Hydrometeorological Discussion
Issued by NWS West Gulf RFC

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AGUS74 KFWR 051737
HMDFWR
HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX
1136 AM CST MON DEC 5 2016

                VALID DECEMBER 5 THROUGH DECEMBER 10

...ONE MORE DAY OF LIGHT TO MODERATE RAIN, FOLLOWED BY COLDER, DRIER
CONDITIONS LATER THIS WEEK...

                  ...METEOROLOGICAL DISCUSSION...

The deep low pressure system responsible for bringing rainfall to
much of the WGRFC area the past two days is finally moving
northeastward this morning.  The low is south of the Texas Big Bend
and will be moving over south Texas this afternoon. As this occurs
rainfall will continue, impacting portions southeast and east central
Texas the most, with widespread lighter amounts elsewhere.  By late
tonight and Tuesday morning, the upper level low will to weaken and
move to the northeast across Texas and eventually into Arkansas. This
will put an end to the rainfall across the WGRFC area.

Storm total rainfall amounts for this event are expected to approach
13.00 inches in far southeast Texas. During the past 24 hours the
heaviest amounts were over the Gulf of Mexico. But there have been
reports of nearly 4.00 inches over southern Texas west of Corpus
Christi near Alice and Three Rivers.  Widespread 1.00 to 3.00 inches
of rain fell across the southern half of Texas.  With this much
rainfall, widespread minor flooding has been reported and will
continue, with some isolated moderate flooding downstream of San
Antonio. However, widespread moderate and major flooding is not
expected.

After a relatively dry day Tuesday, a strong cold front is forecast
to move across Texas on Wednesday.  This front may create some
showers and thunderstorms along and ahead of the front, but due to
the speed of the front these storms are not expected to produce heavy
rainfall. There may still be some rainfall over deep south Texas into
Thursday as the front moves through but it will not be heavy.

A ridge of high pressure will move over most of the WGRFC area on
Friday, so most of the precipitation will end and the coldest air of
the season will set in.  A minor upper air disturbance is forecast
to move across Colorado late Friday into Saturday which may produce
some precipitation there. But elsewhere dry weather is expected
Friday into Saturday.

                    ...PRECIPITATION FORECAST...
For Today into Tuesday morning, Mean Areal Precipitation (MAP)
amounts of 0.25 of an inch or more are forecast over the southeast
half of Texas and Louisiana.  The heaviest rain, with MAP amounts of
1.00 to 1.50 inches, are forecast over extreme southeast Texas and
much of southwestern Louisiana.  Lighter amounts of less than 0.25 of
an inch are forecast for most of the WGRFC area except for New
Mexico, southern Colorado, and northwest Texas.

For Tuesday into Wednesday morning, MAP amounts of 0.25 of an inch
are forecast for extreme northern New Mexico and southern Colorado.
Lighter amounts of less than 0.25 of an inch are forecast for
northern New Mexico and most of Colorado.

For Wednesday into Thursday morning, MAP amounts of 0.25 to 0.50 of
an inch are forecast from southeast Texas through the Toledo Bend
Country into northern Louisiana.  Lighter amounts of less than
0.25 of an inch are forecast for the southeast third of Texas
into most of Louisiana, as well as over extreme northern New Mexico
and southern Colorado.

For Thursday into Saturday morning, no significant MAP amounts are
forecast for the WGRFC area.  Light amounts of less than 0.25 of
an inch are forecast for deep south Texas.

The rainfall early in November helped to improve (slightly) the
ongoing drought conditions across the WGRFC area. The rainfall
which is ongoing is no doubt bringing additional drought relief. In
Texas, the areas considered to be abnormally dry is at 34%. Also,
14% of Texas is experiencing moderate drought conditions and 3% is
in severe drought, primarily over extreme east Texas. In New Mexico,
around 54% of the state is experiencing abnormally dry conditions,
with 5% remaining in moderate drought. The heaviest rainfall the
next 5 days will fall over east central and southeast Texas, which
also happens to be the one of the drier parts of Texas.  While some
additional runoff will occur it will not be enough to significantly
add to the ongoing stream flows. Elsewhere, little or no runoff is
expected.

                     ...HYDROLOGIC DISCUSSION...
...San Antonio Basin...
...Moderate Flooding...
Heavy rainfall over the past two days in the San Antonio area has
caused creeks  to swell rapidly.  Salado Creek and the San Antonio
mainstem in and  around San Antonio city reached moderate to major
flood levels.  Elmendorf (ELMT2) on the mainstem crested  above
moderate flood levels.  Cibolo Creek at Sutherland  Springs (SUPT2)
and near Falls City (FCTT2) were also affected with high levels.
The San Antonio River at State Highway 72 near Runge (SRRT2) is still
rising
from upstream flood waters. It is forecast to reach moderate flood
levels later today and may reach major flood levels at its peak
tomorrow morning.

...Guadalupe Basin...
...Minor Flooding...
Heavy rains in the Guadalupe River basin over the past 72 hours have
caused minor rises along portions of the Guadalupe.  Occasional
light rain will continue through the day today but should not cause
any new flooding. Several sites in the middle and lower part of the
basin have reached or are forecast to reach action stage, and the
Guadalupe River at DuPont Plant near Bloomington (DUPT2) is
expected to reach minor flood levels by the middle of the week due
to routed flows.

...Neches Basin...
...Minor Flooding...
Recent rainfall has caused overbank to minor flood levels across
parts of the Neches River basin.  If additional rainfall occurs it
will aggravate the existing flooding.

...San Bernard Basin...
...Higher Flow Non-Flood Forecasts...
Heavy rain over the past 72 hours will cause  the San Bernard River
near East Bernard (EBBT2) to reach action stage early this week.
Additional rainfall is expected through the day today but is not
expected to impact the forecast river height.

...Lavaca-Navidad Basin...
...Higher Flow Non-Flood Forecasts...
Heavy rains over central and southeast Texas have caused some minor
runoff responses to creek and rivers in the area.  The West Mustang
Creek near Ganado (GNDT2) is expected to crest above action stage
tonight.

...San Jacinto Basin...
...Higher Flow Non-Flood Forecasts...
Heavy rainfall has caused some minor runoff events in the San
Jacinto basin.  Most notably Lake Creek at Sendera Road (FCWT2) near
the Conroe area, the East Fork of the San Jacinto River, and Cypress
Creek, are above/will rise above action stage.

...Brazos Basin...
...Higher Flow Non-Flood Forecasts...
With moderate rains in portions of the Brazos, Davidson Creek near
Lyons (LYNT2)crested slightly above action stage overnight and will
experience a second crest later today at nearly the same level.

...Remainder of WGRFC Basins...
Widespread rainfall fell over central, southeast and far east Texas.
So far the rainfall has been beneficial to the portions of Texas
that were beginning to suffer from drought conditions.  Bankfull to
moderate flooding has been occurring from the weekend rainfall.
Additional rain is occurring this  morning but should not cause any
significant runoff.  The area should clear of any rains by tomorrow.

              ...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.weather.gov/wgrfcfop

The West Gulf River Forecast Center is now on Facebook:
http://www.facebook.com/NWSWestGulf

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

The forecast rainfall amounts (QPF) can be viewed on our webpage at:
http://www.weather.gov/wgrfc/wgrfcqpfpage

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

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

STORY

$$




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