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FGUS73 KFGF 252034
Probabilistic Hydrologic Outlook
National Weather Service Eastern North Dakota/Grand Forks ND
333 PM CDT Mon Sep 25 2017
...DEVILS LAKE OUTLOOK FOR FLOOD POTENTIAL...
Devils and Stump Lakes
Long-Range Probabilistic Outlook
The National Weather Service is providing long-range probabilistic
hydrologic outlooks for Devils and Stump lakes between January
and September. They will not be provided between October and
The AHPS graphics associated with this outlook will be on the web
no later than 10:30 AM this Friday under the experimental
long-range flood risk tab at...
Depending on the season, the high or low water probabilities may
be omitted due to their applicability to the hydrologic situation.
Refer to the scheduling section farther on in this message.
. Chances of Devils and Stump Lakes falling below given lake
The probability of not exceeding a given lake level is the
percentage of lake level falls that are below that level for
all the years that were run through the model using the
precipitation and temperatures for those years during the
valid period of the outlook.
Interpretation Aid...There is a 50 percent chance that Devils
Lake will fall below 1449.9 feet during the valid period and
only a 5 percent chance that it will fall below 1449.8 feet.
Probabilities for non-exceeding listed lake levels
FROM SEPTEMBER 24, 2017 TO DECEMBER 30, 2017
LOCATION 95% 90% 75% 50% 25% 10% 05%
-------- ------ ------ ------ ------ ------ ------ ------
CREEL BAY 1450.1 1450.1 1450.0 1449.9 1449.8 1449.8 1449.8
EAST STUMP LAKE 1450.1 1450.1 1450.0 1449.9 1449.8 1449.8 1449.8
The non-exceedance value for a listed percentage is the value
where that percentage of all model cases run were below that
lake level for the specified valid period of the outlook.
- Between January and May, only the high water exceedances will be
provided with valid periods ending at the end of September.
- Special Spring Flood and Water Management Outlooks will be issued
in late February and, two weeks later, in early March.
- For June and July, both high-water and low-water exceedances
will be provided.
- For August and September, only the low-water exceedances will be
provided with valid periods ending at the end of November.
- No probability of exceedance/non-exceedance information will be
given from October through December, since lake freeze-up
levels will be given in the fall outlooks previously issued.
. Additional Information...
Wind and Wave forecasts for Devils and Stump lakes are available for
a seven day period when the lakes are sufficiently ice-free at:
The long-range probabilistic outlook is based on high and low lake
levels that were calculated for the valid period using multiple
scenarios of temperature and precipitation from 1949 to 2012 and
current conditions of the lake, snowcover (in winter), and soil
A YouTube video on "How to Interpret River Outlook Products" is at:
By providing the complete range of lake level probabilities, the
amount of risk associated with long-range planning decisions can
be determined. These probabilistic outlooks are part of Noah`s
National Weather Service`s Advanced Hydrologic Prediction
This outlook is also presented as probability graphs of lake height
for the full period as well as weekly probabilities. The outlook
graphics and explanations that help in interpreting these outlooks
are available from...the NWS Grand Forks AHPS web page at:
When available (see schedule above) the AHPS graphics for monthly
outlooks should be available by mid-morning or early afternoon.
Monthly probabilistic outlooks are issued on the Friday of the week
following the first Thursday after the 15Th of the month. Special
spring flood and water management outlooks are issued on Thursday
afternoons in late February and then again, two weeks later in
March to coincide with the spring snow melt. Due to the lake
freeze-up will not be issued from October through December.
If you have any questions, contact the NWS at 701-772-0720
You can follow us on Facebook at: www.facebook.com/NWSGrandForks
and on Twitter at: @NWSGrandForks.
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