Flood Potential Outlook
Issued by NWS Denver/Boulder, CO

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Water Supply Outlook
National Weather Service Denver CO
338 PM MST Thu Feb 29 2024

...SPRING FLOOD AND WATER RESOURCES OUTLOOK FOR NORTH CENTRAL AND
NORTHEAST COLORADO...

...Spring Flood and Water Resources Outlook for North Central and
Northeast Colorado Issuance Number 2...

This is the second 2024 spring runoff outlook for North Central
and Northeast Colorado covering all or portions of the Upper North
Platte...Upper South Platte and Upper Colorado River Basins.

Flood and Water Supply Outlook Summary
--------------------------------------

Spring flood potential is near to slightly below normal at this
time for the South Platte River Basin, the Upper North Platte
River Basin and the far Upper Colorado River Basin. Any widespread,
significant flooding is not likely due to snowmelt alone. It should
be emphasized that it is very early and snow typically accumulates
into April, therefore conditions may change before the runoff begins.

Water supply forecasts issued in mid-February by the National
Weather Service project generally below average April through
July runoff volumes for Upper Colorado and South Platte Basins.
The one exception being the Upper North Platte basin, and the Fraser
River Basin which are expected to produce a slightly above average
runoff volume if current conditions persist.

Appreciable mountain snowmelt runoff in a normal year starts in
late April to early May. Mountain snowmelt generally peaks in
mid-May to mid-June. It is still very early to make long range
predictions on the magnitude of flooding from mountain snowmelt
runoff. Heavy rainfall, a cold spring, or unseasonably warm
temperatures during the snowmelt season can affect total runoff
volume and peak flow, increasing the threat of flooding.

Observed Precipitation...Snowpack and Temperatures
--------------------------------------------------

The average higher elevation total water year precipitation for
the Upper Colorado, Upper South Platte and the Upper North Platte
Basins are near to slightly below normal with and Cache La Poudre
Basin below normal.

For the water year the percent of normal precipitation is still
below normal for the central and northern part of the Denver
metro area extending out into most of the northeastern plains. The
exception with along the north Weld county border and most of
Sedgwick and Phillips counties with near normal precipitation. Southern
part of the Denver metro area into the Palmer Divide and adjacent
foothills are near to slightly above normal.

Precipitation in October through November was well below normal
for most of Northeastern Colorado including the eastern plains,
the urban corridor and mountains. In December the far eastern
plains over to the Palmer Divide and into the foothills had above
normal precipitation for the month. The northern part of the metro
area east and north had much less than normal precipitation. Weld and
Morgan counties had the least precipitation. January continued the
dry trend over most of the eastern plains and Denver metro area. The
Palmer Divide and portions of the mountains received some much needed
moisture and spotty areas above normal for the month.

The very end of January and into February brought much needed
precipitation to the area. The eastern plains and into the
foothills have received well over normal precipitation for the
month of February so far. The mountains also received much needed
snow and increased the snowpack to near to slightly below normal
for the water year.

Temperatures on average since the beginning of the water year
through December have been well above normal. In January temperatures
were below normal. So far in February temperatures have been above
normal. The northern part of the Front Range mountains has had less
snow and precipitation than normal including the St Vrain, Big
Thompson, and Cache La Poudre Basins.

Basin snowpack conditions for the period
October 1 2023 to February 28 2024:
---------------------------------

(Snow is percent of Median)
(Total precipitation is percent of Average)

Basin                                Snow    Precip
-----                                ----    ------
Upper Colorado                         99     100
South Platte                           93      89
Upper North Platte                     97      97

Subbasin                             Snow    Precip
--------                             ----    ------
Colorado Headwaters                   102     102
Blue                                  103     102
South Platte Headwaters               104      94
Clear Creek                           100     102
St Vrain                               88      86
Big Thompson                           92      87
Cache La Poudre                        88      83
North Platte Headwaters                93      94

Climate Outlook
---------------

The current ENSO pattern is El Nino and is forecast to transition
to the neutral phase later this spring. The chance of ENSO changing
to neutral later this spring reaches 79 percent.

The outlook for March favors equal chances of either above, below or
normal temperatures with a better chance of above normal precipitation
over the mountains and along the urban corridor with a slightly
smaller chance of above normal precipitation on the eastern plains.

Farther out, the March through May seasonal outlook favors equal
chances of either above, below or normal temperatures and equal
chances of either above, below or normal precipitation for
Northeastern Colorado.


Numerical River Outlooks
------------------------

In Table 1 below, the current (CS) and historical (HS) or normal
probabilities of exceeding minor...moderate...and major flood stage
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 greater 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: 03/02/2024 - 09/30/2024

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:South Platte River
South Platte         7.0    8.5    9.5 :  <5    5   <5   <5   <5   <5
Denver              11.0   13.0   15.0 :  <5   <5   <5   <5   <5   <5
Henderson           11.0   13.0   15.0 :  <5   <5   <5   <5   <5   <5
Fort Lupton         11.0   13.0   15.0 :   5    5   <5   <5   <5   <5
Kersey              10.0   11.5   13.5 :  15   15   11    8   <5   <5
Weldona             10.0   11.0   12.0 :  12    9    9    8    8    6
Fort Morgan         17.5   19.5   21.5 :  12   13   10   10    8    7
Balzac              10.0   11.0   12.5 :  12   12   11   11    9    9
Atwood              11.5   13.0   14.5 :  11   11   10   10   <5   <5
Julesburg           10.0   11.0   12.5 :  10   10   <5   <5   <5   <5
:Plum Creek
Sedalia              8.0   10.0   12.0 :   6   <5   <5   <5   <5   <5
:Bear Creek
Morrison             9.0   10.0   10.5 :  <5   <5   <5   <5   <5   <5
Sheridan             8.0   10.0   10.5 :  <5   <5   <5   <5   <5   <5
:Clear Creek
Golden               8.5    9.5   10.5 :  <5   <5   <5   <5   <5   <5
Derby               10.5   11.5   12.5 :  <5   <5   <5   <5   <5   <5
:N Fk Big Thompson River
Drake                5.5    6.0    7.0 :  <5   <5   <5   <5   <5   <5
:Cache la Poudre River
Fort Collins 9NW     7.5    9.0   10.5 :   5   10   <5    6   <5   <5
Fort Collins        10.5   11.5   13.0 :  <5   <5   <5   <5   <5   <5
Greeley              8.0    9.5   10.5 :  14   17    7   12    5    7
:North Platte River
Northgate            8.0    9.5   11.0 :   8   13   <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: 03/02/2024 - 09/30/2024
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:South Platte River
South Platte          3.9    4.0    4.2    4.4    4.8    5.3    6.6
Denver                4.7    5.0    5.5    5.9    6.4    7.3    7.4
Henderson             5.5    5.8    6.6    7.1    7.8    8.5    9.0
Fort Lupton           5.3    5.6    6.9    7.8    8.9    9.6   11.1
Kersey                4.3    4.5    6.1    7.5    8.4   12.3   13.0
Weldona               3.6    3.6    5.2    6.2    7.5   10.3   13.3
Fort Morgan          10.3   10.4   11.8   13.4   14.9   19.5   22.5
Balzac                3.5    3.7    5.1    6.8    7.7   11.7   13.7
Atwood                4.5    4.6    5.9    7.7    8.4   12.6   14.2
Julesburg             6.2    6.2    7.1    8.1    8.5   10.0   10.6
:Plum Creek
Sedalia               4.2    4.2    4.4    4.9    5.5    7.0    9.1
:Bear Creek
Morrison              6.4    6.5    6.8    7.0    7.2    7.5    7.6
Sheridan              3.2    3.3    3.7    4.4    5.0    5.4    5.5
:Clear Creek
Golden                4.7    5.1    5.7    6.0    6.5    6.8    7.3
Derby                 4.9    5.0    5.4    6.1    6.6    7.0    7.5
:N Fk Big Thompson River
Drake                 2.9    3.0    3.1    3.3    3.8    4.0    4.6
:Cache la Poudre River
Fort Collins 9NW      4.0    4.1    4.7    5.1    5.9    7.1    7.5
Fort Collins          2.3    2.4    3.4    4.7    5.4    7.2    9.0
Greeley               1.9    1.9    2.9    5.2    6.1    8.5   10.4
:North Platte River
Northgate             4.4    4.7    5.7    6.3    7.2    7.7    8.5

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: 03/02/2024 - 09/30/2024
LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:South Platte River
South Platte          2.8    2.8    2.8    2.8    2.8    2.8    2.8
Denver                3.0    2.9    2.9    2.9    2.9    2.9    2.8
Henderson             3.6    3.5    3.5    3.5    3.5    3.5    3.5
Fort Lupton           3.5    3.3    3.3    3.2    3.2    3.2    3.2
Kersey                2.6    2.4    2.2    2.1    2.0    2.0    2.0
Weldona               2.2    2.2    2.2    2.1    2.1    2.0    2.0
Fort Morgan           9.2    8.9    8.5    8.4    8.4    8.4    8.4
Balzac                2.4    2.3    1.9    1.4    0.7    0.6    0.6
Atwood                3.1    2.8    2.2    2.0    1.8    1.6    1.6
Julesburg             3.3    3.3    3.3    3.3    3.3    3.3    3.3
:Plum Creek
Sedalia               3.7    3.7    3.6    3.5    3.5    3.5    3.5
:Bear Creek
Morrison              5.7    5.7    5.7    5.6    5.5    5.4    5.3
Sheridan              2.5    2.4    2.3    2.1    2.0    2.0    1.9
:Clear Creek
Golden                3.4    3.3    3.3    3.3    3.3    3.3    3.2
Derby                 2.9    2.7    2.7    2.7    2.7    2.7    2.7
:N Fk Big Thompson River
Drake                 2.4    2.4    2.4    2.4    2.4    2.4    2.4
:Cache la Poudre River
Fort Collins 9NW      2.8    2.8    2.8    2.8    2.8    2.7    2.7
Fort Collins          0.1    0.0    0.0    0.0    0.0    0.0    0.0
Greeley               0.8    0.8    0.7    0.7    0.7    0.7    0.7
:North Platte River
Northgate             2.4    2.4    2.4    2.4    2.4    2.4    2.3


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.

Following are the forecasts for selected locations:
                                        Median Forecast
                                      Volume      Percent
Stream and Station         Period     1000 AF     of Avg
__________________         ______     _______     _______
South Platte River
 Antero Reservoir inflow   Apr-Sep      12          85
 Spinney Mtn Res inflow    Apr-Sep      36          80
 11-Mile Canyon Res inflow Apr-Sep      40          79
 Cheesman Lake inflow      Apr-Sep      74          79
 South Platte              Apr-Sep      149         73

Bear Creek
 Morrison                  Apr-Sep      17          63

Clear Creek
 Golden                    Apr-Sep      98          75

South Boulder Creek
 Eldorado Springs          Apr-Sep      34          85

Boulder Creek
 Orodell                   Apr-Sep      51          98

Saint Vrain Creek
 Lyons                     Apr-Sep      75          69

Cache La Poudre River
 Canyon Mouth              Apr-Sep     184          88

North Platte River
 Northgate                 Apr-Sep     332         112

Colorado River
 Granby                    Apr-Jul     193          86

Willow Creek
 Willow Creek Res          Apr-Jul      46          92

Fraser River
 Winter Park               Apr-Jul      21         113

Williams Fork River
 Williams Fork Reservoir   Apr-Jul      82          85

Blue River
 Dillon Res                Apr-Jul     148          89
 Green Mtn Res             Apr-Jul     259          93

Muddy Creek
 Wolford Mtn Res Blw       Apr-Jul      47          91

Colorado River
 Kremmling                 Apr-Jul     792          91

These forecasts reflect natural flow only. Actual observed flow
will likely be affected by upstream water management.

It should be emphasized that snow accumulation and snow pack
conditions could change before the runoff begins.

Changing hydrometeorological conditions can have a significant
impact on water supply forecasts. Additional products will be
issued as conditions evolve.

Additional supportive information
---------------------------------

- Visit the Missouri Basin RFC information webpage for water
supply forecasts east of the divide at weather.gov/mbrfc/water.
- Visit the Colorado Basin RFC for water supply forecasts west of
the divide at cbrfc.noaa.gov/lmap/lmap.php?interface=wsup.
- Visit our website at weather.gov/bou for additional local
weather...climate and stream information.
- Long range precipitation and temperature outlooks are available
at www.cpc.ncep.noaa.gov/products/predictions/.
- Snowpack and reservoir data are available from the Natural
  Resources Conservation Service at www.wcc.nrcs.usda.gov/snow/.

$$

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