air.

The airmass coming in is going to be very dry…dewpoints at least down into the 20s.  Couple that with clear skies and the calm wind locations should have a hard freeze Saturday and Sunday nights.  I think the only spots that will avoid this will be east Portland out through the west end of the Gorge.  Will the wind drop off Saturday or Sunday night at PDX?  Seems unlikely with 6-7 mb of gradient through the Gorge and a cool airmass, but it could happen.  Cooler east wind hangs on at the Airport overnight much better than the warmer wind we get in early Fall.

Okay, out of time for now.  Still looks wet beginning Tuesday.

Chief Meteorologist Mark Nelsen

Early Season “Cold” Snap

October 7, 2009

junkThis is a forecast “time-height” diagram from the WRF-GFS model run by the UW.  It shows the forecast atmosphere over PDX during the next 24 hours.  Time moves from right to left;  the opposite of what you might expect.  The time goes from 5pm tonight ot 5pm Saturday.  Two things to notice here.  One is the green shaded area on Friday morning…possibly another morning cloud day coming up like today.  The second is a bit more significant for our weekend weather.  Strong easterly flow arrives overhead and down here at the surface by Friday afternoon.  Notice the drop in temps and humidity.  This is quite similar to a wintertime arctic front.  In fact all of the atmosphere over Portland above about 2,000′ is at or below 40 degrees!  That’s amazingly cold for this early in the season.  I didn’t put the image here, but 850mb temps east of the Cascades (over The Dalles for example) are forecast down to -6!  That means low-mid 20s at the 5,000′ elevation.  It doesn’t get any colder than that in early-mid October.  Models (especially the GFS) are pushing the colder air much closer to us than 24 hours ago;  that’s why we dropped the 7 Day forecast temps quite a bit.  They may still be slightly high.

This will be about the driest airmass you could get in early October as well.  Looks like dewpoints down into the 20s at least Saturday and Sunday.  I don’t remember a time before Halloween when we’ve had such low dewpoints.  Yes, a few years ago we had a cold blast right at the end of October, but that is 2+ weeks farther into the cool season.  With such dry air, it should be easy to get temps into the mid-upper 20s in the coldest Willamette Valley spots that see the wind go calm at night.

Still looking rainy next week, starting sometime later Monday or Tuesday

Chief Meteorologist Mark Nelsen