Stubborn ridge to continue … for awhile … NWS

 

.LONG TERM...(Monday night through Saturday)
Issued at 225 AM MST Sun Dec 10 2017

The ridge out west will hang on through most of the upcoming week.
There will be a compact clipper type system survive a trip over
the top of the ridge and dive into the High Plains on Wednesday.
Cooler air arrives aloft in the wake of this system and it may
weaken the inversions just a tad but models have not been handling
this feature very well the past few days. A more significant
Pacific wave crashes into the ridge going into Friday.
Unfortunately there is no consistency with this feature this
morning. The best hope is the Euro which weakens but keeps this
wave intact as it swings across the Rockies Friday night. The GFS
splits the energy dropping a low down to the Baja while swinging
the northern split across the Dakotas. This second pattern is more
familiar lately so will probably need most of the week to sort
this out. Otherwise plan in dry conditions continuing.

GFS – US – 500mb – Loop

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New insights into the Ridiculously Resilient Ridge & North American Winter Dipole

A timely example: Persistent Western ridge, Eastern trough next 2+ weeks

In the coming days, a remarkably persistent weather pattern will begin to develop across North America and adjacent ocean regions. Characterized by strong high pressure near the West Coast and low pressure over the Eastern Seaboard, this “quasi-stationary,” high-amplitude atmospheric wave pattern will essentially become locked in place for at least the next 2 weeks. Patterns like this have a tendency to become self-reinforcing, lasting for much longer than more typical transient weather patterns and leading to prolonged stretches of unusual weather. This particular event will be no exception: California (and much of the West Coast) will almost certainly experience an extended, multi-week warm and dry spell, while much of the East Coast shivers through repeated blasts of cold, Arctic air.

~~~  READ ON  ~~~

From Mountain Weather Master Joe Ramey

Here is another emergence of the “Ridiculously Resilient Ridge” that we saw in 1995-96 winter and that led to severe drought across southern California and much of the Great Basin. Dr Jennifer Francis has talked about Arctic Amplification for many years now. Her hypothesis is with less hemispherical thermal gradient (due to stronger warming at higher latitudes), the jet stream weakens and amplifies. This leads to long persisting or ‘stuck’ weather patterns. Here is a quick summary of her theory: https://www.youtube.com/watch?v=_nzwJg4Ebzo

 

 

San Juan Mountains Weather Forecast ~ Friday, December 1, 2017 @ 11:05

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The full court press autumn blocking pattern (high) that has dominated our weather for such a long time continues to cover the west & drives potential Pacific storms to our north. I’ve seen this happen so many times especially in la Niña fall/winters so it’s no surprise, just hope for an occasional outlier storm and accept the dry and warm.

The Gulf of Alaska storm from last week was a victim of this high… and now what looked like a decent storm for the San Juan Mountains will be spitting a few inches of snow on the Central and Northern ranges with maybe a flake or two for the North SJ’s late Sunday/early Monday.

And the future doesn’t look so good either. The models I follow aren’t encouraging for precipitation events for the next ten days at least, but we all know how fast that can change. Looks like cooler weather through the first week of December and then a little warming. Things just look dry as a bone through mid month.

Ten Day Forecast GFS vorticity map.

 

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Watch the blocking pattern (high) develop over the west coast and dominate through the 11th of Dec. pushing all potential storm north and then dropping into the eastern U.S. 

Weather/Climate discussion with Joe Ramey, former NWS forecaster and now a Mountain Weather Master

November 2017 has felt more like October. I have been riding and hiking in shorts on many afternoons. Of course all climate sites in the region are warm and dry for the month. As of November 26 the warmth is impressive,ranging from 9.1 degrees above average at Aspen to +4.4 at the Durango airport. Dry conditions are widespread across the SW region for the last 30 days (1st attached). For November through the 26th, deficits run from -1.09 inches at Durango to -0.34 inch at Craig. You have to go up to central Wyoming (Riverton and Yellowstone) to begin the find climate sites that have above average monthly precipitation.
The near-record warmth will be modified tonight, Monday night, as a cold front sweeps over the region. The southern and central mountains will be favored with a forecasted 2-6 inches of snow. The remainder of November looks dry with temperatures down 10 to 15 degrees cooler than Monday’s highs but still remaining above normal.
A significant change towards more winter-like conditions is currently timed for early next week. This storm is currently forecast to have a strong cold core and 150kt jet with significant moisture. If this storm does turn out to be that strong, it could be the start of the Colorado ski season.
Beyond 10 days we look to the state of the Pacific for clues to storm track and intensity. The northern Pacific basin, as measured by the Pacific Decadal Oscillation, has lost the record heat that has been in place since  2014. In the equatorial eastern Pacific, the Nino 3.4 region has been near -1.0C for the last few weeks (2nd attached). La Nina conditions are present and are expected to continue through the winter (3rd attached).
La Nina tends to produce a storm track across the northern tier of states and you can see that trend in the December and Dec-Jan-Feb outlooks (4th attached). Our climate record shows a snowy January often occurs during La Nina winters. Though the second La Nina in a row, like this winter, often is drier. Spring seasons after La Nina tend to be drier than normal.
Beyond the winter outlook the confidence decreases to near zero. Since 1950 we have had two La Nina winters in a row occur six times. The third winter is nearly evenly split, La Nina 3 times, El Nino twice, and ENSO Neutral once.
So the 12 month precipitation outlook (5th attached) beyond this winter  show no skill, as the entire nation is in the ‘EC’ or equal chances category. The 12 month temperature outlook shows its typical strong tendency towards climate change with above normal temperatures for much of the nation except across the northern tier (assumed storm track) this winter.
So today may be the last really mild day of fall. Get out and enjoy!
Joe
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San Juan Mountains Weather Forecast ~ Sunday, November 26, 2017 @ 09:59

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With the ridge of high pressure still spread over the west, temperature records in some of the lower elevations like Grand Junction could be broken today and tomorrow (low to mid-60’s), records set early in the last century.  The high pressure ridge will begin to move east today and by Monday evening the upper level air flow will transition from NW to SW accompanied by high cloudiness & gusting winds. The low pressure disturbance will arrive by Monday evening.

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Models seem to be in agreement of a fast moving closed low building over the 4-corners but lacking good moisture. Orographic lift over the San Juan’s should be enough dynamic to squeeze a few inches (2-5″) from this fast moving system above 11,000′ favoring southwest aspects. By Tuesday afternoon most of the actions will be over.

Late Wednesday there’s another system moving into the area into Thursday morning. Models are not in agreement on this storm so it’s a wild card.. Late Thursday  high pressure builds back through the end of November but looking out into the Pacific there is a big storm system developing in the Gulf of Alaska and could bring decent moisture to our mountains as it slides down the west coast and moves onshore by next weekend. OpenSnow below seems excited about it …  Stay tuned.

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From OpenSnow

Between about December 3-6 expect the potential for snowflakes each day, with the deepest amounts in the southern mountains.

The map below shows the average precipitation forecast from multiple models through December 5th. To estimate snowfall for the December 3-6 storm, multiply the numbers by about 13 and subtract a few inches for the potential storms on November 27-28 and 29-30.

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The southern mountains are favored (Wolf Creek, Purgatory, Silverton, less for Telluride due to the southwest winds). Snow amounts in the south could be 13-26 inches.

The graphic below shows 51 versions of the precipitation forecast for the European model for Wolf Creek. The green bars at the bottom are the average of the 51 versions, and they top out at about 1.8 inches of precipitation or multiplied by an estimated snow-to-liquid ratio of 13-to-1, about 23 inches of snow.

San Juan Mountains Weather Forecast ~ Wednesday, November 22, 2017 @ 09:10

Warm/dry weather on tap for the rest of the week and into the middle of next week.  The large high pressure covering the innermountain west is forcing any potential storm system to the north. During the low snow years (some call it drought) 76/77, 80-81 and 89-90 all had similar very large high pressure (called it the Great Basin High then) systems that brought the same conditions that we’re experiencing from this La Niña year so far. Look at the map below to see how the high pressure is splitting two low pressure systems know as an Omega Block.. see the Omega sign?

It looks like there are a couple of storms lined up in the Pacific that should arrive by the end of the month hopefully bringing cooler temps and moisture.

Happy Thanksgiving

 

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San Juan Mountains Weather Forecast ~ Monday, November 20, 2017 @ 09:30

 

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Our weather through mid-week of November 26-30th looks dry and warming up with a probable 60 degree Thanksgiving Day at 7,000′!  But a strong chance of a pattern change is coming our way next week around the 29th according to various models especially the European that you can see below from OpenSnow.  No snow on the horizon for the San Juan until then.

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OpenSnow

The good news is that most models show a more active pattern setting up next week, with the first storm arriving on or near November 29th. Here is the average forecast from 51 versions of the European model. Blue colors indicate cooler and stormier weather.

2017-11-20.009.jpgThe even better news is that most models show a continuation of the active pattern as we move into early December. Again, the average of 51 versions of the European model.

2017-11-20.010.jpgNone of this means that we are guaranteed big snow on November 29th and every day after. It simply means that the weather pattern will likely become stormier and colder across the western US, and this could translate into more consistent snow here in Colorado.

 

San Juan Mountians Snow & Weather Nowcast

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Well, a new ski season is happening and the San Juan snowpack is so typical.  Early October snowfall, cold mean daily air temperatures that drive the faceting & weakening of the new snow and early season backcountry folks who are looking for happiness of the turning ski…

Too often many backcountry riders don’t have their guard up yet.  Mostly thinking of the turn, suffering from ‘POWDER SHOCK‘.  They’re not using their avalanche eyeballs yet.

Already a death this past week (one in the Montana avalanche) with the new snow and high winds which are two important variables that are often ignored/discounted or not yet morphed into thoughts or warnings because of powder shock and maybe the stampede of the herd mentality.

One needs to think before chasing the turn.  It’s a new year and each year is a new experiment.  Most folks put new batteries in their transceivers, check that their bindings aren’t set on FEMUR & stock up on ski swap woolies, but somehow don’t spend as much time considering the changing environmental variables or reining in ego and desire…  Make your forecast for the day, but rely on your NOWCASTING skills for an ever-changing environment.  Be there now…

chant the conservative Republican mantra…..               J.R.

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Mark Rawsthorne photo

San Juan Mountains Weather Forecast ~ Thursday, November 15, 2017 @ 09:15

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I have been watching mid-range models this week advertising a Pacific storm arriving in the Colorado mountains late Thursday and until late last night the forecasts favored the central/northern mountains and still do, but the latest model runs show the storm energy dipping a little further south. It looks decent for a possible 4-8″ of snow in the higher elevations above 11,000′ and probably rain/sleet/turning to snow early Friday morning for the lower north & west valleys of the San Juan.

GFS – US – 500mb – Loop

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This Pacific trough that has been sliding down the west coast and now coming onshore will be on us very late Thursday/early Friday through Friday evening … Storm energy looks good with a combination of a cold front and a 140+ kt jet meeting over the mountains Friday with potential high precipitation rates.  The west-southwest winds will probably be ugly occasionally but beneficial for orographic lift favoring snow production on WSW aspects of the higher terrain (above 11,000′) which could stack up, if it isn’t blown away.

The weekend and probably through Thanksgiving week will see a return of the warm/dry la Niña conditions.

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OpenSnow

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Here is the University of Utah ensemble forecast showing multiple versions of the American GFS and Canadian models for Red Mountain Pass, in the southern mountains roughly between Telluride and Silverton. The forecast range is about 3-19 inches with an average of 10 inches. These numbers are trending higher compared to the forecast a few days ago.

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