Back to Work: Wind & Snow

December 12, 2006

I still feel a bit under the weather today, but after looking at the weather maps I just couldn’t stay away!  Plus Andy is sick too so that leaves no one to cover me tonight.  What a team player eh?

First for tonight…nice pacific system moving onshore.  Looks like a good slug of heavy rain briefly overnight then back to shower tomorrow.  Deep low moving towards Queen Charlotte Islands.   A windy/rainy night but nothing too unusual for mid December.  By the way, don’t forget that today is the anniversary of the Dec. 12, 1995 windstorm.

Speaking of windstorms, all of our eyes are obviously scanning every single possible map/model for clues as to who is going to get hammered.  Of course as I write this there is no 00z model guidance available yet so I’ll post again later with my thoughts on 00z info.  It is pretty clear that a low is going to develop explosively and land probably on the NW Washington coast…they sure like to go up there don’t they?   You may recall that after November’s storms I decided the NAM-WRF is no longer my friend, so I’m leaning heavily on the GFS this time (that includes the UW-MM5 GFS).  As some of you have discussed at great length below…by the way, are you all employed?…there is a heck of a gradient to the south of the low as it moves onshore.  My 37 year old eyes could barely see the isobar packing between Portland & Eugene.  But I get 20-22 millibars from EUG-OLM!  The old rule of 3.15 x EUG/OLM gradient = 60-70 mph gusts in the metro area.  If so it’ll be a big windstorm from Eugene to Kelso.  But of course only a slight deviation in track to the north or a weaker cyclone could just give us the usual 45-50 mph.  Timing isn’t much of a debate…looks to be between 7pm-midnight Thursday evening.  I am impressived by the insistence through several runs of the GFS that there will be an "elongated" low with the big isobar packing over us.  It’ll be real interesting to see if it really sets up that way.

Now behind that storm a much colder airmass comes in.  Looks like a 1,500′ snow level at the lowest during the daytime Friday since it’s such strong onshore flow.  Remember that this is immediately following the gusty southwest wind and it’ll still be windy/breezy the rest of the day Friday.  I doubt we can get snow down to or below 1000′ in that pattern.  Then a quick shutoff of showers overnight Friday night and into Saturday morning when it’s finally cold enough for everyone to see snow.  With weak ridging then until sometime early Monday (via the ECMWF & 18z GFS), I just see a partly cloudy and chilly weekend.  Next system arrives from the northwest on Monday and pulls up southerly breezes again.  I see that as very similar to the late November one where the cold air was gone in a snap since the low is going by to the north.  For these reasons I’m downplaying the snow threat quite a bit.  Too warm Friday, too dry Saturday/Sunday, too warm Monday w/ precip…I’ll update later when 00z models arrive…Mark

11PM UPDATE: 00z models not too much different, landfall near the NW tip of Washington Thursday evening.  Notable again is the tight packing of isobars between 7-midnight over our region.  Hmm, could be a GREAT windstorm, but we’ll see.  It’ll be fast, over by early morning.


Wind Ends, Rain Begins

December 8, 2006

What a crazy east wind episode…3 days of gusts over 60 mph at the west end of the Gorge and the average windspeed at Corbett Grade School has been above 39 mph for 24 hours now.  Peak gust there was at least 71 mph earlier today.  Our own "blogette"? Tyler Mode recorded a 95 mph gust with his hand-held anemometer at Vista House about 2 miles east of there…no wonder the place was falling apart!  It just went through a several years-long renovation.  The wind continues strong or may increase slightly through tonight as the gradient holds around 9-11 millibars PDX-DLS.  A wave moving north along the coast tightens the gradient slightly until about daybreak, then the wind should die down to much more reasonable gusts to 50 mph tomorrow and tomorrow night.  We won’t lose the east wind completely until Monday when a gusty southerly wind develops across the metro area.

Rain showers arrive overnight, and it will be rain, except closer to 1000′ at the west end of the Gorge and 500′ at the east wind.  Considering current temps/dewpoints, it appears the upper hills around Corbett/Washougal, Stevenson & the Hood River Valley will see freezing rain.

Very wet system Monday and another wetter one later Wednesday/Thursday pretty much all agreed upon by models.  I don’t see deep low pressure to give us damaging southerly winds.

As I mentioned last night, a chilly airmass Friday-Saturday next week.  Maybe snow to 1000′, possibly lower, but that’s 7-9 days away.  We ARE in prime time for snow or arctic air, as much prime time as you can get here at sea-level in the Northwest.  Keep in mind that 34 years ago quite an arctic blast sat over the Northwest.  Redmond hit their all-time low of -28 on this date.  PDX dropped to 8 with highs only in the lower 20’s…So I’ll keep my eyes peeled for any sign in the models…Mark


A Change in Sight

December 7, 2006

I suppose a change will be nice for those exposed to the strong Columbia Gorge outflow this evening.  Troutdale Airport gusted to 41 mph earlier and Corbett School had a gust to at least 68 mph again this evening.  That makes for about 48 hours of gusts over 50 mph now.  Even after all these years of living on the east side of the metro area (since 1991), I still find it amazing that the wind can gust to 70 mph at the west end of the Gorge yet be calm only 15 air miles to the west.  All that fast-moving air fans out across the metro area.  And I had a gust to 16 mph at my home while it was gusting up around 70 just a mile & a half away.  I get blocked by hills about 1,500′ just to my northeast and only get gusty easterly wind when it comes down off the Cascades too.  Gradient from PDX-DLS peaked at around 9 millibars earlier today, dropped to around 7 early afternoon, and is now back to 8.5 or so.  It should peak again sometime tomorrow, then drop off dramatically tomorrow night as this east wind episode ends.  Someone earlier on the comments asked if there was any damage with these windspeeds.  Generally since 65-70 mph gusts occur at times during the winter, it takes gusts higher than that to cause lots of trouble. I think it has to get up around 80-90 mph or so to bring down lots of trees or damage roofs.  That hasn’t happened at the west end of the Gorge since the cold spell just before the Feb. 1996 flood.  I know several anemometers recorded 90-100 mph gusts then.

Now, on to the rainy season resumption.  Weak system tomorrow night and another Sunday still get torn apart a bit by the split offshore.   Then much more active fronts Monday through the rest of next week as strong westerly flow of one sort or another resumes.  It’s going to get wet again!

As for cold or snow? I too noticed the 00z GFS yesterday had significant cold air dropping in with a trough about next Friday-Saturday (15th-17th timeframe), not really an arctic blast but cold and showery behind Thursday’s front.  New 00z GFS and 00z Canadian just out show a chilly 1000′ snow level or a bit less, but definitely no arctic air and just a brief cooldown before more rain follows.  How surprising that the GFS would back off on cold air!!!  Of course I meant that sarcastically…enjoy one last dry day tomorrow and head up to Crown Pt. in the morning (or afternoon) if you want to feel some wind…Mark


Wind & Fog

December 6, 2006

Quite a difference in weather across the metro area this evening.  Dense fog and low clouds covers the entire Willamette Valley south of about a Newberg-Oregon City line.  McMinnville never got above 38 today.  At the other extreme it’s crystal clear with great visibility on the east side of the metro area…but wind has gusted over 40 mph at Troutdale Airport and 60 mph at Corbett as of 9pm.  By the way, if you own a wind instrument, please post your peak speeds in the previous post.  In between the two extremes is downtown Portland, Clark County, and Western Metro Area with hazy skies, but very little fog expected tonight as the dry east wind fights the fog to the south.  It should continue to be a stalemate the next 24 hours which means mucky down south and windy up north.

One noticeable change today is the slow deepening of the cold pool east of the Cascades.  Check out Condon today, at 2,800′.  They were 41 at 11am, but soon after noon it dropped into the 20’s.  They were basically "swallowed" up by the deepening cold airmass.  We do a forecast for our sister station KFXO in Bend, and forecasting Redmond’s temperature tomorrow is a nightmare.  Either 56 or 30 for a high there at 3,000′.
Because of this there is an obvious cooling in the airmass flowing through the Gorge this evening.  Both TTD and Corbett are running 4-5 degrees cooler tonight.  I like those 2 sites since the east wind was blowing hard last night and is doing so tonight…a great comparison of the "airmass" temperature.  As a result I think we’ll drop 3-4 degrees at PDX tomorrow for a high, so I went 43.  Did you notice Timberline was in the 50’s?  Looks like winter inversions are here!  Mark


East Wind Gusts (12/6-12/8)

December 5, 2006

Something new for our east wind event…this link is for unofficial MEASURED windspeeds only.  Place the Time, Location, and Peak Gust  in a comment below.  No discussion here please and I’ll take care of the mesonet/NWS peak speeds too…Mark


Quiet (Most Spots) Tuesday

December 5, 2006

Not much change tonight except the next weather system offshore is clearly pumping up the upper-level ridging over us.  In response, high pressure at the surface is developing quickly.  The PDX-DLS gradient (easterly through Gorge) is past 6 millibars already this evening and the wind gusts are responding.  Over 30 mph at TTD and 51 mph at 9:15pm up in Corbett.  We are now in a similar setup to last week’s east wind event, although a bit warmer for now.  I assume the gradient will pop up to 10 millibars or so by tomorrow evening.  One difference this time will keep the wind going through Friday…a surface trough or low approaches from the southwest Friday, which is always good for very strong wind at the end of an east wind event.  So this will probably be the strongest wind event of the season so far.
A pretty obvious change on the long range maps this evening.  We transition to an active westerly jet and rainy weather Friday night and into next week.  Earlier GFS today had quite a bit of rain over us Sunday-Monday, newer model does not have that.
Tie everything down if you live east of I-205!  Mark


Quiet Monday

December 4, 2006

Wow…to be honest the weather is really boring this evening.  The system moving by to the north the last 12 hours or so just about killed the cold high pressure in the Columbia Basin, but it’s still there and wind in the Gorge never turned westerly.  Now it’s back to ridging overhead later tomorrow.  That allows the surface high eastside to strengthen again, bringing back the cool easterly wind.  Not much wind though until Wednesday.
Next chance for rain is Friday and long range maps definitely have a switch back to more active weather beginning this weekend.  There still seems to be some sort of split-flow, but wet either way.  Maybe just not so wild like the weather we saw in November.
No sign of arctic air or low snow levels in the next 10 days for you snow lovers…Mark