Hydrometeorological Discussion
Issued by NWS West Gulf RFC

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AGUS74 KFWR 221624
HMDFWR
HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX
1122 AM CDT FRI MAY 22 2015

                     VALID MAY 22 THROUGH MAY 27

...NO END IN SIGHT TO THE STORM SYSTEMS WHICH COULD BRING PARTS OF THE
WGRFC AREA LOCALLY HEAVY RAIN THE NEXT FIVE DAYS...

                  ...METEOROLOGICAL DISCUSSION...

Little change in the overall pattern is expected.  The southwesterly
flow aloft will continue as an upper level storm system over
the Rockies will move northeast, with yet another storm system taking
its place near the Four Corners area.  At the surface, cooler air will
retreat as southerly winds return to the area.  Deep moisture will
spread northward through the weekend.  Precipitable Water (PW) values
are already running 150 percent of normal, and will likely increase
through the weekend.

With a favorable pattern aloft, and deep moisture in place,
widespread showers and thunderstorms are expected across most of the
WGRFC area.  Upper level disturbances will help initiate thunderstorms
across the area. Other sources of lift, including the warm front as it
moves north and residual outflow boundaries from previous
thunderstorms could also help in the development of thunderstorms
across the region.  Where thunderstorm activity becomes more
organized, locally heavy rainfall can be expected.

At this time, the most favorable timing for locally heavy rainfall
starts Saturday and continues into Sunday for most of Texas.

More showers and thunderstorms are forecast early next week as only
subtle changes in the upper level pattern are expected.  The exact
timing and amounts of heavy rainfall will be dependent on upper
level disturbances in the southwesterly flow aloft and the placement
of residual surface boundaries.  However, most of the WGRFC area
will see precipitation, with many areas seeing an additional 1 to 3
inches of rain, with some locations receiving 4 to 6 inches (locally
higher) in the more organized thunderstorm complexes.

                    ...PRECIPITATION FORECAST...
For Today into Saturday morning, Mean Areal Precipitation (MAP)
amounts of 0.25 to 0.50 inches are forecast over areas of north
Texas, southwest Texas, the Texas panhandle, and southeast Texas
along the Texas gulf coast.  The above said map amounts are also
forecast over areas of eastern New Mexico.

For Saturday into Sunday morning, MAP amounts up to 2 inches are
forecast over south-central, central, and north central Texas.

For Sunday into Monday morning, MAP amounts of 1.5 to 2 inches are
forecast over the eastern half of Texas.

For Monday into Wednesday morning, MAP amounts of 1.5 to 2 inches are
forecast over southeast Texas along the Texas gulf coast.

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 northern and
south central Texas will be heavy enough to produce significant
runoff, and minor runoff is expected over extreme eastern New Mexico
and the remainder of Texas.  Elsewhere over the WGRFC area no
significant runoff is anticipated.

                     ...HYDROLOGIC DISCUSSION...
...Trinity Basin...
...Major Flooding...
Ongoing widespread, 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.

...Nueces Basin...
...Major Flooding...
With the majority of rainfall falling downstream of the river system,
most forecasts are trending as expected and Asherton should fall below
major later today.  However there is more significant rainfall in the
forecast that may extend the flooding situation.  This water has
arrived a little faster than originally forecasted. Expect it to be a
little higher into major flood but leave the area quicker as well.  It
will take some time for the  water to reach Tilden, but Tilden should
remain around the moderate  flood stage for some time.  Three Rivers
has dropped below major and  will continue to fall over the next few
days. Lake Corpus Christi has  raised its releases to 14,000 which
pushes Mathis, Bluntzer, and  Calallen even further into their current
conditions comparable to the flood in July of 2002.

...Guadalupe Basin...
...Moderate Flooding...
The flood wave has moved down past Cuero and is cresting at Victoria in
moderate flood stage. Downstream at Bloomington will continue to push
close to major but maintain in moderate before dropping off.  Further
rainfall this weekend may exacerbate the situation.

...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.

...Sabine Basin...
...Moderate Flooding...
Moderate flooding continues in the Sabine River Basin as Toledo Bend
Reservoir continues to pass large inflows.

...Brazos Basin...
...Minor Flooding...
Several sites along the lower Brazos remain in flood.  With the
exception of the extreme lower end of the Brazos, most of these sites
have crested and are starting to fall.  The Navasota River is also in
minor flood due to recent local rainfall.

...Lavaca-Navidad Basin...
...Higher Flow Non-Flood Forecasts...
Higher than normal flows are expected to continue in the Lavaca River
Basin.

...San Jacinto Basin...
...Higher Flow Non-Flood Forecasts...
Higher than normal flows will continue across most of the San Jacinto
River system throug the weekend. Additional rainfall over the next 2-3
days may cause higher rises.

...Colorado Basin...
...Higher Flow Non-Flood Forecasts...
The Llano River near Mason (MLRT2) is continuing to fall below criteria
this morning. The Colorado River at Wharton (WHAT2) ia also falling and
should continue to fall below criteria the next 24 hours. Additional
rainall forecasted over the next 2-3 days. may cause rivers to rise
above minor flood this weekend or early next week.

...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

SHULTZ


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