Hydrometeorological Discussion
Issued by NWS West Gulf RFC

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AGUS74 KFWR 271603
HMDFWR
HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX
1102 AM CDT TUE SEP 27 2016

                VALID SEPTEMBER 27 THROUGH OCTOBER 2

...EXCEPT FOR THE LOWER TEXAS GULF COAST, MOSTLY DRY WEATHER CAN BE
EXPECTED THE REST OF THE WEEK INTO THE WEEKEND...

                  ...METEOROLOGICAL DISCUSSION...

A strong upper level low pressure system is located over the Baja of
California this morning.  This low has pushed excessive moisture into
Texas the past several days.  As a result, widespread precipitation
has occurred, and over the past 24 hours the heaviest rain was over
central, east and Deep South Texas. Localized amounts in excess of 2
inches were observed in several locations, with the area around San
Marcos receiving nearly 7.00 inches of rain. The rain began to
diminish considerably last evening, and this morning very light
rainfall persists over the western parts of north Texas as well as
over northern Mexico.  Also, a trough of low pressure lies along the
lower Texas Gulf coast this morning, and this trough is producing
heavy rain just offshore from South Padre Island. Deep South Texas
may continue to see locally heavy rainfall for another 24 to 36
hours, but it is doubtful the rain will get far enough inland to
have an adverse affect on the Rio Grande. Elsewhere the rainfall is
forecast to gradually diminish.

The upper level low pressure system located over the Baja of
California is forecast to weaken and not have much influence on the
weather over the WGRFC area after today.  Meanwhile, a strong low
pressure system is located over Lake Superior.  This low has pushed a
cold front across Texas, which now extends along the Texas coast.
This front aided in producing the wet weather in the WGRFC region.
But now the cold front has ushered in some cooler, drier air into
much of the WGRFC area.

Much drier and noticeably cooler weather is expected for the rest of
the week. The low pressure system over the upper Great Lakes is
forecast to drop southward to northern Kentucky and will deepen by
Thursday morning.  This will cause a ridge of high pressure to build
over west Texas. Because of the location of the ridge, any showers
and thunderstorms that develop Thursday or beyond will be confined to
far west Texas, northern Mexico, western New Mexico and southwest
Colorado. Dry weather is forecast over the remainder of Texas and
Louisiana Wednesday through Saturday morning. By Sunday morning the
low pressure system over Kentucky will move east and a more zonal
flow of air will develop.  Even with this change, no major storm
systems will be approaching the WGRFC area until sometime next week.

                    ...PRECIPITATION FORECAST...
For Today into Wednesday morning, Mean Areal Precipitation (MAP)
amounts of 0.25 inch or more are forecast for portions of the lower
Texas Gulf coast of Deep South Texas.  The heaviest rain of 2.00
inches are forecast along South Padre Island and over the Gulf of
Mexico.  MAP amounts of less than 0.25 of an inch are forecast
for Deep South Texas and most of northern Mexico, as well as over
western New Mexico.

For Wednesday into Thursday morning, MAP amounts of 0.25 to 0.50
inch are forecast for portions of the lower Texas Gulf coast of Deep
South Texas.  MAP amounts of less than 0.25 of an inch are forecast
for Deep South Texas, parts of northern Mexico, western New Mexico
and extreme southwest Colorado.

For Thursday into Friday morning, MAP amounts of 0.25 inch are
forecast for portions of west central and northwest New Mexico into
southwest Colorado.  MAP amounts of less than 0.25 of an inch are
forecast for the Mexican Gulf coast, northern Mexico, the western
half of New Mexico and western Colorado.

For Friday into Sunday morning, no significant MAP amounts are
forecast for the WGRFC area.  MAP amounts of less than 0.25 of an
inch are forecast for far west Texas, much of New Mexico and
Colorado.

Because of the widespread rain over the past few weeks over parts
of New Mexico and Texas, drought conditions are minimal. The U.S.
Drought Monitor categorizes Texas as 4.5% abnormally dry, with
almost 1% in severe drought. New Mexico remains unchanged this
week with 47% of the state abnormally dry and 4% in the moderate
drought category. The heavy rain forecast over Deep South Texas
today will be too close to the coast to create runoff in the Rio
Grande.  Elsewhere, no significant runoff is expected the next 5
days.

                     ...HYDROLOGIC DISCUSSION...
...Nueces Basin...
...Major Flooding...
Very heavy rain fell early Sunday morning in the uppermost sections of
the Nueces River and several tributaries. Large flood waves moved
through the West Fork of the Nueces, Frio River, and the mainstem
Nueces on Monday. This water will route downstream through the
escarpment and out into the coastal plains. While the Frio River water
will end up in Choke Canyon Reservoir which is well below conservation
pool, the mainstem wave will take several weeks to route to Three
Rivers and eventually Lake Corpus Christi. The water has arrived this
morning at Asherton, which will help determine how much flow survived
the well known groundwater recharge region along the escarpment.


...San Antonio Basin...
...Minor Flooding...
The primary flood crest has moved past Elmendorf which has dropped
below moderate and is moving towards Floresville which will crest in
minor flood stage later today.  This wave will continue to move down
the river this week causing nothing more than minor flooding as it
progresses.  No further rainfall is expected to impact this flood wave.


...Remainder of WGRFC Basins...
All other rivers, while wetter than normal for most of the area, are
mostly inside their banks.  Rainfall forecast has diminished for the
next few days allowing some of these flood waters to work their way
into the Gulf.  No additional significant flooding expected at this
time.


              ...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/reservoirs/statewide

STORY

$$




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