Wednesday, April 4th, 2018

..NOW THROUGH THE WEEKEND...
Mild weather is expected through Thursday. A few light showers are possible today and Thursday, mainly well north of Interstate 80. A strong atmospheric river will impact northeast California and western Nevada Friday into Saturday, bringing periods of moderate to heavy rain, high elevation snow, gusty winds, and concerns for flooding along rivers and streams.

..MORE DETAIL...
(Translated from NWS but added in some detail and our own outlook)
A strong late season Atmospheric River (AR) will bring periods of heavy precipitation to the region Friday and Saturday. With a strong sub-tropical influence and the jet stream (cold air to the north of this) forecast to stay well north of the region during most of precipitation event. Precip will fall
primarily as rain, even in the higher elevations above 9,000 and 10,000 feet. The main concern continues to be flooding, both for small creeks and streams, and for main stem rivers. There is a flood watch in effect from late Friday afternoon through Saturday for the Sierra and the Sierra foothills.

It is late in the atmospheric river season and this AR is forecast to be solidly in the strong category, which is quite rare for this time of year. PWAT (moisture) and IVT (moisture + transport) anomalies are on the very high end of their respective scales for this time of year, and between Friday afternoon and Saturday morning, several inches of water or more will fall on thew west slopes of the Sierra Nevada.

Precipitation will begin to move into the Sierra and NE California by Thursday night with periods of light to moderate precipitation through Friday afternoon as warm advection precipitation begins to push into the Sierra. A 6-12 hour period of very heavy precipitation is expected Friday night into Saturday morning as the core of the low pressure nears the Pacific Northwest coast, bringing increased forcing to the moisture laden
environment over the Sierra. The very warm temperatures aloft will promote more efficient warm rain processes and will likely result in impressive rain rates Friday night (heavy rain and flooding likely).

Current forecast for QPF is up to around 3-4 inches along the Sierra crest with 1.5-2 inches along the immediate lee of the Sierra and 0.5-1.0 inch spilling into western Nevada. During the period of heaviest precipitation the jet stream and the cold core of the low is forecast to remain well north of the
Sierra. Very warm subtropical air is forecast to move into the area from the southwest with mid-level temperatures potentially rising to around +3C to +5C during the heaviest precipitation. This will likely push snow levels to 10,000+ to 11,000 feet later Friday through early Saturday. CM

NEXT WEEK...
Early through mid next week looks busy with storms, colder this time, with snow levels to resort bases... Moderate to heavy snow is expected Tuesday and again next Thursday (9th/ 11th), followed by some sunshine and warming. After the 15th/ 16th or so we see high pressure build in across the eastern Pacific and west US coast, with sunny skies and warming temperatures, quite spring-like. CM
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Fri, August 31st, 2018 (begun this article)
Sunday September 23, 2018 (I finally finished it!)

MODOKI EL NINO = bad, REGULAR EL NINO = usually good, WEAK EL NINO to ENSO Neutral = can be good (due also to other factors)! There are many possibilities with the last one (the one we think is coming) but we will nail it down for you! 

Central and Western Colorado, Aspen-Snowmass to Durango
FALL and WINTER SEASON FORECAST FROM SNOWFORECAST.COM!

...WHAT IS THE FORECAST?...
OCTOBER - (Slightly above average snowfall and below average temperatures) Early season cold and October snows are expected for the ski resorts, with most snow and coldest temperatures being east of Vail Pass and the divide, but more than the average of 10" of snow that Aspen averages in town (more on the mountain), as storms drop in out of Canada for the most part, carrying the bulk of moisture and cold air to northern Colorado and to the east of the Vail Pass and the divide. There will be enough cold and snow to test out snowmaking equipment. The early snows will open the usual 10,000ft+ resorts early, and help to chill the soil for good base building as we move into November... We also expect the usual transition season cut-off and closed low pressure systems to move in from the west and deliver some surprises (snow then best for Aspen and southwest Colorado)... "Cut-off" means the low is cut off from and not being pushed around by, the storm steering flow (usually at 500mb).
NOVEMBER - (Near to above average snowfall, and below average temperatures) Near to above average early season snow overall across the region and no snow level issues, with cold systems out of Canada diving through and hitting all areas, as high pressure ridging offshore of the west coast allows storms to develop and move south from out of Canada, moving in with below average temperatures and some extreme record cold. We expect some early opening days on good bases. Snow is expected to be well preserved as colder than usual air helps to protect the snow...
DECEMBER - (Near to above average snowfall and near to below average temperatures through mid December, then dropping off to near average snowfall and near average temperatures in late December on some good bases). Some significant snowfall events through mid and maybe into late December, and near to below average temperatures should combine to be great for Christmas-New Year skiing/ boarding, then incoming storms start shifting to the south on a different storm track, with lighter snows for Aspen and good for southwest Colorado as we move into the holidays.
JANUARY ONWARD, MORE COMING SOON - ? Stay tuned, but a brief synopsis: Dry for most of January with above average temperatures as high pressure ridging builds in, and the east coast gets hammered with cold and snow. Storms return in February with near to above average snowfall and near average temperatures for Aspen-Snowmass, then March through the rest of the season looks near to warmer than average in temperature, with below average snows. April could produce some big storms and powder days to pass through the region, building the late season snowpack. More details are coming, and I will be naming resorts and forecasting long range snow totals. CM

...WHAT ARE THE FACTORS AND OPINIONS?...
Here are my August 31 observations: An El Nino that "wants" to happen, but meager warming to even some cooling in the key Nino regions (recent), and a mostly neutral status (currently) is not showing much hope for any El Nino pattern that may be classified as moderate or strong. In fact, I will say that we will not see a moderate or strong El Nino SST pattern this 2018-2019 season, and the NOAA forecasted weak El Nino is looking like a "maybe".
And, my September 15 observations: Latest guidance indicates that the El Nino SST anomaly will be weak, at best, in my opinion. Here is why: Cooler eastern Pacific waters (Nino 3.4 region)/ Subsurface waters heat content (180-100W Lat) has decreased/ and the current pattern is showing mostly a general cooling and not warming overall, though in the last 7 days, eastern Pacific surface waters off the coast of Ecuador (means "Equator") have warmed . Its mid September and this El Nino event should be a bit more evident. Its not. Even NOAA has backed off a bit with a 65% chance of El Nino formation, instead of the 70% they had called for early on in the summer when this anomaly looked more likely. For them to back off a bit like that indicates definite lost confidence, and this is not surprising, as I lost confidence in it occurring myself, back in July. Things work a bit slower in these large organizations, while us "loose cannons" (whatever in the hell that means) can blast off at will. Haha.


*An El Nino is still favored according to the above Climate Prediction Center chart*



*We have seen some areas of cooling in the Nino 1+2 and 3 regions, as this El Nino struggles to form. This is indicating cooling in the subsurface waters, which is a factor that is looked at for potential SST's*



*As of Sep 12, there is some warming going on again in the referenced "Nino 3" region, so overall there is a positive SST anomaly, but mostly less than +.5 (in yellow on the above chart), which is the threshold that needs to be met for 3 consecutive months before an actual El Nino pattern is recognized. For now we are in an "ENSO neutral" status.

SOLAR MINIMUM: In terms of sunspot activity, there is currently almost none, or even "none", zero, zilch, nada, many days. Decreased or zero sunspot activity also affects our weather patterns. The chart below shows how we are in a solar "grand minimum" right now:


We have seen some recent serious weather extremes this Summer of 2018, and have no reason to believe that we will not see similar extremes this fall and winter in North America:

From extreme heat in Europe, notably northern Europe:




To extreme snow and cold in August:

 NOAA: So to reiterate, NOAA (the National Oceanic and Atmospheric Administration) was forecasting a 60% likelihood for formation of an El Nino SST pattern this fall, and a 70% chance for the winter, 2018-2019, while now those forecasts are down to 50-55% and 65-70%, respectively. Large organizations like NOAA are not going to go backward on the forecast (decreased % chance), like this without very good reason, like, "its not happening like we thought it would guys"...

SNOWFORECAST.COM: At this point, a "weak" El Nino SST anomaly is the forecast from NOAA. I have believed since June that this would be a weak El Nino pattern that sets up, based on the afore-mentioned trend, but am now wondering if this El Nino will even show up at all. We think that the weak El Nino or no El Nino is going to turn out well for Aspen and southwest Colorado as it is combined with weak sunspot activity (solar minimum) for expected colder air (and stronger storms that reach the area) this winter overall. If an El Nino, weak, does form, it is looking more likely to be the Modoki version, which on average, sucks (dry) all across the western US. Thankfully, as a weak factor (there are other factors), a weak El Nino of any kind will have a "weaker" influence on the weather patterns we see this fall and winter, THANKFULLY. We are also looking (currently) at a weakly negative PDO (Pacific Decadal Oscillation, more of a long term state of ocean water temps), which will not help in the El Nino department. Neutral to "very weak El Nino" is what we are forecasting as we move into fall and maybe through the winter, at best +.5 which is barely classified as an El Nino. As well, with the Grand Solar Minimum, expect the unexpected, and so far, that has proven true in many parts of the world. How will all of these factors; Weak El Nino, or even "ENSO Neutral" SST anomaly, neutral PDO, GSM (solar), and my own intuition, affect the southwest and western Colorado forecast? Just scroll back to the top to find out!

Feel free to share this, but please cite credit to snowforecast.com. Thank you! CM

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Some References:
COLD AND SNOW:  https://www.theweek.info/index.php?newsid=3760 (Salzburg, over 1 foot of snow in August!)
HEAT:  https://www.washingtonpost.com/news/capital-weather-gang/wp/2018/07/17/scorching-scandinavia-record-breaking-heat-hits-norway-finland-and-sweden (90+ degrees in Norway, all time record high temps!)
Great resource for current SST’s and anomalies:
https://www.tropicaltidbits.com/analysis/ocean/
International Research Institute:
https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/?enso_tab=enso-cpc_plume
Latest ENSO Discussion:
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.php
Space Weather ("Solar Minimum"):
https://www.swpc.noaa.gov/products/solar-cycle-progression
NCEP model forecast SST anomalies (1 model forecasting La Nina):
http://www.cpc.ncep.noaa.gov/products/NMME/current/tmpsfc_Seas2.html
The ONE outlier model forecasting La Nina:
http://www.cpc.ncep.noaa.gov/products/NMME/current/images/NASA_GEOS5v2_ensemble_tmpsfc_season2.png
Loads of the latest SST charts from ESRL, knock yourself out:
https://www.esrl.noaa.gov/psd/map/clim/sst.shtml
Best anomaly chart (in my opinion):
https://www.esrl.noaa.gov/psd/map/images/sst/sst.anom.hov.gif

Detailed ENSO Discussion from NOAA:
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf
More info/ charts on Modoki El Nino:
http://www.jamstec.go.jp/frcgc/research/d1/iod/enmodoki_home_s.html.en
El Nino/ La Nina years/ ONI:
http://ggweather.com/enso/oni.htm
A GREAT resource for "no BS" historical ski season info:
http://bestsnow.net/
Latest PDO and history:
http://research.jisao.washington.edu/pdo/PDO.latest.txt