Hydrometeorological Discussion
Issued by NWS West Gulf RFC

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AGUS74 KFWR 271732
1132 AM CST FRI NOV 27 2015



                  ...METEOROLOGICAL DISCUSSION...
A major storm system continues to be present to the west of the WGRFC
area. At the surface, a moist southerly flow of Gulf moisture is
occurring, and aloft high level moisture is also present from the
eastern Pacific Ocean.  As upper disturbances in the southwest
flow increased the past 24 hours, widespread rain and embedded
thunderstorms developed over most of Texas, as well as over a
good part of New Mexico and Colorado.  Higher elevation snow
occurred over the western mountains, and more snow can be expected
today over the mountains of northern New Mexico and Colorado, and
this snow should continue the next few days. A mixture of wintry
precipitation is possible at lower elevations from eastern New
Mexico through the Texas panhandle into western Oklahoma the next
few days.  The heaviest rain the past 24 hours was north of Dallas,
with 6.50 to 7.00 inches noted near Anna and McKinney.

More significant rainfall will persist over most of Texas through
Sunday night.  The strong upper level low pressure system is located
over western Utah this morning. This low is forecast to shift
westward through Saturday 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
this flow, additional precipitation is expected. At the surface,
a strong cold front moved through north Texas early this morning and
is over central Texas now.  The front will move slowly the rest of
today. The cold front and upper level pattern will combine to produce
conditions favorable for locally heavy rainfall over much of the
WGRFC area, especially over north and central Texas, along an behind
the front through Monday morning.

In addition, the weather models are also forecasting that eastern
Pacific Hurricane Sandra will move over southwestern Mexico as a
tropical storm early on Saturday 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, rainfall amounts of up to 6.00 inches are expected for
areas east of I-35 and north of I-30 from today through Sunday, with
the highest amounts near the Red River. Amounts of over 4.00 inches
will be widespread across central and north Texas. We will continue
to monitor the model guidance for any changes, and will update

Drier air from the west should shut down the prospects of significant
rainfall on Monday as the upper low shifts eastward over Nebraska and
Iowa.  But on Tuesday a new, but weaker, upper air disturbance will
approach Texas from the west.  There may be some residual rainfall
development from central into east Texas and Louisiana from later
Tuesday into Wednesday morning as this upper disturbance crosses the
WGRFC area.

                    ...PRECIPITATION FORECAST...
For Today into Saturday morning, Mean Areal Precipitation (MAP)
amounts of 0.25 inch or more are forecast for southern Colorado into
northern New Mexico, and from the southeastern quarter of New Mexico
into most of Texas.  The heaviest rain, with MAP amounts of 2 to 4
inches, are forecast from central into north central and northeastern
Texas and eastern Oklahoma.  MAP amounts of less than 0.25 inch are
forecast for most of the rest of the WGRFC area.

For Saturday into Sunday morning, MAP amounts of 0.25 inch or more
are forecast for extreme southeast New Mexico into a good portion of
Texas into southwest Arkansas.  The heaviest rain, with MAP amounts
of 2.00 inches, are forecast for most from central into northeastern
Texas.  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, northeast New Mexico and southern

For Monday into Wednesday morning, MAP amounts of 0.25 inch are
forecast 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 6 inches, on top
of what rain has already fallen, are forecast over the next couple
days through the weekend. This will lead to some new or additional
significant runoff because of the wet soil moisture and cold season
vegetation patterns.

                     ...HYDROLOGIC DISCUSSION...
...Trinity Basin...
...Moderate Flooding...
Overnight rains has pushed several sites back into flood levels
while others are forecast to go above flood levels.  The West Fork
Trinity River at Grand Prairie (GPRT2) is expected to crest slightly
above moderate flood levels by early Saturday.  The Elm Fork Trinity
River near Carrollton (CART2) is near a crest of 11 feet this
morning and should fall quickly over the next 24 hours.  Further
downstream at Dallas (DALT2), the Trinity river is expected to crest
near 40 feet late tomorrow night.  Another round of heavy rains in
the next 24 hours could push the Dallas reach into major flood
levels. Sister Grove Creek near Blue Ridge (BVWT2) is expected to
crest slightly above moderate flood levels this afternoon.

...Sabine Basin...
...Moderate Flooding...
Localized heavy rainfall in the upper Sabine will push Greenville
and Quinlan into moderate and minor flood respectively.  More
rainfall is expected which could push these smaller creeks even
higher over the next few days.

...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.  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 another round of significant
flooding in the headwaters of the  Sabine, Neches and portions of
the Trinity and Brazos over 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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