Friday, December 26, 2008

Plant Damage, Snow, Rain, Melt Out, and Avalanche Danger


Walking to the bus stop this morning I saw increasing evidence of damage to plants and trees. Large branches broken off by the weight of snow, bushes bent over to the ground or broken. At the UW, the main road was blocked because of heavily leaning fir tree...snow loading had done the trick. Anyway, I suspect many of you will find quite a bit of broken or bent vegetation around your homes and in our parks.

A major weather system is now approaching rapidly...with a warm front tonight and cold front tomorrow morning) and it should be precipitating over the western interior around lunchtime (see satellite and radar images). It is raining on the coast and Quillayute turned from rain to snow.

So what will happen here as it begins to precipitate? Temperatures are generally above freezing at the surface and the Sand Point profiler indicates the freezing level is at 1000 ft. The snow level (the level where all the snow is melted) is usually about 1000 ft below that....sea level in this case. So we may initially see some wet snow at higher elevations (above 300-500ft), and very, very wet snow and rain near sea level. You all know whether you are in the high or low elevation category.
During the afternoon the cold air will hold in place at low levels, but this evening it will be replaced by warm, southwesterly flow and strong winds. You WILL be able to tell when the warm Pacific air hits tonight. Attached is a time-height cross section showing temperatures (C), winds, and humidity forecast over Seattle. You can see the 0C freezing line move nearly straight up in the evening. The heights are in pressure...850 mb is about 5000 ft, 700 mb about 10,000 ft.
This system will be wet, but not a pineapple express. Seattle, partially rain shadowed, will have less than .5 inches....minimizing the threat of urban flooding from the combination of melting snow and rain (but please clean out your street drains to make sure!). Temperatures tomorrow will get back to normal...into the mid-40s and most streets should become passable by late tomorrow.

The mountains will get several feet of snow...and then we come to another issue....avalanches. The snowpack is not large right now, but it has a number of weak embedded layers. With massive snowfalls on top of it, a large avalanche threat will exist by tomorrow...so be very careful if you are skiing out of controlled areas. Even better is to avoid such locations.

And finally...there will probably be strong southeasterly winds over northwest Washington waters tonight as the front approaches.

59 comments:

Don said...

It would be interesting to show the dew point as opposed to the rel humidity, the dew point being the more related explicitly to the weather mass....

gshall said...

Snow began at 10 a.m. at 500 ft. on the west side of San Juan Island. Temp about 33 F. It has stopped as of 11 a.m.

mb in Port Angeles said...

No precip yet this morning in Port Angeles. This is my first winter in this neighborhood. I didn't know to pay attention before, and I wish I knew where the street drains are under all that ice... :-(

mb in Port Angeles said...

should have specified: West side of Port Angeles, elevation about 125 feet. Temp just above freezing (windshield frost melted, street traffic no longer crunching); no precipitation.

Anonymous said...

Where are all the comments?

Are the weather junkies back at work, or is there nothing exciting going on?

Anonymous said...

Melting temp at 550-580 ft of elevation (Sammamish). We're getting quite a bit of very wet snow falling while the trees are "dripping".

Anonymous said...

A question, we got about 12" in Port Orchard over this event. What would that equal in inches of rain?

Mary-Clayton said...

An mix of icy rain & snow began briskly falling in Mill Creek at 12:10 pm. Temp 33 F.

Anonymous said...

Steadily snowing for the past hour and a half in Sedro Woolley. Sidewalks are covered after shoveling yesterday. Temps staying around 33.2 degrees.

Scott K said...

In lake stevens right now it's snowing very very lightly, but temps are around 35 (SE side of the lake).

We went out this morning and cleared away the drains around the house, expecting lots of standing water over the weekend.

Scott K said...

Ok change to the lake stevens weather...it's snowing heavy/hard right now.

Anonymous said...

Foothills of Bellingham have light snowfall as of 12:30PM. Temperature 32 degrees.

Anonymous said...

It's raining in Redmond (MS campus) since at least 12:00 noon.

Road report from 10:30am: all main arterials clear between Ballard and Redmond. Market Street has been cleared, 45th (thru Wallingford) to I-5 is great. What slush I had to go over (my street to 15th, then pulling over in Wallingford for a quick errand) was not hard or impassable. Roads were wet but at all points along I-5 and 520, drivers moved briskly at at least the posted speeds.

Apologies for those who already are aware of the above. But since I didn't find reports posted on the usual blogs this morning, I offer up these comments in case (like I was for 2 days) anyone is hiding out indoors, unsure whether it's yet safe to go out.

I'm not sure why I saw 2 Metro busses with problems earlier. The ones going thru Ballard & Wallingford were fine, but an eastbound 255 was moving cautiously at the upward slope at the east end of the bridge. There was also one which appeared abandoned at the 40th street exit.

I think we're all weather junkies now! (weather activists?) Cliff's blog & my neighborhood blog were lifelines w/the on-the-ground reporting for what was really happening & what to expect next.

I'll check UW Bookstore to see if there are any planned bookstore or Kane Hall talks by Cliff soon. I have a feeling the Lake Forest Park event will be mobbed!! Cheers :-)

Julianne said...

After about 1/2 hour of rain and sleet, I'm seeing consistent snow here in the Madison Valley (MLK & Olive). Also, great advice about clearing storm drains. I also checked the downspout diverters around our house. The weight of ice build-up had caused some of them to detach from the downspouts causing water to drain directly into the ground close to the house.

Anonymous said...

Capitol Hill, 1pm--Steady snow now for about an hour. Our neighborhood roads and sidewalks are still a thick slushy mess, so it is hard to tell if the snow is adding to the accumulation. It seems to be melting on the wet/bare spots where cars were previously parked, but sticking where we still have about 6 inches of thawing snow.

cp said...

SNOW, the rain turned to snow in the Haller Lake area of north Seattle about a half hour ago.

Hopeing the roads clear up soon, I'm out of CHOCOLATE.

theartist said...

It is DUMPING snow in south Mukilteo, some of the hardest I have seen. Hoping to see that changeover to rain soon. My wife barely got out of the driveway this morning and it'd be nice to melt off about an inch before she gets home in 4 hours. ;)

Bob Moore said...

Update from SE Lake Forest Park:

First, I was glad to hear on KUOW that Cliff is "on vacation" and thought that he richly deserves some relax time, but this posting suggests that you're back at work on our campus, Cliff! Is there any way that we on the Comment team can carry the weight on this blog and donate some real "free time" to you and your family? I think you deserve all the help we can provide, and I'll bet that many (probably most) of your blog addicts will agree.

Here, our roof panels are reporting 40 degrees F, and the shed 35 degrees. We have moderate rain, with some bright-colored "large drops" or "mostly melted flakes". Several neighbors' roof crests are melted free, with gutters looking about 1/3 open, and ruts on 39th Ave NE between NE 148th and NE 151st are clear down to pavement, with manhole covers also clar, but ther's still some sludge in about 1/2 of the ruts and maybe as much as 1 ft crests between and next to the ruts: progress but far to go!

We plan to go out this afternoon by car, and I'll shovel out several water grates to help get as much meltwater as possible into the storm sewers to protect our downhill pals above and on the Burke Gilman and lake from flooding and (much worse) landslides in this layered clay soil! (We have water-pervious sand layers between dense impervious clay layers, which both lube clay flow and marinate the clay into half-liquid form, so we need both stormwater drains and healthy plant roots to protect us from slides that often cut out or cover long stretches of the Burke Gilman and the street below, with major risk of pushing lakeside homes into the water or at least plugging up garages and front doors.

Time for lunch! More later..

This time, my first 3 tries have failed .. why?

nocurling said...

capitol campus, olympia. now a steady rain and 35f.

Molly said...

It is snowing steadily at Hwy 9 and Maltby Road, with 1/2 inch in past hour. I've been trying to dig out my car and clear in front of it, but with a three-foot snowplow berm at the end of my driveway, this may take me awhile!

Anonymous said...

30 in Snohomish and snowing steadily for the last hour

J-Ren said...

Shoreline - was mixed rain & snow at noon but now its just snow w/ big juicy flakes. Been going like this for at least 45 minutes.

Anonymous said...

Yup, we're back to snow in Sammamish, now too. Respectable flakes and lots of them.

Snow is starting to feel like torture! Just tighten those screws a little more will you? Ugh.

Anonymous said...

33F, heavy snow past hour in Fairwood (out toward Maple Valley).

Anonymous said...

It's been snowing hard in Everett for about two hours. Temp 34. I can't wait to see the rain!
Warmer tonight then more cold air tomorrow, does that mean more snow Saturday?

Noel said...

Snowing in La Conner--had been a classic rain and snow mix, but now it's just plain snow. Criminy, this is getting old.

Anonymous said...

It started to snow again on the Tulalip Indian Reservation about 2pm Friday. It's wet and we're right by the water. Big flakes.

Anonymous said...

It's been snow and rain mix most of the day, but is now 36 and has been snowing steadily for the last hour in Redmond-Bridle Trails area.

Kerry said...

Two hours of snow in Madrona and it's just now starting to stick at spots which have been cleared of snow and ice.

Sidewalks and roads are still in very bad shape on the west side of Madrona hill and the east side of Cap Hill. MLK, Union and Madison are passable but lots of cars are still getting stuck on the side roads. Sidewalks are deep slush and packed ice. Very little bus service and nothing going downtown. I hear the west of Cap Hill and downtown are much better so if you can get that far you're probably OK.

Anonymous said...

I'll second that "criminy" and raise you an "omg."

Bothell 300 ft elevation

Like everyone else, rain/snow mix has turned into ginormous snow flakes.

If I can't get out of the house by Sunday, I'm going to post my address so that you can send Search and Rescue over with a big green salad.

(Seriously, I have plenty of food, just no fresh greens.)

Anonymous said...

2:15pm, snow on capitol hill again, medium flakes, a lot of them.

Anonymous said...

Duvall 2:15pm 32F
Snowing hard, small to mid-size flakes. Looking at the radar on weather.com there is a vertical band in the Snoqualmie Valley that seems to be the steady transition point from ice/mix (pink) on the west side to snow (blue) on the east side. Before today's snow, we measured 23" on our picnic table. The peaked roofs in our neighborhood have a very thick layer of snow. Fingers crossed they are strong and make it through this crazy weather! We dug out pathways leading away from various locations around our house and cleared the nearby drains. When will Duvall warm up????????

Anonymous said...

Pouring massive huge snow flakes in Canyon Park/Bothell since about 1:30ish.

Anonymous said...

Will this EVER end? It's now snowing lightly again on Phinney Ridge near the Woodland Park Zoo at 2:23 p.m. Friday, and the temp has dropped a bit from this morning. I thought we'd see warmer weather and consistent rain by now. Sigh. The minor arterials are in good shape but the side roads are still pretty bad. You wouldn't want chains, because once you went three blocks you'd be out of the mush and would need to take them off.

Magi Lightdancer said...

slushy rain an hour ago has turned to moderate snow in Kirkland/Juanita. temp says 34 degrees, but LordiLoo!

Anonymous said...

Capitol Hill update--2:30.

The snow has not let up. Steady snow since noon. No one is driving the slushy roads in our neighborhood. My sister called and reported white-out driving conditions on I-5 between Lynwood and Seattle with roads staying clear, but white accumulation atop the gray snow on the shoulders.

Weatherfreak said...

Light snow and 34 in SE Auburn @ 2:20pm. This storm started just like the one last Saturday but much warmer. 25 deg. snow is much more enjoyable than 33 deg. snow. Made a large snow pile in the back yard. Will be fun to see how long it lasts.

Anonymous said...

Cliff, please reassure us...it is going to stop snowing isn't it? Snowing large flakes in Kirkland, near Rose Hill...please make it stop!!

mle_ii said...

Huge flakes up here on Education Hill in Redmond. Temp 34.5 degrees F. Hope it stops soon and starts to clear, my wife had a heck of a time getting out on her flight (delayed a few hours due to snow) and now I'm worried that it's going to be even worse on her way back tomorrow.

Anonymous said...

Hollywood Hill, Woodinville, 1/2 in. new snow since 1:30. 28 degrees, no sign of lettin up soon.

Anonymous said...

We are still snowing here in Fairwood, have been most of the day. The main roads are staying wet but our parking lot is a treacherous place! Accumulated about a foot of snow, cars are spinning out - it's so frustrating to hear and watch, and especially to be in their shoes I suppose.

I'm so sick of the snow. This San Diego native was not made for this kind of weather.

fjblau said...

Sammamish.... DUMPING snow again up here. Huge flakes.. 33.1F outside at Beaver Lake....

Anonymous said...

Snowing hard in Lake Forest Park (~400' elevation) and sticking on the recently shoveled driveway. Arrgh...

Anonymous said...

I live in the eastside on the border of Woodinville and Redmond on a hill. Its snowing heavily for about an hour (at 3:00 PM). I guess I am at a higher elevation. Shoveling this snow is hard as it seems heavier than the snow we got on Sunday.

Anonymous said...

Duvall 3:05pm 32F
Snowing hard, big flakes! All those pathways we dug for melting snow to drain away from the house are now slowly filling up with fresh snowfall. Doh!

Anonymous said...

Lynnwood City Center (196th SW, 1 mile west of I-5): I think it might have been raining at 1pm, but then it started snowing hard. Looks like we've gotten at least 2 inches in the 2 hours since. The flakes are falling at a 45 degree angle, so there's some wind (rom the south) out there, too. (No weather instruments here, I'm afraid.) I don't have a working thermometer, but the SchoolNet shows temps of 30-31F, and that sounds about right. Rain sounds like a fond dream, never to be realized. We'e in a top-floor apartment in a building with a flat roof. I'm beginning to wonder how much more the roof can take! Lyn in Lynnwood

Mikey said...

It's been snowing since this morning @ 300' east woodinville. Started out big fat flakes but now they are medium-sized. There were 8-12" ruts in the ice at woodinville-duvall road and avondale this morning.

fjblau said...

Sammamish Pics:

More Snow

Steve Snyder said...

Snowing heavily in Woodinville again. Probably 2" new snow. It's 32.5 degrees... Will it ever end?

Alex said...

It is snowing heavily in Redmond Ridge right now.

Anonymous said...

It finally stopped (for now) in Everett. I hope that was the last of it. My neighbor was telling me how much it reminds him of his home in the Ukraine.
Cliff..you say were supposed to get more cold air moving in tomorrow. A little reassurance please - it is going to rain this weekend, right?

Scrantz said...

report from Portland, oregon- it is RAIN here-- warmish- in the low 40s-- hope this gives you all a bit of hope! to know we are sending the warm air north...

Kevin Purcell said...

The forecast seems to be panning out at 5pm: the KSEW profiler is showing the temps cooing up quite steeply. Though the forecast plot shows this about 8 hours later.

Compare this current sounding

http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?profiler+1+-st

to the forecast plot Cliff posted (time on the bottom axis more recent at the left in date/UTC time so match up the date/UTC).

The profiler is going up to 1600m or 5000 feet or 850mb or so.

Anonymous said...

The parking lots at stores have very, very deep slush - I was in over my ankles for long stretches and it felt like I was barefoot wading through a river, so wear rubber boots or galoshes or something

Matt said...

Here in Kitsap county near Indianola, just off of Miller Bay at 300' elevation, it has been 36 degrees all day long, and still is. We had mixed rain/snow until around 1pm, at which point it became a steady rain which let up in the late afternoon.

Now, as of 9pm, the wind has picked up considerably, so it seems as if that Pacific front is blowing in.

Doug Carer said...

Had heavy snow in NE Bothell (183rd and SR-527) from 1:30 PM to 3:30 PM today before it tapered off and quit. Everything quite wet as it warms up. Realized it's a lot harder to drive on deep slush than dry snow. Few of my neighbors could drive up the hill to their homes.

JewelyaZ said...

Holy cow. I just finishing playing Animal Crossing: City Folk (thanks, Santa!) and I'm getting ready to go to bed... and I noticed that it's 41.5F outside!!!

We couldn't even get our car back into our driveway tonight at about 8 because it was so slippery in the slushy ice... but tomorrow it really will all be melted away and we will just drive around as normal. I CAN'T WAIT.

Thanks for the rain, Cliff! :-)

Anonymous said...

TIDES

I would love to get some reliable information on how our weather affects the tides day to day.

for instance, wouldn't a freeze lower the highs? and flooding from melting snow raise them?

Also, wind on Saratoga Passage, the eastern side from Everett to Deception Pass. Big Southerlies and high tides can damage us pretty good but how does one get the warning?

Kevin Purcell said...

@anon who asks "I would love to get some reliable information on how our weather affects the tides day to day. for instance, wouldn't a freeze lower the highs? and flooding from melting snow raise them?"

The temperature and volume of the mass of water in the Sound is (practically) unaffected by atmospheric temperature runoff or runoff temp.

For climate work the temperature changes the volume of water on the planet but not in an observable day to day usage.

So the runoff has no effect on tide or tide height.