Flood Potential Outlook
Issued by NWS North Platte, NE

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FGUS73 KLBF 022044 CCA
ESFLBF
NEC005-009-015-017-029-031-041-049-063-069-071-075-085-089-091-101-
103-111-113-115-117-135-149-161-171-183-150000-

Probabilistic Hydrologic Outlook...Corrected
National Weather Service North Platte NE
200 PM CST Thu Mar 02 2017

...Spring Flood and Water Resource Outlook Number 2...

...Around Average Flood Potential this Spring...

This Spring Flood and Water Resource Outlook is for the North Platte
Hydrologic Service Area, which covers western and north central
Nebraska. The river basins include: The North Platte and South
Platte, as well as, the Platte River in western Nebraska, Frenchman
Creek and Stinking Water Creek in southwest Nebraska, the Loup and
Dismal Rivers in the Sandhills of Nebraska, and portions of the
Elkhorn and Niobrara Rivers in north central Nebraska.

.Flood Outlook Summary...

At this time, the probability of spring flooding from March through
May is generally around average for most of central and western
Nebraska. An elevated potential for minor flooding exists along the
North Platte, South Platte and Platte River basins.  The potential
for flooding in southwestern Nebraska, including Frenchman and
Stinking Water Creeks, is below average.

The potential for ice jam related flooding is below average. Most of
the ice has already come off the lakes and rivers due to recent warm
spells and only minimal amounts of ice remain.

The potential for rainfall induced flash flooding is below average
is not quantifiable. This type of flooding is most likely to occur
during the later spring and summer months.

.Snow Cover and Liquid Water Content...

As of March 2nd, areas of snowpack remained across the eastern
panhandle and north central Nebraska, mainly in the Niobrara and
Elkhorn River basins. With above normal temperatures forecast over
the next few weeks, any remaining snow cover will melt.

.Reservoir and Mountain Snowpack Conditions...

Normal operations are ongoing at reservoirs along the North Platte
River for this time of year. Releases from these dams have been
limited through the winter months, with inflows generally coming
from melted snow. Because of these operations, reservoir levels have
risen through the winter months. The current reservoir storage
across Wyoming, as well as Lake McConaughy, are slightly above
average for this time of year.

As of early March, the snowpack in the North Platte and South Platte
River Basins in Colorado and Wyoming were slightly above average and
higher than last year. Flooding from snowmelt runoff is highly
dependent on how quickly snowmelt occurs in the low to mid
elevations of the mountains, typically 8500 feet and lower.

.Soil Conditions and Frost Depths...

Soil moisture across northern Nebraska is above average with near
average soil moisture elsewhere. Soil temperatures sensors indicate
that most areas have a 4 inch soil temperature in the lower to mid
30s. Therefore, the frost depth is minimal and runoff will be able
to be easily absorbed into the ground.

.River and Lake Ice Conditions...

Most of the ice cover on the larger lakes has melted with mostly
open water reported. Most of the ice has come off, with only minimal
amounts of shore ice remaining. River flows in areas that are ice
free range from normal to above normal for this time of year.

.Seasonal Precipitation...

Precipitation so far this water year, since October 1, 2016, has
been above average, with the exception of central and southwestern
Nebraska where it has been below average. Most locations have
received between three and six inches of precipitation since late
fall, about one to three inches more than usual.

.Weather Outlooks...

Water temperatures in the tropical Pacific Ocean are around average,
indicating neutral conditions. The outlook for the spring and summer
is for neutral conditions to continue. Neutral conditions generally
bring a warmer and wetter pattern to the southern half of the United
States with a cold polar jet stream diving across Canada into the
northeastern United States. The western high plains will be in the
transition zone between the two air masses that would create varying
conditions for the region.

According to the Climate Prediction Center, the latest 8 to 14 day
outlook for March 9 to March 15 calls for above average temperatures
with a greater chance for below average precipitation.

The latest 90 day outlook for March, April and May indicates a
greater chance for above normal temperatures, and equal chances for
above, below or average precipitation.

.Numerical River Outlooks...

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 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:  03/04/2017  - 06/02/2017

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:North Platte River
Lisco                4.0    5.0    6.0 :   9   15    7   12    6    7
Lewellen             7.5    8.5    9.5 :  72   37    9   14    6    7
North Platte         6.0    6.5    7.0 :  21   26   12   20   10   10
:South Platte River
Roscoe               9.0   11.0   13.0 :  15   15    8    8   <5    5
North Platte        13.0   14.0   15.0 :   7    7   <5    5   <5   <5
:Elkhorn River
Ewing 1N             9.0   10.0   12.0 :  <5   <5   <5   <5   <5   <5
:Platte River
Brady North Chann    7.5    9.0   11.0 :  20   22   13   12    5    6
:Frenchman Creek
Palisade             7.0    8.0    9.0 :  <5   <5   <5   <5   <5   <5
:Stinking Water Creek
Palisade 2NW        10.0   11.0   12.0 :  <5   <5   <5   <5   <5   <5
:Niobrara River
Sparks               6.0   10.0   12.0 :  <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: 03/04/2017  - 06/02/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:North Platte River
Lisco                 1.8    1.9    2.3    2.7    2.9    3.8    7.3
Lewellen              6.7    6.8    7.4    7.7    7.9    8.4   10.7
North Platte          5.6    5.6    5.6    5.6    5.8    6.9    8.3
:South Platte River
Roscoe                4.6    4.7    5.2    6.5    8.0    9.7   12.2
North Platte          7.1    7.1    7.3    8.5    9.8   11.1   13.4
:Elkhorn River
Ewing 1N              3.4    3.4    3.5    4.4    4.8    5.5    7.5
:Platte River
Brady North Chann     4.5    4.5    4.5    4.9    7.1    9.5   10.9
:Frenchman Creek
Palisade              2.7    2.7    2.8    3.2    4.3    5.5    6.5
:Stinking Water Creek
Palisade 2NW          2.7    2.8    3.2    3.5    4.5    6.0    7.0
:Niobrara River
Sparks                3.2    3.2    3.3    3.4    3.7    4.0    4.4

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: 03/04/2017  - 06/02/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:North Platte River
Lisco                 1.1    1.1    1.1    1.1    1.1    1.1    1.1
Lewellen              5.8    5.8    5.8    5.7    5.7    5.7    5.7
North Platte          4.0    3.9    3.6    3.5    3.5    3.5    3.5
:South Platte River
Roscoe                3.9    3.3    2.6    2.5    2.4    2.4    2.4
North Platte          7.1    7.0    7.0    7.0    7.0    7.0    7.0
:Elkhorn River
Ewing 1N              2.7    2.5    2.5    2.3    2.2    2.2    2.1
:Platte River
Brady North Chann     2.3    2.1    2.0    2.0    2.0    2.0    2.0
:Frenchman Creek
Palisade              2.7    2.7    2.7    2.7    2.6    2.6    2.6
:Stinking Water Creek
Palisade 2NW          2.6    2.6    2.4    2.3    2.2    2.1    2.0
:Niobrara River
Sparks                2.8    2.8    2.7    2.6    2.5    2.5    2.5

These long-range probabilistic outlooks contain forecast values that
are calculated using multiple season scenarios from 30 or more years
of climatological data...including 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/lbf for more weather and water
information.

This is the second spring flood and water resource outlook for 2017.
Long-range probalistic outlooks are issued near the middle of the
month throughout the year.

$$

Roberg/Smith/Taylor


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