April 17 2013 Updated Red River Basin Flood Outlook

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

...RED RIVER BASIN OUTLOOK FOR RIVER FLOOD POTENTIAL...

         THIS OUTLOOK COVERS THE RED RIVER OF THE NORTH
         AND ITS MINNESOTA AND NORTH DAKOTA TRIBUTARIES.

...MORE SNOW AND DELAYED THAW INCREASES FLOOD RISK YET AGAIN...

. OUTLOOK SUMMARY...

 * THIS OUTLOOK COVERS THE PERIOD FROM APRIL 23, 2013...
                                             TO JULY 22, 2013

 * THE PROBABILITIES OF MINOR, MODERATE AND MAJOR FLOODING...

  - NEW WEB PAGE DISPLAYING GRAPHICAL RISK OF FLOODING IS AT:

        WATER.WEATHER.GOV/AHPS/LONG_RANGE.PHP?WFO=FGF&PERCENT=50

. OUTLOOK DISCUSSION...HYDROLOGIC AND CLIMATE CONDITIONS WHICH
  AFFECT EACH OF THE SEVERAL FACTORS THAT DETERMINE SPRING SNOWMELT
  FLOODING WITHIN THE RED RIVER OF THE NORTH BASIN ARE DISCUSSED
  BELOW:

  * SNOWPACK CONDITIONS...

   - SNOW STORMS AND FREEZING RAIN HAS ADDED SNOW WATER TO THE
     SNOWPACK ON THE ORDER OF ONE AND A QUARTER INCHES IN THE
     DEVILS LAKE...UPPER SHEYENNE AND THE HEADWATERS OF THE NORTH
     DAKOTA WILD RICE RIVER BASINS. THERE WAS ABOUT THREE QUARTERS
     TO ONE INCH OF ADDED MOISTURE TO THE RED RIVER BASIN FROM FARGO
     SOUTH TO THE SOUTH DAKOTA BORDER. ABOUT A THIRD OF AN INCH WAS
     ADDED TO THE MIDDLE OF THE BASIN AND A TENTH OF AN INCH NORTH
     OF GRAND FORKS. THE SNOWPACK IS RIPE, PRIMED AND READY TO MELT
     WITH SNOW TEMPERATURES APPROACHING THE THAW TEMPERATURE IN THE
     SOUTHERN BASIN. LONGER DAYS AND HIGHER SUN ANGLES WILL WORK TO
     PRIME THE SNOW PACK DESPITE BELOW AVERAGE AIR TEMPERATURES.
     THESE FACTORS WILL BEGIN TO ERODE THE SNOWPACK FROM SOUTH TO
     NORTH BY THE UPCOMING WEEKEND.

  * SOIL CONDITIONS AND FROST DEPTHS...

   - BARE SPOTS IN THE BASIN ARE SEEING A FEW INCHES OF TOPSOIL
     MELT WHICH MAY BE HOLDING AN INCH OR SO OF MELT WATER BEFORE
     RELEASING IT INTO DITCHES AND EVENTUALLY RIVERS AND STREAMS.
     THERE IS STILL A DEEP LAYER OF FROZEN GROUND UNDERNEATH THE
     MELTED LAYER THAT TYPICALLY PREVENTS OR INHIBITS FULL MOISTURE
     INFILTRATION UNTIL IT THAWS. THIS WILL ENHANCE THE QUANTITY AND
     SPEED OF THE SNOW MELT RUNOFF REACHING THE RIVER CHANNELS.

  * RIVER FLOWS AND ICE...

   - RIVER FLOWS AND STAGES ARE RESPONDING SLOWLY TO LOCAL RUNOFF.
     SOME RIVER LOCATIONS IN THE SOUTHERN BASIN HAVE RISEN MARKEDLY
     TO NEAR MINOR FLOOD STAGE EARLY THIS WEEK. RIVER FLOWS WILL
     INCREASE STEEPLY ONCE THE SNOW MELT STARTS IN EARNEST LATER
     THIS WEEK OR EARLY NEXT WEEK IN THE SOUTHERN BASIN.

   - RIVER ICE IS GETTING OLD AND MORE ROTTEN AS THE DAYS GET
     LONGER AND THE SUN ANGLE BECOMES MORE DIRECT. AFTERNOON HIGHS
     ABOVE FREEZING AND OVERNIGHT LOWS HOVERING JUST BELOW THE
     FREEZING MARK ALSO HELPS TO TRANSFER HEAT ENERGY TO THE ICE AND
     PROMOTE ITS EVENTUAL MELT, COLLAPSE AND DESTRUCTION.

   - AS RUNOFF FLOODING BEGINS IN EARNEST...RIVER ICE BREAKUP WILL
     ACCELERATE AND SOME LOCALLY ENHANCED ICE JAM FLOODING IS
     POSSIBLE. THIS GENERALLY OCCURS NEAR TIGHT BENDS IN THE RIVERS
     OR STREAMS...WHERE DEBRIS AND STRUCTURES ACT TO CONSTRICT FLOWS
     AND NEAR CONFLUENCES WITH TRIBUTARY STREAMS.

  * FACTORS YET TO BE DETERMINED...

   - A DELAYED THAW...RAIN ON SNOW OR DENSE FOG ARE ALL POSSIBLE
     SCENARIOS FOR RAPID SNOW MELT. SINCE THE SPRINGTIME THAW AND
     SNOWMELT HAS NOW BEEN DELAYED INTO LATE APRIL...THE RISK FOR A
     MORE RAPID WARM UP AND THUS A SHORTENED OVERALL THAW CYCLE ARE HIGH.
     FURTHERMORE...AS WE MOVE TOWARD THE END OF THE MONTH...WE HAVE A
     HIGHER RISK OF HAVING A HEAVY THUNDERSTORM RAINFALL EVENT OCCUR OVER
     THAWING SNOW AND FROZEN GROUND DURING THE PERIOD OF HIGH WATER.
     THUS...AN OVERALL INCREASED RISK OF MODERATE TO MAJOR FLOODING IS
     EXPRESSED IN THIS OUTLOOK.

  * SHORT TERM WEATHER FORECAST...

   - OVERALL TEMPERATURES...CONTINUED MUCH BELOW NORMAL TEMPERATURES
     WILL GRADUALLY MODERATE THROUGH THE WEEKEND. HOWEVER IT WILL
     REMAIN UN SEASONALLY COOL THROUGH THE APRIL 21ST TIME PERIOD WHICH
     WILL RETARD THE MELT. MEANWHILE THERE ARE SLIGHT CHANCES OF
     PRECIPITATION...MAINLY IN THE FORM OF SNOW.

  * SPRING FLOOD SEASON CLIMATE OUTLOOK...

   - TEMPERATURES ARE EXPECTED TO CONTINUE A SLOW WARMING TREND...BUT
     CONTINUED COOLER THAN LATE APRIL NORMALS SUGGEST. PRECIPITATION
     WILL LIKELY CONTINUE ABOVE MEDIAN. DURING THE LAST FULL WEEK OF
     APRIL IT WOULD APPEAR THAT A SIGNIFICANT AMOUNT OF VARIABILITY
     IN TEMPERATURES WILL DEVELOP. BASED ON CLIMATOLOGY AS WELL AS
     THE FORECAST PATTERN OF TEMPERATURE VARIABILITY THERE IS AN
     ENHANCED RISK OF A MODERATE RAIN EVENT DURING THE LAST WEEK OF
     APRIL. IT IS NOT POSSIBLE TO MAKE ANY PREDICTIONS OF RAIN AMOUNTS
     BUT IT COULD OCCUR AT A TIME THAT IS SENSITIVE TO THE MELT.

.  THE MONTHLY AHPS PROBABILISTIC HYDROLOGIC OUTLOOKS WILL RESUME
   FOR THE RIVERS IN THE RED RIVER BASIN FOLLOWING THE SPRING FLOODS
   AND AFTER THEY RETURN TO THEIR BANKS.

  * FLOOD WARNINGS AND 7-DAY RIVER LEVEL FORECASTS WILL BE ISSUED
    WHEN THE RIVER FORECAST LOCATIONS ARE EXPECTED TO REACH FLOOD
    STAGE WITHIN THE 7 DAY PERIOD OR THE RIVER LOCATION WILL
    INCREASE IN FLOOD CATEGORY. THESE FORECASTS WILL BE UPDATED
    AT LEAST DAILY AND MORE FREQUENTLY IF NEEDED BY CHANGING
    CONDITIONS.

. FLOOD OUTLOOK PROBABILITIES TABLES...

THE FOLLOWING MESSAGE HAS TWO SECTIONS...THE FIRST GIVES THE
CURRENT AND NORMAL/HISTORICAL CHANCES OF RIVER LOCATIONS REACHING
THEIR MINOR...MODERAT AND MAJOR FLOOD CATEGORY...THE SECOND
GIVES THE CURRENT CHANCES OF RIVER LOCATIONS RISING ABOVE RIVER
STAGES LISTED.

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

             VALID FROM APRIL 23, 2013  TO JULY 22, 2013

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 A FLOOD CATEGORY
BASED ON HISTORICAL OR NORMAL CONDITIONS.

WHEN THE VALUE OF CS IS MORE THAN HS...THE PROBABILITY OF
EXCEEDING TAT 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...MODERAGE AND MAJOR FLOODING
                VALID PERIOD:   4/23/2013 - 7/22/2013

                                         : CURRENT AND HISTORICAL
                                         :  CHANCES OF EXCEEDING
                                         :    FLOOD CATEGORIES
                                         :   AS S PERCENTAGE (%)
                         CATEGORICAL     :
                      FLOOD STAGES (FT)  :  MINOR   MODERATE  MAJOR
LOCATION            MINOR    MOD   MAJOR :  CS HS    CS HS    CS HS
--------            ------ ------ ------ : --- ---  --- ---  --- ---
RED RIVER OF THE NORTH.....
  WAHPETON            10.0   12.0   14.0 : >95  48  >95  21  >95  <5
  HICKSON             30.0   34.0   38.0 : >95  <5  >95  <5   19  <5
  FARGO               18.0   25.0   30.0 : >95  62  >95  21  >95  12
  HALSTAD             26.0   32.0   37.5 : >95  16  >95   9  >95   6
  GRAND FORKS         28.0   40.0   46.0 : >95  50  >95  24  >95  <5
  OSLO                26.0   30.0   36.0 : >95  56  >95  48  >95  11
  DRAYTON             32.0   38.0   42.0 : >95  38  >95  25  >95   8
  PEMBINA             39.0   44.0   49.0 : >95  40  >95  35  >95  17
MINNESOTA TRIBUTARIES.....
  SABIN               12.0   15.0   19.0 : >95  45  >95  <5   <5  <5
  HAWLEY               7.0    9.0   11.0 : >95  32  >95  12   12  <5
  DILWORTH            12.0   20.0   26.0 : >95  59  >95  11   12  <5
  TWIN VALLEY         10.0   12.0   14.0 :  93   6   61  <5   40  <5
  HENDRUM             20.0   28.0   32.0 : >95  38  >95  11   66  <5
  SHELLY              14.0   20.0   23.0 : >95  14   58  <5   12  <5
  CLIMAX              20.0   25.0   30.0 : >95   9  >95   6   50  <5
  HIGH LANDING        12.0   12.5   13.0 :  75  19   71  14   59   9
  CROOKSTON           15.0   23.0   25.0 : >95  48   58   9   27   6
  ABOVE WARREN        67.0   71.0   76.0 :  48  12    9  <5   <5  <5
  ALVARADO           106.0  108.0  110.0 :  71  12   35  11    6  <5
  HALLOCK            802.0  806.0  810.0 : >95  46  >95  24   19  <5
  ROSEAU              16.0   18.0   19.0 :  61  16   35   6   22  <5
NORTH DAKOTA TRIBUTARIES.....
  ABERCROMBIE         10.0   12.0   18.0 : >95  33  >95  21  >95  <5
  VALLEY CITY         15.0   16.0   17.0 :  79   9   66   8   46   6
  LISBON              15.0   17.0   19.0 : >95   9   74  <5   35  <5
  KINDRED             16.0   19.0   20.5 : >95  19  >95   9   91  <5
  WEST FARGO DVRSN    18.0   20.0   21.0 : >95  21  >95  11  >95   9
  HARWOOD            884.0  886.0  891.0 : >95  16  >95  12   66   9
  ENDERLIN             9.5   12.0   14.0 : >95  14   77  <5   <5  <5
  MAPLETON           905.0  908.0  910.0 : >95  22  >95  12   <5  <5
  HILLSBORO           10.0   13.0   16.0 : >95   6  >95  <5   25  <5
  MINTO                6.0    8.0   11.0 : >95  11  >95  <5   <5  <5
  GRAFTON             12.0   13.5   14.5 : >95  11  >95  <5  >95  <5
  WALHALLA            11.0   16.0   18.0 : >95  12    8  <5   <5  <5
  NECHE               18.0   19.0   20.5 : >95  21  >95  16  >95   9

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


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

             VALID FROM APRIL 23, 2013  TO JULY 22, 2013


LOCATION              95%    90%    75%    50%    25%    10%    05%
--------            ------ ------ ------ ------ ------ ------ ------
RED RIVER OF THE NORTH.....
  WAHPETON            16.9   17.0   17.4   17.8   18.5   19.2   19.5
  HICKSON             36.5   36.6   36.8   37.2   37.8   38.4   38.6
  FARGO               39.3   39.4   39.8   40.3   41.3   42.1   42.4
  HALSTAD             38.6   38.6   38.8   39.3   39.7   40.1   40.4
  GRAND FORKS         47.3   47.5   48.2   49.6   50.9   52.0   54.3
  OSLO                37.6   37.7   38.0   38.5   39.1   39.5   40.4
  DRAYTON             42.5   42.5   42.8   43.4   44.0   44.4   45.3
  PEMBINA             52.5   52.6   52.7   53.4   53.8   54.2   54.8

MINNESOTA TRIBS:      95%    90%    75%    50%    25%    10%    05%
--------            ------ ------ ------ ------ ------ ------ ------
SOUTH FORK BUFFALO RIVER.....
  SABIN               17.2   17.3   17.5   17.9   18.3   18.8   18.8
BUFFALO RIVER.....
  HAWLEY               9.7    9.8    9.9   10.3   10.7   11.1   11.6
  DILWORTH            24.1   24.1   24.4   24.8   25.5   26.1   26.3
WILD RICE RIVER.....
  TWIN VALLEY         10.0   10.3   11.1   13.0   14.5   15.8   16.5
  HENDRUM             31.5   31.5   31.8   32.5   33.2   33.5   34.1
MARSH RIVER.....
  SHELLY              18.3   18.4   19.3   20.2   21.6   23.6   24.4
SAND HILL RIVER.....
  CLIMAX              27.6   27.8   28.9   30.3   32.2   34.0   35.8
RED LAKE RIVER.....
  HIGH LANDING        10.7   11.6   12.2   13.5   14.5   15.1   15.5
  CROOKSTON           21.6   21.8   22.5   23.7   25.1   26.0   27.3
SNAKE RIVER.....
  ABOVE WARREN        66.1   66.2   66.3   66.7   68.2   71.0   73.2
  ALVARADO           105.5  105.6  105.9  107.2  108.4  109.7  110.1
TWO RIVERS RIVER.....
  HALLOCK            807.7  807.9  808.1  808.9  809.8  811.6  812.4
ROSEAU RIVER.....
  ROSEAU              14.0   14.1   14.8   16.3   18.7   20.8   21.6

NORTH DAKOTA TRIBS:   95%    90%    75%    50%    25%    10%    05%
--------            ------ ------ ------ ------ ------ ------ ------
WILD RICE RIVER.....
  ABERCROMBIE         26.0   26.1   26.4   26.8   27.3   27.9   28.4
SHEYENNE RIVER.....
  VALLEY CITY         12.9   13.4   15.3   16.9   19.3   21.3   21.7
  LISBON              16.3   16.4   17.0   18.2   19.8   22.2   23.1
  KINDRED             20.5   20.5   20.7   21.1   21.2   21.2   21.2
  WEST FARGO DVRSN    22.9   22.9   23.0   23.2   23.2   23.2   23.2
  HARWOOD            890.3  890.5  890.7  891.3  891.9  892.1  892.2
MAPLE RIVER.....
  ENDERLIN            11.8   11.9   12.0   12.3   12.6   13.2   13.4
  MAPLETON           908.2  908.2  908.4  908.6  908.8  909.4  909.6
GOOSE RIVER.....
  HILLSBORO           13.4   13.6   14.1   14.8   16.2   16.9   17.3
FOREST RIVER.....
  MINTO                8.9    9.0    9.3    9.6    9.9   10.3   10.4
PARK RIVER.....
  GRAFTON             15.0   15.2   15.5   15.9   16.9   18.2   19.1
PEMBINA RIVER.....
  WALHALLA            12.9   13.1   14.0   14.7   15.2   16.0   16.1
  NECHE               21.3   21.3   21.4   21.5   21.5   21.6   21.6

.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 THAT WERE EXPERIENCED FOR THOSE PAST YEARS
DURING THE TIME-FRAME OF THE OUTLOOK PERIOD. 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 COMARING THIS
YEARS CURRENT SPRING 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 1949 THROUGH 2009.

. ADDITIONAL INFORMATION SOURCES...

THE AHPS LONG RANGE PROBABILISTIC HYDROLOGIC OUTLOOKS ARE ISSUED
EACH MONTH TYPICALLY BETWEEN THE FIRST AND SECOND FRIDAY AFTER
MID-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 GRAND FORKS AHPS WEB
PAGE ON THE INTERNET AT:

        WWW.WEATHER.GOV/GRANDFORKS OR WEATHER.GOV/FGF

  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 RIVER FORECAST POINTS IN THE RED
RIVER OF THE NORTH AND DEVILS/STUMP LAKE CONDITIONS ARE ALSO
AVAILABLE ON OUR WEB SITE...AS WELL AS THE 7-DAY FORECASTS WHEN
THE RIVER AT THE FORECAST POINT IS IN OR NEAR FLOOD.

IF YOU HAVE ANY QUESTIONS...CONTACT THE NWS AT 701-772-0720.

A NEW...POINT SPECIFIC FLOOD BRIEFING WEB PAGE IS AVAILABLE AT:

   WWW.CRH.NOAA.GOV/FGF/BRIEFING/FLOODBRIEFING.PHP (USE LOWER CASE)

ALSO...7-DAY DETERMINISTIC FORECASTS WILL BE ISSUED AT LEAST ONCE A
DAY WHEN THE RIVER FORECAST LOCATIONS WILL BE AT FLOOD DURING THAT
PERIOD.

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

REFER TO THE SEPARATE DEVILS LAKE PROBABILISTIC HYDROLOGIC OUTLOOK
FOR DEVILS AND STUMP LAKES PROBABILITY OF EXCEEDANCE LEVELS AND LOW-
WATER NON-EXCEEDANCE LEVELS.



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