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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