Hydrometeorological Discussion
Issued by NWS West Gulf RFC

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AGUS74 KFWR 181625
HMDFWR
HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX
1125 AM CDT SAT APR 18 2015

                   VALID APRIL 18 THROUGH APRIL 23

...HEAVY RAINFALL HAS DIMINISHED, BUT SOME RAINFALL IS EXPECTED TO
CONTINUE OVER MOST OF THE WGRFC AREA THE NEXT FIVE DAYS...

                  ...METEOROLOGICAL DISCUSSION...
A large low pressure system moved from just east of the four
corners region to central Colorado the past 24 hours.  Showers and
thunderstorms developed ahead of this low the past 24 hours over
a good part of Texas and southwestern Louisiana.  Also, rain and
high elevation snow was reported over portions of southern Colorado
and northern New Mexico.  The heaviest rainfall the past 24 hours was
in an area from near San Antonio through Victoria to Houston with 4 to
5.50 inches noted.  Over the coming days, the upper low will move
eastward into Kansas by Sunday morning.  During this time period
additional small upper air disturbances embedded within the upper
level flow may interact with the dry line to produce scattered
showers and thunderstorms over central and east Texas this afternoon
and tonight.  Thereafter, drier air will move in from the west,
leading to diminishing rainfall by Sunday.  Mostly dry weather is
forecast for Sunday.

By Monday a ridge of high pressure system will form over Oregon.  This
will put the northern parts of the WGRFC area in a northwesterly upper
air flow. While no major storms are forecast to move through the
southern plains within this flow, a minor storm may produce light
precipitation over northern New Mexico and southern Colorado.  Over
the south, an upper air disturbance will move eastward from Mexico
which will move across south Texas late Monday into Tuesday.  This
disturbance will bring some rain to south Texas, especially the
lower Rio Grande valley. At this point, heavy rainfall is not expected
during this period.

By Wednesday a new low pressure system is forecast to develop off the
Baja California coast.  This will again put the WGRFC region in a
southwesterly upper air flow, which will increase the atmospheric
moisture.  As this low moves slowly eastward there could be a few
periods of showers and thunderstorms Wednesday into Thursday. At this
point south Texas is the most likely location for measurable rainfall,
and again it does not appear that heavy rainfall will fall.

                    ...PRECIPITATION FORECAST...
For Today into Sunday morning, Mean Areal Precipitation (MAP) amounts
of 0.25 of an inch or more are forecast over southeast Texas into
most of Louisiana.  Lighter amounts of MAP are forecast over the
eastern half of Texas, Louisiana, Colorado, and northern New Mexico.

For Sunday into Monday morning, MAP amounts of 0.25 to 0.50 inch are
forecast for Deep South Texas...mainly from Falcon Reservoir to near
Corpus Christi.  Also,  MAP amounts of 0.25 inch are forecast
along the Colorado/New Mexico border.  Lighter amounts of MAP are
forecast over the southern third of Texas, southern Colorado, and
northern New Mexico.

For Monday into Tuesday morning, MAP amounts of 0.25 to 0.50 inch are
forecast for southern Texas, mainly south of a line from Del Rio to
Victoria. Lighter amounts of MAP are forecast for the southern third
of Texas, a good part of Colorado, the northeast third of New Mexico,
and the Texas panhandle.

For Tuesday into Thursday morning, MAP amounts of 0.25 inch or more
are forecast for a good part of south and central Texas. MAP amounts
of 0.25 of an inch are also forecast along the Colorado/New Mexico
border. The heaviest rain, with MAP amounts of 0.50 inch, are forecast
along and near the lower Texas Gulf coast. Lighter amounts of MAP are
forecast for much of the WGRFC region...except for far west Texas and
the southwestern two thirds of New Mexico.

Moderate or worse drought conditions continue across parts of New
Mexico and Texas. In Texas, about a third of the state is experiencing
moderate or worse drought (35%), and about 15% has extreme to
exceptional drought conditions. In New Mexico, about two thirds of the
state is experiencing moderate or worse drought (62%). Lake levels in
the extreme drought areas of Texas are at or near historical lows for
this time of year. Recent precipitation events have brought drought
relief to parts of far west Texas, Deep South Texas and roughly the
southeast third of the state. The rainfall expected over the next five
days over the WGRFC area could produce some minor runoff over south
Texas where soils are moist from recent rainfall. No runoff is
expected over the northern or western parts of the WGRFC area.

                     ...HYDROLOGIC DISCUSSION...
...Guadalupe Basin...
...Major Flooding...
Major flooding is currently occurring on Coleto Creek near
Schroeder. It is cresting now above 17 feet and should begin to drop
off sharply over the next coming hours.  Some residences and low
water crossings are being threatened by this flood wave. Other sites
along the lower Guadalupe River basin remain flooded starting at
Sandies Creek near Westhoff down to Bloomington.  Bloomington is
forecast to reach moderate flood within the next day.

...San Bernard Basin...
...Moderate Flooding...
All three sites along the San Bernard are in flood, with East
Bernard nearing its crest in minor flood now and should remain there
for several days.  Near Boling, the local rainfall caused a
significant rise into moderate and is forecast to pass 30 feet.
The routed water from East Boling will keep this site in flood for
the forecast period.  Sweeney is currently in action, but the one
daily observation came in near minor flood and may push the site
into minor flood tomorrow.

...Lavaca-Navidad Basin...
...Minor Flooding...
Very heavy rains over the entire basin have generated excess runoff
pushing many points into minor flood stage.  The Navidad River at
Strane Park near Edna (LSNT2) is forecast to rise to near moderate
flood stage and will be monitored closely for any changes.

...Neches Basin...
...Minor Flooding...
Rainfall overnight contributed to the ongoing widespread minor
flooding over the Neches River basin.  No significant changes in the
ongoing flood except that Steinhagen reservoir will slowly begin to
increase releases to clear some space.  The first increase was from
15,000 cfs to 17,000 cfs this morning, and an additional increase
will occur tomorrow morning to 19,000.  This will still keep Evadale
well below flood stage as the reservoir intends to keep the flow
near 20,000 for that area.  Sour Lake gauge has also hopped down a
half a foot but appears to operating correctly as it approaches its
broad crest.

...San Antonio Basin...
...Minor Flooding...
Heavy rainfall over the lower portions of the San Antonio have
caused a rapid rise and crest above action stage at Cibolo Creek
near Falls City ((FCTT2). Further downstream, the San Antonio River
at Goliad (GLIT2) is expected to react to storm runoff and rise
above action stage early Monday and continue to rise into minor
flood stage by Tuesday and crest near 28 feet.

...Sabine Basin...
...Minor Flooding...
Rainfall over the past week continues to compound the flooding,
with a couple of sites added over the past 24 hours.  Mineola has
crept into minor flood and should stay there with the water still
working its way down from the upper basins.  Quinlan rose close to
action stage but will crest just below criteria.  Deweyville will
remain in flood stage for the forecast period as the water from Bon
Weir continues to push towards the Gulf.

...San Jacinto Basin...
...Higher Flow Non-Flood Forecasts...
Localized heavy rainfall over many parts of the San Jacinto basin
raised river levels over multiple areas, with West Fork at San
Jacinto in particular rising into action stage.  The backwater
effect into Lake Houston should keep the flow above action stage
for a few days.

...Colorado Basin...
...Higher Flow Non-Flood Forecasts...
Rainfall over the lower Colorado River Basin has caused a rise at
Wharton (WHAT2) and is expected to reach around bankfull levels by
late Sunday or early Monday.

...Nueces Basin...
...Higher Flow Non-Flood Forecasts...
Local heavy rainfall over night near the Gulf Coast cause the
Aransas River near Skidmore to reach action stage.  It appears to
be close to cresting and is not expected to reach flood stage at
this time.

...Brazos Basin...
...Higher Flow Non-Flood Forecasts...
Localized heavy rainfall on already elevated river levels pushed a
couple of points into action stage overnight.  Navasota River at
Easterly (EAST2) and Normangee (NGET2) rose into bankfull stage
overnight. Both will remain around bankfull through the weekend.
The Brazos at Richmond (RMOT2) has risen above bankfull and is
expected to remain high for a few days.

...Remainder of WGRFC Basins...
Rainfall for the Gulf Coast has seem to come to an end for now, as
the water will continue to make its way downstream.  Forecast
rainfall should not impact the few other basins through out the
forecast period.

              ...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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