910  
FGUS73 KBIS 271755  
ESFBIS  
 
PROBABILISTIC HYDROLOGIC OUTLOOK  
NATIONAL WEATHER SERVICE BISMARCK ND  
1255 PM CDT WED MAR 27 2019  
   
..SPRING FLOOD AND WATER RESOURCES OUTLOOK
 
 
THIS SPRING FLOOD AND WATER RESOURCES OUTLOOK IS FOR THE SOURIS  
(MOUSE) RIVER BASIN OF NORTH DAKOTA AND COVERS THE PERIOD OF LATE  
MARCH THROUGH THE END OF JUNE. THIS OUTLOOK UPDATES THE MOST RECENT  
SPRING FLOOD AND WATER RESOURCES OUTLOOK FOR THE SOURIS.  
 
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
 
 
FLOOD RISK ACROSS THE SOURIS RIVER BASIN HAS FALLEN, MOSTLY DUE TO  
A LACK OF NORMAL MOISTURE SINCE THE MOST RECENT OUTLOOK, AND A  
FAIRLY BENIGN MELT WHICH HAS ALREADY REMOVED MUCH OF THE SWE  
(SNOW-WATER EQUIVALENT) ACROSS PARTS OF THE SOURIS RIVER BASIN.  
IN CANADA, SNOWPACK AND EXPECTED RUNOFF IN THE HEADWATERS OF THE  
SOURIS ABOVE BOTH RAFFERTY AND GRANT DEVINE (ALAMEDA) DAMS HAS THUS  
FAR BEEN BELOW NORMAL. A DECENT SNOWPACK STILL REMAINS ACROSS MUCH  
OF THE NORTH DAKOTA PORTION OF THE SOURIS RIVER BASIN, BUT DOES NOT  
POSE A GREAT THREAT AT THIS POINT IN THE MELT SEASON UNTIL YOU LOOK  
AT WILLOW CREEK.  
 
WILLOW CREEK STILL PRESENTS THE GREATEST RISK OF AT LEAST MINOR  
FLOODING, BUT THAT WILL NOT TAKE PLACE UNTIL EARLY APRIL.  
 
IMPORTANTLY, THE PROBABILITIES SHOWN IN TABLES 1 AND 2 DO NOT  
INCLUDE THE RISKS ASSOCIATED WITH ICEJAM RELATED FLOODING. ICEJAMS  
DEFY MATHEMATICAL PREDICTIONS, BUT ARE KNOWN TO INCREASE DURING  
EARLY AND RAPID SPRING RUNOFFS WHERE THE ICE BECOMES MOBILIZED, ONLY  
TO GET STUCK AT SOME DOWNSTREAM CONSTRICTION SUCH AS BRIDGES AND  
BENDS IN THE RIVER.  
   
..CURRENT CONDITIONS
 
 
LAKE DARLING, RAFFERTY RESERVOIR, AND GRANT DEVINE (FORMERLY  
KNOWN AS ALAMEDA RESERVOIR) ARE OPERATING WELL WITHIN THEIR EXPECTED  
RANGES FOR THE AMOUNT OF SNOW THAT HAS MELTED ACROSS THE BASIN. ONE  
SHOULD CONTINUE TO EXPECT THEM TO EXERT A GREAT AMOUNT OF CONTROL  
OVER RUNOFF FROM THE UPPER BASIN AREAS. SOIL MOISTURE LEVELS  
ARE BELOW NORMAL AT DEPTH, AND AS FROST LEAVES THE GROUND, IT WILL  
ALLOW MORE INFILTRATION OF MELTWATER AND ANY FUTURE PRECIPITATION.  
   
..WEATHER OUTLOOK
 
 
BELOW NORMAL TEMPERATURES AND NEAR NORMAL TO SLIGHTLY ABOVE NORMAL  
PRECIPITATION IS FAVORED IN THE 8-14 DAY OUTLOOK. LONGER TERM,  
THE ONE-MONTH AND THREE-MONTH OUTLOOKS SLIGHTLY FAVOR BELOW  
NORMAL TEMPERATURES AND HOLD THE AREA IN AN EQUAL CHANCE DESIGNATION  
FOR ABOVE NORMAL, NEAR NORMAL, OR BELOW NORMAL PRECIPITATION.  
   
..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: 04/01/2019 - 06/30/2019  
: 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 11 <5 <5 <5 <5  
FOXHOLM 1573.0 1576.0 1578.0 7 31 <5 12 <5 <5  
MINOT 4NW 1562.0 1565.0 1570.0 <5 11 <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 16 <5 <5 <5 <5  
SAWYER 1524.0 1526.0 1528.0 <5 7 <5 <5 <5 <5  
VELVA 1507.0 1512.0 1517.0 <5 14 <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 26 57 6 24 <5 5  
BANTRY 1440.0 1441.0 1443.0 25 56 17 38 <5 6  
WILLOW CREEK  
WILLOW CITY 1442.0 1446.0 1448.0 >95 38 <5 14 <5 <5  
SOURIS RIVER  
WESTHOPE 1414.0 1418.0 1420.0 32 47 8 23 <5 17  
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: 04/01/2019 - 06/30/2019  
LOCATION 95% 90% 75% 50% 25% 10% 5%  
-------- ------ ------ ------ ------ ------ ------ ------  
:DES/ LACS RIVER  
FOXHOLM 1641.1 1641.1 1641.1 1641.4 1642.8 1644.4 1647.1  
:SOURIS RIVER  
SHERWOOD 1608.3 1608.3 1608.3 1609.1 1611.8 1617.9 1619.7  
FOXHOLM 1570.8 1570.8 1570.8 1570.8 1570.9 1571.6 1574.9  
MINOT 4NW 1554.4 1554.4 1554.4 1554.4 1554.4 1555.6 1561.0  
MINOT BRWY BRDG 1543.2 1543.2 1543.2 1543.2 1543.2 1544.1 1546.9  
LOGAN 1527.0 1527.0 1527.0 1527.0 1527.7 1532.4 1535.8  
SAWYER 1512.5 1512.5 1512.5 1512.5 1513.8 1519.2 1521.8  
VELVA 1496.6 1496.6 1496.6 1496.6 1497.9 1505.1 1506.2  
:WINTERING RIVER  
KARLSRUHE 1504.7 1504.7 1504.7 1504.7 1506.1 1507.8 1508.9  
:SOURIS RIVER  
TOWNER 1453.0 1453.0 1453.0 1453.0 1454.2 1455.8 1456.2  
BANTRY 1439.5 1439.5 1439.5 1439.5 1440.1 1441.4 1441.7  
:WILLOW CREEK  
WILLOW CITY 1442.2 1442.5 1443.1 1443.5 1444.6 1445.7 1445.9  
:SOURIS RIVER  
WESTHOPE 1413.1 1413.1 1413.2 1413.4 1414.8 1417.6 1419.7  
 
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: 04/01/2019 - 06/30/2019  
LOCATION 95% 90% 75% 50% 25% 10% 5%  
-------- ------ ------ ------ ------ ------ ------ ------  
DES LACS RIVER  
FOXHOLM 1640.4 1640.0 1639.8 1639.6 1639.5 1639.5 1639.5  
SOURIS RIVER  
SHERWOOD 1606.6 1606.2 1605.9 1605.6 1605.5 1605.5 1605.5  
FOXHOLM 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5  
MINOT 4NW 1551.4 1551.2 1551.1 1551.0 1551.0 1551.0 1551.0  
MINOT BRWY BRDG 1540.1 1539.2 1538.8 1538.3 1538.0 1537.9 1537.9  
LOGAN 1521.4 1520.6 1520.2 1520.1 1520.0 1520.0 1520.0  
SAWYER 1508.1 1507.8 1507.5 1507.1 1506.8 1506.7 1506.7  
VELVA 1491.9 1491.5 1491.0 1490.4 1490.2 1490.2 1490.2  
WINTERING RIVER  
KARLSRUHE 1503.8 1503.5 1503.0 1502.8 1502.8 1502.8 1502.8  
SOURIS RIVER  
TOWNER 1446.9 1445.9 1445.1 1444.4 1444.4 1444.4 1444.4  
BANTRY 1432.8 1432.0 1431.2 1430.8 1430.6 1430.5 1430.5  
WILLOW CREEK  
WILLOW CITY 1436.6 1436.4 1436.3 1436.1 1435.6 1435.5 1435.5  
SOURIS RIVER  
WESTHOPE 1411.7 1411.0 1410.2 1409.7 1409.4 1409.2 1409.2  
 
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.  
 

 
AJS  
 
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