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Spring Flood Outlook |
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Snow Water Equivalent Streamflow Analysis 30 Day Rainfall Departure Soil Moisture Percentile 1-Month Precip Outlook 1-Month Temp Outlook 3-Month Precip Outlook 3-Month Temp Outlook |
Probabilistic Hydrologic Outlook
National Weather Service ST. LOUIS MO
230 PM CST THU FEB 25 2021
...Spring Flood and Water Resources Outlook Number 2...
...Minor flooding likely along the Mississippi, Missouri, and
Illinois Rivers...
...Most local streams have a near normal flood risk this spring...
This outlook uses the term St. Louis Service Area to refer to the
Mississippi River from above Canton Missouri to above Cape Girardeau
Missouri, the Missouri River above Jefferson City Missouri to its
confluence with the Mississippi River, the Illinois River downstream
from its confluence with the LaMoine River to its confluence with the
Mississippi River, and for tributary rivers in eastern Missouri, and
west central and southwest Illinois.
There is no ongoing flooding anywhere within the St. Louis Service
Area, so probabilities within this outlook are not skewed by any
ongoing flooding.
This outlook is based on current streamflows and soil moisture over
the area, and upstream snowpack, particularly in the Mississippi,
Missouri, and Illinois river basins. The statistics are based on
about 30 to 60 years of historical rainfall and stream crests. More
than normal rainfall could cause higher-than-expected crests at
individual forecast locations, while less than normal rainfall could
keep streams from reaching "likely" crests.
The Mississippi and Missouri rivers are experiencing near normal
streamflow for this time of year, while flows along the Illinois
River have experienced well below normal streamflow through most of
the past winter. This is providing a low to mostly average starting
point for these rivers to accept future runoff. Soils have dried out
considerably across the Midwest since last summer, leaving local
areas with near to below normal soil moisture. Drier soils are the
rule from Minnesota and the Dakotas through western Kansas. This
will provide the upper Mississippi River and middle Missouri River
basins with additional storage, which acts as a deterrent to
flooding. Finally, snowpack and snow water equivalent in this
snowpack are well below average from northern Wisconsin, most of
Minnesota, and the Dakotas. In fact, the Plains states north through
the Dakotas are essentially snow-free, except for a small area over
southeastern Nebraska. However, this snow water equivalent is well
above average from southern Nebraska through much of Iowa, northern
Illinois, and southern Wisconsin. Due to close proximity of this
above normal snowpack, look for a likelihood of minor flooding for
the Illinois, Missouri, and Mississippi rivers. However, given the
below normal snowpack in other portions of these basins, the
likelihood of significant (moderate or greater) flooding is not as
great, and in many locations the threat of significant flooding is
well below historical averages for the spring months.
For local basins, the chances for flooding at most locations
throughout the St. Louis service area are near or above average.
Minor flooding is likely along the Fabius rivers, the Middle Fork
Salt River, the Cuivre River, the Meramec River, the Bourbeuse River,
the Big River, the Moreau River, and the Kaskaskia River. Soil
moisture and wintertime precipitation have left these areas with
moist soils, but not much different from normal. Most local forecast
points have minor flood probabilities close to or slightly above
normal, while these locations have near normal probabilites for
significant flooding.
In the near term, the Climate Prediction Center calls for above
normal temperatures throughout the bi-state region and near normal
precipitation chances in the 6 to 10 day outlook. By days 8 through
14, temperatures should remain above normal, while there`s a slightly
better than average chance of above normal precipitation. For the
month of March, there`s a slightly better than average chance of
warmer than normal temperatures across the bi-state region. March
precipitation should be close to normal over eastern Missouri while
Illinois has a better than average chance of above normal
precipitation. Looking ahead to the next 3 months of March through
May, temperatures are expected to be above normal throughout the St.
Louis service area, while precipitation chances will be very similar
to March: near normal chances for typical precipitation amounts for
the spring months in Missouri and better chances for above normal
precipitation across Illinois.
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: 03/01/2021 - 05/30/2021
: 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
-------- ----- ----- ----- : --- --- --- --- --- ---
:Mississippi River
Canton 15.0 20.0 25.0 : 70 63 16 16 <5 <5
LaGrange 17.0 23.0 25.0 : 52 52 9 10 <5 <5
Quincy 19.0 22.0 26.0 : 56 56 24 27 9 10
Lock & Dam 21 18.0 21.0 25.0 : 55 53 24 26 9 10
Hannibal 17.0 22.0 24.0 : 69 61 15 15 9 10
Saverton 16.0 20.0 24.0 : 73 64 31 38 10 11
Louisiana 15.0 20.0 25.0 : 84 71 28 33 6 8
Clarksville 25.0 31.0 33.0 : 84 72 26 28 14 14
Winfield 26.0 30.0 34.0 : 79 65 37 40 9 10
Grafton 20.0 24.0 29.0 : 68 72 28 36 7 6
Mel Price LD 21.0 29.0 34.0 : 72 73 24 40 <5 6
St. Louis 30.0 35.0 40.0 : 56 66 27 47 7 11
Chester 27.0 35.0 40.0 : 81 79 39 57 17 27
:North Fabius River
Ewing 11.0 17.0 20.0 : 63 54 15 15 10 10
:Middle Fabius River
Ewing 12.0 17.0 20.0 : 56 50 14 14 8 8
:South Fabius River
Taylor 10.0 14.0 19.0 : 52 52 17 17 <5 <5
:North River
Palmyra 13.0 16.0 22.0 : 24 27 11 11 <5 <5
:Mid Fork Salt River
Holliday 17.0 22.0 26.0 : 51 51 6 5 <5 <5
:Salt River
New London 19.0 25.0 27.0 : <5 <5 <5 <5 <5 <5
:Cuivre River
Troy 21.0 25.0 29.0 : 51 51 24 24 7 7
Old Monroe 24.0 27.0 30.0 : 55 61 28 25 14 14
:Dardenne Creek
St. Peters 18.0 20.0 23.0 : 30 30 17 16 <5 <5
:Meramec River
Steelville 12.0 20.0 25.0 : 48 41 <5 <5 <5 <5
Sullivan 11.0 20.0 29.0 : 71 67 15 12 <5 <5
:Bourbeuse River
Union 15.0 22.0 26.0 : 52 51 11 11 <5 <5
:Meramec River
Pacific 15.0 23.0 27.0 : 44 43 7 7 <5 <5
:Big River
Byrnesville 16.0 20.0 28.0 : 55 49 24 22 <5 <5
:Meramec River
Eureka 19.0 26.0 31.0 : 46 44 18 17 7 7
Valley Park 18.0 21.0 27.0 : 46 50 37 42 18 19
Fenton 23.0 29.0 32.0 : 47 56 16 20 10 12
Arnold 24.0 35.0 38.0 : 81 76 25 30 17 24
:Kaskaskia River
Vandalia 18.0 24.0 26.0 : 74 82 34 35 17 19
Carlyle TW 423.5 431.0 435.0 : 23 43 <5 <5 <5 <5
:La Moine River
Ripley 22.0 23.0 27.0 : 42 41 33 35 11 12
:Moreau River
Jefferson City 17.0 25.0 29.0 : 79 87 40 40 17 15
:Maries River
Westphalia 10.0 15.0 20.0 : 42 52 18 19 <5 <5
:Gasconade River
Rich Fountain 20.0 25.0 30.0 : 34 34 24 26 5 6
:Missouri River
Jefferson City 23.0 25.0 30.0 : 43 60 31 53 14 17
:Osage River
St. Thomas 23.0 30.0 35.0 : 14 16 <5 <5 <5 <5
Mari-Osa Campgrou 19.0 22.0 25.0 : 36 64 17 27 8 13
:Missouri River
Chamois 17.0 28.0 31.0 : 71 77 11 11 6 6
Hermann 21.0 26.0 33.0 : 76 81 33 57 12 13
Washington 20.0 28.0 31.0 : 57 69 13 16 9 10
St. Charles 25.0 30.0 36.0 : 64 71 23 33 8 9
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: 03/01/2021 - 05/30/2021
Location 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Canton 10.9 11.9 14.3 16.3 18.3 21.7 23.0
LaGrange 11.8 12.8 15.2 17.2 19.2 22.6 23.9
Quincy 14.2 14.9 17.4 19.4 21.8 25.6 27.6
Lock & Dam 21 12.3 13.2 16.2 18.2 20.5 24.6 26.9
Hannibal 13.8 14.6 16.2 18.4 20.4 23.6 26.5
Saverton 12.0 13.2 15.8 18.4 20.9 24.1 26.5
Louisiana 12.7 13.7 15.9 18.3 20.5 23.1 25.3
Clarksville 22.0 23.4 26.0 28.9 31.1 33.7 35.5
Winfield 22.2 23.6 26.2 29.0 31.1 33.5 35.6
Grafton 16.1 16.6 18.3 21.7 24.6 28.4 29.7
Mel Price LD 15.4 17.1 20.9 24.2 28.7 31.2 33.5
St. Louis 17.9 21.4 26.6 30.8 35.9 39.1 41.3
Chester 20.0 24.4 29.1 32.8 37.6 42.3 44.1
:North Fabius River
Ewing 6.8 7.2 9.5 12.3 14.7 19.9 21.4
:Middle Fabius River
Ewing 5.8 6.8 9.1 12.6 15.3 19.2 21.8
:South Fabius River
Taylor 5.6 6.5 8.0 10.1 13.2 16.4 18.3
:North River
Palmyra 6.3 6.9 8.7 10.4 12.9 16.5 18.1
:Mid Fork Salt River
Holliday 10.6 11.3 14.6 17.1 18.3 20.8 22.0
:Salt River
New London 5.7 7.4 9.2 9.9 11.2 13.1 13.4
:Cuivre River
Troy 12.0 13.2 16.8 21.6 24.9 27.1 29.7
Old Monroe 17.6 20.1 22.0 24.5 27.6 30.6 31.3
:Dardenne Creek
St. Peters 8.4 9.5 11.9 15.2 19.1 20.6 22.0
:Meramec River
Steelville 3.8 5.7 8.1 11.7 14.4 16.2 19.9
Sullivan 7.5 7.9 10.2 14.4 18.4 21.6 26.3
:Bourbeuse River
Union 8.9 10.5 11.8 15.2 18.7 22.9 25.4
:Meramec River
Pacific 7.3 7.7 11.4 14.8 18.6 22.3 26.3
:Big River
Byrnesville 8.5 9.9 12.2 16.6 19.7 22.9 25.7
:Meramec River
Eureka 10.2 10.7 14.4 17.8 23.6 29.3 35.6
Valley Park 8.2 9.3 13.4 17.2 25.5 31.8 36.6
Fenton 14.0 16.2 19.7 22.4 27.4 32.1 36.1
Arnold 18.7 19.9 25.8 29.5 34.8 39.0 41.2
:Kaskaskia River
Vandalia 12.8 14.0 17.2 22.6 25.3 27.1 28.7
Carlyle TW 415.9 416.5 418.3 420.2 423.4 424.0 424.7
:La Moine River
Ripley 10.9 12.4 16.3 19.8 24.7 27.4 28.3
:Moreau River
Jefferson City 9.5 13.7 17.6 22.0 27.2 33.6 40.1
:Maries River
Westphalia 2.5 3.6 5.0 8.4 13.2 16.5 18.4
:Gasconade River
Rich Fountain 5.5 8.3 10.5 16.0 24.1 28.4 31.0
:Missouri River
Jefferson City 11.1 14.8 19.0 21.7 25.6 33.1 36.0
:Osage River
St. Thomas 7.9 8.7 11.9 13.4 16.6 24.9 27.1
Mari-Osa Campgrou 10.5 11.7 15.0 17.6 19.6 24.7 29.0
:Missouri River
Chamois 9.2 12.3 16.7 19.1 22.5 28.3 31.2
Hermann 14.1 18.3 21.1 24.5 27.2 34.3 36.0
Washington 10.6 14.3 17.1 20.8 23.6 30.6 34.5
St. Charles 17.9 21.1 23.4 26.7 29.1 35.4 37.4
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: 03/01/2021 - 05/30/2021
Location 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Canton 4.7 4.6 4.4 4.2 4.0 3.5 3.1
LaGrange 5.6 5.5 5.3 5.0 4.8 4.4 4.0
Quincy 11.8 11.8 11.7 11.6 11.5 11.2 11.0
Lock & Dam 21 5.3 5.2 5.0 4.7 4.5 4.1 3.7
Hannibal 10.4 10.4 10.2 10.1 10.0 9.9 9.8
Saverton 6.2 6.1 5.9 5.6 5.3 4.9 4.7
Louisiana 12.0 12.0 11.9 11.9 11.9 11.9 11.9
Clarksville 16.5 16.4 16.1 15.7 15.3 14.7 14.2
Winfield 16.3 16.2 15.9 15.6 15.0 14.5 14.1
Grafton 15.2 15.2 15.2 15.1 15.0 14.8 14.7
Mel Price LD 7.7 7.5 7.3 6.8 6.1 5.1 4.5
St. Louis 7.1 7.0 6.6 5.6 4.4 3.2 1.7
Chester 10.9 10.7 10.3 9.3 7.9 6.6 4.9
:North Fabius River
Ewing 3.8 3.7 3.5 3.4 3.2 3.1 3.0
:Middle Fabius River
Ewing 3.3 3.2 3.1 3.0 2.9 2.8 2.8
:South Fabius River
Taylor 2.3 2.2 2.0 2.0 1.8 1.7 1.6
:North River
Palmyra 4.5 4.5 4.5 4.3 4.2 4.1 3.8
:Mid Fork Salt River
Holliday 3.9 3.9 3.9 3.9 3.9 3.8 3.7
:Salt River
New London 6.2 5.1 4.8 3.9 2.4 2.1 2.1
:Cuivre River
Troy 6.3 6.2 5.9 5.6 5.4 5.3 5.2
Old Monroe 12.5 12.3 12.0 11.5 10.8 10.2 9.8
:Dardenne Creek
St. Peters 1.7 1.7 1.4 1.3 1.2 1.1 1.1
:Meramec River
Steelville 2.1 2.0 1.8 1.6 1.5 1.4 1.3
Sullivan 3.3 3.2 2.9 2.7 2.6 2.4 2.3
:Bourbeuse River
Union 2.7 2.6 2.5 2.4 2.3 2.1 2.0
:Big River
Byrnesville 3.6 3.3 2.9 2.5 2.1 2.0 1.8
:Meramec River
Eureka 4.4 4.3 4.0 3.7 3.5 3.3 3.2
Fenton 4.5 4.2 3.6 2.7 2.1 1.7 1.5
Arnold 8.2 8.1 7.9 7.5 7.2 6.7 6.6
:Kaskaskia River
Vandalia 6.7 5.3 3.5 3.1 2.9 2.7 2.6
Carlyle TW 415.7 415.6 413.3 411.2 411.2 411.2 411.2
:La Moine River
Ripley 5.9 5.8 5.5 5.2 4.9 4.7 4.5
:Moreau River
Jefferson City 2.2 2.1 2.1 2.0 1.9 1.8 1.8
:Maries River
Westphalia 1.9 1.8 1.6 1.4 1.3 1.1 1.1
:Gasconade River
Rich Fountain 4.2 4.2 3.9 3.7 3.3 3.1 3.0
:Missouri River
Jefferson City 5.7 5.4 5.1 5.0 4.4 3.9 3.7
:Osage River
St. Thomas 3.2 3.2 2.8 2.5 2.5 2.1 1.5
:Missouri River
Hermann 6.6 5.9 5.6 5.5 5.5 5.3 4.8
Washington 3.5 2.9 2.6 2.4 2.4 2.2 1.6
St. Charles 10.4 9.7 9.4 9.3 9.2 9.0 8.4
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/lsx for more weather and water
information.
The next outlook update will be issued in two weeks, on Thursday,
March 11th.
$$
Fuchs
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