The following is the preliminary 2011 Spring Flood Outlook. There is a significant risk at many forecast points of major flooding, based on the January 18 run of the Advanced Hydrologic Prediction Services (AHPS). Below are some highlights.
While most of the United States has now received part of its winter snow cover, the Red River of the North and Devils Lake Basins have already received more than a typical winter’s snowpack and stand poised to receive twice their normal snowfall throughout this winter season. The typical winter season is about halfway through and Fargo ND has received 55.8 inches of snow, or 15.8 inches above its long term annual average for an entire winter season. West central Minnesota, southeastern North Dakota, and portions of northeast North Dakota (which includes the Devils Lake Basin) are in similar stead. [compare: Fargo had 66.3” as of 1/17/97]
To compound this problem, most of this same area received 50 percent above normal summer and fall precipitation (10-12 inches above normal rainfall), which means that area lakes, rivers and streams are freezing in at (seasonally adjusted) record high levels. Climatologically, our current La Nina pattern is expected to hold through the spring, which means we have the possibility of a colder and snowier winter plus the possibility of a cooler, stormier, and wetter spring. Thus excessive and residual rainfall in calendar year 2010, coupled with excessive winter snow to date, and with the prospects for a cool and wet spring to come, means that we can expect major spring flood issues for many area lakes and rivers.
A snapshot comparative: Snowfall totals from past winters November 1 - January 17th
Snowfall to date Following Spring Crest
Grand Forks Fargo Grand Forks Fargo
1996/97 57.1R 66.3R 54.35 39.57
2005/06 15.0 25.4 47.93 37.13
2008/09 36.0 42.5 49.34 40.84
2010/11 36.2 55.8
As of January 17th, Fargo is in 3rd place for snowfall, UND/NWS Climate Station is in 8th place.*
A snapshot Comparative: Rainfall past fall and winters – totals September 1 - January 17th
Rainfall to date
Grand Forks Fargo
1996/97 6.30 10.57
2005/06 5.48 10.03
2008/09 13.18R 12.97R
2010/11 8.92 10.93
R = Record Values
As of January 17th, Fargo is in 3rd place for the wettest fall & winter, while the UND/NWS Climate Station is the 6th wettest.*
* Preliminary figures, subject to final review and quality control
For the Southern Red River Basin: Current spring flood outlooks indicate that much of the southern basin, including the Fargo-Moorhead area, already has a higher risk of spring flood levels than were seen in advance of the 2006 or 2010 major flood events. There is a 20 to 25 percent chance that areas near Fargo-Moorhead could see flood levels approach the record levels set back in the early spring of 2009. Continued much above normal snowfall through the remainder of the winter will likely continue to drive that risk slightly upward in later outlooks.
The Otter Tail River Sub-Basin has seen especially high flows through this past summer and fall, with ice jam flooding affecting some areas through the early winter. The Buffalo, Bois de Sioux, Wild Rice (ND), and Sheyenne sub-basins are all freezing in (still some flow) at winter time record levels. Water management agencies which operate dams and reservoirs across the southern basin are once again faced with a significant challenge to plan for major to near-record inflows and the possibility for more than one snow-melt and rainfall induced crest in their respective systems.
For the Northern Red River Basin: Current spring flood outlooks indicate that most of the mainstem Red River also has a similar risk of major spring flooding, as was seen there in advance of the 2006, 2009 and 2010 major flood events - but also a 10 percent chance of experiencing the record levels which occurred back in 1997. As in 2009 and 2010, the northern basin has substantially lower snow amount and snow-water equivalent (SWE) amounts than in southern (Fargo) or western (Devils Lake) areas. Snowfall amounts here are running only slightly above normal for the current winter, but they are also higher than last year’s amounts. Likewise, summer-fall rainfall amounts were 5-8 inches above normal, but lower than southern basin amounts. Thus base stream flows are currently high, but generally not at record levels. With higher base stream-flows and snow amount than in 2010, most tributaries in the northern valley have a higher risk than last year of at least moderate flooding, especially the Roseau, Red Lake, and Pembina Rivers.
For the Devils Lake Basin: The initial spring flood outlook released on December 23, 2010, indicates that Devils Lake and Stump Lake will likely rise (60-80 percent probability) to a new record height in excess of 1454 ft elevation, and could rise (33 percent probability) to a height in excess of 1455 ft. At these levels portions of the community of Minnewauken ND will be inundated, along with additional homes, businesses and critical infrastructure surrounding these lakes. The next outlook for the Devils Lake Basin is scheduled for January 27, and will likely show an increased risk of a 2-3 foot rise, based on the much above normal snowfall that continues there. Note: Devils Lake and Stump Lake reached a new record height of 1452.1 feet late this past summer, but they have now frozen over at their highest level ever recorded, currently within a half a foot of the summertime record level. At Creel Bay the latest gauge at 1451.67; at East Stmp Lake the level was 1451.63, both as of January 18 2011.
For the latest probablistic outlooks, click here. Click on the forecast location you wish to view, then click on the tab titled "Chance of Exceeding Values During Entire Period"
Below are the statistical probabilities of exceedance for forecast points on the Red River as well as Creel Bay and East Stump Lake.
Below are graphics showing the snow water content as of January 17 2011 compared to January 17 2009.
Click on the above graphic for a larger image.
Climate outlook for the spring 2011 snow-melt. At this time a moderate La Niña is ongoing in the equatorial Pacific and is expected to continue through the spring months of 2011. So far this winter the more classic La Niña impacts have been evident across the Red River Valley and Devils Lake Basins. Above normal snowfall and generally below normal temperatures have been affecting the region since the start of the winter season. Based on outlooks from the Climate Prediction Center (CPC) as well as historical information during previous La Niña events, there is an enhanced risk for below normal temperatures to continue through the February, March and April time period. There is also an enhanced risk for above normal precipitation during the late winter and early spring months of March, April and May. Historical data suggests that La Niña springs see a slightly delayed warm up, with a risk for a more rapid rise in temperature in April than is climatologically normal. There is also an enhanced risk for significant rain or snow near the time of the melt.
The following is neither a forecast nor an outlook, but is provided as a historical reference of previous La Niña springs. On balance during an El Niño or ENSO neutral year the average date warm enough to initiate melting is near the end of March or the first few days of April. During years with a La Niña the average date with temperatures consistently warm enough to initiate snow-melt flooding is about 10 days later. While this example is for the Fargo area, it represents general conditions within the Red River Valley. As we get into the late winter and early spring additional risk assessments of potential La Niña impacts on the 2011 flood will be available.
For additional information please contact the National Weather Service in Grand Forks at 701.795.5198