Flood Potential Outlook
Issued by NWS Bismarck, ND

000
FGUS73 KBIS 211527
ESFBIS
NDC009-013-023-049-061-069-075-079-101-251800-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
1025 AM CDT THU MAR 21 2013


...SPRING FLOOD AND WATER RESOURCES OUTLOOK...

THIS PROBABILISTIC FLOOD OUTLOOK IS FOR THE SOURIS (MOUSE) RIVER
BASIN OF WESTERN AND CENTRAL NORTH DAKOTA...COVERING THE TIME PERIOD
OF 25 MARCH THROUGH LATE JUNE.

THE FOLLOWING MESSAGE HAS FOUR SECTIONS...THE FIRST PROVIDES SOME
TEXT ON HIGHLIGHTS OF THIS PRODUCT AND CONDITIONS AFFECTING LOCAL
HYDROLOGY. THE SECOND GIVES THE CURRENT AND NORMAL/HISTORICAL
CHANCES OF RIVER LOCATIONS REACHING THEIR MINOR...MODERATE AND
MAJOR FLOOD CATEGORY...THE THIRD GIVES THE CURRENT CHANCES OF
RIVER LOCATIONS RISING ABOVE RIVER STAGES LISTED...AND THE FINAL
SECTION COVERS THE RISK OF RIVERS FALLING BELOW LISTED STAGES.

...FLOOD OUTLOOK OVERVIEW HIGHLIGHTS...
THE ADDITION OF ROUGHLY 0.5 TO 0.75 INCHES OF WATER OVER MUCH OF THE
BASIN IN THE FORM OF SNOW DURING THE PAST TWO WEEKS HAS INCREASED
FLOOD RISKS AT NEARLY EVERY POINT IN THE BASIN. HOWEVER...THE
INCREASED FLOOD RISK HAS ALSO PROMPTED THE INTERNATIONAL SOURIS
RIVER BOARD TO DECLARE A FLOOD SEASON WHICH DOES IMPACT THE
OPERATING RULES FOR THE SERIES OF DAMS ALONG THE SOURIS RIVER
ITSELF. THE CHANGE IN OPERATIONS ARE INCORPORATED INTO THIS NEW
SUITE OF PROBABILITIES FOR REACHING SPECIFIED STAGES. THE RECENT
ADDITIONAL SNOW WATER EQUIVALENT (SWE) ALSO RAISED THE RISK OF
FLOODING ALONG THE WINTERING AND DES LACS RIVERS.

...CURRENT CONDITIONS...
THE SNOWPACK IN THE SOURIS RIVER BASIN HAS UNDERGONE VIRTUALLY NONE
OF THE USUAL RIPENING PROCESS AND WITH THE CURRENT TEMPERATURE
FORECASTS...NOT MUCH IS EXPECTED DURING THE NEXT WEEK TO 10 DAYS. IN
LAYMAN TERMS...THE SNOWPACK LOOKS LIKE IT SHOULD IN JANUARY AND
FEBRUARY...NOT WHAT IT NORMALLY LOOKS LIKE AS WE APPROACH APRIL. THE
INCREASED DISCHARGE FROM LAKE DARLING OVER THE PAST WEEK IS EXPECTED
TO START WEAKENING THE ICE DOWNSTREAM OF THE DAM OVER THE COMING
DAYS AND WEEKS.

...WEATHER OUTLOOK...
AN INCOMING SYSTEM TODAY THROUGH EARLY SATURDAY WILL MOST LIKELY
AFFECT WESTERN NORTH DAKOTA WITH 3 TO 5 INCHES OF SNOW POSSIBLE IN
THE SOURIS RIVER BASIN OF CANADA AND 1 TO 3 INCHES OF SNOW IN THE
WESTERN SOURIS RIVER BASIN OF NORTH DAKOTA. AFTER THIS SYSTEM PASSES
THROUGH...THE 6 TO 10 AND 8 TO 14 DAY OUTLOOKS SUGGEST BELOW NORMAL
TO NEAR NORMAL TEMPERATURES WITH BELOW NORMAL PRECIPITATION. THIS IS
FAVORED TO TRANSITION INTO A NEAR NORMAL TEMPERATURE REGIME FOR
APRIL WITH A SLIGHTLY ABOVE NORMAL PRECIPITATION PATTERN.

...SUMMARY OF HYDROLOGIC CONDITIONS...
THE SOURIS RIVER BASIN HAS BEEN IMPACTED RECENTLY BY SEVERAL
SIGNIFICANT SNOWSTORMS BRINGING ITS OVERALL SNOW WATER CONTENT TO
AROUND 4 TO 4.5 INCHES ACROSS BROAD AREAS OF THE SOURIS RIVER BASIN
IN NORTH DAKOTA AND THE AREA IN CANADA BELOW RAFFERTY AND ALAMEDA
DAMS. WHILE MINOR TO MODERATE FLOODING ALONG THE SOURIS RIVER ABOVE
MINOT AND MODERATE TO MAJOR FLOODING ARE FAVORED DOWNSTREAM OF
VELVA...THE LARGEST IMPACTS ARE LIKELY TO BE FELT IN THE RURAL
AREAS. SIMILARLY...THE RECENT INCREASE IN SWE ACROSS THE SOURIS
RIVER BASIN SUGGESTS THERE WILL BE BE A FAIR AMOUNT OF OVERLAND
FLOODING ACROSS THE BASIN WITH ANYTHING BUT AN UNUSUALLY GENTLE MELT
SEASON.


...LONG-RANGE PROBABILISTIC RIVER OUTLOOK BY FLOOD CATEGORY...


                           SOURIS RIVER BASIN
                    LONG-RANGE PROBABILISTIC OUTLOOK
             VALID FROM MARCH 25, 2013  TO JUNE 23, 2013

THE TABLE BELOW GIVES BOTH THE CURRENT CHANCES (CS) AND THE
NORMAL/HISTORICAL CHANCES (HS) FOR EXCEEDING THE MINOR...MODERATE
AND MAJOR FLOOD STAGES AT THE RIVER FORECAST POINT LOCATIONS DURING
THE VALID PERIOD OF THIS OUTLOOK.

        PROBABILITIES FOR MINOR...MODERATE AND MAJOR FLOODING
                     FROM  3/25/2013 TO 6/23/2013

TABLE 1                                  : CURRENT AND HISTORICAL
                                         : CHANCES OF EXCEEDING FLOOD
                                         : CATEGORY IN PERCENT (%)
                         CATEGORICAL     :
                      FLOOD STAGES (FT)  :  MINOR   MODERATE  MAJOR
LOCATION            MINOR    MOD   MAJOR :  CS HS    CS HS    CS HS
--------            ------ ------ ------ : --- ---  --- ---  --- ---
DES LACS RIVER.....
  FOXHOLM             16.0   18.0   19.0 :  19  <5   13  <5   11  <5
SOURIS RIVER.....
  SHERWOOD            18.0   20.0   25.0 :   9  <5   <5  <5   <5  <5
  SOURIS NR FOXHOLM   10.0   13.0   15.0 : >95  49   27  36   <5  <5
  MINOT 4NW           14.0   17.0   22.0 :  27  16   14  <5   <5  <5
  MINOT             1549.0 1551.0 1555.0 :  13  <5    8  <5   <5  <5
  LOGAN               34.0   36.0   38.0 :  75  21   14   6   <5  <5
  SAWYER              22.0   24.0   26.0 :  70  19   27  11    6  <5
  VELVA             1505.0 1510.0 1515.0 :  65  14   <5  <5   <5  <5
WINTERING RIVER.....
  KARLSRUHE            7.0    9.0   10.0 :  49   8   <5  <5   <5  <5
SOURIS RIVER.....
  TOWNER              52.0   54.0   56.0 : >95  62  >95  44   23   8
  BANTRY              11.0   12.0   14.0 : >95  62  >95  49   18  <5
WILLOW CREEK.....
  WILLOW CITY         10.0   14.0   16.0 : >95  37   70  13   19  <5
SOURIS RIVER.....
  WESTHOPE            10.0   14.0   16.0 : >95  50   80  21   60  16

LEGEND:
    CS  =  CONDITIONAL SIMULATION (OUTLOOK FOR CURRENT CONDITIONS)
    HS  =  HISTORICAL SIMULATION  (HISTORICAL RISK FOR THIS SEASON)
    FT  =  FEET ABOVE GAGE ZERO DATUM


...LONG-RANGE PROBABILISTIC OUTLOOK BY RIVER STAGE...


                          SOURIS RIVER BASIN
                    LONG-RANGE PROBABILISTIC OUTLOOK

THE TABLE BELOW GIVES THE CURRENT 95 THROUGH 5 PERCENT CHANCES FOR
EXCEEDING RIVER STAGES AT THE RIVER FORECAST POINT LOCATIONS DURING
THE VALID PERIOD OF THIS OUTLOOK.

EXAMPLE: DURING THE VALID TIME OF THIS OUTLOOK...THERE IS A
         95 PERCENT CHANCE FOR THE SOURIS RIVER AT SHERWOOD TO RISE
         ABOVE 11.4 FEET AND ONLY A 5 PERCENT CHANCE THAT
         IT WILL RISE ABOVE 20.6 FEET.

           PROBABILITIES FOR EXCEEDING LISTED RIVER STAGES
                     FROM  3/25/2013 TO 6/23/2013
TABLE 2

LOCATION              95%    90%    75%    50%    25%    10%    05%
--------             -----  -----  -----  -----  -----  -----  -----
DES LACS RIVER.....
  FOXHOLM             11.4   12.3   13.1   14.2   15.6   19.9   20.6
SOURIS RIVER.....
  SHERWOOD            13.6   14.6   15.3   16.3   16.8   18.0   19.8
  SOURIS NR FOXHOLM   11.2   12.5   12.9   12.9   13.7   14.2   15.2
  MINOT 4NW           11.8   12.0   12.5   13.3   14.5   19.9   21.5
  MINOT             1544.2 1544.4 1544.6 1545.2 1545.9 1550.8 1554.7
  LOGAN               32.9   33.4   34.1   34.7   35.2   37.0   37.2
  SAWYER              20.3   21.0   21.6   23.3   24.2   25.7   26.2
  VELVA             1503.6 1504.0 1504.5 1505.5 1506.3 1508.5 1510.0
WINTERING RIVER.....
  KARLSRUHE            5.5    5.8    6.4    7.0    7.6    8.2    8.5
SOURIS RIVER.....
  TOWNER              54.8   54.9   55.2   55.6   56.0   57.1   58.1
  BANTRY              12.8   12.9   13.1   13.4   13.8   14.6   15.1
WILLOW CREEK.....
  WILLOW CITY         12.2   12.7   13.9   14.9   15.7   16.5   16.6
SOURIS RIVER.....
  WESTHOPE            13.2   13.4   15.6   17.5   18.8   20.2   21.0



...LONG-RANGE PROBABILISTIC OUTLOOK BY RIVER STAGE...


                          SOURIS RIVER BASIN
                    LONG-RANGE PROBABILISTIC OUTLOOK

THE TABLE BELOW GIVES THE CURRENT 95 THROUGH 5 PERCENT CHANCES FOR
THE RIVERS TO FALL BELOW THE LISTED RIVER STAGES AT THE RIVER
FORECAST
POINT LOCATIONS DURING THE VALID PERIOD OF THIS OUTLOOK.

EXAMPLE: DURING THE VALID TIME OF THIS OUTLOOK...THERE IS A
         95 PERCENT CHANCE FOR THE SOURIS RIVER AT SHERWOOD
         TO REMAIN ABOVE 4.6 FEET AND ONLY A 5 PERCENT
         CHANCE THAT IT WILL FALL BELOW 4.6FEET.

         PROBABILITIES FOR FALLING BELOW LISTED RIVER STAGES
                        3/25/2013 - 6/23/2013

TABLE 3

LOCATION              95%    90%    75%    50%    25%    10%    05%
--------             -----  -----  -----  -----  -----  -----  -----
DES LACS RIVER.....
  FOXHOLM              4.6    4.6    4.6    4.6    4.6    4.6    4.6
SOURIS RIVER.....
  SHERWOOD             1.1    1.1    1.1    1.1    1.1    1.1    1.1
  SOURIS NR FOXHOLM    4.7    4.7    4.5    4.5    4.5    4.5    4.5
  MINOT 4NW            4.1    4.1    4.0    4.0    3.9    3.9    3.9
  MINOT             1537.2 1537.2 1536.8 1536.4 1535.7 1535.6 1535.5
  LOGAN               20.0   19.8   19.4   19.0   18.8   18.8   18.8
  SAWYER               6.2    6.0    5.7    5.5    5.4    5.4    5.4
  VELVA             1490.0 1489.7 1489.1 1489.0 1489.0 1489.0 1489.0
WINTERING RIVER.....
  KARLSRUHE            1.2    1.2    1.2    1.2    1.2    1.2    1.2
SOURIS RIVER.....
  TOWNER              43.2   43.2   43.2   43.2   43.2   43.2   43.2
  BANTRY               1.7    1.7    1.7    1.7    1.7    1.7    1.7
WILLOW CREEK.....
  WILLOW CITY          4.6    4.6    4.6    4.6    4.6    4.6    4.6
SOURIS RIVER.....
  WESTHOPE             5.1    5.1    5.1    5.1    5.1    5.1    5.1


...THE OUTLOOK PRODUCTION PROCESS...

THIS LONG RANGE PROBABILISTIC OUTLOOK IS BASED ON A SERIES OF PEAK
RIVER LEVELS OR CRESTS TAKEN FROM THE FORECAST HYDROGRAPH RESULTS
OF THE NWS ENSEMBLE STREAMFLOW PREDICTION MODEL (ESP). THE MODEL
IS RUN FOR MULTIPLE SCENARIOS STARTING AT CURRENT RIVER...SNOW AND
SOIL CONDITIONS AND USING NEARLY 50 YEARS OF PAST PRECIPITATION AND
TEMPERATURE CONDITIONS IN THE HISTORICAL RECORD. THESE CRESTS CAN
THEN
BE RANKED FROM LOWEST TO HIGHEST...AND THEN BE ASSIGNED AN
EXCEEDANCE PROBABILITY. FOR EXAMPLE...FOR A SERIES OF 50 YEARS...
THE LOWEST RANKED CREST HAS 49 CRESTS ABOVE IT AND SINCE 95 PERCENT
OF THE CRESTS ARE ABOVE IT...IT IS ASSIGNED A 95 PERCENT PROBABILITY
OF EXCEEDANCE (POE).

THE PROBABILITIES CAN BE USED FOR RISK MANAGEMENT BY COMPARING THIS
YEARS CURRENT TEMPERATURE AND PRECIPITATION OUTLOOKS WITH
THOSE OF PAST YEARS USED IN THE HYDRO OUTLOOK. THEY CAN ALSO BE
USED AS AN INDICATION OF THE RANGE OF CRESTS THAT MAY BE EXPECTED
DURING THE VALID PERIOD OF THE OUTLOOK.

BY PROVIDING A RANGE OF PEAK RIVER LEVEL PROBABILITIES..THE NWS IS
IS CONTRIBUTING TO THE AREAS DECISION SUPPORT SERVICES THAT HELP
WITH LONG RANGE FLOOD PLANNING AND RESPONSE READINESS.  THIS OUTLOOK
IS A PART OF NOAA/S NATIONAL WEATHER SERVICE/S AHPS (ADVANCED
HYDROLOGIC PREDICTION SERVICES).

THIS OUTLOOK WAS PRODUCED USING PRECIPITATION AND TEMPERATURES
FOR THE YEARS 1948 THROUGH 2006.

...ADDITIONAL INFORMATION SOURCES...

THE AHPS LONG RANGE PROBABILISTIC HYDROLOGIC OUTLOOKS ARE ISSUED
NEAR THE END OF EACH MONTH. HOWEVER...SPRING FLOOD AND WATER
RESOURCES OUTLOOKS ARE ISSUED SEVERAL TIMES DURING THE CRITICAL
SPRING MELT PERIOD...USUALLY ON THURSDAYS BEGINNING IN LATE
FEBRUARY OR EARLY MARCH AND ENDING IN EARLY APRIL...DEPENDING
ON THE SPRING FLOODING CONDITIONS.

THIS OUTLOOK IS ALSO PRESENTED AS GRAPHS OF THE PROBABILITY OF STAGE
EXCEEDANCE FOR THE FULL PERIOD AND FOR WEEKLY INTERVALS DURING THE
PERIOD. THESE GRAPHS...TOGETHER WITH EXPLANATIONS THAT HELP IN
INTERPRETING THEM ARE AVAILABLE FROM THE NWS BISMARCK AHPS WEB
PAGE ON THE INTERNET AT:

        WWW.WEATHER.GOV/BISMARCK OR WEATHER.GOV/BIS

  THEN CLICK ON THE "RIVERS AND LAKES AHPS"ON THE TAB ABOVE THE
MAP...OR ON THE LINK IN THE BLUE-LEFT-HAND BANNER.

CURRENT RIVER CONDITIONS FOR ALL FORECAST POINTS WITHIN THE SOURIS
RIVER BASIN ARE AVAILABLE ON OUR WEB SITE...AS WELL AS THE FORECASTS
WHEN THE RIVER AT THE FORECAST POINT IS IN OR NEAR FLOOD.

IF YOU HAVE ANY QUESTIONS...CONTACT THE NWS AT 701-250-4495.

PROBABILISTIC HYDROLOGIC OUTLOOKS WILL BE ISSUED MONTHLY THROUGHOUT
THE REST OF THE YEAR DURING THE LATER PART OF THE MONTH OR AS
CONDITIONS WARRANT.


$$
AJS