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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Mostly light additional snow, then a mostly sunny weekend, and  more snow next Tuesday and Wednesday (heavier)!

HOW ARE WE DOING (please contact chris@snowforecast.com or comment below)? Let us know please...

Light snow for most areas including Aspen, and  across southwest Colorado...

-The latest storm absolutely dumped RAIN and snow across southern California, is headed mainly along the Mexico border now, and taking a southern track... El Nino style, with a few" of snow across southwest Colorado to Aspen's mountains, under a moist southwest flow of moisture across the mountains, while most energy passes to the south

This coming weekend we expect a high pressure ridge to build in, with cooler air dragged into Colorado initially on Saturday, as the southern tracking low pressure system exits (northwest/ north flow of winds from the colder north), and sunshine pops through in the then drier air... Powder + sunshine, what Colorado is known for!

LONGER RANGE:
It looks like El Nino is not an official anomaly yet, as I expected in my September LR forecast (for Aspen and SW Colorado / For northern Colorado resorts) so we are in an ENSO Neutral phase, though in the latest update from NOAA, we are seeing warming waters, still a weak El Nino at best. This may explain the more southerly tracking storm systems we have seen, and will likely see in the coming weeks of December and January. CM

Next week, the 11th onward, we expect a couple of snow storms and some moderate to significant snow for western Colorado. Because these look like strong and cold systems (ask Niseko, Japan) with a good fetch of moisture across the Pacific, they are capable of good snowfall across all of western Colorado if the track is right (a bit more north). It looks like 2 storms total for next week, one Tuesday/ Wednesday and another late next week. CM

(NO CHANGE from the last LR update) : It is looking like we may see a busy time as we approach the Christmas and New Year holiday period, with some significant storms possibly lining up to affect all of the western US including Colorado... We expect to see a 7-14 day period of down time and mostly sunny skies following this series of storms, that may start around/ after Christmas. In January we see that down time to start the month (a week-ish), then storms should kick in again on a more regular basis, but possibly favoring northern resorts this time as the east coast gets hit hard and these systems brush mainly northern Colorado. More updates are coming. Do you have any ideas on what you want to see in our discussions? Please contact through the site! We do not charge for any of our info, and have been providing it all for free since 1998, "Predicting Sick Days since 1998"! CM