Flood Potential Outlook
Issued by NWS Hastings, NE

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Probabilistic Hydrologic Outlook
National Weather Service Hastings NE
115 PM CST Thu Mar 01 2018

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

This outlook is for the Hastings Hydrologic Service Area (HSA). In
South Central Nebraska this outlook includes the
Platte...Loup...Little Blue...and Republican Rivers and their
tributaries. In North Central Kansas...the Solomon River and its
tributaries are included.

...The potential for ice jam flooding in the Loup and Platte River
Basins is above normal, while the overall threat for spring flooding
after the ice is out (and across the other river basins of south
central Nebraska and north central Kansas) will be slightly
below normal to near normal...

...Short Term Hydrologic Outlook...March 1st - March 15th...

We will be very warm through Sunday with widespread 60s and 70s
across the region this weekend. In addition, even the overnight lows
will be above freezing Friday night and Saturday night with lows
only falling into the 40s Saturday night. Furthermore, there will be
a gusty south wind Friday through Sunday that with the warm
temperatures will act to begin breaking up the river ice. This
year`s river ice has been reported to be over 12 inches thick in
many locations from our abnormally cold winter. Given the abnormally
thick river ice and the potential for a quick breakup this weekend
we believe there is a heightened threat for ice jams and ice jam
flooding in ice jam prone areas along the Platte and Loup Rivers
especially this weekend. After this weekend the temperatures will
fall back to below normal for much of next week although afternoon
highs will still be above freezing. The threat for ice jams will
persist until the river ice has melted enough to be completely
flushed out of the system. This could be as early as this weekend or
it may linger for another week or two. Most of the Platte River
upstream of Overton is already largely ice free and is unlikely to
see an ice jam. A Platte and Loup River fly-over earlier this week
indicates that there is still a lot of river ice on the Loup River
and on the Platte River downstream of Overton.

There is a chance for thunderstorms late Sunday afternoon into
Sunday night. There is always a concern when we get thunderstorms
over frozen ground, given that our frost depth as of March 1st
generally ranges from around 12-16 inches. However, given the
expected warming this weekend we will likely thaw the top several
inches allowing for some infiltration to take place. In addition,
any thunderstorms late Sunday would likely be quick moving, making
it hard to put down heavy rainfall amounts, but we will still have
to monitor this weather setup closely in the coming days.


...Long Term Hydrologic Outlook...March 15th - June 1st...

The latest Drought Monitor indicates that most of our forecast area
generally south of the Platte River has been abnormally dry with the
driest conditions across Kansas. Our soil moisture for this time of
year ranges from a little above normal north of the Platte River, to
below normal across northern Kansas. There are not many good long
range forecasting clues this spring and thus the 3-month
precipitation outlook is mainly indicating equal chances of above,
below or near normal precipitation with below normal just slightly
favored across our Kansas zones. The Platte River basin over the
Rocky Mountains has experienced a near normal snow year thus far.
The reservoirs on the Platte River are a little fuller than average,
but have plenty of space to handle the expected spring runoff.
Therefore, runoff from spring snowmelt is not expected to result in
flooding concerns this year.

The long range river flow models indicate that most of the rivers
across south central Nebraska and north central Kansas are more
likely to be near or slightly below normal levels in the spring
period running through June 1st. It`s important to remember that
even in dry seasons, localized heavy rainfall can still result in
areas of flash flooding.


...Climatological Review (Winter 2017-18 and recent precipitation
trends)...

In the previous issuance of this product back on Feb. 15, this
section contained a detailed narrative and table outlining
precipitation totals and departures from normal for the entire year
2017 across the 30-county NWS Hastings coverage area (24 counties in
Nebraska and 6 in Kansas). Please refer to this previous issuance
for details regarding 2017 precipitation.

From this point forward, the focus will be on more recent
precipitation trends over the past three months, specifically what
transpired during "meteorological winter" of 2017-18, which just
ended on Feb. 28 (meteorological winter consists of the three full
calendar months of Dec-Jan-Feb).

As evidenced in the data presented in the table below (and supported
by NWS AHPS precipitation analysis), meteorological winter featured
a fair amount of variability in precipitation across the local 30-
county area, but as a whole, roughly three-fourths of the area was
below normal (this was the opposite of last winter, when most areas
were above normal). The farthest-below-normal locations concentrated
within southern and southeastern counties, especially north central
Kansas, along with south central Nebraska areas near the state line
and also extending north up Highway 81 into Fillmore and York
counties. The majority of the roughly one-fourth of the total area
that measured slightly above normal precipitation this winter
included several Nebraska counties along/especially north of
Interstate 80. This was largely due to the significant snow
storm/blizzard of Jan. 21-22. For parts of the area, this was the
overall-biggest snow storm in nearly two years, with most counties
north of Interstate 80 measuring 10-14 inches. However, snow amounts
with this storm tapered off sharply south of there, with most places
south of I-80 only averaging 1-4" (with a notable exception of
southern Rooks County KS which saw around 6"). In terms of
meteorological winter 2017-18 extremes, one of the overall driest
NWS stations from Dec-Feb was Beloit KS with merely 0.61" (1.86
below normal). On the wetter side of the spectrum, one site that
really stood out was St. Paul with 2.71" (1.11 above normal).

Winter drought trends:
According to weekly updates by the U.S. Drought Monitor, much of the
30-county area was "stuck" in Abnormally Dry (D0) conditions most of
the winter. However, a series of snow events that mainly impacted
northern sections of the area from late-January into early-February
resulted in some improvement there. More specifically, nearly all
areas roughly along and especially north of the Platte River in the
local Nebraska area are now void of all drought categories
whatsoever. Unfortunately, on the drier side of the area, things
have gradually degraded in parts of north central Kansas. As of this
writing, much of Mitchell, Osborne and southern Rooks counties are
indicated to be in Moderate Drought (D1). So in summary, roughly
half of the total 30-county area is currently Abnormally Dry (D0),
while several northern counties are drought-free, and a few far
southern counties are in Moderate Drought (D1). Keeping things in
perspective though, one must keep in mind that no matter how much
precipitation falls during the winter, it usually only accounts for
a small percentage of total annual precipitation, the vast majority
of which falls during the spring and summer.

This next table below highlights precipitation totals and departures
from normal/percent of normal for meteorological winter 2017-18 (Dec-
Feb). The table features data for 26 locations scattered throughout
the local area. Most of these stations are official NWS Cooperative
Observers, along with a few official airport sites:


 Location          Precip                            Percent of
North Central KS  Dec 1-Feb 28    Normal   Departure    Normal
--------           --------       ------   ---------  --------
Alton 2SW            0.78          2.16      -1.38        36
Beloit               0.61          2.47      -1.86        25
Burr Oak             1.06          2.11      -1.05        50
Logan                0.98          1.71      -0.73        57
Plainville 4WNW      1.49          2.10      -0.61        71
Smith Center         0.74          1.73      -0.99        43


  Location          Precip                            Percent of
South Central NE  Dec 1-Feb 28    Normal   Departure     Normal
--------           --------       ------   ---------  --------
Aurora 4N            1.60          2.22      -0.62        72
Cambridge            1.38          1.59      -0.21        87
Clay Center          1.23          2.02      -0.79        61
Elwood 8S            1.07          1.69      -0.62        63
Franklin             0.87          1.89      -1.02        46
Geneva               1.01          1.92      -0.91        53
Grand Island Arpt    2.28          1.84      +0.44       124
Greeley              1.56          1.88      -0.32        83
Hastings Airport     1.30          1.51      -0.21        86
Hebron               1.50          2.44      -0.94        61
Holdrege             1.36          1.65      -0.29        82
Kearney Airport      1.90          1.61      +0.29       118
Loup City            1.60          1.93      -0.33        83
Minden               1.08          1.48      -0.40        73
Ord Airport          1.79          1.40      +0.39       128
Osceola              2.24          2.25      -0.01       100
Ravenna              1.61          1.66      -0.05        97
Shelby 3NE           2.18          2.00      +0.18       109
St. Paul             2.71          1.60      +1.11       170
York 3N              1.50          2.91      -1.41        52


...Weather/Climatological Outlook For The Next Week Through The Next
Three Months...

It`s now time to switch gears and look ahead to expected weather
conditions over the next several days and expected climate trends
over the next several months:

The forecast through the next week (through March 8th):
According to the latest NWS Hastings 7-day forecast, the upcoming
week as a whole looks to feature generally near-to-above normal
temperatures, with a few of the warmest days with widespread highs
in the 60s-70s being Saturday-Sunday (March 3rd-4th), before highs
cool back into mainly the 40s next week. Precipitation-wise, the
majority of the next week looks dry. The exception is Sunday-Monday
(March 4th-5th), which could feature a chance of both
rain/thunderstorms and snow as a strong low pressure system passes
through. However, it is still too soon to determine whether this
system will produce widespread, beneficial precipitation or only
paltry amounts.

8-14 Day Outlook (valid March 8-14):
Looking out a bit farther into mid-March, the latest 8-14 day
outlook from the Climate Prediction Center favors a "near-normal"
regime for both temperatures and precipitation across the majority
of the area.

March outlook (one-month):
Looking ahead to the upcoming month of March as a whole, the latest
one-month outlook from the Climate Prediction Center (CPC) released
Feb. 28 has changed a bit from the previous version issued two weeks
ago, especially in terms of temperatures. Starting with
precipitation, the March outlook still favors generally "equal
chances" of seeing above, near or below normal precipitation through
the month (except in far southwestern areas where it slightly favors
below normal precipitation). However, the temperature outlook now
leans slightly toward above normal temperatures (33-40 percent
chance), instead of the previously-favored below normal
temperatures. However, this still means there is one-in-three chance
(33 percent) that temperatures could average near normal (within the
middle one-third of climatology), and a lesser (27-33 percent
chance) that temperatures could actually average below normal, or
slightly opposite of expectations. The "equal chances" forecast for
precipitation (across much of the area) means there is no clear
signal in current longer-term forecasts to support one outcome over
another (above normal, near normal, below normal). However, as a
point of reference, normal March precipitation across the local area
ranges from around 1.40" in the western-most counties (such as
Dawson/Furnas), up to around 2.10" in far eastern counties along and
near Highway 81 (such as York/Thayer). Temperature-wise, long-term
30-year normals (based on 1981-2010 data) indicate that March high
temperatures across South Central Nebraska and North Central Kansas
gradually climb from averages in the mid-40s/near-50 early in the
month to the upper 50s/low 60s by month`s end. Average daily low
temperatures gradually increase from around 20 to around 30 degrees.

Three-Month Outlook for March-May:
Turning to the meteorological spring months of March-April-May as a
whole, the latest three-month outlook valid for March-May (released
Feb. 15) shows no truly strong climate signals, with much of the
local area assigned "equal chances" for both temperatures and
precipitation. However, roughly the southwestern one-third to one-
half of the local area very slightly favors (33-40 percent chance)
above normal temperatures and below normal precipitation. Again,
"equal chances" means that long range forecast tools just do not
present enough of a signal to support one of these possible outcomes
over another. Although there are no truly strong signals regarding
upcoming spring precipitation trends, one can keep in mind that 30-
year normal precipitation from March-May across the NWS Hastings
coverage area typically ranges from 7-10 inches, with the lowest
amounts generally west of Highway 183 and highest amounts in the far
east near the Highway 81 corridor.

Seasonal Drought Outlook (March-May):
Finally, the latest U.S. Seasonal Drought Outlook (issued by CPC
on Feb. 15) indicates that there are no strong indications to
suggest drought conditions will degrade/worsen from the current
situation across south central Nebraska and north central Kansas.

(The longer range forecasts issued by CPC and referenced in the
preceding paragraphs are based on output from various forecast
models, as well as forecaster expertise, and take into consideration
ongoing global/tropical atmospheric and oceanic states, recent
trends in observed data, soil moisture conditions, etc. More
information about these longer-range forecasts can be obtained from
the CPC web site at: http://www.cpc.noaa.gov)


...Long Range Probabilistic 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:  03/03/2018  - 06/01/2018

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Little Blue River
Deweese             10.0   16.0   17.0 :  16   21   <5   <5   <5   <5
:North Fork Solomon
Glade               11.0   16.0   18.0 :   6    7   <5   <5   <5   <5
:Bow Creek
Stockton             9.0   12.0   13.6 :   7    7   <5   <5   <5   <5
:Platte River
Cozad                6.5    8.0   10.0 :  21   23    8    9   <5   <5
Overton              7.5   12.0   14.0 :  14   15   <5   <5   <5   <5
Kearney              7.0    8.0    9.0 :   8   13   <5    6   <5   <5
Grand Island         6.5    7.0    7.5 :  14   19   10   16    7    9
:Wood River
Gibbon              15.0   16.0   16.5 :  13   19   10   14    9   12
Alda                10.0   11.0   12.2 :  14   25   13   20    9   13
:South Loup River
Ravenna              5.0    8.0   10.0 :  24   28   <5   <5   <5   <5
:Mud Creek
Sweetwater          16.5   18.0   21.0 :  15   10   <5   <5   <5   <5
:South Loup River
Saint Michael        7.5   12.0   15.0 :  12   14   <5   <5   <5   <5
:Middle Loup River
Saint Paul           8.0   10.0   12.0 :  <5   <5   <5   <5   <5   <5
:North Loup River
Saint Paul           7.0   10.0   12.0 :  <5   <5   <5   <5   <5   <5
:Cedar River
Fullerton            9.0   17.0   18.0 :  <5   <5   <5   <5   <5   <5
:Loup River
Genoa               10.5   12.0   13.0 :   8    8   <5   <5   <5   <5
:Beaver Creek
Genoa               15.0   17.0   19.0 :   8    9    6    6   <5   <5
:Republican River
Riverton             9.0   10.5   13.5 :  <5    5   <5   <5   <5   <5
Guide Rock          12.5   15.0   17.0 :   6    5   <5   <5   <5   <5
Hardy               11.0   14.0   15.5 :  <5    8   <5   <5   <5   <5
:South Fork Solomon River
Woodston            12.0   16.0   27.0 :  16   26   11   16   <5   <5
:South Fork Solomon
Osborne             14.0   20.0   27.0 :  18   30   10   17   <5   <5
:North Fork Solomon
Portis              15.0   20.0   25.0 :  30   26   22   15   <5   <5
:Solomon River
Beloit              20.0   25.0   30.0 :  23   37    9   10   <5   <5
:Republican River
Cambridge            9.0   10.0   16.0 :  <5   <5   <5   <5   <5   <5
Orleans              9.0   11.0   13.0 :   5    5   <5   <5   <5   <5
:Beaver Creek
Beaver City         11.0   13.0   15.0 :   7    7    6    6   <5   <5
:Sappa Creek
Beaver City         16.0   18.0   20.0 :  <5   <5   <5   <5   <5   <5
Stamford            19.0   22.0   26.0 :  <5   <5   <5   <5   <5   <5
:Prairie Dog Creek
Woodruff            21.0   24.0   30.0 :  <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: 03/03/2018  - 06/01/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Little Blue River
Deweese               2.2    3.3    5.3    7.6    9.4   11.5   13.1
:North Fork Solomon
Glade                 2.8    2.9    2.9    5.0    8.5   10.7   11.1
:Bow Creek
Stockton              3.6    3.6    3.6    4.0    6.8    8.4    9.5
:Platte River
Cozad                 1.8    2.0    3.5    4.7    6.4    7.6    8.3
Overton               3.8    3.8    4.1    4.7    6.0    7.8    9.7
Kearney               2.9    2.9    3.0    3.6    4.7    6.3    7.9
Grand Island          4.2    4.2    4.3    4.7    5.8    6.9    7.7
:Wood River
Gibbon                4.1    4.1    4.2    7.4   10.2   15.9   17.0
Alda                  4.5    4.5    4.5    6.9    8.4   12.0   12.8
:South Loup River
Ravenna               3.0    3.1    3.5    4.1    4.9    5.6    5.8
:Mud Creek
Sweetwater            7.7    7.7    9.2   12.1   14.8   17.1   17.8
:South Loup River
Saint Michael         3.2    3.2    3.8    4.8    6.3    7.6    8.0
:Middle Loup River
Saint Paul            2.6    2.6    2.9    3.5    4.2    5.1    5.7
:North Loup River
Saint Paul            3.4    3.5    4.0    4.2    4.7    5.2    5.3
:Cedar River
Fullerton             3.6    3.8    4.7    5.5    6.3    7.0    7.6
:Loup River
Genoa                 3.6    3.6    6.5    8.0    9.0   10.2   10.9
:Beaver Creek
Genoa                 4.4    4.8    6.3    7.9   10.2   11.8   17.3
:Republican River
Riverton              1.6    1.7    2.1    3.5    4.5    6.4    7.9
Guide Rock            2.4    2.7    5.1    7.0    8.8   10.8   12.9
Hardy                 1.9    2.7    3.9    5.5    6.7    8.6   11.0
:South Fork Solomon River
Woodston              4.2    4.2    4.7    6.2    8.5   16.4   18.9
:South Fork Solomon
Osborne               3.8    3.8    5.1    6.3   10.7   20.1   21.4
:North Fork Solomon
Portis                4.0    4.0    5.2    7.9   16.0   21.8   24.1
:Solomon River
Beloit                3.5    3.5    4.4    9.5   19.1   24.1   29.2
:Republican River
Cambridge             3.4    3.4    3.4    3.6    4.6    6.2    6.9
Orleans               3.2    3.2    3.3    4.3    6.0    8.0    8.7
:Beaver Creek
Beaver City           2.6    2.6    2.7    3.4    7.3    9.8   13.6
:Sappa Creek
Beaver City           2.8    2.8    2.8    3.4    7.9   10.8   11.9
Stamford              6.5    6.6    6.7    8.1   11.4   13.9   17.3
:Prairie Dog Creek
Woodruff              1.2    1.2    2.1    4.7    7.3    9.3   11.9

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: 03/03/2018  - 06/01/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Little Blue River
Deweese               2.2    2.2    2.2    1.8    1.8    1.8    1.8
:North Fork Solomon
Glade                 2.8    2.8    2.6    2.4    2.3    2.3    2.3
:Bow Creek
Stockton              3.6    3.6    3.5    3.5    3.4    2.9    2.4
:Platte River
Cozad                 1.2    0.5    0.5    0.5    0.5    0.5    0.5
Overton               3.6    3.3    3.1    2.8    2.6    2.6    2.6
Kearney               2.5    2.4    1.9    1.6    1.3    1.2    1.2
Grand Island          4.1    3.9    3.7    3.4    3.2    3.1    3.1
:Wood River
Gibbon                4.1    4.1    4.1    4.1    4.0    4.0    4.0
Alda                  4.5    4.4    4.4    4.4    4.3    4.3    4.3
:South Loup River
Ravenna               2.7    2.7    2.6    2.5    2.5    2.5    2.5
:Mud Creek
Sweetwater            6.8    6.8    6.6    6.5    6.4    6.3    6.3
:South Loup River
Saint Michael         2.7    2.7    2.5    2.4    2.3    2.2    2.2
:Middle Loup River
Saint Paul            2.4    2.4    2.2    2.2    2.1    2.1    2.0
:North Loup River
Saint Paul            3.3    3.2    3.1    3.0    2.9    2.8    2.7
:Cedar River
Fullerton             3.2    3.2    3.1    3.0    2.7    2.5    2.5
:Loup River
Genoa                 3.6    3.6    3.6    3.6    3.6    3.6    3.6
:Beaver Creek
Genoa                 3.8    3.7    3.7    3.5    3.4    3.3    3.3
:Republican River
Riverton              1.5    1.5    1.5    1.5    1.5    1.5    1.5
Guide Rock            2.3    2.3    2.3    2.3    2.3    2.3    2.3
Hardy                 1.2    1.1    1.0    1.0    1.0    1.0    1.0
:South Fork Solomon River
Woodston              4.2    4.2    4.2    4.2    4.2    4.2    4.2
:South Fork Solomon
Osborne               3.8    3.8    3.8    3.8    3.8    3.8    3.8
:North Fork Solomon
Portis                4.0    4.0    4.0    4.0    4.0    4.0    4.0
:Solomon River
Beloit                3.4    3.4    3.3    3.0    2.8    2.8    2.8
:Republican River
Cambridge             1.8    1.7    1.5    1.4    1.4    1.4    1.4
Orleans               1.6    1.6    1.3    1.1    1.0    0.9    0.9
:Beaver Creek
Beaver City           2.6    2.5    2.4    2.2    2.2    2.2    2.2
:Sappa Creek
Beaver City           2.8    2.8    2.8    2.8    2.8    2.8    2.8
Stamford              6.3    6.3    6.2    5.8    5.8    5.8    5.8
:Prairie Dog Creek
Woodruff              1.2    1.2    1.2    1.2    1.2    1.2    1.2

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.


...Future Outlooks...

The next routine probabalistic hydrologic outlook will be issued on
or around March 21st.

&&

Visit our local NWS office website for current weather/hydrological
and climate information for South Central Nebraska and North Central
Kansas at: www.weather.gov/hastings

Additional climate information for the region can be obtained at:
www.hprcc.unl.edu

Additional information on climatological outlooks can be found at:
www.cpc.ncep.noaa.gov

Further information on drought conditions can be obtained at:
www.drought.gov www.drought.unl.edu www.droughtmonitor.unl.edu

Information on mountain snowpack can be found at:
www.wcc.nrcs.usda.gov/ftpref/downloads/wsf/201802wsfwww.pdf
www.wcc.nrcs.usda.gov

NWS AHPS precipitation analysis maps can be found at:
http://water.weather.gov

National snow analysis page can be found at: www.nohrsc.noaa.gov/nsa

Soil Moisture:
www.cpc.ncep.noaa.gov/products/Soilmst_Monitoring/US/Soilmst/Soilmst.
shtml

Reservoir Levels: www.usbr.gov/gp/hydromet/curres_google.htm

For training on NWS probabilistic graphics:
www.youtube.com/watch?v=pSoEgvsnpv4

For training on NWS river forecast graphics:
www.youtube.com/watch?v=psIByj8EZY0

$$

Wesely/Pfannkuch




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