On the Line

Snapshot2SnapshotA tough forecast again for the next two days as the wet westerly jet stream sets up over Washington and southern British Columbia.  As you can see to the right, the forecasts for Seattle and Eugene are quite simple…either warm and dry or wet and cool.  From Longview down to Portland we are on the line though.  Both the 00z MM5 and our own RPM model continue to show the rainfall line staying just barely north of Portland Thursday and just about down to Portland later Friday.  Whew…it’s going to be close.
Easier forecasting Saturday and Sunday;  a cold front sweeps inland late Saturday with plenty of pre-frontal rain.  Then showers taper off during the day Sunday.  We may get a brief break Monday before more "troughiness"  arrives Tuesday-Thursday.  Oregon spring break is looking very wet.  Maybe at least you Washingtonians can get nice weather the following week for your spring break.

66 Responses to On the Line

  1. josh"fromEverettWA" says:

    Hmmm…snow perhaps Thur/Fri next week up here.
    BTW, it snowed here on Tuesday for about 20 minutes at 460′.
    Similar pattern setting up for next week.

  2. Hehe the weather was odd today – it was sunny but hazy, and then clouds rolled in and it started raining. To the west I could see a band of yellow on the horizon of clear sky. Weird, but cool.

  3. AtmosphericWrath -Southeast Portland- says:

    Lol You guys crack me up.
    It was a nice day today.
    I just saw a rainbow along with a very nice sunset.
    Hoping next weeks trough will bring some hail/isolated t-storms.
    Rob

  4. Derek-West Gresham says:

    I didnt post that to rile ya up Anti. šŸ™‚ That was just for support of what Camas Mom said. I certainly dont base past experiences as the sole logic in the future, thats what improving forecasters should learn.

  5. I realise that by some fluke it snowed in April at one point, and nobody predicted it, but just because it happened one time doesn’t mean that every time the models forecast 2000 ft snow levels we have to start saying “OMG its going to snow down to 1000 ft!!!” Just keep that in mind.

  6. Derek-West Gresham says:

    Here is what Mark said in his last blog before the April 15th surprise.
    “ETA 00z cross-sections show freezing levels down to around 2000′ Saturday and Sunday. I don’t think snow will fall much lower than that”

  7. josh "fromEverettWA" says:

    Hey guys. Just thought I’d add some fuel to the discussion:
    From KING5:
    Wednesday a strong cold front will drop down out of the northern Gulf of Alaska for a rainy day. Unseasonably cold air behind the front will lower snow levels to 1,000-1,500 feet Thursday and Friday of next week possibly bringing wet snow or mixed rain and snow showers to sea level. Daytime highs will only be in the mid 40’s.
    BTW, only 41 here with heavy rain. Isn’t March great!!

  8. Camas Mom says:

    Oh, and the GFS I looked at just a little bit ago still has snow on the 29th and 30th for my elevation. Yes, it’s a long way out and I don’t expect it to hold – but what are models for if not to speculate the long term?

  9. Camas Mom says:

    Can I just say, as one who actually got the snow last April 15th (and in March around this time, btw) that NO ONE called for it – it was supposed to be a “typical cold wet spring day.”
    Face it, we won’t know until it gets here – and in the meantime it’s fun to speculate until the models take the expected dump.
    That said, today is awesome and I’m ready to be done with the snow and on to getting the outdoors ready for summer!

  10. Derek-West Gresham says:

    Regardless of what LI’s my be forecasted to be I know a good set up when I see one and that is about as good as it gets in March. I am begging the models to hold.

  11. Sean (Lebanon, Indiana) says:

    I don’t think the thunderstorm threat is really that great. With LIs looks weak, and temps of around 50. Not really the best ingredients for thunderstorms in the Northwest.

  12. Derek-West Gresham says:

    I wasn’t going to argue further anyway..lol

  13. That’s OK, Derek – we are all entitled to our own opinions, which is one of the things that makes the blog so great, and that we can have discussions on things like this. Moving on, what do you think about thunderstorms over the next week or two?

  14. Derek-West Gresham says:

    Antipex you are irritating me. I don’t freaking care, I know what I saw and you are not going to change what happened by telling me so. Leave me alone please.

  15. Small hailstones that have partially melted on the way down will appear slushy – and look similar to snow. There is a difference, however. By the way – the trees and flowers are finally blooming up here! A few days ago I took my dog for a long walk up and down some hills – I went from 500 ft to about 320 ft and noticed that there were many more flowers in full bloom. Coming back up to 500 ft it just wasn’t quite at the same level yet. Funny how even small changes in elevation can do that!

  16. Derek-West Gresham says:

    Wrong Ryan. It produced plenty of snow when either A. it was a northwest flow or B. there were places that didnt get rainshadowed.
    I give up, this is hopeless. I can only hope this pans out so that people can see it is not that hard to get a snow level below 2000ft with the right airmass, no matter how brief it is.

  17. Ryan (Da Couve) says:

    In most the -8C events during the winter we had borderline snow in the city and rural areas. Now that we are in March I think all it does is give us a cold rain event with highs in the upper 40’s.

  18. Derek-West Gresham says:

    To your small hail stone comment though there was hail at times during that shower..not only did it look like wet snow but it made the familiar splat on the cars of a snowflake. About 5 little dots with each one that slid down the car together and melted. It was happening in many spots too without a hail sound. Oh well, just forget it Anti.

  19. Derek-West Gresham says:

    To your small hail stone comment though there was hail at times during that shower..not only did it look like wet snow but it made the familiar splat on the cars of a snowflake. About 5 little dots with each one that slid down the car together and melted. It was happening in many spots too without a hail sound. Oh well, just forget it Anti.

  20. Derek-West Gresham says:

    Antipex Mark has said he has seen snow fall at 47 degrees alrighty. I have seen it snow in the fourties plenty of times and I know what I saw. I dont need anybodys approval to tell me that.

  21. Sean (Lebanon, Indiana) says:

    Nothing like temps near 70 at 7am in the morning, which for mid-march is very unusual. Got wokeup just after 6am this morning, when a Svr TStorm Watch was issued shortly after 6am. Looking at the radar a very nasty looking line of storms moving towards my location. What an exciting way to start the morning!

  22. By the way – good night everyone – I’ll be back in the morning!! And thanks, Mark, for the update as usual.

  23. First off, weather models are simply that and it doesn’t matter which one you use. They all have tendancies and inaccuracies, and a good forecaster uses a combination of several models along with experience and environmental variables taken into account.
    Second, I’m sorry but real snowflakes are just not going to be falling when the temperature is 45-50 degrees. While it was hailing here I did see what *looked like* mixed snow – basically very slushy raindrops – but upon hitting the ground I noticed they were most likely very small hailstones that, due to their comparative lightness and size, were able to drift a little differently than the larger stones falling. This past season I have seen it all – hail, graupel, snow, sleet, and rain – within one storm. And the stuff that fell the other day was certainly not snowflakes.
    Being that the atmosphere just wasn’t very cold up above, and taking into account the fact that I’m about 200 ft higher up here and my temperature was no lower than 46 degrees while this stuff was coming down, I’m quite positive that snow was not falling at any lower elevations around the area.
    Also, Derek, please note that I’m not trying to go against you in any way, and I consider this some friendly discussion. Being able to throw messages back and forth across this blog is pretty cool, and allows others to chime in as well – so let’s keep it something positive, ok? šŸ™‚

  24. Justin says:

    Agreed winterhawk, 1999 is a great example, late March/early April 2001 is another recent similar one. These are nothing special, generally highs in the mid to upper 40’s with intermittent fronts cutting through followed by showery days. Hope for the occasional thunderstorm/hail event, and the mountains usually get great snow out of these as well. Very rarely the early morning snow level may fall to 1000′ or so, but that is rare and obviously remains to be seen. The 00z is the oly run of the GFS so far with any sort of dynamics at 500mb, and these are ‘mid December’ offshore flow kind of dynamics, not what we see in late March or early April. Admittedly though, in an extreme case you could see snowflakes out of this in a heavy enough shower (March 22, 1994 and April 4, 1999 come to mind), but come on folks, its spring, we’re not going to see big cutting troughs that pull down polar air like we do i winter. Gotta get familiar with our climate and the 500mb dynamics as the year changes, and to me this looks classic.
    Not to say that I don’t enjoy these troughs though, this is what spring is all about. Hopefully the GFS won’t change its tune rapidly and we do get a fairly solid trough out of this, with more rain and chill then we’ve been seeing. Its been awhile since we’ve had a nice, wet and chilly spring since the parade of them that we had in the mid and late 90’s, hopefully this is a good start.

  25. winterhawk says:

    Oh boy!!! They’ve polished the turd!!!

  26. Derek-West Gresham says:

    No because there was snow down to levels below 2000ft in Oregon. I saw some wet flakes, I KNOW what they look like, during a very heavy shower. BTW I am not using the stupid GFS alone, the BRAND NEW REFORMATTED GFS as well. Please notice that!! ugh..

  27. I’m sure, Derek, that we made it quite clear that convergence zones can bring the snow level a bit lower than expected. That is one of the reasons they are notoriously tricky and difficult to predict. Down here in Oregon, however, our forecasts panned out pretty much right on the nose as far as snow level is concerned – maybe even a bit higher.

  28. winterhawk says:

    Freaky things are just that. Freaky. Microclimates and convective activity can cause all kinds of monkey wrenches in a large scale forecast. There’s no point in trying to pin them down.

  29. I fully expect that on the days the GFS is predicting colder air, it will swing them around to something more reasonable as they get nearer. Even one to two days out, the GFS this time of year can be pretty innacurate if you are looking at temperatures and other values exactly as it shows. For example, looking at the IGES I see that it should be 51 degrees on Friday for a high temperature. However, being that it is late March, with a bit of a southerly breeze, on the south side of the upper-level flow, and the fact that it will be dry, I would probably forecast a temperature along the lines of lower to mid 60s. The weather models are not there to do the predicting for you – common sense and a variety of environmental variables must be taken into account while using the models for guidance.

  30. Derek-West Gresham says:

    One more note for all those who assured me that snow would not go below 2000ft in the last cold spell…up in central Washingon at 1200ft in the C zone there was 6 inches of snow. So freaky things can and do happen.

  31. winterhawk says:

    I’ve seen the nuts and bolts of the 00z. It’s a ridiculous run. A true outlier.
    Like Justin said, this looks like a classic early spring trough. Heck, April/May of 2003 saw a parade of these lows through most of April/May. It seemed like every 4-5 days it was a new round of convective activity. Next week’s low is so common it even has a name given the fact that these seem to always time themselves during Oregon’s spring break. Ridging is almost guaranteed during the following week as Washington always seems to benefit from waiting.

  32. Derek-West Gresham says:

    http://www.cascadeaccess.com/~mnelsen/Models/avn00z500mb.html
    No 500mb support? hmmm I see plenty, but thats for the 6z to decide I guess. šŸ™‚

  33. Haha, Mat, that reminds me tonight…I was in the parking garage leaving work and I pulled out very slowly. This car was about to drive by – which I couldn’t see due to a massive SUV to my right – and they were going too fast. They slammed on the brakes and skidded several feet due to their studded tyres. Not only are they not necessary here (as well as the fact that there are non-studded alternative tyre types that are just as or more efficient) but they wear down the road and are actually more dangerous on bare pavement.

  34. Derek-West Gresham says:

    00z GFS in particular winterhawk. Note my last post about this is what I see..but this is what I know will happen. I do have some logic in me. šŸ™‚

  35. Justin says:

    No chance of snow with next week’s system, missing 500mb dynamics. Just a typically cool, chilly early spring airmass, with good snow in the mountains down to 2000 or 2500′.

  36. Most weather forecasters do not take each model run directly into account – it takes several model runs to smooth things out and come to agreement. This time of year the GFS loves to forecast lower temps than what we will actually see, happening time and time again. For that reason, it is better to simply forecast a more reasonable temperature – especially when dealing with day five and beyond – and then make minor tweaks and adjustments as the day gets nearer. Nine times out of ten you will be much more accurate with this approach. Thus I am ignoring the crazy GFS runs at this point – besides, there are many other models to look at! šŸ™‚

  37. Mat says:

    I laugh every time I hear studded tires on road now. Ridiculous!!!!! East coast, they laugh at us.

  38. winterhawk says:

    Are you looking at the 5,384 hour GFS?
    It does show a nice omega block with an undercutting SW jet at hour 5,200.

  39. Derek-West Gresham says:

    “And while one year we may have had snow down to 1000 ft in April, it does not happen very often and we need a very cold airmass to support it.”
    Also nobody saw this coming and the airmass wasn’t that cold but something freaky happened, it might have been -6 850mb temps I think.

  40. Derek-West Gresham says:

    “What I do see for the coming week is lifted index values close to 0, which could give us a wee bit of thunder and lightning. 850mb temps during this time are right around -1 to 0C, so don’t expect any snow mixed in.”
    Not to be rude but your wrong. For one most runs get it down to -8 to -9 and sub 516 thickness which is almost certain snow any time of year. I acknowledge that GFS is likely overdone, very likely infact, but what it does show is a 1000ft snowlevel or perhaps lower. Expect it to correct itself but that IS what is says.

  41. Mat says:

    With La Nina next year, could be a very exciting winter. This year is over for snow. I predict 2 feet next year total. It’s already setting up. Keep fingers crossed for some crazy east winds. Its going to happen.

  42. winterhawk says:

    The trough for next week looks like a classic early spring, cold, upper low. The GFS is out to lunch on the 00z. Given the fact the apex of this trough is still 180+ hours out, the thickness progs are laughable. This will be similar to late March/early April of ’99 if it does actually verify. That was last year in which the studded tire restriction beginning April 1 was pushed back 15 days due to the anomalous cold and snowy weather.

  43. Again, right now, I still don’t see any chance for snow below 2000 ft or so during the next few weeks. And while one year we may have had snow down to 1000 ft in April, it does not happen very often and we need a very cold airmass to support it. Something which, at this point, I just don’t see. Also, most likely the snow that most people seemed to see in the hail showers was just lighter hail – I had the same thing here too. Not quite snowflakes. Though I don’t doubt that Cherie had some snow mixed in, as her temperatures were quite a bit lower (around 40 compared to mid to upper 40s out here).
    What I do see for the coming week is lifted index values close to 0, which could give us a wee bit of thunder and lightning. 850mb temps during this time are right around -1 to 0C, so don’t expect any snow mixed in.

  44. Derek-West Gresham says:

    First of all Antipex I am not predicting snow for the low lands but dont forget that there was sticking snow at 1000ft and slightly under on April 15th last year and it was unexpected.
    Now onto the forecast for next week. The old GFS and new GFS are both latching onto the idea of a very interesting week. The old one is insane and probably would support some snow showers for even me…lol The new one is slightly more conservative and is borderline..but what I expect is very heavy showers with hail/wet snow mixed in/heavy rain/lighting…etc It looks quite active. If this trough verifies it will be one of the most vigerous ones in late season history for PDX in a long time. It shows thickness below 516 for days on end and 500mb heights at like 524dm or something.

  45. Gregg-Troutdale says:

    Thanks for the update Mark.

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