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gb
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PostThu Jan 19, 2017 12:44 pm 
Get your picnic basket and head up into the mountains the end of next week as the freezing level looks to rise to 10-12,000' for the first time this winter. For a while cool temperatures may persist east slopes and there should be a nice refrigerated fog in Eastern Washington.

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Pyrites
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PostThu Jan 19, 2017 11:55 pm 
Makes us avalanche weinies nervous.

Keep Calm and Carry On? Heck No. Stay Excited and Get Outside!
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Bedivere
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PostFri Jan 20, 2017 6:17 pm 
gb - where do you get your long-range forecasts from? I'm not seeing any indications of this either in the forecast or forecast discussions from the NWS and NWAC doesn't predict that far out... http://forecast.weather.gov/MapClick.php?zoneid=WAZ568

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gb
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PostFri Jan 20, 2017 7:33 pm 
For the long term forecasts I look at The 500mb GFSX as presented on Unisys. The easiest model to look at for long term macro scale wx is "500 mb heights/SL pressure". Three days later, the warming now looks even more dramatic towards the end of the month. Now looking at 14,000 foot freezing levels and record 500mb winter heights just along the coast. While 5000' temperatures may not seem that warm, at high elevations it will be corn snow or bust.......or a picnic. I'd bet Eastern Washington will be cool and foggy to some elevation. The ridge extends by that time all the way from Southern California through BC and well into the Yukon and NW territories with 6000' freezing levels at least 2-300 miles into the NW territories. The Cascade snowpack is now near normal but will fall to 70% or so of normal by the end of January.....

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AlpineRose
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PostFri Jan 20, 2017 9:41 pm 
Whoa. I get my short term forecasts from NOAA, even though I understand its limitations. The interface is easy (very important) for me to use. The current WA near-term forecast (1/27-2/2 and 1/26 - 1/30 ) is for below normal temps and precip. How does that compute to 14,000 ft FLs and the 70% snowpack reduction by the end of January?

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Bedivere
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PostSat Jan 21, 2017 3:49 am 
Okayyyy... I have no idea what that is. Whatever it is I sincerely hope it's really wrong. But, I think I understand what gb is saying about snowpack - we're at 100% now but the snowpack should continue to build. If we get no new snow by the end of January the current amount of snow would translate to 70% of normal at that time. That seems like a helluva lot of snow should be falling in the next ten days... Perhaps gb is expecting some melt if it gets that warm?

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Jake Neiffer
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PostSat Jan 21, 2017 8:38 am 
FWIW, the 6 to 10 day & 8 to 14 day outlooks are both predicting below normal temps and below normal precip 6 to 10 day outlook 8 to 14 day outlook

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gb
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PostSat Jan 21, 2017 9:02 am 
Exactly, on climatology of the snowpack which one can look up every 1st and 15th of the month on the www.nwac.us website We get average snowfall of 500-550" of snow annually at the heavier snowfall west side mountain areas. December and January are very important to that total snowfall. The last half of December and thus far in January it has been much colder than normal and as corollary, much drier than normal. California meanwhile is having record January precipitation while Northern British Columbia is basically bone dry and has until the last couple of days been extremely cold. Accordingly, there is an avalanche warning for all of the mountains of British Columbia north of Golden with human triggered full depth avalanches likely anywhere the snowpack is less than 150cm, which is most everywhere. If after we were under Arctic high pressure we go under a high amplitude ridge we will fall behind on snowfall and snowpack depth. It probably won't melt much even if it gets warm with overnight freezes and short days. The 500mb charts that I look at occasionally or more when trip planning or when interesting represent but one of several Global Forecasting Models. The NWS, of course, takes the time to look at all of the models and has much more sophisticated graphics than what can be found on the web. The current 500mb charts and precipitation models show some precipitation in Washington the next 3-4 days and temperatures in the mountains look near normal through about Friday morning. A high amplitude ridge then begins to build in after that. Looking out ten days (limit of the model) the highest freezing levels in Washington look to be Saturday-Sunday. At pass levels and along the east slopes there will be a cool layer that would gradually erode as time goes on in the mountains but the cool air would build in the lowlands under stagnant high pressure. That results in fog and cool air building up at low levels. (This condition would represent what would happen at our latitude and location absent outside weather influences - just as Arctic air builds up in more northern latitudes in winter.) So warm aloft and cool at the surface. The shape of the ridge in the models will vary in each succeeding run as well the amplitude of the ridge for farther out time periods. But the ridge being built is a major feature and is highly likely to exist in some form for the period after about Friday. Further, it may be very difficult to get rid of because a deep trough extends in the eastern half of the US all the way to central Florida. Tallahassee may see some snow, we'll be warm aloft and so will be northern Europe. The pattern could be long lasting.
This image will change with each succeeding model run every 12 hours and the shapes depicted in the model and to some degree their significance will also change. But I doubt the overall pattern will be much different. Real meteorologists look at a number of different forecast models and know which ones have performed best both recently and in certain situations (like forecasting snow in Seattle). You can also look t what are called "Spaghetti plots" that go out 15 days and plot the different 500mb expectations from the different models and from varying the input into the models (like looking at Climate Change). When the various models align reasonably well the spaghetti plots and longer term forecasts are better, when scattered they are near meaningless. Obviously, they get more scatter as they go farther out in time and are more scattered in different situations. https://www.esrl.noaa.gov/psd/map/images/ens/ens.html Looking out fifteen days, the average of the 500mb plots show the trough along the east coast becoming less deep and the ridge along the west coast retrogressing, allowing systems (if this happens) to once again begin to drop along the west coast as they have been not only this winter but as they were doing after mid-summer, too. So maybe....the ridge won't last that long and hopefully it is currently over forecast.

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nordique
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PostSat Jan 21, 2017 10:10 pm 
Thanks, Gary, great information!

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