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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