SPRING FLOOD OUTLOOK
NATIONAL WEATHER SERVICE
MISSOURI BASIN RIVER FORECAST CENTER
PLEASANT HILL, MO
MARCH 10, 2021
NARRATIVE PART 1 OF 1
ATTN WFO'S SERVED BY MBRFC.
This Spring Flood Outlook is not for public release until Thursday,
11 March 2021.
This Spring Outlook is for the Missouri River drainage which includes
rivers in Montana, Wyoming, Colorado, North and South Dakota,
Nebraska, Kansas, Iowa, Minnesota, and Missouri.
SPRING FLOOD OUTLOOK
Flood risk this Spring within the Missouri River basin is generally
below normal.
To provide context, a normal risk indicates that a location that
typically experiences Spring time flooding is likely to see
flooding again this year. A normal risk for flooding does not
necessarily mean that a location will flood, however. For those
locations which do not typically experience flooding, a normal risk
simply indicates that flooding is again not expected this year. By
the same token, a reduced risk of flooding does not necessarily
mean that flooding is not expected. On the other hand, an
increased risk does not necessarily indicate flooding is likely.
Mountain snowpack is generally near normal. Widespread, significant
flooding in the mountainous west is not likely due to mountain
snowmelt alone. Water supply forecasts issued in early March by the
National Weather Service project lower than normal April-September
runoff volumes for the mountainous west.
No appreciable plains snow exists in the Missouri River basin.
December 2020 and January 2021 were the fourth warmest December-
January in 127 years of record. The mild start to winter, coupled
with the ongoing drought conditions across most of the Missouri
River basin have precluded the development of a deeply frozen
ground condition. The arctic blast which gripped the basin in
February resulted in increased frost depths. Soils, while cold,
remained porous, however. Anomalously warm temperatures over the
past two weeks have allowed for a northward progression of thaw.
Therefore, frozen ground is not expected to play a significant role
in runoff production this year.
Even with the mild start to winter 2020-21, river ice formation
has resulted in elevated stages at many locations across the
Missouri River basin. So far this season, freeze-up ice jams
have been reported along the Wind River in Wyoming, the Jefferson and
Yellowstone Rivers in Montana, and the Niobrara, Platte, and North
Platte Rivers in Nebraska. The Missouri River below Kansas City
experienced an ice jam in mid-February, an occurrence not seen since
the 1980's. There have been localized impacts with some of these
situations. However, warmer-than-normal March temperatures, coupled
with the lack of plains snow, soil moisture deficits, and low
streamflows, have greatly reduced river ice concerns over most of the
basin. River ice remains in the northern tier, including Montana,
Wyoming, and the Dakotas, with ice thicknesses of 1 to 2 feet being
reported along some northern streams. As long as river ice is
present, the public needs to be vigilant to the possibility of river
ice breakup and jamming. However, for most of the basin, risk for
ice jam flooding is lower than normal. Please be aware, the
probabilistic quantifications that form the basis for this Spring
Flood Outlook do not take into account the presence of river ice.
Springtime flooding in the lower one-third of the basin, including
southern Iowa, eastern Kansas, and the state of Missouri, is driven
by typical thunderstorm activity. Flooding is projected to occur
again this Spring in this region of the basin. Two rounds of rain-
induced flooding have already occurred this year in central and
southern Missouri, reminding us that flooding can, and does
occur within the lower basin year-round.
The following state by state flood potential discussions are based
on long-range probabilistic river outlooks developed this week.
Again, it must be stressed, these outlooks do not take into account
river ice that may yet be present.
In Iowa, the Little Sioux River is projected to experience minor
level flooding.
Kansas streams likely to experience minor flooding this Spring
include the Big Blue, Black Vermillion, and Marais des Cygnes
Rivers. The Little Osage River and Stranger Creek are both
expected to see moderate level flooding.
In the state of Missouri, the Chariton, Marmaton, Big Piney, Platte,
Gasconade, Little Osage, Maries, and Osage Rivers are projected to
experience minor level flooding. Moniteau and Roubidoux Creeks are
also expected to see minor flooding. The Grand, Crooked, Blackwater,
Lamine, Sac, Moreau, and South Grand Rivers are likely to see
moderate level flooding. Wakenda, Petite Saline, and Big Creeks are
expected to reach moderate level flooding as well.
The Missouri River downstream of Kansas City is also projected to
experience minor flooding this Spring. The National Weather Service
remains in close contact with the US Army Corps of Engineers with
regard post-2019 levee repair.
These projections of river stages are based on current observed
states of streamflow, soil moisture, and snowpack, coupled with
future precipitation and temperature patterns and anticipated
operational hydrologic changes such as reservoir releases and canal
diversions. "Outlooks" are provided for long-range (weeks to months)
projections based on climatological patterns of precipitation and
temperature. "Forecasts" are provided for short-term (days)
projections based on forecast patterns of precipitation and
temperature. The uncertainty of these products varies from
season to season and location to location. The uncertainty of
forecasts tend be less than the uncertainty of outlooks due to
their shorter lead time.
Users of these products are encouraged to contact their nearest
National Weather Service Forecast Office for continued updates of
meteorological conditions which can have significant impacts on
flood preparedness planning and flood fighting activities.
For additional quantitative information please refer to AHPS products
for probabilistic outlooks of potential flooding. Refer to short-term
flood forecasts and products, if any are currently issued, for
information about ongoing or near-term anticipated flooding.
This is the last scheduled Spring Outlook of the season. If
significant changes occur subsequent to this Outlook, additional
Outlooks can be released to address needs.
Additional river information, including the monthly Water Supply
Outlook, can be accessed at the following URL:
http://weather.gov/mbrfc
Current Snow Conditions
Much of the snow across the lower elevations of the Missouri River basin
has melted due to the warm weather over the past two weeks.
The snow conditions listed below are based on observations and model
data as of Wednesday morning, March 10th.
Montana, Wyoming, and Colorado Plains
A storm system is currently moving across the plains of Wyoming. Snow totals
are generally less than 5 inches with water equivalents less than half an inch.
There is little to no snow across the plains of Montana and Colorado.
Mountainous West
Snowpack conditions in the mountainous areas of the basin are generally
near normal. In Montana, the Jefferson, Musselshell, Missouri headwaters,
Sun, Teton, and Marais River basins are reporting a near normal snowpack
(95-110%). The St. Mary and Milk basins are reporting a near to slightly
above normal snowpack (100-115%). In Wyoming, the Tongue, Bighorn, Powder,
Wind, and Yellowstone River basins are reporting a near normal snowpack (90-110%).
The higher elevations of the North Platte River basin are reporting a below
normal snowpack (80-90%). In Colorado, the higher elevations of the South
Platte River basin are also reporting a below normal snowpack (80-90%).
North Dakota
There is little to no snow across North Dakota at this time.
South Dakota
The Black Hills in South Dakota have 3-6 inches of snow depth
with water equivalents in the 0.5-2.0 inch range. Snow depths
across the remainder of South Dakota are generally less than 2 inches
with water equivalents less than half an inch.
Nebraska
A storm system is currently moving across northwestern Nebraska. Snow
totals are generally less than 3 inches with water equivalents less than
a quarter of an inch. The remainder of Nebraska has no snow.
Iowa, Kansas, and Missouri
There is no snow across Iowa, Kansas, and Missouri at this time.
Current Soil Moisture Conditions
The US Drought Monitor indicates much of the Missouri River basin
is experiencing below normal soil moisture conditions. The exception
is across the state of Missouri and eastern Kansas, where normal to
above normal soil moisture is occurring. Exceptional drought is
indicated across central and eastern Colorado. An area of extreme
drought is indicated across western Kansas, southwestern Nebraska,
central Wyoming, southeastern South Dakota, and northwestern Iowa.
A large area of moderate to severe drought is indicated across Montana,
North Dakota, South Dakota, Wyoming, Nebraska, western Iowa, and
much of Kansas.
Isolated frost depth reports suggest that soils across Montana, Wyoming,
South Dakota, and North Dakota have frost penetration ranging from
1.0-3.0 feet. Frost depths of less than 1.0 foot are being reported
across Nebraska, Iowa, Colorado, Kansas, and Missouri.
Current River Conditions
The majority of the rivers in the northern one-third of the basin are
ice-affected. River levels in this portion of the basin are
currently running near to below normal, or estimated to be so if the
rivers are frozen. In the southern two-thirds of the basin, rivers
are generally running near normal with the exception of Colorado,
western Kansas, and southwest Nebraska where flows are below historical
medians.
A summary of river flow conditions at selected river stations for
March 10th follows:
Long Term Current
Mean (CFS) (CFS)
James River - Huron, SD 220 225 (EST)
Big Sioux River - Akron, IA 1000 1690 (EST)
Platte River - Louisville, NE 9000 9900
Kansas River - Desoto, KS 3390 1940
Gasconade River - Jerome, MO 2520 1750
Missouri River - Omaha, NE 19700 22300
Missouri River - Rulo, NE 32500 31800
Missouri River - St. Joseph, MO 36000 35700
Missouri River - Waverly, MO 42600 40700
Missouri River - Hermann, MO 70100 49900
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