Hydrometeorological Discussion
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AGUS74 KFWR 241624
HMDFWR
HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX
1124 AM CDT SUN MAY 24 2015

                     VALID MAY 24 THROUGH MAY 29

...STORM SYSTEMS WILL CONTINUE TO BRING PARTS OF THE WGRFC AREA
LOCALLY HEAVY RAIN THROUGH EARLY TUESDAY...

                  ...METEOROLOGICAL DISCUSSION...
Little change in the overall weather pattern is expected the next
couple of days.  The southwesterly upper air flow aloft will continue
as upper level storm systems continue to move out of the southwestern
U.S.  Deep moisture will persist over the region through at least
Monday, with Precipitable Water (PW) values running 150 percent of
normal and higher.  With a favorable pattern aloft and deep moisture
in place, widespread showers and thunderstorms are expected across
much of Texas and Louisiana.  Eastern Texas and western Louisiana will
see the heaviest precipitation now through Tuesday, with an additional
2 to 4 inches of rain expected.  Some locations will receive 5 to 7
inches (with locally higher amounts) in the more organized
thunderstorm complexes. Right now the most likely locations to receive
the heaviest amounts are centered west of Shreveport LA, but this
could change somewhat with time.

One upper level low pressure system was located over northwest
Colorado this morning.  As this low pulled northeastward widespread
showers and thunderstorms developed across Texas.  Where the
thunderstorm activity was most organized, locally heavy rainfall
fell. The area over the Texas Hill Country received the most rain
with 9 to nearly 12 inches noted north and west of San Antonio.  The
shower and thunderstorm activity is moving across east Texas at this
time, with a secondary area of thundershowers southwest of the DFW
metroplex near Comanche.  This rain should move east into northeast
Texas this afternoon and evening and eastward into Louisiana, then the
focus for new rain will shift to southwest and central Texas on
Monday.

More showers and thunderstorms are forecast on Monday as the next in a
series of upper air disturbances moves out of New Mexico and on across
Texas.  This disturbance will move northeastward rather quickly and
should be out of the region by Tuesday morning. While some locally
heavy rain is possible, amounts should be lower than what we observed
this past week.  A weak ridge of high pressure is forecast to move
across Texas Tuesday and Wednesday which should bring a break to the
widespread 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 move further northeast
into the northwest half of Texas during the day Thursday into
Friday morning. Right now additional excessive rainfall is not
forecast, but the WGRFC will continue to monitor this storm and
update as needed.

                    ...PRECIPITATION FORECAST...
For Today into Monday morning, Mean Areal Precipitation (MAP) amounts
of 0.25 of an inch or more are forecast for the eastern half of Texas
and Louisiana. The heaviest rain, with MAP amounts of 3.00 inches, are
forecast north of Beaumont TX.  MAP amounts of 1.00 inch are forecast
over all of eastern Texas and western Louisiana.  Lighter amounts of
MAP are forecast for much of the remaining areas of the WGRFC area of
responsibility except for southern New Mexico and far west Texas.

For Monday into Tuesday morning, MAP amounts of 0.25 of an inch or
more are forecast for the southeast two thirds of Texas and Louisiana.
The heaviest rain, with MAP amounts of 3.00 inches, are forecast over
parts of central and northeast Texas.  MAP amounts of 1.00 inch are
forecast over a good part of the southeastern half of Texas.  Lighter
amounts of MAP are forecast for much of the remaining areas of the
WGRFC area of responsibility except for eastern New Mexico and far
west Texas.

For Tuesday into Wednesday morning, MAP amounts of 0.25 of an inch or
more are forecast for extreme southeast Texas into most of Louisiana.
The heaviest rain will be well east of the WGRFC area.  Lighter
amounts of MAP are forecast for roughly the eastern third of Texas,
extreme northern New Mexico and Colorado.

For Wednesday into Friday morning, MAP amounts of 0.25 of an inch or
more are forecast for eastern New Mexico and west Texas.  The heaviest
rain, with MAP amounts of 1.00 inch, are forecast over southwest
Texas between Midland, Lubbock and Abilene. Lighter amounts of MAP are
forecast for much of the remaining areas of the WGRFC area of
responsibility except for the central and western parts of New
Mexico and deep south Texas.

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...
...Colorado Basin...
...Major Flooding...
Rapid rises in and near Austin from overnight rains has caused Barton
Creek (ABTT2) to rise above major flood category and Onion Creek
(ATIT2) to rise above flood stage this morning. This kind of flooding
is usually short term, so expect the creeks to rapidly decrease this
afternoon. However, this water will work its way into the mainstem of
the Colorado River which will cause another wave of non-flood level
water to make its way to the Gulf. Additional rises are possible with
another round of rainfall expected on Monday.

...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. The Trinity River at
Dallas is forecast to crest in major flood category overnight.

...Nueces Basin...
...Major Flooding...
The heaviest of rainfall last night was limited to north of the Nueces
mainstem river, hitting the Frio river and tributaries and sparing the
ongoing major flood on the mainstem.  The Frio River at Concan and
Uvalde as well as the Sabinal River are all forecast to reach moderate
flood stage from a final shot of rainfall early this morning.  This
water will push the Frio near Derby potentially into moderate
flooding.  San Miguel Creek in the upper portion of the basin through
received 4 to 5 inches of rainfall which will take some time to get
downstream but current forecast could push it into major flood as
well.  On the Nueces, the missed rainfall will bring down the
forecasts as they continue to recede.  Cotulla has crested and will
push Tilden into major flood later this week.  Lake Corpus Christi
will maintain its flow for the time being so for the current forecast
both Bluntzer and Calallen looks to be currently cresting followed by
a slow recession.

...Guadalupe Basin...
...Moderate Flooding...
Very heavy, short duration rainfall (6-9in) overnight across the
headwaters caused flash flooding and major river flooding thru Wimberly
(WMBT2) and Kyle (KYET2) along the Blanco River.  This flood wave is
expected to cause major flooding as it moves downstream along the San
Marcos at Luling (LLGT2) into the mainstem thru 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 thru Bloomington (DUPT2).

...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 couple days.  This will
likely cause additional flooding.

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

...Brazos Basin...
...Moderate 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.

...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 this morning, but is expected to increase
again by tomorrow morning with expected inflow increases due to
forecast rainfall runoff.

...San Bernard Basin...
...Minor Flooding...
Higher than normal flows will continue across the lower San Bernard
river.

...San Jacinto Basin...
...Higher Flow Non-Flood Forecasts...
Minor rises are occurring across the San Jacinto and nearby bayous. No
flooding at this time, but with possible heavy rains over the next 24
to 36 hours, the flashier basins may rise into flood criteria.

...Rio Grande Basin...
...Higher Flow Non-Flood Forecasts...
Reservoirs El Cuchillo and Marte Gomez along the lower Rio San Juan in
Mexico continue releasing, which are now bringing higher flows into the
mainstem Rio Grande near Rio Grande City (RGDT2).

...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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