Hydrometeorological Discussion
Issued by NWS West Gulf RFC

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AGUS74 KFWR 281721
1121 AM CST SAT NOV 28 2015



                  ...METEOROLOGICAL DISCUSSION...
A major storm system continues to be present to the west of the WGRFC
area. At the surface, deep Gulf moisture exists over most of Texas,
and aloft high level moisture is also present from the eastern
Pacific Ocean.  As upper disturbances in the southwest flow
moved across the region the past 24 to 48 hours, widespread rain and
embedded thunderstorms developed over most of Texas, as well as over
the southeast half of New Mexico.  Higher elevation snows also
occurred over the mountains of southern Colorado, and more snow can
be expected over the mountains of northern New Mexico and Colorado
the next few days. A mixture of wintry precipitation is possible at
lower elevations from west Texas through the Texas panhandle into
western Oklahoma the next day or so.  The heaviest rain the past 24
hours was over north Texas into southeast Oklahoma, with 4.20 inches
noted at Morgan Mill.  Close to 10.00 to 11.00 inches has been noted
near Anna and McKinney for this storm system.

More rainfall will persist over most of Texas through Sunday night.
The strong upper level low pressure system is located west of Las
Vegas Nevada this morning. This low is forecast to redevelop over
Utah through tonight before moving northeastward to Wyoming by
Sunday night. Southwesterly flow aloft will continue over the WGRFC
area of responsibility through the weekend. Due to the persistence of
upper disturbances within this flow, additional precipitation is
expected. At the surface, a strong cold front moved through most of
Texas the past 36 hours.  The front will move slowly over east Texas
and western Louisiana the rest of today. The cold front and upper
level pattern will combine to produce conditions favorable for
additional rainfall over much of Texas and Louisiana, especially over
northern and central Texas along an behind the front through Monday

In addition, the weather models are also forecasting that eastern
Pacific tropical storm Sandra will move from its current position
near Cabo San Lucas Mexico into central Mexico today before
dissipating over land as it moves northeastward on Sunday. This
system could cause some additional moisture to interact with the
upper level storm system and cold front to enhance the heavy rainfall
threat in Texas and western Louisiana through Sunday.

In general, additional rainfall amounts of up to 3.00 inches are
expected for areas east of I-35 and north of I-20 from today through
Sunday, with the highest amounts near the Red River across the
Arklatex.  We will continue to monitor the model guidance for any
changes, and will update accordingly.

Drier air from the west should shut down the prospects of significant
rainfall on Monday as the upper low shifts eastward over Nebraska.
But on Tuesday a new, but weaker, upper air disturbance will
approach Texas from the northwest.  There will be some residual
rainfall development from central into east Texas and Louisiana (and
eventually over deep south Texas) from later Tuesday through
Wednesday as this upper disturbance crosses Texas.  After this
disturbance moves east of the WGRFC area on Thursday all the
precipitation should push east of our region.

                    ...PRECIPITATION FORECAST...
For Today into Sunday morning, Mean Areal Precipitation (MAP) amounts
of 0.25 inch or more are forecast for a good portion of Texas into
northwest Louisiana.  The heaviest rain, with MAP amounts of 2.00
inches, are forecast for extreme northeast Texas into central
Arkansas.  MAP amounts of less than 0.25 inch are forecast for most
of the rest of the WGRFC area.

For Sunday into Monday morning, MAP amounts of 0.25 to 0.50 inch are
forecast for central and northeast Texas into northern Louisiana. MAP
amounts of less than 0.25 inch are forecast for most of the rest of
Texas, western Louisiana, northern New Mexico and southern Colorado.

For Monday into Tuesday morning, MAP amounts of 0.25 inch are
forecast for southeast Texas into most of Louisiana.   MAP amounts of
less than 0.25 inch are forecast for the southeast third of Texas and
Louisiana, as well as a small part of northern New Mexico into
southern Colorado.

For Tuesday into Thursday morning, MAP amounts of 0.25 inch are
forecast over deep south Texas, as well as for central and east Texas
into most of Louisiana. MAP amounts of less than 0.25 inch are
forecast for most of the rest of Texas and Louisiana.

Topsoil moisture is very high due to recent rainfall events which
means it will require less rainfall for runoff to occur. That, along
with the vegetation being dormant now that the growing season has
come to an end, means runoff will be quicker. Over Texas only 7% of
the state is abnormally dry, while over New Mexico, 26% of the state
is abnormally dry. Heavy rainfall amounts of up to 3 inches, on top
of what rain has already fallen, are forecast through the weekend.
This will lead to some new or additional runoff because of the wet
soil moisture conditions and the cold season vegetation patterns.

                     ...HYDROLOGIC DISCUSSION...
...Trinity Basin...
...Major Flooding...
Overnight rains have pushed several sites back into flood levels.
Many of the Trinity tributaries are experiencing minor to moderate
flooding with the additional rains.  The Trinity mainstem at Dallas
(DALT2) is near crest above major flood levels at 41 feet now.  It
is expected to remain at this level for at least 24 hours then begin
a slow recession.  Points downstream from Trinidad (TDDT2) through
Long Lake (LOLT2) will rise once again into moderate flood levels.

...Sabine Basin...
...Moderate Flooding...
Localized heavy rainfall in the upper Sabine will push Greenville
(GNVT2) and Quinlan (QLAT2) into moderate and minor flood
respectively.  More rainfall is expected which could push these
smaller creeks even higher over the next few days.  Routed water and
local runoff will then push Mineola (MLAT2) and Gladewater (GDWT2)
above flood stage.

...Neches Basin...
...Minor Flooding...
Minor flooding is expected on the Neches River from Lake Palestine
to Alto.  Future rainfall will likely prolong the higher river

...Brazos Basin...
...Minor Flooding...
Locally heavy rainfall has generated some rises on the Brazos River
System.  At this time, minor river flooding is expected around the
De Leon basins of the Sabana and Leon Rivers.  River flooding is
also expected between Possum Kingdom and Granbury Reservoirs.
Higher flows should be expected as the threat for rainfall continue
into next week.

...Remainder of WGRFC Basins...
Heavy rainfall occurred overnight in portions of the Brazos, Trinity
and the upper Sabine.  Additional rainfall is expected tonight
through Sunday that could cause prolonged flooding in the headwaters
of the Sabine, Neches and portions of the Trinity and Brazos
through the weekend.

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:

The Flood Potential Outlook can be viewed on our webpage at:

The West Gulf River Forecast Center is now on Facebook:

National Precipitation Analysis:

The forecast rainfall amounts (QPF) can be viewed on our webpage at:

The US Drought Assessment:

The latest on Reservoir Information for Texas:



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