169  
FGUS73 KBIS 131631  
ESFBIS  
NDC009-049-069-075-101-282359-  
 
PROBABILISTIC HYDROLOGIC OUTLOOK  
NATIONAL WEATHER SERVICE BISMARCK ND  
1030 AM CST THU FEB 13 2020  
   
..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  
MID-FEBRUARY THROUGH MIDDLE OF MAY. THIS OUTLOOK IS THE FIRST IN  
THE SPRING FLOOD AND WATER RESOURCES OUTLOOK SERIES AND WILL BE  
UPDATED ON 27 FEBRUARY AND 13 MARCH. AFTER THOSE UPDATES, THE NWS  
WILL REVERT BACK TO THE REGULAR MONTHLY ISSUANCE ON THE FOURTH  
THURSDAY OF EACH MONTH.  
 
THE FOLLOWING MESSAGE HAS FOUR SECTIONS. THE FIRST PROVIDES SOME  
DISCUSSION 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
 
 
MOST LOCATIONS ACROSS THE SOURIS RIVER BASIN OF NORTH DAKOTA ARE NEAR  
NORMAL FOR FLOOD RISK DURING THE SPRING MELT SEASON. HOWEVER, THE RISK  
OF FLOODING INCREASES SUBSTANTIALLY FOR THE SOURIS NEAR TOWNER,  
BANTRY, AND WESTHOPE. SIMILARLY, WILLOW CREEK NEAR WILLOW CITY HAS  
A SIGNIFICANTLY ABOVE NORMAL RISK OF FLOODING THIS SPRING. THE REASON  
FOR THIS DISPARITY ACROSS THE SOURIS RIVER BASIN OF NORTH DAKOTA IS  
THE DIFFERENCE IN SNOW-WATER EQUIVALENT (SWE). THE SNOWPACK ABOVE  
MINOT AND LAKE DARLING IS UNREMARKABLE AND GENERALLY CONTAINS LESS  
THAN ONE INCH OF SWE. AS ONE APPROACHES THE EASTERN SIDE OF THE BASIN  
IN NORTH DAKOTA, THE SWE CONTENT OF THE SNOWPACK RANGES FROM ONE TO  
TWO INCHES. WHILE THIS IS NOT NECESSARILY AN UNUSUALLY HIGH AMOUNT OF  
SWE GOING INTO SPRING, SOIL CONDITIONS TEND TO BE MUCH WETTER THAN  
NORMAL AND THESE WETTER SOILS WILL INHIBIT INFILTRATION AND ENHANCE  
RUNOFF DURING THE SPRING MELT SEASON.  
   
..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. THE WET FALL HAS GENERALLY PUT THE SOIL  
MOISTURE ABOVE THE 95TH PERCENTILE. WHILE THIS HIGH SOIL MOISTURE  
EXTENDS INTO THE SOURIS RIVER BASIN IN CANADA, THE SNOWPACK IS  
NOT SIGNIFICANT WITH GENERALLY LESS THAN AN INCH OF SWE ABOVE  
LAKE DARLING. IN THE TOWNER AND UP THROUGH THE WILLOW CREEK  
BASIN, A SLIGHTLY GREATER SNOWPACK EXISTS WITH BETWEEN ONE AND TWO  
INCHES OF WATER AVAILABLE FOR THE SPRING MELT SEASON.  
   
..WEATHER OUTLOOK
 
 
THE NEAR TERM 6-10 AND 8-14 DAY OUTLOOKS SUGGEST A CONTINUATION OF  
THE VERY BENIGN WEATHER PATTERN THE AREA HAS EXPERIENCED OVER THE  
PAST FEW WEEKS. THIS BELOW NORMAL PRECIPITATION PATTERN AND NEAR  
NORMAL TO ABOVE NORMAL TEMPERATURES WILL HELP LOWER FLOOD RISKS  
EVEN MORE AS WE GO INTO MARCH. LOOKING FARTHER INTO THE FUTURE, THE  
3-MONTH OUTLOOKS SUGGEST A SLIGHTLY COOLER AND WETTER THAN NORMAL  
PATTERN FOR THE ENTIRE FEBRUARY, MARCH, AND APRIL PERIOD.  
   
..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 STAGE  
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 A FLOOD CATEGORY  
BASED ON HISTORICAL OR NORMAL CONDITIONS.  
 
WHEN THE VALUE OF CS IS GREATER 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:  
VALID PERIOD: 02/17/2020 - 05/17/2020  
: 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  
FOXHOLM 1651.0 1653.0 1654.0 : 6 <5 5 <5 <5 <5  
:SOURIS  
SHERWOOD 1623.0 1625.0 1630.0 : <5 11 <5 <5 <5 <5  
FOXHOLM 1573.0 1576.0 1578.0 : 21 35 <5 12 <5 <5  
MINOT 1562.0 1565.0 1570.0 : 7 11 7 5 <5 <5  
MINOT 1551.0 1553.0 1557.0 : 6 <5 <5 <5 <5 <5  
LOGAN 1536.0 1538.0 1540.0 : 10 17 7 <5 <5 <5  
SAWYER 1524.0 1526.0 1528.0 : 7 7 6 <5 <5 <5  
VELVA 1507.0 1512.0 1517.0 : 12 15 <5 <5 <5 <5  
:WINTERING  
KARLSRUHE 1509.0 1511.0 1512.0 : 18 6 <5 <5 <5 <5  
:SOURIS  
TOWNER 1454.0 1456.0 1458.0 : >95 55 51 24 7 <5  
BANTRY 1440.0 1441.0 1443.0 : >95 51 92 37 7 <5  
:WILLOW CREEK  
WILLOW CITY 1442.0 1446.0 1448.0 : >95 35 18 13 <5 <5  
:SOURIS  
WESTHOPE 1414.0 1418.0 1420.0 : >95 45 65 23 32 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: 02/17/2020 - 05/17/2020  
LOCATION 95% 90% 75% 50% 25% 10% 5%  
-------- ------ ------ ------ ------ ------ ------ ------  
:DES LACS  
FOXHOLM 1641.9 1642.1 1642.8 1643.9 1645.7 1647.5 1653.0  
:SOURIS  
SHERWOOD 1608.7 1608.9 1611.3 1615.9 1619.0 1620.3 1620.9  
FOXHOLM 1569.5 1569.7 1570.3 1570.8 1572.8 1573.9 1575.6  
MINOT 4NW 1554.0 1554.5 1555.0 1555.6 1556.7 1558.1 1567.0  
MINOT BRDWY BRDG 1543.1 1543.3 1543.4 1543.8 1544.4 1545.6 1552.8  
LOGAN 1527.6 1528.5 1529.3 1530.2 1532.2 1535.7 1538.4  
SAWYER 1514.7 1515.7 1516.6 1517.6 1519.7 1522.6 1526.4  
VELVA 1500.6 1501.7 1502.6 1504.0 1505.7 1507.5 1510.7  
:WINTERING  
KARLSRUHE 1507.7 1507.8 1508.0 1508.4 1508.9 1509.1 1509.4  
:SOURIS  
TOWNER 1455.0 1455.4 1455.6 1456.0 1456.6 1457.2 1459.1  
BANTRY 1440.7 1441.1 1441.2 1441.5 1441.9 1442.5 1443.8  
:WILLOW CREEK  
WILLOW CITY 1443.0 1443.1 1444.0 1445.0 1445.7 1446.7 1447.5  
:SOURIS  
WESTHOPE 1415.5 1415.7 1417.2 1419.0 1420.2 1421.6 1425.1  
 
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: 02/17/2020 - 05/17/2020  
LOCATION 95% 90% 75% 50% 25% 10% 5%  
-------- ------ ------ ------ ------ ------ ------ ------  
:DES LACS  
FOXHOLM 1640.2 1640.2 1640.2 1640.1 1639.8 1639.7 1639.7  
:SOURIS  
SHERWOOD 1605.5 1605.5 1605.5 1605.5 1605.5 1605.5 1605.5  
FOXHOLM 1567.2 1566.7 1566.5 1566.5 1566.5 1566.5 1566.5  
MINOT 4NW 1551.6 1551.6 1551.5 1551.4 1551.3 1551.2 1551.2  
MINOT BRDWY BRDG 1541.2 1541.2 1540.9 1540.2 1539.5 1539.2 1539.1  
LOGAN 1522.5 1522.5 1522.4 1521.9 1521.1 1520.9 1520.7  
SAWYER 1509.0 1509.0 1508.9 1508.4 1508.0 1507.9 1507.8  
VELVA 1492.5 1492.5 1492.5 1492.2 1491.8 1491.7 1491.5  
:WINTERING  
KARLSRUHE 1505.8 1505.8 1505.7 1505.7 1505.5 1505.4 1505.3  
:SOURIS  
TOWNER 1444.5 1444.5 1444.4 1444.4 1444.4 1444.4 1444.4  
BANTRY 1430.7 1430.5 1430.4 1430.2 1430.2 1430.1 1430.1  
:WILLOW CREEK  
WILLOW CITY 1436.0 1436.0 1436.0 1436.0 1436.0 1436.0 1436.0  
:SOURIS  
WESTHOPE 1411.3 1411.3 1411.3 1411.1 1410.1 1409.5 1409.5  
 
THESE LONG-RANGE PROBABILISTIC OUTLOOKS CONTAIN FORECAST VALUES THAT  
ARE CALCULATED USING MULTIPLE SEASON SCENARIOS FROM 30 OR MORE YEARS  
OF CLIMATOLOGICAL DATA...INCLUDING 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 FEBRUARY 27.  
 

 
 
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