Flood Potential Outlook
Issued by NWS New Orleans/Baton Rouge, LA

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Probabilistic Hydrologic Outlook
National Weather Service New Orleans/Baton Rouge, LA
1220 PM CST Thu Mar 1 2018

...2018 Spring Flood Potential Outlook for Southeast Louisiana...Southwest
Mississippi...and Coastal Mississippi...

...Flood Risk is Average to Above Average on Rivers Across the Region...

This outlook considers antecedent rainfall, snowpack, soil moisture, streamflow
and water supply conditions compared to climatology, combined with longer-term
90-day climate outlook forecasts for temperatures and precipitation across the
forecast area.

The primary factor in the development of significant river flooding over most
of the region is the occurrence of excessive rainfall in relatively short
periods of time, even for areas where drought conditions persist or have
developed.

Until a couple of weeks ago, the flood season was uneventful on the Ohio and
Mississippi Rivers. However, rainfall of 5 to 15 inches over the past two weeks
has changed conditions across the lower Mississippi Valley.

Snow water equivalents over the upper Mississippi River Basin range from 0.5 TO
4 inches. The snow is not expected to have any significant impacts on the lower
Mississippi River.

Soil moisture conditions are well above normal over the lower Ohio,
Mississippi, and Tennessee Valleys due to recent rainfall.


...Lower Mississippi River and Atchafalaya River...

Major rises are occurring over the lower Ohio and Mississippi Rivers.
Streamflows are above normal and moderate to major flooding is forecast over
the next few weeks.

See the chart below for specific locations showing percent of normal
streamflows:

                                            3/1
Mississippi River          Vicksburg, MS    201%
Mississippi River             Natchez MS    158%
Mississippi River   Red River Landing LA    154%
Mississippi River         Baton Rouge LA    152%
Mississippi River         New Orleans LA    151%
Atchafalaya River          Simmesport LA    205%


Based on existing soil moisture...streamflow conditions...and normal spring
rainfall patterns...an ABOVE AVERAGE flood potential is expected along the
lower Mississippi River and Atchafalaya River.


...Lower Pearl River...

Soil moisture content and streamflows are above seasonal averages. Minor
flooding is occurring at several locations.

Observed daily streamflows as a percent of median are given below.

                                             3/1
Pearl River                  Columbia MS     200%
Pearl River                  Bogalusa LA     113%

Based on existing soil moisture, streamflows, and normal spring rainfall
patterns; an AVERAGE Flood Potential is expected over the Pearl River Basin.


...Amite/Comite/Northshore Drainage Basins...

Soil moisture is near normal over the area and recent rainfall has caused
streamflows to rise above seasonal levels.

Observed daily streamflows as a percent of median are given below.

                                             3/1
Amite River                Darlington LA     556%
Amite River            Denham Springs LA     648%
Comite River             Olive Branch LA     249%
Tchefuncte River               Folsom LA     532%
Tickfaw River                  Holden LA     672%
Tangipahoa River               Robert LA     529%

Based on existing soil moisture, streamflows, and normal spring rainfall
patterns; an ABOVE AVERAGE Flood Potential is expected over the Amite, Comite,
and Northshore River Basins.


...Pascagoula Basin in South Mississippi...

Soil moisture is near seasonal levels and recent rainfall has caused
streamflows to rise above normal levels.

Observed daily streamflows as a percent of median are given below.

Pascagoula River              Merrill MS     171%

Based on existing soil moisture, streamflows, and normal spring rainfall
patterns; an AVERAGE Flood Potential is expected over the Pascagoula River
Basin.

...Extended Temperature and Precipitation Outlook...


The 8-14 DAY Outlook issued by the NWS Climate Prediction Center indicates
chances of above normal precipitation and below normal temperatures.

The 30-DAY Outlook indicates chances of above normal temperatures and
precipitation.

The 90-DAY Outlook issued by the NWS Climate Prediction Center indicates
chances of above normal temperatures and chances of above normal precipitation
over the Tennessee and Ohio Valleys and chances of below normal precipitation
over the gulf coast.

The next spring Flood Outlook is scheduled to be released on March 14, 2018.


$$



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