649  
FGUS73 KFGF 231751  
ESFFGF  
 
NDC005-027-071-281200-  
 
PROBABILISTIC HYDROLOGIC OUTLOOK  
NATIONAL WEATHER SERVICE GRAND FORKS ND  
1247 PM CDT THU SEP 23 2021  
   
..DEVILS LAKE OUTLOOK FOR FLOOD POTENTIAL
 
 
DEVILS AND STUMP LAKES  
LONG-RANGE PROBABILISTIC OUTLOOK  
 
THE NATIONAL WEATHER SERVICE PROVIDES LONG-RANGE PROBABILISTIC  
HYDROLOGIC OUTLOOKS FOR DEVILS AND STUMP LAKES BETWEEN JANUARY  
AND SEPTEMBER. THEY WILL NOT BE PROVIDED BETWEEN OCTOBER AND  
DECEMBER. DEPENDING ON THE SEASON, THE HIGH OR LOW WATER  
PROBABILITIES MAY BE OMITTED DUE TO THEIR APPLICABILITY TO  
THE HYDROLOGIC SITUATION.  
   
OUTLOOK SUMMARY
 
 
NOTE: THE AUGUST AND SEPTEMBER NON-EXCEEDANCE OUTLOOKS INCORPORATED  
A DAILY AVERAGE OF 75 CFS WORTH OF PUMPING OPERATIONS ON DEVILS LAKE  
THROUGH THE END OF SEPTEMBER. THE JUNE AND JULY NON-EXCEEDANCE  
OUTLOOKS INCORPORATED A DAILY AVERAGE OF 200 CFS WORTH OF PUMPING  
OPERATIONS THROUGH THE END OF OCTOBER.  
 
SINCE THE LAST OUTLOOK ISSUANCE ON AUGUST 26TH, MUCH OF THE AREA  
RECEIVED ADDITIONAL, AND MUCH NEEDED, PRECIPITATION. AMOUNTS FOR  
THIS TIME PERIOD WERE NEAR TO ABOVE NORMAL FOR MUCH OF THE BASIN BUT  
STILL SLIGHTLY BELOW NORMAL ACROSS NORTHERN REACHES OF THE BASIN.  
THIS PRECIPITATION DID HELP IMPROVE DROUGHT CONDITIONS SLIGHTLY OVER  
THE COURSE OF THE LAST MONTH. ALTHOUGH THE HEART OF THE BASIN  
REMAINS IN THE EXTREME DROUGHT CATEGORY, SOME OF THE AREA HAS SEEN  
IMPROVED CONDITIONS AND IS NOW CLASSIFIED AS SEVERE DROUGHT.  
ADDITIONALLY, ANY MENTION OF EXCEPTIONAL DROUGHT HAS BEEN REMOVED  
FOR MOST OF THE STATE OF NORTH DAKOTA. ALL IN ALL, RECENT  
PRECIPITATION AND DROUGHT IMPROVEMENT HAS LED TO VERY LITTLE CHANGE  
IN THE NON-EXCEEDANCE NUMBERS WITH THIS OUTLOOK AS COMPARED TO THE  
AUGUST 2021 OUTLOOK.  
 
CLIMATE OUTLOOKS FOR THE END OF SEPTEMBER AND INTO THE BEGINNING OF  
OCTOBER INDICATE ABOVE NORMAL TEMPERATURES AND BELOW NORMAL  
PRECIPITATION TO RETURN. THE ABOVE NORMAL TEMPERATURES LOOK TO  
CONTINUE THROUGH THE REMAINDER OF THE FALL BUT BY WINTER, EQUAL  
CHANCES FOR ABOVE, BELOW, OR NEAR NORMAL TEMPERATURES AND  
PRECIPITATION ARE FORECAST.  
 
   
CHANCES OF DEVILS AND STUMP LAKES RISING ABOVE GIVEN LAKE LEVELS
 
 
THE PROBABILITY OF EXCEEDING A GIVEN LAKE LEVEL IS THE PERCENTAGE  
OF MAXIMUM LAKE LEVEL RISES THAT ARE ABOVE 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.  
 
EXCEEDANCE INFORMATION IS NOT PUBLISHED IN SEPTEMBER.  
 
   
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 1446.4 FEET DURING THE VALID PERIOD AND  
ONLY A 5 PERCENT CHANCE THAT IT WILL FALL BELOW 1446.3 FEET.  
 
PROBABILITIES FOR NON-EXCEEDING LISTED LAKE LEVELS  
 
FROM SEPTEMBER 20, 2021 TO DECEMBER 26, 2021  
 
LOCATION 95% 90% 75% 50% 25% 10% 05%  
-------- ------ ------ ------ ------ ------ ------ ------  
DEVILS LAKE.....  
CREEL BAY 1446.7 1446.6 1446.5 1446.4 1446.3 1446.3 1446.3  
STUMP LAKE.....  
EAST STUMP LAKE 1446.7 1446.6 1446.5 1446.4 1446.3 1446.3 1446.3  
 
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 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
 
 
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 2018 AND  
CURRENT CONDITIONS OF THE LAKE, SNOWCOVER (IN WINTER), AND SOIL  
MOISTURE.  
 
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 NOAA'S  
NATIONAL WEATHER SERVICE'S ADVANCED HYDROLOGIC PREDICTION  
SERVICES (AHPS).  
 
A YOUTUBE VIDEO ON "HOW TO INTERPRET RIVER OUTLOOK PRODUCTS" IS AT:  
 
WWW.YOUTUBE.COM/WATCH?V=PSOEGVSNPV4  
 
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 ON THE NWS GRAND FORKS AHPS WEB PAGE AT:  
 
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?/WFO=FGF  
 
WIND AND WAVE FORECASTS FOR DEVILS AND STUMP LAKES ARE AVAILABLE FOR  
A 7-DAY PERIOD WHEN THE LAKES ARE SUFFICIENTLY ICE-FREE AT:  
 
WWW.WEATHER.GOV/FGF/LAKE_INFO  
 
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  
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