This Precip and Storm Report Excel Workbook contains the current and past 13 seasons of CSAS winter storm data, including:

  • Dates, times and duration of each winter storm event (2003-current)
  • Change in the height of snow at both our alpine Senator Beck study plot and our subalpine Swamp Angel site.
  • Peak gust data from our Putney site.
  • Mean and maximum precipitation intensity during each storm
  • Total new water accumulation in mm for each storm event.
  • Summary data for each month of the season.
  • Cumulative annual precipitation graph by month

See our Current Conditions for the latest hourly dataAll times shown are in Mountain Standard Time (MST)

2018-2019 Winter Storm Reports

CSAS Winter Storm #9 and #10

Greetings from Silverton,

A nice period of active storm patterns occurred over the last ten days or so, and expected to start up again on January 21, all of which delivering wide spread precipitation.  However the next event this Monday/Tuesday is expected to deliver on the lower end of the original 6-12” forecasted with higher amounts in Northern/Central Colorado and less towards the South.  This string of precipitation is expected to give way to a ridge by the middle of next week resulting in a general drying trend except maybe for some week systems in Central/Northern Colorado that could produce light precipitation totals.

Storm #9 hit the Northern San Juans Tuesday, January 15, lasting 21 hours and bringing 19 mm (0.75”) precipitation over 23.6 cm (9.3”) of snow accumulation.  Winds were strong at times mostly out of the SW, peaking at 42.3 mph during the event and afterwards getting as high as 50 mph.

Storm #10 (Jan. 17 – Jan 18) was a wonderful dumping of snow, closing 550 in both directions. This was rather a high intensity event, bringing 31 mm (1.2”) of precipitation over 27 hours at SASP.  Average precipitation intensity (precipitation/duration) was 1.15 mm/hr with max hourly precipitation reaching 5 mm (0.2”).  This storm also had strong winds mostly out of the N-NW redistributing the newly fallen snow.  Gusts reached 70 mph at Putney station, the fact that SASP gained ~10″ and SBSP gained 3.7″ snowdepth after it was all said and done is testament to the vast redistribution of snow mainly above treeline.  This gave CAIC and road crews a lot to deal with.

Since the latter part of November storm systems have moved through pretty regularly bringing between 12 mm (0.47”) – 52 mm (2”) precipitation.  We have received about the average number of storms so far this season and after this past storm sit on an average snowpack in terms of SWE.

Avalanche Fatality Report: The final CAIC report on the avalanche fatality at Red Mt. Pass has been published on the CAIC website:

It is important that anybody who spends time in the backcountry read this report.  It highlights the crucial role of being informed, and integrating and acting on information in avalanche terrain.  If you haven’t heard, on January 5 a skier was caught, buried, and killed in an avalanche in Upper Senator Beck.  The skier was part of an avalanche level 2 field class with Silverton Avalanche School – not affiliated with CSAS. In all, six people were caught in the avalanche and five people made it out ok.

Snow School: There is still space available in our Snow School for Water Professionals, our two and half day combination classroom and field class designed for water professionals wanting to learn more about snow and our mountain systems.  Please contact me with any questions.

Please see Storm #9 and Storm #10 windroses and summary attached.

CSAS Winter Storm #8, January 5-7

Greetings from Silverton,

Some folks could not immediately see our last update on the Storm Report page until a few hours had passed, the webpage was slow to refresh for certain devices.  We are currently working to revamp our Storm Report page so it isn’t so clunky, hopefully that will help with the problem.  Until I am positive there are no problems viewing our newly issued Storm Reports I will attached the Report in pdf format to these notification emails.

The tail end of a nice day and a half day storm is now departing the Northern San Juans.  In it’s wake the 37 hour storm left close to 11″ new snow accumulation at SASP (11,060′) and slightly more at SBSP (elevation 12,180′).  19 mm (0.75″) precipitation is what we recorded at SASP.  Strong S-SW winds, particularly in the Red Mountain Pass and Telluride area, periodically accompanied the storm, redistributing some of this freshly fallen snow.  As of today the San Miguel/Dolores/Animas Basin is showing 72% of median, and it sure is good to see the Rio Grande in the green at 94% of median – hopefully it will only get better……..The NWS forecast is calling for a ridge of high pressure moving into place Tuesday-Thursday.  Friday a weak trough moves through with models indicating this system will not bring significant snowfall.  On Saturday afternoon another system might bring light flurries along the continental divide – this will pass Saturday night into Sunday.  And yet another Pacific expected to move in early next week, possibly resulting in light moisture for the Four Corners ahead of a closed low.  Most of this is a bit too far out to nail down.  In summary the 7-day precipitation forecast maps do not look encouraging.

In what has become a rarity, a good bit of the National Monument/Four corners area has a little bit of snow cover (or had as of January 4).  Every bit helps and if it keeps the soils wetted, inhibiting dust mobilization, then all the better.

On January 5 a skier was caught, buried, and killed in an avalanche in Upper Senator Beck.  The skier was part of an avalanche level 2 field class with Silverton Avalanche School – not affiliated with CSAS. In all, six people were caught in the avalanche and five people made it out ok.  Our condolences to family, friends, and all impacted.  The CAIC will investigate the details of the avalanche and post a comprehensive report once the weather clears and they are able to access the Upper Basin. The preliminary report can be found here:

Please see this storm report with a few snow and forecast images here:

The report is also attached.

More soon

CSAS Winter Storm  #7, December 31 – January 1, 2019

Another storm, our third in the last week, has now left Colorado. Since Christmas Eve we have received 52 mm (2”) of precipitation at SBB.  Storm #7, arriving early December 31 and departed early evening January 1.  This storm greatly benefitted the southern part of the state.  The Upper Rio Grande and San Miguel/Dolores/Animas Basins both advanced 10% closer to median SWE.

As the below plots show we have received about average precipitation (and resulting SWE) as of the end December at Red Mt Pass.  But Red Mt is a bit of an anomaly as SNOTEL stations around the San Miguel/Dolores/Animas Basin are consistently showing mostly between 35%-89% of median with the Basin overall reporting 71% of median SWE.  Similarly, the Rio Grande Basin received a nice bump from this passing storm and four SNOTEL’s are showing 100% of median or much better, but eight are below median with the average being 76%.  The Gunnison Basin advanced 2% to 91% of median from this last storm.  And thankfully the rest of Colorado’s major basins are currently above 100%.  No dust-on-snow has been observed at SBB to date, and if history holds, we have not received a dust event in January in our period of record starting 2005.

With this system having now passed, we can expect the atmosphere drying out and clear cold nights.  My truck thermometer displayed -21F in Silverton this morning!  A trend of warmer temperatures will continue through Saturday.  A broad upper-level trough will move through Colorado next Sunday, forecast guidance with this slightly colder system for Western Colorado anticipates lower snow levels and higher accumulation throughout mountains.  Preliminary guesses are for 5-10” from Sunday through Monday.
CSAS Winter Storm #5 and #6, December 24-26, 2018

Greetings from Silverton,

An active weather pattern started bringing precipitation to Southern Colorado the day before Christmas (bringing 0.47” water with 7.5” accumulation), took a 24 hour break, and began again the afternoon on Christmas Day (bringing 0.71” water with 7” additional accumulation).  The current system in our area has moved along by early this morning.  Another system is expected arrive midday Sunday for the Park and Gore ranges with precipitation starting Sunday night in the San Juan Mountain area and exists by Wednesday, followed by dry and cool weather through the end of the week.  Please see images below.

More Soon

CSAS Winter Storm #4: December 13, 2018
Greetings from Silverton,
Storm #4 rolled in straight out of the north yesterday (Wednesday) afternoon with strong winds peaking at 63 mph.  This north-northwesterly flow as it moved through the Ouray area caused what is called a “gorge event”.  Orographic lifting produced almost 1′ of new snow accumulation in some locations between Ouray and Red Mt Pass.
At our study basin at Red Mt Pass, snow accumulation amounted to 20 cm (7.9″) at Swamp Angel (elevation 11,060′) with total precipitation being 13 mm (0.5″).  At Senator Beck Study Plot (elevation 12,200′) what snow accumulation occurred was quickly scoured away from the strong winds.
We will see cold temperatures starting to give way to warmer temps by Friday.  Our next chance for snow will come about on Monday/Tuesday with the details on this one still to far out to say much about it.
If you are new to our Storm Reports, please see our websites to orient yourself as to our location and what we do:
More Soon
CSAS Winter Storm #2 and #3: December 11, 2018
Greetings from Silverton,

November Recap:  The first 5-days of November started out nicely with 26 mm (1.0”) precipitation, which constituted Storm #1 at Senator Beck Study Basin (SBB).  However the 18 days that followed we observed only 9 mm (0.35”) precipitation.  Thankfully, complex multiple frontal systems came through the Western U.S. resulting in 2 significant storms systems occurring Thanksgiving Day and then two days later on November 24.  The precipitation from these two events totaled 21 mm (0.83”) at SBB (CSAS Storm #2).  Overall boosting Mountain snowpack 8-10%, although the Upper Rio Grande mostly missed out on this round of precipitation, only gaining 1%.  But the month wasn’t over, the last day of November a low pressure trough that dipped south enough on southwest flow to give the San Juans a good shot of precipitation, 34 mm (1.3”) over a 4 day period to make it Storm #3 in the study basin.

Coming Week:  The short-term forecast is calling for a weak trough to move across the area today thru tonight bringing scattered snow in the mountains.  A more optimistic trough will move in Wednesday in the Northern Rockies and by the afternoon the trough will dip south with a strong jet moving over southern UT and the Four Corners region, resulting in 4” in the Northern San Juans and 1” in the Southern San Juans.  By latter Thursday a ridge builds in the West keeping things dry and sunny. This ridge breaks down late Friday but the next trough is expected to stay north.  But it’s nice to active weather so far this winter season, compared to last year at this time we were stuck under the wrong end of a high amplitude blocking pattern (the Ridiculously Resilient Ridge) that shut down storm activity in Colorado, and routed storms north of Colorado.

Seasonal Forecast:  The current NWS seasonal forecast has 80% chance of a weak to moderate El Nino this winter and 55-60% chance of it continuing through spring.  This type of El Nino (Modoki) seems to have the best analog in the 2006/07 and 2014/15 winter seasons, with 2014/15 being the better.  In both years, most of Colorado was at or above snowpack by mid-winter, then crashing in late winter with most of the state having below average snowpack.

Snow School:  There is still space available in our Snow School for Water Professionals, our two and half day combination classroom and field class designed for water professionals wanting to learn more about snow and our mountain systems.  Please contact me with any questions.

CSAS Winter Storm #1: November 4-5, 2018

Greetings from Silverton,

A number of active weather patterns have passed through Colorado over the last few weeks giving the Colorado snowpack a good jump on the season.  In October we recorded 20 days with precipitation along with the first 6 days of November.  Our first storm since we experienced permanent snowcover in the majority of Senator Beck Basin occurred Nov. 4-5.  Our definition of storm, which determines when we issue a storm report, is at least 12 mm (0.47″) of precipitation with no break in precipitation longer than 12 hours. We have received a number of recent events that just fell short of meeting that threshold, such as on Nov. 3 and Oct 30 we received 11 mm (0.43″).  Since the start of Water Year 2019 we have recorded 157 mm (6.2″) of precipitation (the average is closer to 4.3″).  And this is the theme throughout the Colorado mountains, above average snow accumulation is laying down the base for the rest of the snow season.  Unfortunately, the forecast is calling for a general drying and warming trend with any new system bringing minimal moisture, thus not much rain/snow expected.


I do not want to overload Storm Report subscribers with large emails, so I posted current meteorological and snowpack plots on our Storm Reports page:
Please follow the above link to view these images.
Snow School: Please see the attached flier for details about Snow School for Water Professionals, our two and half day combination classroom and field class designed for water professionals wanting to learn more about snow and our mountain systems.  Please contact me with any questions.
More Soon,
Jeff Derry

Past Winter Storm Reports