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gb
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PostSat Feb 23, 2019 7:43 am 
Like the Weather party.gif Here, in a nutshell, is what it currently looks like to the Seattle forecasters - it is worth a read, because it is actually pretty funny. (This is not just one forecaster but involves a discussion among many meteorologists before issuing the morning forecast.)
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The big headache in the forecast comes with Sunday night and through the day Monday as snow levels plunge again without much in the way of recovery. Model solutions have been slightly schizophrenic when it comes to precip...precip type...how far north it will reach and...come to think of it...most forecast details. Prior solutions maintained a somewhat consistent trend with precip remaining generally well south of the Seattle Metro with the occasionally trending wetter or drier...but no major deviations. That changed with the 12Z ECMWF yesterday...apparently advertising the potential for significant snowfall. Fortunately...the 00Z ECMWF has backed well away from that solution...making it a significant aberration in the forecast trend. As such...primary thinking this shift is to return forecast to a state similar to 24 hours ago...ignoring that 12Z solution...especially given that 00Z solutions are favoring those pre-established trends. All that being said...there still is a prospect for lowland snow during this time period but total accumulations at this time look to be less than 2 inches for the entire 24 hour period starting after midnight Sunday night through midnight Monday night. As it is just coming in at the time of this writing...the 06Z GFS has any precip being well south of the CWA for this time period...turning the snowpocalypse advertised in the 12Z ECMWF from yesterday into a big old nothing burger. The main reason of pointing that out is to display the wide spectrum of solutions out there. Until a consistent set of solutions present themselves...persistence forecasting in the vein of the already established trend of prior solutions seems to be the safest bet. Tuesday looks to see a drying trend continue...even though current ECMWF is in some disagreement...easing on POPs for the first half of the day then bringing a slug of moisture for the evening and overnight period. Snow levels would still allow for snow or mixed precip during this time...but given that the models are struggling with Monday...not sure if it would be proper to assign much confidence to Tuesday either. SMR .LONG TERM /WEDNESDAY THROUGH SATURDAY/...Models agree on an upper level low off the coast influencing the weather over W WA Wednesday...they just disagree on how much moisture will be with it...the GFS generally dry with some showers possible while the ECMWF is rather juicy. Opted to split the difference. The good news is that snow levels recover rather nicely...climbing back above 1000 ft and as such...any precip would be rain. The best part is that they stay that way for most locations throughout the long term forecast period...hopefully marking an end to the threat of lowland snow for this winter season. Fingers crossed. This low pushes through the area Thursday with rain expected. Getting into Friday...models once again fall into disagreement...with the GFS bringing a pretty sizable ridge over the Pacific and thus going for dry conditions. The ECMWF on the other hand ends up retrograding the aforementioned low...pushing it back out the Pacific and thus W WA remains dry as this system reloads so it can bring rain back to the area late in the weekend. To be honest...this solutions just looks odd. Opted to lean more toward the GFS...but tipped my hat to the Euro with weak POPs under 20 percent...just in case. SMR

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neek
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PostSat Feb 23, 2019 9:21 am 
Ah, chaos. Stupid butterflies. A question I've had for a long time: why don't forecasts come with some indication of confidence? Is it that most people don't know what to do with a statement like "we are 60% sure there's a 40% chance of rain next Tuesday"?

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Chief Joseph
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PostSat Feb 23, 2019 10:18 am 
One could roll some dice and be about as accurate, at least for mountain forecasts more than a day or so out. They were calling for 1-2" of snow here and we got 7-8".

Go placidly amid the noise and waste, and remember what comfort there may be in owning a piece thereof.
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gb
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PostSat Feb 23, 2019 11:11 am 
neek wrote:
Ah, chaos. Stupid butterflies. A question I've had for a long time: why don't forecasts come with some indication of confidence? Is it that most people don't know what to do with a statement like "we are 60% sure there's a 40% chance of rain next Tuesday"?
Which is the value of reading the NWS Forecast Discussion. The forecaster that writes the discussion usually makes a statement about reliability at the point in time of the forecast, trends, and differences in various forecasting models. This looks to be about the most difficult situation for forecast models to resolve because it is so highly unusual, and looks even more difficult in a couple of days, and perhaps going forward, as there is essentially a battle royale between a modified arctic airmass that is driven by a very strange but persistent polar jet and an undercutting warm moist subtropical jet that appears that it will be undercutting the ridge to our west, and eventually portends a likely Pineapple express not far to our south. This shows the extremely strange Polar/Subtropical jet as forecast for Tuesday morning. What a bizarre loop in the Jetstream.
The local situation of the exact position of low pressure systems off or near the coast and the temperature and depth of any modified Fraser outflow add to the confusion. It is right to say in this situation that the weather forecasts may only be valid day to day or even not at all.

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PostSat Feb 23, 2019 12:51 pm 
So what's the deal then? Its gonna snow sunday night??

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neek
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PostSat Feb 23, 2019 12:58 pm 
Chief Joseph wrote:
One could roll some dice and be about as accurate, at least for mountain forecasts more than a day or so out. They were calling for 1-2" of snow here and we got 7-8".
Yeah, one can always find failures, despite the steady increase in forecasting skill since numerical modeling became a reality in the 50s, not to mention step functions in accuracy such as ensemble forecasting in the 90s. BTW it's usually a dart board in the analogy. The joke never gets old but of course it's wrong and in fact countless lives have been saved by weather services (when people actually listen). Thus gb's point that the uncertainty of the next few days does qualify as news in the man-bites-dog sense. I'm just hoping we don't get another big dump next week. Enough already!

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PostSat Feb 23, 2019 2:07 pm 
For me the relevance beyond the amazement with this situation comes in evaluating the opportunities for activity. I finally skied day before yesterday after a ridiculously warm December/January and persistent avalanche weakness when colder snow arrived in early February and also back in January. My friend at Alpental tells me that the snow at her place is still really unconsolidated and has sent me a bunch of funny videos of her dog after the big dump. Another friend described skiing with 4' of loose snow on rocks and dirt, and had a whale of a time dealing with Alder...... I don't know about Cougar Mountain, but my guess is all trails have snow coverage including Tiger and in valleys like Darrington and Baker Lake, and in the Eastern Olympics. Ashford still had something like a foot. With low elevation roads snowed in it is also not realistic to backcountry ski other than the main corridors and ski areas.

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Malachai Constant
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PostSat Feb 23, 2019 3:44 pm 
We live on Squak and skied across early in the storm the snow is consolidated now and crusty. There is over a foot at Forest Rim @1200’. Tiger has at least a couple feet on WT3 we went up Section Line Thursday. Cougar has at least a foot at the Radar Peak Parking lot which has not been plowed nor the road. Today we have had rain, snow, gravel, and hail. Mabel a half nice stuck yesterday but has melted higher up the trees are snowy.

"You do not laugh when you look at the mountains, or when you look at the sea." Lafcadio Hearn
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grannyhiker
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PostSun Feb 24, 2019 3:35 pm 
As with a policeman's lot, a weather forecaster's lot is not a happy one. Especially here in the NW!

May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view.--E.Abbey
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gb
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PostMon Feb 25, 2019 7:03 am 
The value of experience in evaluating forecast model runs: NWS Monday:
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So...here is Monday...the highlight of previous discussions for some time...and models remain consistent in the trend that the passing system will indeed remain to the south of the CWA today keeping dry conditions in place for the vast majority of W WA. In reflection though...this provides a good learning opportunity to keep in mind the broader trends of model forecasts throughout the run up to an event and within that context then consider some of the more dramatic solutions that may arise. Both the GFS and ECMWF show some precip creeping a little northward this evening...each model retaining their characteristic nature with the GFS being a bit more restrained and the ECMWF being a touch overzealous. Opted to split the two...allowing for some slight chance pops to be present in some zones...but expecting little or nothing to come out of it. Snow levels remain near sea level...so anything that does fall will take the form of snow. Models agree on continued dry conditions for Tuesday but start to differ for Wednesday morning very similar to how they differ for today and this evening. As such...opted to lean toward the GFS solution and while it too eventually brings in some precip chances by Wednesday afternoon...these chances look to be minimal with pops only getting into slight chance range. The upper level low responsible will finally push to the east through the day Thursday according to the GFS while the system lingers off the coast into Thursday night. Once again...opted toward the more progressive GFS if for not other reason than what could best be classified as event fatigue. As already briefly touched upon...snow levels throughout the short term will have difficulty recovering...not straying too far from sea level for most locations and certainly remaining below 500 ft through Thursday. So...any precip that falls...even though odds are against it..will fall as snow. Afternoon high temperatures will remain in the lower 40s...so really no chance of anything that does fall accumulating or hanging around for any amount of time. SMR

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PostTue Feb 26, 2019 7:18 am 
"Fingers crossed." Yes it would be great to have that kind of "flexibility" in job performance. Being able to say "its not my job" to be accurate would be great. My observation over the last 3-4 ski seasons is most of the major storms (with significant mountain snow accumulation) have been missed in the near term (2-3 days out) forecasts - but were forecasted correctly in the long term (4-6 days out) forecasts. It seems there is a reluctance for forecasters to believe near term weather models that go against the "it will be warm and never snow again" narrative. That reluctance hasn't really applied to the the long term models because those models are "accepted" to be more "speculative" - so when they contain a prediction that goes against the narrative no one cares.

Out There, carrying the self-evident truth I am endowed by my Creator with unalienable rights of self-defended Life, Liberty, and the pursuit of Happiness.
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gb
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PostThu Mar 07, 2019 6:17 pm 
Good observations, Vertec. Forecasting snow in Seattle is a crap shoot because the conditions are usually so marginal. Fraser outflow, a system to the south, low level on, or offshore, and convergence zones all wreck havoc. Nearly every snow event in Seattle is a crapshoot and this is widely publicized. This particular forecaster has a great sense of humor and is fun to read. After referring to this cold weather as a "bad house guest who doesn't know when to leave", he went on to say this in this afternoon's discussion:
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Temps in the extended actually look to rise with highs Sunday approaching 50 in many lowland locations. Likewise...snow levels throughout this period look to remain above 1000 feet. While all of this seems promising...much the story of this winter has been models agreeing on an optimistic scenario for days 7 and 8 only to yank the rug out from many an unsuspecting forecaster and perpetuating this slog of a winter. Still...with it now being March...one would hope that spring would indeed be on the doorstep...so there is reason for cautious optimism. Although...not helping this argument is that there will not be a whole lot of fluctuation in overnight lows...maybe a little bit of headway into the mid to upper 30s Monday night/Tuesday morning...but the remaining days look to be ranging in the upper 20s to lower 30s still...so the ritual scraping of frost and preheating the car each morning will likely continue. SMR

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PostFri Mar 08, 2019 6:09 am 
Back to the original question-yeah I think it would be fun to a weather forecaster and I appreciate a little levity in the forecast discussion. I would like to have the expertise to analyze the data they are assessing on a short term, long term basis as well as analyzing climate change. As for accuracy, I sometimes think people want the exact number of raindrops, snowflakes falling in a specific spot-I think in general accuracy is excellent for 3 to 7 days out if you take into account the Forecast Discussion and apply some common sense and a little local knowledge if happen to have it.

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PostThu Mar 28, 2019 9:25 am 
Pretty tough right now to have anything in the way of a reliable forecast. Probably not very wet, but other than that, make a guess, win a prize. NWS Discussion this morning:
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SYNOPSIS...The front that brought pockets of light rain to the area overnight is dissipating over northern portions of Western Washington early this morning. An upper level trough will give a few mainly afternoon and evening showers to the area through Friday and perhaps into Saturday, mainly over the mountains. A system may bring a chance of rain to the area Monday into Tuesday. Temperatures will likely remain near or slightly above normal for the next several days. SHORT TERM /TODAY THROUGH SATURDAY/...The front that moved north through the area overnight is now over the northern fourth of the state and is dissipating as it moves toward British Columbia. Rainfall with this front was much spottier and lighter than what was anticipated a couple of days ago. As this front moves northward, the area will come under the influence of a slightly unstable but not overly moist air mass that is rotating around an upper low centered near 43N 132W. Most of the showers and thunderstorms associated with this upper low will remain well offshore. Short term models continue to have difficulty in this split flow regime we are seeing, especially Friday into Saturday. The ECMWF, put more emphasis on the southeastward movement of the blocking high aloft now over far NW British Columbia. Winds aloft over the area in the ECMWF model world are E to SE, 500 mb height rise to around 564 DAM, and the air mass is rather stable. The ECMWF world would result in, at most, only isolated mountain PM showers Friday into Saturday. The GFS/Canadian GEM model world has a completely different view of the world -or the Pacific NW anyway. The southern stream upper low over the SW Oregon offshore waters lifts northward to off the mouth of the Columbia River by Friday night. With more ample moisture, increased instability, and more diffluent upper level southerly flow, rather widespread convection is seen over the mountains, mainly during the PM hours, that possibly shift into the lowlands as they rotate around the offshore circulation. Either solution is plausible. So the forecast at this time follows the middle road. A slight chance of late afternoon and evening thunderstorms was maintained for the south portions of the area today and for the southern portion of the Cascades on Friday. Highs both days will be in the 50s to lower 60s and lows will be in the mid 30s to mid 40s. The forecast for Saturday will either be partly cloudy with no shower activity per the ECMWF or quite showery per the GFS. Models are sticking to their guns and are not converging on a solution. The middle ground may not be a good forecast - but with either solution being plausible in this split flow regime is the best way to go for now. The forecast will be for partly cloudy conditions, a rather low chance of mainly PM mountain showers, and temperatures in the upper 50s to mid 60s for daytime highs will be maintained into Saturday. Albrecht

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