Flood Potential Outlook
Issued by NWS Bismarck, ND

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
000
FGUS73 KBIS 270348
ESFBIS

NDC009-013-023-049-061-069-075-079-101-281800-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
1000 PM CST THU MAR 26 2015


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

This probability based Spring Flood and Water Resources Outlook is
for the Souris River Basin of North Dakota, covering the time period
of late March through late June.

The following message has four distinct sections. The first provides
text on the notable highlights of the probabilities found in this
outlook. The second gives the current probabilities based on
existing conditions (CS) and the normal, or historical (HS) risk of
those locations reaching their respective Minor, Moderate, or Major
flood categories. The third section provides the current
probabilities of the river reaching the listed stages. Finally, the
fourth section contains the probability of each site falling to the
specified levels.


...FLOOD OUTLOOK OVERVIEW HIGHLIGHTS...

As of late March, the Rafferty and Alameda reservoirs in Canada have
reached full supply level and have begun to increase outflows to
draw down the reservoirs to summer operating levels. Lake Darling
will match its outflows to inflows from Canada to keep the reservoir
at a desired operating level for summer. The Souris river immediately
downstream of Lake Darling will be in flood into at least early April
from reservoir releases. These higher flows will also eventually lead
to flooding along the lower portions of the basin, especially in the
Bantry and Towner areas. Backwater effects will also likely lead to minor
flooding on Willow Creek near Willow City.


...CURRENT CONDITIONS...
Soil moisture levels are generally near normal across the Souris basin.
Soils are continuing to thaw with greater capacity for infiltration.


...WEATHER OUTLOOK...
Climate outlooks from the Climate Prediction Center favor below normal
temperatures and above normal precipitation across western and central
North Dakota for late March into early April. For the longer term period
of April through June, above  normal temperatures are expected for the
three month period with near normal precipitation. However, as we enter
early summer and the thunderstorm season, precipitation patterns become
highly variable and localized.


...SUMMARY OF HYDROLOGIC CONDITIONS AND RISKS...

Hydrologic conditions across the Souris basin the remainder of this
spring will largely be determined by reservoir release schedules
from snowmelt runoff earlier in the season and adjustments based
upon precipitation patterns that will become more localized and
variable as we enter the spring and summer shower and thunderstorm
season.

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

The table below give both the Conditional Simulation (CS) risk of
flooding based on current conditions and the Historical Simulation
(HS) risk of flooding. Risks of reaching Minor, Moderate, and Major
flood categories are presented.

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

                           Souris River BASIN
                    LONG-RANGE PROBABILISTIC OUTLOOK
              VALID FROM MARCH 30, 2015  TO JUNE 28, 2015

The table below give both the Conditional Simulation (CS) risk of
flooding based on current condtions and the Historical Simulation
(HS) risk of flooding. Risks of reaching Minor, Moderat, and Major
flood categories are presented.


       PROBABILITIES FOR MINOR, MODERATE, AND MAJOR FLOODING
                      FROM  3/30/2015 TO 6/28/2015

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 :  <5  <5   <5  <5   <5  <5
Souris River.....
  Sherwood            18.0   20.0   25.0 :  <5   6   <5  <5   <5  <5
  Souris nrFoxholm    10.0   13.0   15.0 :  >95 46   27  35   <5  <5
  Minot 4NW           14.0   17.0   22.0 :   6  16   <5  <5   <5  <5
  Minot             1549.0 1551.0 1555.0 :  <5  <5   <5  <5   <5  <5
  Logan               34.0   36.0   38.0 :   6  20   <5  10   <5  <5
  Sawyer              22.0   24.0   26.0 :  <5   9   <5  <5   <5  <5
  Velva             1505.0 1510.0 1515.0 :  <5  16   <5  <5   <5  <5
Wintering River.....
  Karlsruhe            7.0    9.0   10.0 :  <5  12   <5  <5   <5  <5
Souris River.....
  Towner              52.0   54.0   56.0 :  >95 63   27  46   <5  10
  Bantry              11.0   12.0   14.0 :  >95 63   29  49   <5   9
Willow Creek.....
  Willow City         10.0   14.0   16.0 :  >95 40   <5  16   <5  <5
Souris River.....
  Westhope            10.0   14.0   16.0 :  38  52    6  24   <5  18

LEGEND:
    CS  =  Conditional Simulation
    HS  =  Historical Simulation
    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 probabilities
for exceeding river stages at the listed Forecast Points during the
valid period of this outlook.

For example: During the valid time period, there is a 50% chance for
             the Des Lacs River near Foxholm to rise above a
             stage of 6.9 ft and only a 10% chance it will rise
             above a stage of 9.7 ft.


           PROBABILITIES FOR EXCEEDING LISTED RIVER STAGES
                      FROM  3/30/2015 TO 6/28/2015
TABLE 2

LOCATION              95%    90%    75%    50%    25%    10%    05%
--------             -----  -----  -----  -----  -----  -----  -----
Des Lacs River.....
  Foxholm             5.3    5.3    5.7    6.9    8.4    9.7   13.0
Souris River.....
  Sherwood            9.6    9.6    9.7   10.0   14.8   15.5   15.8
  Souris nrFoxholm   11.8   11.8   11.9   12.0   13.2   13.9   14.2
  Minot 4NW           9.2    9.3    9.3    9.4   10.7   12.8   15.4
  Minot             1542.8 1542.8 1542.9 1542.9 1543.6 1544.7 1546.8
  Logan               29.1   29.1   29.1   29.1   30.1   32.9   36.0
  Sawyer              16.1   16.1   16.1   16.1   16.5   18.6   22.2
  Velva             1501.6 1501.6 1501.6 1501.7 1502.7 1503.8 1506.7
Wintering River.....
  Karlsruhe            2.4    2.4    2.4    2.8    3.5    4.1   5.8
Souris River.....
  Towner              53.6   53.6   53.6   53.6   54.1   54.6   55.9
  Bantry              11.7   11.7   11.7   11.8   12.3   12.6   13.7
Willow Creek.....
  Willow City         10.3   10.3   10.3   10.5   11.2   12.2   13.8
Souris River.....
  Westhope             9.6   9.6    9.6    9.7    10.6   12.3   15.2


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


                          SOURIS RIVER BASIN
                    LONG-RANGE PROBABILISTIC OUTLOOK

The table below represents the likelihood of the river remaining
above the listed stages.

For example: The Des Lacs River near Foxholm has a 95% chance the
             river will remain above 5.3 ft and only a 5% chance it
             will fall below 4.6 ft.


              PROBABILITIES FOR FALLING BELOW LISTED RIVER STAGES
                             3/30/2015 - 6/28/2015

TABLE 3

LOCATION              95%    90%    75%    50%    25%    10%    05%
--------             -----  -----  -----  -----  -----  -----  -----
Des Lacs River.....
  Foxholm              5.3    5.2    5.0    4.8    4.6    4.6    4.6
Souris River.....
  Sherwood             2.9    2.9    2.3    2.0    1.6    1.2    1.1
  Souris nr Foxholm    6.1    5.8    4.5    4.5    4.5    4.5    4.5
  Minot 4NW            5.3    4.7    4.3    4.1    3.9    3.8    3.8
  Minot             1541.1 1540.1 1538.1 1537.0 1535.7 1535.4 1535.4
  Logan               22.6   21.2   19.5   18.9   18.7   18.5   18.5
  SAWYER               5.5    5.5    5.5    5.5    5.4    5.3    5.3
  VELVA             1491.8 1491.2 1490.3 1489.4 1489.0 1489.0 1489.0
Wintering River.....
  Karlsruhe            2.0    1.8    1.6    1.6    1.6    1.6    1.6
Souris River.....
  Towner              47.9   46.3   44.8   43.8   43.3   43.2   43.2
  Bantry               5.8    4.2    2.9    1.9    1.7    1.7    1.7
Willow Creek.....
  Willow City          5.0    4.9    4.6    4.6    4.6    4.6    4.6
Souris River.....
  Westhope             8.2    7.6    7.0    6.2    5.8    5.7    5.7


...THE OUTLOOK PRODUCTION PROCESS...
This long-range probabilistic outlook is based on a series of peak
river levels, or crests, takeing 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 using 25 or more years of past precipitation and
temperature conditions in the historical record. These crests can
then be ranked from lowest to highest, and assigned an exceedance
probability. For example, using a series of 50 years, the lowest
ranked cerst has 49 crests above it. As 95% of the crests are above
this value, it is assigned a 95% Probability Of Exceedance (POE).

The probabilities can be used for risk management by comparing this
year`s current temperature and preciptitation outlooks with those
of past year used in the hydrologic outlook. They can also be used
as an indication of the range of crests expected during the valid
period of the outlook.

By providing a range of peak river level probabilities, the NWS is
contributing to the region`s Impact-Based Decision Support Services
that help with long-range flood planning and response readiness.
This outlook is a part of the National Weather Service`s Advanced
Hydrologic Prediction Services (AHPS).

This outlook was produced using precipitation and temperatures for
the years 1948 through 2011.


...ADDITIONAL INFORMATION SOURCES...
The AHPS long-range probabilistic hydrologic outlooks are issued
near the end of each month. However, the Spring Flood and Water
Resources Outlooks are issued several times in advance of the
critical spring melt season starting in mid-lake February and
going through Marck...or until the melt season is in full effect.

This outlook is also available in graphic form on the NWS website
along with explanations that help in interpreting them. They are
available at:

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

Click on the "Rivers and Lakes" tab above the map, or the AHPS
link in the blue banner on the left side of the screen.

Current river conditions for all forecast points are available
on our website, as well as forecast when the location is near or
above flood stage.

If you have any questions, contact the NWS at 701-250-4495.

$$

PA/ACOOP






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.