Monthly Water Supply Outlook Reports will be available by the 5th business day of each month January through June. If you would like to start receiving notifications when the Montana Water Supply Outlook Reports are released, please click hereto be added to the GovDelivery List.
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The Water Supply Outlook Report (WSOR) was redesigned after water year 2020. It is now abbreviated compared to earlier versions. The MT Snow Survey webpage was redesigned at the same time as the WSOR updates. The new webpage format summarizes both statewide and specific river basin conditions in near real-time.
The current condition summaries can be found by using the navigation bar above and selecting "Monthly Statewide Overview", or by selecting an individual river basin summary. There are numerous added benefits for the water user when comparing these new tools with the legacy static report. The new webpages are all interactive, which allows the user scroll and click on the tools to get more information than before from the included maps, plots and tables.
We know that our customers rely on the information we provide, so a monthly report with the summaries of the past weather and climate, snowpack, precipitation, reservoir storage, and streamflow forecasts will continue to be published for the state. However, water users are encouraged to look at the new monthly river basin webpages (and new daily river basin summaries) as a replacement for the individual river basin narratives.
If there are ways we can improve upon these products, we would appreciate your feedback. Are there pieces of the legacy reports that are missing that you need for your planning purposes? Tools you would like to see included? Please let us know!
June 1st, 2020. (PDF 9.0MB). Rapid melt at the end of May has decreased streamflow prospects within some river basins for the summer. Most basins west of the Divide look to receive near normal water yield, however forecasts vary widely east of the Divide. Water users are encouraged to read this month's report for their basin(s) of interest to gauge the impact of this May's anomalous weather.
May 1st, 2020. (PDF 9.0MB). As of May 1st, high elevation SNOTEL sites like Black Bear continue to gain or hold onto snow water on May 1st. Lower elevations began melting during April, starting the snowmelt driven runoff across the state. Accelerated melt during the last week of the month at these lower elevations, coupled with well below April average precipitation, has decreased the volumes forecasted from April 1st for the May 1st – July 31st period for some river basins.
April 1st, 2020. (PDF 9.6MB). Snowpack across Montana has made a significant recovery since January 1st. Although March was below normal for snowfall in some locations, the abundant January and February snowfall and below-average temperatures during the month have resulted in snowpack on April 1st that is holding strong across the state. Water users are encouraged to view their specific river basin of interest to better under the relationship between snowpack, water year precipitation, and streamflow forecasts for their area of interest this year.
March 1st, 2020. (PDF 9.6MB) Snowpack improves across the state due to abundant snowfall in February. Streamflow forecasts indicate near to above average streamflows are possible for the April 1st - July 31st period.
February 1st, 2020. (PDF 6.6MB) A steady stream of moisture from the Pacific yielded a significant amount of snowfall in the northwest River basins between December 30th, 2019 and February 1st, 2020. All major river basins in the state are now near or above normal for snowpack for this date.
January 1st, 2020. (PDF 6.3MB) A wet September and October boosted snowpack early in the water year, but persistent dry weather patterns through November and December resulted in water year precipitation totals that are well below normal for this date. Snowpack ranges from below normal west of the Divide to above normal in north-central Montana.
June 1st, 2019 (PDF 19.8MB) - Snowmelt was in full swing during the month of May, only slowed for a period of cool weather during the third week of the month. Precipitation ranged from well above average in the Rocky Mountain Front and parts of the Upper Yellowstone, to well below average in northwest river basins. Seasonal snowmelt peaks have occurred for many rivers west of the Divide, and peaks are expected to occur during the second week of June in the higher elevation basins of southern Montana.
May 1st, 2019 (PDF 18.0MB) - Snowpack in Montana reached it's peak at low and mid-elevations during the month of April, with many areas peaking at or near normal levels. High elevations continue to gain snow water due to the end of month cool-down. Snowpack for this date is near normal in many basins, but is lacking in some southwest and northern basins. Streamflows forecasts for the spring and summer range widely and can be found in the individual river basin narratives of the report
April 1st, 2019 (PDF 70.9MB) - The state of Montana experienced well-below average to record-setting low precipitation during March. Fortunately, February’s abundant snowfall helped to offset the decreases in snowpack totals for April 1st. However, snowpack in the northern half of the state is below normal and water supply is anticipated to be below average in these areas this runoff season. Further details on individual river basins of interest can be found in this month’s report.
March 1st, 2019 (PDF 70.6MB) - Well above normal to record-setting February snow totals boosts snowpack across Montana. February was cold, very cold. Abundant moisture from the Pacific collided with this cold air mass to produce significant snowfall across the state, which resulted in above normal to record-setting snowfall for the month. The continuous storms approaching from the southwest that impacted southern Montana set new records for February monthly snowfall totals at many snowpack monitoring locations.
February 1st, 2019 (PDF 19.6MB) - Snowfall during January was below normal in many western basins during the month of January, with late month storms lacking the snowfall to make up for early winter deficits. Basins along and east of the Divide in central and southern Montana, benefitting from early winter storms, and the end of month storms, remain near to slightly above normal on February 1st.
January 1st, 2019 (PDF 19.5MB) - Early winter storms roll into the state, but favor river basins along the Continental Divide in the southern and western half of the Montana. Snowpack percentages range from slightly above normal in favored basins, to below normal in north central and northwest Montana. With El Nino forming, what will this mean for the snowpack as we approach runoff this spring and summer? Only time will tell.
June 1st, 2018 (PDF 70.0MB) - Rapid snowmelt during the month of May caused significant impacts across the state of Montana from high river volumes. 52 streamgages set new records for monthly flows for May, 12 gauges were second highest. Loss of snowpack to melt during the month has decreased the streamflow forecasts for the summer, but forecasts generally remain near to above average in most basins.
May 1st, 2018 (PDF 70.5MB) - Snowpack peaked at record levels in some basins in the state this water year, and all basins have well-above normal snowpack for May 1st. Water supply this spring and summer will be abundant with May 1st forecasts indicating above average to record streamflows possible for some rivers. Future weather will play a critical role in determining the timing of runoff this year, and water users are strongly encouraged to monitor official weather and flood forecasts issued by the National Weather Service during the months of May and June.
April 1st, 2018 (PDF 70.5MB) - The cool and wet weather pattern continued across most of the state of Montana through March, with all river basins near to well above normal for snowpack for April 1st. Some river basins have record snowpack for not only this date, but on record. April and May weather will be critical in determining if the snowpack will continue building, or will begin melt. With more cold and wet weather forecasted, the former seems more likely given this year's weather patterns. Water users should continue to monitor the snowpack in some regions for potential implications of runoff this spring.
March 1st, 2018(PDF 20.4MB)- Record breaking February snowfall in some regions of the state over the month built on a strong early season snowpack, resulting in streamflow forecasts that are above to well above average state-wide.
February 1st, 2018 (PDF 19.8MB) - La Nina continues to deliver. Passing storms continue to build Montana's snowpack during the month of January, currently all basins are normal to well above normal for this date.
January 1st, 2018 (PDF 19.6 MB) - Across the state of Montana, snowpack is near to above normal in all river basins. Storms during November and December added substantial amounts of snow water equivalent to the early season snowpack, resulting in above normal snow totals in many mountain ranges across the state. It's still very early in the snow season, but we're off to a good start.
June 1st, 2017 (PDF 20.5 MB) - - Sunny and warm days during the month of May started the melt of the seasonal snowpack at all elevations. Snowpack totals for June 1st are near to above normal in many basins. Long duration streamflow forecasts for the summer time period look to be near to above average.
May1st, 2017 (PDF 20.5 MB) - Abundant preciptiation this water year, combined with well above normal snowpack totals for May 1st lead to water supply forecasts that are above average for the May 1st - July 31st time period for many river basins. One central Montana river basin could experience below average flows due to lack of snowfall this year.
April 1st, 2017 (PDF 21.2 MB) - Wet weather increases snowpack percentages west of the Divide from March 1st. Lack of snowfall and low-elevation melt drops basin percentages east of the Divide. Many basins are near to above normal for April 1st, but a few central and SW basins are below normal for this date.
Mar 1st, 2017 (PDF 20.5 MB) - A return to more favorable weather patterns dropped significant amounts of snow in the river basins during the first two weeks of February. Continued snowfall in most basins improves snowpack totals to near or above normal for March 1st, 2017.
Feb 1st, 2017 (PDF 19.4 MB) - Cold and mostly dry month lowers snowpack totals for February 1st. Northern basins snowpack well below normal, southern basins snowpack near to above average in certain locations.
Jan 1st, 2017 (PDF 19.4 MB) - The new water year started with record breaking October precipitation at many SNOTEL sites in MT. A warm November left little snow on the ground entering winter, but above average snowfall during December helped to improve snowpack conditions for Jan 1.
June 1st, 2016 (PDF 21,368 KB) - Snowmelt continued through the month of May, basins west of the Divide saw the most dramatic movement of snow water. This has resulted in lowered summer streamflow forecasts from May 1st. Some basins look to experience well below average flows during the June 1st - July 31st time period.
May 1st, 2016 (PDF 21,246 KB) - High pressure with abundant sunshine and causes snowpack to transition to melt well ahead of schedule. Basin-wide snowpack peaked across the state at the beginning of April, with most basins reporting near to slightly below average water year peaks. Sun-Teton-Marias snowpack is near record low and snowmelt runoff is anticipated to well below average.
April 1st, 2016 (PDF 20,568 KB) - Snow and Precipitation during the month of March increase snowpack percentages for April 1st, increasing streamflow forecasts for the April-July timer period to near or above average in most basins. The Sun-Teton-Marias River basin is still well below normal for snowpack and precipitation and will be monitored this spring and summer.
March 1st, 2016 (PDF 8,131 KB) - Storms favor higher elevations in the northwest and some basins along the MT/ID border where snowpack percentages increased during the month. Other basins experienced declines from Feb 1st due to below normal snowfall. Valley precipitation below to well below average across the western half of the state.
February 1st, 2016 (PDF; 8,022 KB, please allow time to download images)- Two weeks of mostly dry conditions across the state cause basin percentages to drop since Jan 1st. Northern basins are below to well below normal, while southern basins remain near to above normal for Feb 1st.
January 1st, 2016 (PDF; 15, 808 KB, please allow time to download images)- Late Fall and Early winter storms favor the southern portion of the state with near to above normal snowpack on Jan 1, northern basins below normal for the date
June 1, 2015 (PDF; 10,285 KB) - Below normal snowpack this year and early runoff this spring will have an impact on summer streamflows.
May 1, 2015 (PDF; 9,569 KB) - After a disappointing winter, water users in Montana should prepare for early and below average snowmelt runoff in streams this spring and summer.
April 1, 2015 (PDF; 9,296KB) - Third straight month of declines in snowpack percentages causes drops in streamflow forecasts to below average this spring and summer.
March 1, 2015 (PDF; 4,018KB) - Continued decline of regional snowpack leaves some near to above normal, while others are well below)
February 1, 2015 (PDF; 2,262 KB) - Snowpack percentages drop from above normal to near normal due to lack of snow and above average temperatures.
January 1, 2015 (PDF; 2,364KB) - After a slow start to winter, holiday storms build Montana's snowpack.
June 1, 2014 (PDF; 2,970 KB) - Transition to snowmelt at all elevations during May causes peaks in rivers across Montana. May 1, 2014 (PDF; 2,209 KB) - As Mountain Snowpack Transitions Into Spring, Runoff Should Be Monitored. April 1, 2014 (PDF; 2,783KB) - Snowpack & runoff require watchful eye this spring. March 1, 2014 (PDF; 3,710 KB) - Statewide improvement make for excellent water supply outlook. February 1, 2014 (PDF; 2,118 KB) - Current conditions support near normal 2014 runoff streamflow predictions. January 1, 2014 (PDF; 3,573 KB) - Fall's cold temperatures preserve snowpack for strong start and January 1.
June 1, 2013 (PDF; 2,423 KB) - Transition to spring is in full swing, with less snowpack than usual. Expect below average streamflows this summer. May 1, 2013 (PDF; 2,424 KB) - April showers bring snow & cooler temperature across Montana. April 1, 2013 (PDF; 2,461KB) - Northern reaches of the state improve slightly, elsewhere continues downward slide. March 1, 2013 (PDF; 3,861 KB) - Another slight decrease through February leaves snowpack a little further below, yet still near, average. February 1, 2013 (PDF; 3,410 KB) - Snowpack slid just below normal this January despite two significant storm patterns, dryness prevailed. January 1, 2013 (PDF; 1,781 KB) - Statewide conditions reflect near normal snowpack and precipitation to ring in the new year.
June 1, 2012 (PDF; 2,298 KB) - Late May snowstorm and periodic cold spells improve remaining snowpack. May 1, 2012 (PDF; 8,038 KB) - Record-setting April temperatures drove snowpack to below average levels. April 1, 2012 (PDF; 8,252 KB) - State-wide snowpack increases to slightly above average while Yellowstone River Basin starts early snowmelt. March 1, 2012 (PDF; 8,236 KB) - Southwest Montana's increase in snowpack during February was the only difference from last month's slight statewide snowpack increases. February 1, 2012 (PDF; 4,468 KB) - January started off warm and dry until an upper level trough materialized and brought more seasonable precipitation and temperatures to the state. January 1, 2012 (PDF; 9,850 KB) - The month of December yielded well below average precipitation with state-wide snowpack ending the month near 80 percent of average.