863  
FGUS73 KBIS 291752  
ESFBIS  
 
PROBABILISTIC HYDROLOGIC OUTLOOK  
NATIONAL WEATHER SERVICE BISMARCK ND  
1252 PM CDT WED AUG 29 2018  
   
..FLOOD AND WATER RESOURCES OUTLOOK
 
 
THIS PROBABILITY BASED FLOOD AND WATER RESOURCES OUTLOOK IS  
FOR THE SOURIS (MOUSE) RIVER BASIN OF NORTH DAKOTA AND COVERS THE  
PERIOD OF LATE AUGUST THROUGH LATE NOVEMBER.  
 
THE FOLLOWING MESSAGE HAS FOUR SECTIONS. THE FIRST PROVIDES SOME TEXT  
ON THE HIGHLIGHTS OF THIS OUTLOOK AND CONDITIONS AFFECTING THE LOCAL  
HYDROLOGY. THE SECOND SECTION GIVES THE CURRENT AND NORMAL/HISTORICAL  
RISKS OF FLOODING AS DETERMINED BY THE ENSEMBLE STREAMFLOW FORECAST  
MODEL OF THE NATIONAL WEATHER SERVICE. THE THIRD SECTION GIVES THE  
CURRENT PROBABILITIES FOR REACHING FLOOD STAGE AT THE LISTED FORECAST  
LOCATIONS. AND FINALLY, THE FOURTH SECTION COVERS THE RISK OF THE  
RIVER SITES FALLING BELOW THE LISTED STAGES.  
   
..FLOOD OUTLOOK HIGHLIGHTS
 
 
RISK OF WIDESPREAD FLOODING IS NEAR OR BELOW NORMAL FOR THIS TIME OF  
THE YEAR ALONG THE MAJOR RIVERS AND STREAMS OF THE SOURIS RIVER.  
   
..CURRENT CONDITIONS
 
 
LAKE DARLING, RAFFERTY RESERVOIR, AND GRANT DEVINE (FORMERLY  
KNOWN AS ALAMEDA RESERVOIR) ARE WELL WITHIN THEIR NORMAL RANGES  
FOR THIS TIME OF YEAR. SMALL RIVERS ALSO REMAIN WITHIN THEIR NORMAL  
RANGE FOR THIS TIME OF YEAR. SOIL MOISTURE LEVELS ARE BELOW  
NORMAL, ESPECIALLY IN THE SOUTHEASTERN PART OF THE SOURIS RIVER BASIN.  
   
..WEATHER OUTLOOK
 
 
THE NEAR TERM 6-10 AND 8-14 DAY OUTLOOKS DEPICT NEAR TO BELOW NORMAL  
TEMPERATURES WITH A SLIGHTLY ENHANCED CHANCE FOR PRECIPITATION.  
LOOKING FARTHER INTO THE FUTURE, THE ONE-MONTH OUTLOOK FOR SEPTEMBER  
SHOWS EQUAL CHANCES FOR ABOVE NORMAL, NEAR NORMAL, AND BELOW NORMAL  
TEMPERATURE AND PRECIPITATION. HOWEVER, THE EXPECTATION IS THAT AN  
EL NINO WILL DEVELOP THIS FALL AND THIS IS REFLECTED IN THE THREE-MONTH  
OUTLOOK WITH A FAVORING OF ABOVE NORMAL TEMPERATURES EVEN AS THE  
PRECIPITATION PATTERN REMAINS IN THE EQUAL CHANCES CATEGORY.  
   
..IMPORTANT NOTE ON SUBSTANTIVE CHANGES
 
 
BEGINNING JANUARY 1ST OF 2016, THE NATIONAL WEATHER SERVICE CONVERTED  
ALL RIVER GAGE DATA IN THE SOURIS RIVER BASIN OF NORTH DAKOTA TO FEET  
ABOVE MEAN SEA LEVEL USING THE NORTH AMERICAN VERTICAL DATUM OF 1988.  
THIS INCLUDED RAISES IN FLOOD STAGE DEFINITIONS BY UP TO ONE FOOT AT  
INDIVIDUAL LOCATIONS IN ORDER TO CONTINUE WORKING WITH WHOLE NUMBERS.  
MORE INFORMATION ON THIS CAN BE HAD BY CONTACTING SERVICE HYDROLOGIST  
ALLEN SCHLAG AT 701-250-4495.  
 
IN TABLE 1 BELOW, THE CURRENT (CS) AND HISTORICAL (HS) OR NORMAL  
PROBABILITIES OF EXCEEDING MINOR, MODERATE, AND MAJOR FLOOD STAGES  
ARE LISTED FOR THE VALID TIME PERIOD.  
 
CS VALUES INDICATE THE PROBABILITY OF REACHING A FLOOD CATEGORY  
BASED ON CURRENT CONDITIONS.  
 
HS VALUES INDICATE THE PROBABILITY OF REACHING OF THE MODEL  
PREDICTING A RISE TO FLOOD CATEGORY BASED ON HISTORICAL OR NORMAL  
CONDITIONS.  
 
WHEN THE VALUE OF CS IS MORE THAN HS, THE PROBABILITY OF  
EXCEEDING THAT LEVEL IS HIGHER THAN NORMAL. WHEN THE VALUE OF CS IS  
LESS THAN HS, THE PROBABILITY OF EXCEEDING THAT LEVEL IS LOWER  
THAN NORMAL.  
 
   
..TABLE 1--PROBABILITIES FOR MINOR...MODERATE AND MAJOR FLOODING
 
 
VALID PERIOD: 08/26/2018 - 11/24/2018  
: CURRENT AND HISTORICAL  
: CHANCES OF EXCEEDING  
: FLOOD CATEGORIES  
: AS A PERCENTAGE (%)  
CATEGORICAL :  
FLOOD STAGES (FT) : MINOR MODERATE MAJOR  
LOCATION MINOR MOD MAJOR : CS HS CS HS CS HS  
-------- ----- ----- ----- : --- --- --- --- --- ---  
DES LACS RIVER  
FOXHOLM 1651.0 1653.0 1654.0 <5 <5 <5 <5 <5 <5  
SOURIS RIVER  
SHERWOOD 1623.0 1625.0 1630.0 <5 <5 <5 <5 <5 <5  
FOXHOLM 1573.0 1576.0 1578.0 <5 <5 <5 <5 <5 <5  
MINOT 4NW 1562.0 1565.0 1570.0 <5 <5 <5 <5 <5 <5  
MINOT BRWY BRDG 1551.0 1553.0 1557.0 <5 <5 <5 <5 <5 <5  
LOGAN 1536.0 1538.0 1540.0 <5 <5 <5 <5 <5 <5  
SAWYER 1524.0 1526.0 1528.0 <5 <5 <5 <5 <5 <5  
VELVA 1507.0 1512.0 1517.0 <5 <5 <5 <5 <5 <5  
WINTERING RIVER  
KARLSRUHE 1509.0 1511.0 1512.0 <5 <5 <5 <5 <5 <5  
SOURIS RIVER  
TOWNER 1454.0 1456.0 1458.0 <5 <5 <5 <5 <5 <5  
BANTRY 1440.0 1441.0 1443.0 <5 <5 <5 <5 <5 <5  
WILLOW CREEK  
WILLOW CITY 1442.0 1446.0 1448.0 <5 6 <5 <5 <5 <5  
SOURIS RIVER  
WESTHOPE 1414.0 1418.0 1420.0 <5 <5 <5 <5 <5 <5  
LEGEND  
CS = CONDITIONAL SIMULATION (CURRENT OUTLOOK)  
HS = HISTORICAL SIMULATION  
FT = FEET  
 
IN TABLE 2 BELOW, THE 95 THROUGH 5 PERCENT COLUMNS INDICATE THE  
PROBABILITY OF EXCEEDING THE LISTED STAGE LEVELS (FT) FOR THE VALID  
TIME PERIOD.  
   
..TABLE 2--EXCEEDANCE PROBABILITIES
 
 
CHANCE OF EXCEEDING STAGES  
AT SPECIFIC LOCATIONS  
VALID PERIOD: 08/26/2018 - 11/24/2018  
LOCATION 95% 90% 75% 50% 25% 10% 5%  
-------- ------ ------ ------ ------ ------ ------ ------  
:DES/ LACS RIVER  
FOXHOLM 1639.2 1639.2 1639.2 1639.2 1640.1 1641.1 1642.5  
:SOURIS RIVE8R  
SHERWOOD 1605.5 1605.5 1605.5 1606.4 1607.4 1609.3 1611.2  
FOXHOLM 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1570.0  
MINOT 4NW 1550.9 1550.9 1550.9 1550.9 1551.3 1551.8 1554.2  
MINOT BRWY BRDG 1537.2 1537.2 1537.3 1537.5 1539.3 1541.7 1543.1  
LOGAN 1519.9 1519.9 1519.9 1520.0 1521.0 1523.0 1526.9  
SAWYER 1506.6 1506.6 1506.6 1506.8 1508.0 1509.4 1512.7  
VELVA 1490.2 1490.2 1490.2 1490.3 1491.9 1492.7 1497.8  
:WINTERING RIVER  
KARLSRUHE 1502.8 1502.8 1502.8 1502.8 1503.8 1504.6 1505.1  
:SOURIS RIVER  
TOWNER 1444.7 1444.7 1444.7 1444.7 1446.1 1447.7 1453.4  
BANTRY 1431.1 1431.1 1431.1 1431.1 1432.1 1433.4 1439.3  
:WILLOW CREEK  
WILLOW CITY 1435.5 1435.5 1435.5 1436.2 1436.4 1437.1 1437.5  
:SOURIS RIVER  
WESTHOPE 1409.4 1409.4 1409.4 1409.4 1410.0 1411.2 1412.9  
 
IN TABLE 3 BELOW, THE 95 THROUGH 5 PERCENT COLUMNS INDICATE THE  
PROBABILITY OF FALLING BELOW THE LISTED STAGE LEVELS (FT) FOR THE  
VALID TIME PERIOD.  
   
..TABLE 3--NONEXCEEDANCE PROBABILITIES
 
 
CHANCE OF FALLING BELOW STAGES  
AT SPECIFIC LOCATIONS  
VALID PERIOD: 08/26/2018 - 11/24/2018  
LOCATION 95% 90% 75% 50% 25% 10% 5%  
-------- ------ ------ ------ ------ ------ ------ ------  
DES LACS RIVER  
FOXHOLM 1639.1 1639.1 1639.0 1639.0 1639.0 1639.0 1639.0  
SOURIS RIVER  
SHERWOOD 1605.5 1605.5 1605.5 1605.5 1605.5 1605.5 1605.5  
FOXHOLM 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5  
MINOT 4NW 1550.9 1550.8 1550.7 1550.6 1550.6 1550.6 1550.6  
MINOT BRWY BRDG 1537.1 1537.1 1536.8 1536.4 1536.4 1536.4 1536.2  
LOGAN 1519.9 1519.8 1519.8 1519.8 1519.7 1519.7 1519.7  
SAWYER 1506.6 1506.6 1506.6 1506.6 1506.5 1506.5 1506.5  
VELVA 1490.2 1490.2 1490.2 1490.2 1490.2 1490.2 1490.2  
WINTERING RIVER  
KARLSRUHE 1502.8 1502.8 1502.8 1502.8 1502.8 1502.8 1502.8  
SOURIS RIVER  
TOWNER 1444.4 1444.4 1444.4 1444.4 1444.4 1444.4 1444.4  
BANTRY 1430.7 1430.7 1430.7 1430.6 1430.6 1430.6 1430.6  
WILLOW CREEK  
WILLOW CITY 1435.5 1435.5 1435.5 1435.5 1435.5 1435.5 1435.5  
SOURIS RIVER  
WESTHOPE 1409.2 1409.2 1409.2 1409.1 1409.0 1409.0 1409.0  
 
THESE LONG-RANGE PROBABILISTIC OUTLOOKS CONTAIN FORECAST VALUES THAT  
ARE CALCULATED USING HISTORICAL CONDITIONS FROM 30 OR MORE YEARS OF  
CLIMATOLOGICAL DATA, AND CURRENT CONDITIONS OF THE RIVER, SOIL  
MOISTURE, SNOW COVER, AND 30 TO 90 DAY LONG-RANGE OUTLOOKS OF  
TEMPERATURE AND PRECIPITATION. BY PROVIDING A RANGE OF  
PROBABILITIES, THE LEVEL OF RISK ASSOCIATED WITH LONG-RANGE PLANNING  
DECISIONS CAN BE DETERMINED. THESE PROBABILISTIC FORECASTS ARE PART  
OF THE NATIONAL WEATHER SERVICE'S ADVANCED HYDROLOGIC PREDICTION  
SERVICE.  
 
VISIT OUR WEB SITE WEATHER.GOV/BIS FOR MORE WEATHER AND WATER  
INFORMATION.  
 
THE NEXT OUTLOOK WILL BE ISSUED ON SEPTEMBER 27TH.  
 

 
AJS  
 
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