Hydrologic Outlook
Issued by NWS Eastern North Dakota/Grand Forks, ND
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000 FGUS73 KFGF 252034 ESFFGF NDC005-027-071-281200- Probabilistic Hydrologic Outlook National Weather Service Eastern North Dakota/Grand Forks ND 333 PM CDT Mon Sep 25 2017 ...DEVILS LAKE OUTLOOK FOR FLOOD POTENTIAL... Devils and Stump Lakes Long-Range Probabilistic Outlook The National Weather Service is providing long-range probabilistic hydrologic outlooks for Devils and Stump lakes between January and September. They will not be provided between October and December. The AHPS graphics associated with this outlook will be on the web no later than 10:30 AM this Friday under the experimental long-range flood risk tab at... water.weather.gov/ahps2/index.php?wfo=fgf Depending on the season, the high or low water probabilities may be omitted due to their applicability to the hydrologic situation. Refer to the scheduling section farther on in this message. . Chances of Devils and Stump Lakes falling below given lake levels... The probability of not exceeding a given lake level is the percentage of lake level falls that are below that level for all the years that were run through the model using the precipitation and temperatures for those years during the valid period of the outlook. Interpretation Aid...There is a 50 percent chance that Devils Lake will fall below 1449.9 feet during the valid period and only a 5 percent chance that it will fall below 1449.8 feet. Probabilities for non-exceeding listed lake levels FROM SEPTEMBER 24, 2017 TO DECEMBER 30, 2017 LOCATION 95% 90% 75% 50% 25% 10% 05% -------- ------ ------ ------ ------ ------ ------ ------ Devils Lake..... CREEL BAY 1450.1 1450.1 1450.0 1449.9 1449.8 1449.8 1449.8 Stump Lake..... EAST STUMP LAKE 1450.1 1450.1 1450.0 1449.9 1449.8 1449.8 1449.8 The non-exceedance value for a listed percentage is the value where that percentage of all model cases run were below that lake level for the specified valid period of the outlook. .Outlook Schedule... - Between January and May, only the high water exceedances will be provided with valid periods ending at the end of September. - Special Spring Flood and Water Management Outlooks will be issued in late February and, two weeks later, in early March. - For June and July, both high-water and low-water exceedances will be provided. - For August and September, only the low-water exceedances will be provided with valid periods ending at the end of November. - No probability of exceedance/non-exceedance information will be given from October through December, since lake freeze-up levels will be given in the fall outlooks previously issued. . Additional Information... Wind and Wave forecasts for Devils and Stump lakes are available for a seven day period when the lakes are sufficiently ice-free at: www.weather.gov/fgf/lake_info The long-range probabilistic outlook is based on high and low lake levels that were calculated for the valid period using multiple scenarios of temperature and precipitation from 1949 to 2012 and current conditions of the lake, snowcover (in winter), and soil moisture. A YouTube video on "How to Interpret River Outlook Products" is at: www.youtube.com/watch?v=pSoEgvsnpv4 By providing the complete range of lake level probabilities, the amount of risk associated with long-range planning decisions can be determined. These probabilistic outlooks are part of Noah`s National Weather Service`s Advanced Hydrologic Prediction Services (AHPS). This outlook is also presented as probability graphs of lake height for the full period as well as weekly probabilities. The outlook graphics and explanations that help in interpreting these outlooks are available from...the NWS Grand Forks AHPS web page at: water.weather.gov/ahps2/index.php?/wfo=fgf When available (see schedule above) the AHPS graphics for monthly outlooks should be available by mid-morning or early afternoon. Monthly probabilistic outlooks are issued on the Friday of the week following the first Thursday after the 15Th of the month. Special spring flood and water management outlooks are issued on Thursday afternoons in late February and then again, two weeks later in early March to coincide with the spring snow melt. Due to the lake freeze-up will not be issued from October through December. If you have any questions, contact the NWS at 701-772-0720 You can follow us on Facebook at: www.facebook.com/NWSGrandForks and on Twitter at: @NWSGrandForks. $$ weather.gov/fgf NNNN

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National Weather Service
Eastern North Dakota/Grand Forks Weather Forecast Office
4797 Technology Circle
Grand Forks, ND 58203
(701) 772-0720
Page last modified: 25-Sep-2017 8:34 PM
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