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Flood Potential Outlook
Issued by NWS Pueblo, CO
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PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE Pueblo CO
0730 AM MST Fri Mar 1 2024

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

This outlook is for the Arkansas River Basin in southeast Colorado
and the Rio Grande Basin in south-central Colorado.

This outlook is valid from February 27 to May 27, 2024.

The potential for spring flooding, caused by snowmelt alone, is
near normal for the Arkansas River Basin.

The potential for spring flooding, caused by snowmelt alone, is
below normal for the Rio Grande Basin.

...OUTLOOK FOR THE ARKANSAS RIVER BASIN...

Temperatures have fluctuated between above and below normal levels
since the beginning of the water year (Oct 1, 2023) with minimal
to no drought conditions present throughout the Arkansas River
Basin heading into the winter months. Despite a strong El Nino in
effect, mountain precipitation was off to a slow start with only
68 percent of normal basin-wide snowpack snow-water-equivalent
(SWE) at the end of December. January and the first half of
February, however, have brought beneficial snowfall to the basin
with basin-wide mountain snowpack SWE recovering to 97 percent of
normal as of February 13. A drier couple of weeks has since brought
basin-wide SWE back to 91 percent of normal by the end of February.
Mountain snowpack for the mountains along the Continental Divide of
the upper Arkansas River Basin and sub-basins draining from the
eastern slope of the Sangre de Cristo Mountains are trending at near
normal levels for the middle of February. The potential for spring
flooding due to snowmelt during the next 90 days is limited and near
normal.

Any snowmelt flooding that develops will most likely be minor and
would only result in minimal property damage and minor public threat
or incovenience.

Table 1. below, shows 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:  02/27/2024 - 05/27/2024

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Arkansas River
Leadville            9.0   10.0   12.0 :  <5   <5   <5   <5   <5   <5
Salida               8.0    9.0   10.0 :  <5   <5   <5   <5   <5   <5
Wellsville           9.0   10.0   11.0 :  <5   <5   <5   <5   <5   <5
Parkdale             9.0   10.0   11.0 :  <5   <5   <5   <5   <5   <5
Canon City          10.0   12.0   14.0 :  <5   <5   <5   <5   <5   <5
Portland             9.0   10.0   11.0 :  <5   <5   <5   <5   <5   <5
Pueblo               8.0    9.0   11.0 :  <5   <5   <5   <5   <5   <5
Avondale             7.0    8.0    9.0 :  29   15   20    9   13    5
Nepesta             16.5   17.5   18.5 :  20   <5   12   <5    5   <5
Fowler              13.5   14.0   15.0 :  <5   <5   <5   <5   <5   <5
Rocky Ford          10.0   11.0   12.0 :  <5   <5   <5   <5   <5   <5
La Junta            11.0   13.0   15.0 :  45   20   17    6   <5   <5
Lamar               11.0   13.0   15.0 :  <5    7   <5   <5   <5   <5
:Fountain Creek
Colorado Springs    11.5   16.0   18.0 :  <5   <5   <5   <5   <5   <5
Fountain Creek ne   12.0   14.0   16.0 :  <5   <5   <5   <5   <5   <5
Pinon               12.0   14.0   15.0 :  <5   <5   <5   <5   <5   <5
Pueblo              10.0   12.0   13.5 :  <5   <5   <5   <5   <5   <5
:St. Charles River
Vineland            12.0   15.0   18.0 :   7   <5   <5   <5   <5   <5
:Purgatoire River
Madrid               7.0    9.0   11.0 :  <5   <5   <5   <5   <5   <5
Trinidad Lake       10.0   12.0   14.0 :  <5   <5   <5   <5   <5   <5
Trinidad            11.0   12.0   13.0 :  <5   <5   <5   <5   <5   <5
Las Animas           9.0   12.0   15.0 :  20   10    7   <5   <5   <5

Legend
CS = Conditional Simulation (Current Outlook)
HS = Historical Simulation
FT = Feet

The table above indicates a near normal chance for exceeding flood
stage over the next 90 days. The probability of flooding in most
years is very low and is considered normal for the Arkansas River Basin.
This analysis is for the period ending May 27 with the normal snowmelt
period occurring from late April to mid-June. Those locations where the
probability of exceeding flood stage is greater than 5 percent do not
show a significant difference between the current (CS) conditions and
historical (HS) or normal conditions. These results are consistent with
a near normal snowpack expected.

Any snowmelt flooding that develops will most likely be minor and
would result in minimal property damage or threat to the public and
only minor inconveniences.

Snowmelt flooding should not be confused with other types of
flooding such as those associated with heavy rain from storms,
releases from reservoirs, or extreme runoff from burn scars. This
outlook does not address the potential for those types of floods.
Flooding and flash flooding from heavy rainfall or burn scar runoff
is always a possibility during heavy rain events.

...OUTLOOK FOR THE RIO GRANDE BASIN...

The spring flood potential in the Rio Grande Basin, from snowmelt
runoff alone, is below normal. Any snowmelt flooding that develops
will most likely be minor and would only result in minimal property
damage and minor public threat or inconvenience.

Probabilities of exceeding flood stage or various flood categories
such as those presented for the Arkansas River Basin are not currently
available for the Rio Grande Basin. However, a qualitative
assessment of the spring flood potential for the Rio Grande Basin
is presented below.

After a slow start to the snowpack accumulation season, snowpack
conditions for the Rio Grande Basin have steadily improved over
January and the first half of February with basin-wide mountain snowpack
SWE at 91 percent of normal as of February 13. A drier couple of weeks
has since brought basin-wide SWE back to 86 percent of normal by the end
of February. Snowpack conditions for sub-basins draining from the eastern
San Juan Mountains, La Garita Mountains, and the west slope of the Sangre
de Cristo Mountains range from near normal to slightly below normal for
the end of February. Soil moisture conditions remain below to well below
normal due to widepread drought conditions in place heading into the
winter months. Despite closer to normal snowpack conditions, soil moisture
deficits will likely reduce the probability of excess snowmelt runoff that
would cause flooding for the next 90 days.The probability of flooding in
most years is very low and is considered normal for the Rio Grande Basin.

Any snowmelt flooding that develops will most likely be minor and
would result in minimal property damage or threat to the public and
only minor inconveniences.

Snowmelt flooding should not be confused with other types of
flooding such as those associated with heavy rain from storms,
releases from reservoirs, or extreme runoff from burn scars. This
outlook does not address the potential for those types of floods.
Flooding and flash flooding from heavy rainfall or burn scar runoff
is always a possibility during heavy rain events.

...FLOOD ASSESSMENT QUALIFIER...

A little over a month of the snowpack accumulation season remains until
mountain snowpacks typically peaks in early April for both the Arkansas
River and Rio Grande Basins. March and April, however, are often the
snowiest months of the accumulation season, and the current outlook for
spring snowmelt flooding can change dramatically between now and when the
snowmelt season typically begins in mid to late April. In addition to
peak snowpack levels, meteorological conditions and snowmelt patterns
can also have a substantial influence on the outlook for excess runoff
and flood concerns.

These flood potential assessments are also based on current conditions
and projections of average temperature and precipitation for the coming
months. It does not reflect any flood potential due to more extreme
weather conditions. If unusually warm or wet weather conditions develop
over the region during the next 90 days or during the snowmelt period,
then much more severe flooding is possible.

...SUMARRY OF PAST, PRESENT AND FUTURE CONDITIONS...

Temperatures this winter have fluctuated between above and below
normal through December and mostly below normal temperatures were
experienced throughout the state of Colorado for the month of
January. In contrast, temperatures in February have ranged from near
normal to above normal across the state.

Snowpack conditions for the mountains of the Arkansas River Basin
remain just below normal conditions for this time of year while
snowpack conditions for the Rio Grande Basin range between near
normal and slightly below normal for this time of year. As of
February 29, basin-wide mountain snowpack SWE was 91 percent of
normal for the Arkansas River Basin and 86 percent of normal for
the Rio Grande Basin.

Precipitation for the Water Year (beginning October 1, 2023), as
measured at NRCS SNOTEL stations at the higher elevations, is normal
for the Arkansas River Basin and slightly below normal for the Rio
Grande Basin. As of February 29, the water year-to-date precipitation
was 101 percent of normal for the Arkansas River Basin and 84 percent
of normal for the Rio Grande Basin.

At the end of February, overall reservoir storage was at 105 percent
of normal for the Arkansas River Basin while storage for the Rio Grande
Basin was above normal at 123 percent of normal.

Soil moisture conditions remain favorable for the Arkansas River Basin
coming off a wetter than normal summer and beneficial precipitation
which fell during the fall and early winter. Although some recent
improvement in snow accumulation has been observed, widespread drought
conditions continue to persist throughout the Rio Grande Basin with
the San Luis Valley being the most impacted by drier than normal soil
moisture levels.

The National Weather Service, Climate Prediction Center has indicated
that strong El Nino conditions will likely transition fairly quickly
back to La Nina conditions by the beginning of summer. Due to the
expected persistence of El Nino conditions throughout the spring,
however, the 3-month climate outlook for the February through April
period indicates likely near normal temperatures and near to slightly
above normal precipitation for south-central and southeast Colorado.

...SCHEDULE OF OUTLOOKS...

This is the second of three scheduled Spring Flood and Water Resources
Outlooks for 2024. Additional outlooks may be issued if conditions
change significantly. Long range probabilistic outlooks for the
Arkansas River Basin are issued near the second and fourth Thursdays
of most months. The next probabilistic outlook will be issued on
March 14.

...ADDITIONAL INFORMATION...

Visit our web site at weather.gov/pub for more hydrologic
information including graphs of probabilistic river outlooks.
The National Weather Service Pueblo CO hydrology page can be accessed
by clicking the Rivers and Lakes tab near the top of the page.

$$
National Weather Service Weather Forecast Office
