Hydrometeorological Discussion
Issued by NWS West Gulf RFC

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AGUS74 KFWR 251647
HMDFWR
HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX
1146 AM CDT MON MAY 25 2015

                     VALID MAY 25 THROUGH MAY 30

...STORM SYSTEMS WILL CONTINUE TO BRING PARTS OF THE WGRFC AREA
LOCALLY HEAVY RAIN TODAY AND AGAIN AT THE END OF THE WEEK...

                  ...METEOROLOGICAL DISCUSSION...
One upper level low pressure system was located over western Minnesota
this morning.  As this low pulled northeastward widespread showers and
thunderstorms moved across east Texas and western Louisiana, with a
secondary area of thundershowers following the first from south of the
DFW metroplex across east Texas.  Rainfall amounts the past 24 hours
were heaviest over extreme northeast Texas where over 2.00 inches were
noted.

The focus for new rain has shifted to southwest Texas this morning,
with showers and thunderstorms forecast to spread over the remainder
of Texas this afternoon and tonight.  Deep moisture persists over the
region, with Precipitable Water (PW) values running 150 percent of
normal and higher.  With a second upper air disturbance moving in and
deep moisture in place, widespread showers and thunderstorms have
developed over west and southwest Texas.  Northern and southeastern
Texas as well as southwestern Louisiana will see the heaviest
precipitation now through Tuesday, with an additional 2 to 3 inches of
rain expected.  This upper disturbance will move northeastward rather
quickly and should be out of the region by Tuesday morning.  A weak
ridge of high pressure is forecast to move across Texas Tuesday and
Wednesday which should bring a break to the widespread heavy rainfall.

By Thursday morning a new upper air disturbance is forecast to
approach our region from the west.  This is forecast to produce a new
area of showers and thunderstorms over southeast New Mexico and far
west Texas by Thursday morning.  This rain will then move further
northeast and cover the northwest half of Texas during the day
Thursday into Friday. Some locally heavy rainfall is forecast.  The
first disturbance is forecast to move northeast of our region by
Friday evening. Thereafter, minor upper air disturbances are forecast
to cross north Texas Friday night into Saturday.  Additional excessive
rainfall is not forecast, but the WGRFC will continue to monitor this
storm and update as needed.

                    ...PRECIPITATION FORECAST...
For Today into Tuesday morning, Mean Areal Precipitation (MAP) amounts
of 0.25 of an inch or more are forecast for roughly the southeast
three quarters of Texas and Louisiana.  The heaviest rain, with MAP
amounts of 2.00 inches, are forecast over two locations.  One is over
parts of north central and northeast Texas.  The second area is
over southeast Texas from east of San Antonio through Houston to just
north of Lake Charles LA.  MAP amounts of 1.00 inch are forecast over
a good part of the eastern half of Texas and western Louisiana.
Lighter amounts of MAP are forecast for much of the remaining areas of
the WGRFC area of responsibility except for eastern and southern New
Mexico and far west Texas.

For Tuesday into Wednesday morning, no significant MAP amounts are
forecast for the WGRFC area.  Light amounts of MAP are forecast for
southwest Texas near Del Rio, roughly the eastern quarter of Texas,
western Louisiana, extreme northern New Mexico and Colorado.

For Wednesday into Thursday morning, no significant MAP amounts are
forecast for the WGRFC area.  Light amounts of MAP are forecast for
much of the WGRFC area of responsibility except for the central and
western parts of New Mexico and deep south Texas.

For Thursday into Saturday morning, MAP amounts of 0.25 of an inch or
more are forecast for eastern New Mexico and the northwest half of
Texas.  The heaviest rain, with MAP amounts of 1.50 inches, are
forecast over west Texas between Midland, Childress and Abilene.
Lighter amounts of MAP are forecast for much of the remaining areas of
the WGRFC area of responsibility except for southwestern New Mexico.

Drought conditions continue to improve across most of the WGRFC area.
Recent precipitation events have brought drought relief to many parts
of Texas.  In Texas, only about 15% of the state is experiencing
moderate or worse drought, and extreme to exceptional drought
conditions are no longer being observed.  In New Mexico, a little over
a third of the state is experiencing moderate or worse drought (37%),
and they also are free from extreme or exceptional drought conditions.
Many of the lakes in Texas have levels which have begun to rise due to
recent rainfall, and some lakes are full and are releasing water.  The
rainfall expected over the next five days over especially the
northeastern half of Texas will be heavy enough to produce significant
runoff, and minor runoff is expected over the remainder of Texas.
Elsewhere over the WGRFC area no significant runoff is anticipated.

                     ...HYDROLOGIC DISCUSSION...
...Guadalupe Basin...
...Moderate Flooding...
Very heavy, short duration rainfall (6 to 12 inches) Saturday and
Sunday across the headwaters caused flash flooding and major river
flooding through Wimberly (WMBT2) and Kyle (KYET2) along the Blanco
River and Luling on the San Marcos (LLGT2).  This flood wave has
caused major damage along it`s path of the Blanco and San Marcos River
mainstem.  Furthermore, the remnants of it is expected to cause major
flooding as it moves downstream along the San Marcos into the mainstem
through Gonzales (GNLT2), Cuero (CUET2), Victoria (VICT2), and
Bloomington (DUPT2) to the coastal outlet.

This event comes in the wake of an earlier flood wave still moving
further downstream; now cresting through Bloomington (DUPT2).

...Nueces Basin...
...Major Flooding...
The Frio River for the most part has receded except downstream near
Derby which is in moderate flood now and continues to rise.  San Miguel
Creek in the upper portion of the basin through  received 4 to 5 inches
of rainfall but has still yet to begin to push the wave downstream.
This leads that the wave is being attenuated greatly and could only
push the forecast into minor.  Will wait to see what this water does
over the next day or so.  On the Nueces, the forecasts continue to
recede in the upper portion as Cottula has crested and the flood wave
is forecast to arrive in about 3 days in Tilden pushing it into major
flood.  Lake Corpus Christi has reduced the flow again alleviating the
flood even more downstream at both Bluntzer and Calallen.

...Trinity Basin...
...Major Flooding...
Heavy rainfall across the entire Trinity River drainage has caused
widespread bankfull, minor, and moderate flood flow conditions.  Flood
control reservoirs continue to store flood waters minimizing
downstream flood conditions.

...San Antonio Basin...
...Minor Flooding...
Moderate to Major flooding is forecast in the lower San Antonio River
basin.

...Neches Basin...
...Moderate Flooding...
The Neches River system remains in elevated flow levels with several
locations currently in flood.  The Neches River near Alto (ATOT2) is
at moderate levels.  Multiple other sites will remain in their minor
to action stage levels with the recent rainfalls adding to the already
elevated flows.  Many mainstem forecast points are expected to remain
in minor flood levels for at least the next week.  It should be noted
that heavy rainfall is forecast over the next 24-36 hours.  This will
likely cause additional flooding.

Lake Steinhagen is expected to increase releases as inflows increase
from upstream routed flows and forecast rainfall runoff over the next
few days to keep lake levels from exceeding conservation pool.

...Sabine Basin...
...Moderate Flooding...
Moderate flooding continues on the lower Sabine River Basin through Bon
Wier (BWRT2) and Deweyville (DWYT2) as Toledo Bend Reservoir continues
to pass large inflows.

Toledo Bend reduced inflows again this morning, but is expected to
increase again with expected inflow increases due to forecast rainfall
runoff.

...Brazos Basin...
...Minor Flooding...
Minor to moderate flow conditions are occurring on the Brazos
River system. It should be noted that heavy rainfall is forecast
over the next couple days.  This could cause additional flooding.

...Lavaca-Navidad Basin...
...Higher Flow Non-Flood Forecasts...
Higher than normal flows will continue across the Lavaca River basin.

...Colorado Basin...
...Higher Flow Non-Flood Forecasts...
Higher than normal flows continue down the Colorado River below Austin.

...San Bernard Basin...
...Higher Flow Non-Flood Forecasts...
Higher than normal flows will continue across the lower San Bernard
river.

...Remainder of WGRFC Basins...
Currently, most rivers are have ongoing flooding conditions and
remain very sensitive to further rainfall.  Soil conditions remain
very saturated and any further rainfall will only exacerbate the
ongoing flooding.

              ...SUPPLEMENTARY GRAPHICAL INFORMATION...
The following URLs (all lower case) provide additional graphical
information on current and forecast hydrologic conditions, past and
future precipitation, and drought and climate forecasts.  This
information is provided by a variety of National Weather Service,
NOAA, and private sector entities.

For specific information on river conditions, refer to the AHPS
pages from the local NWS offices at:
http://water.weather.gov/ahps/

The Flood Potential Outlook can be viewed on our webpage at:
http://www.srh.noaa.gov/wgrfc/?n=wgrfcfop

The West Gulf River Forecast Center is now on Facebook:
http://www.facebook.com/US.NationalWeatherService.WGRFC.gov

National Precipitation Analysis:
http://water.weather.gov/precip/

The forecast rainfall amounts (QPF) can be viewed on our webpage at:
http://www.srh.noaa.gov/wgrfc/?n=wgrfcqpfpage

The US Drought Assessment:
http://www.cpc.ncep.noaa.gov/products/Drought

The latest on Reservoir Information for Texas:
http://www.waterdatafortexas.org

STORY

$$




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