038  
FGUS73 KFGF 231722  
ESFFGF  
NDC005-027-071-281200-  
 
PROBABILISTIC HYDROLOGIC OUTLOOK  
NATIONAL WEATHER SERVICE EASTERN NORTH DAKOTA/GRAND FORKS ND  
1222 PM CDT THU AUG 23 2018  
   
..DEVILS LAKE OUTLOOK FOR FLOOD POTENTIAL
 
 
DEVILS AND STUMP LAKES  
LONG-RANGE PROBABILISTIC OUTLOOK  
   
DISCUSSION
 
 
DRIER THAN NORMAL CONDITIONS HAVE PERSISTED INTO THE LATE SUMMER  
MONTHS ALLOWING DROUGHT CONDITIONS TO WORSEN ACROSS THE BASIN. WITH  
RECENT PRECIPITATION AND ASSOCIATED RUNOFF REMAINING LOW (AND  
EVAPORATION IMPACTS INCREASING), THIS OUTLOOK INCREASES THE CHANCES  
OF LAKE LEVELS DROPPING TO 1448 FT.  
 
IT SHOULD BE NOTED THAT THESE OUTLOOK NUMBERS MAY BE A BIT  
CONSERVATIVE (I.E., PREDICTED LAKE LEVELS TOO HIGH) DUE TO COMPUTER  
MODELING LIMITATIONS. ADDITIONALLY, THESE OUTLOOK NUMBERS INCORPORATE  
350 CFS WORTH OF COMBINED PUMPING FROM THE WEST END AND EAST END  
OUTLETS. NOTE THAT THIS OUTLOOK DOES NOT ACCOUNT FOR ANY CHANGES TO  
THE AMOUNT OF ACTUAL PUMPING DUE TO OUTLET MAINTENANCE, EQUIPMENT  
PROBLEMS, OR WATER QUALITY LIMITATIONS.  
 
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.  
 
   
CURRENT AND PREVIOUS RECORD HIGH LAKE LEVELS
 
 
* THE CURRENT HEIGHT OF DEVILS LAKE AT CREEL BAY IS 1448.92 FEET  
* THE CURRENT HEIGHT OF STUMP LAKE NEAR LAKOTA IS 1448.92 FEET  
 
* THE MOST RECENT USGS PROVISIONAL RECORD DAILY AVERAGE HEIGHT  
FOR DEVILS LAKE AT THE CREEL BAY GAGE:  
...1454.30 FEET ON JUNE 27 OF 2011  
* PREVIOUS RECORDS:  
...1452.05 FEET ON JUNE 27 OF 2010  
...1450.93 FEET ON JUNE 27 OF 2009  
...1449.20 FEET ON MAY 9 OF 2006  
...1449.18 FEET ON JUNE 17 OF 2004  
...1449.17 FEET ON AUGUST 2 OF 2005  
 
   
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 1448.0 FEET DURING THE VALID PERIOD AND  
ONLY A 5 PERCENT CHANCE THAT IT WILL FALL BELOW 1447.8 FEET.  
 
PROBABILITIES FOR NON-EXCEEDING LISTED LAKE LEVELS  
 
FROM SEPTEMBER 01, 2018 TO NOVEMBER 30, 2018  
 
LOCATION 95% 90% 75% 50% 25% 10% 05%  
-------- ------ ------ ------ ------ ------ ------ ------  
DEVILS LAKE.....  
CREEL BAY 1448.4 1448.3 1448.1 1448.0 1447.9 1447.8 1447.8  
STUMP LAKE.....  
EAST STUMP LAKE 1448.4 1448.3 1448.1 1448.0 1447.9 1447.8 1447.8  
 
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 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 2012 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).  
 
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  
NNNN  
 
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