Hydrometeorological Discussion
Issued by NWS West Gulf RFC

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AGUS74 KFWR 171628
HMDFWR
HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX
1127 AM CDT FRI APR 17 2015

                   VALID APRIL 17 THROUGH APRIL 22

...ADDITIONAL HEAVY RAINFALL IS EXPECTED ACROSS SOUTH TEXAS THROUGH
SATURDAY BEFORE THE RAIN TAPERS OFF LATER THIS WEEKEND...

                  ...METEOROLOGICAL DISCUSSION...
A large low pressure system was located just east of the four
corners region this morning.  Showers and thunderstorms developed
well out ahead of this low the past 24 hours over primarily the
southeast half of Texas and western Louisiana.  Thunderstorms
also developed along and ahead of the dryline over northwest
Texas.  Lastly, snow was reported over portions of southern Colorado.
The heaviest rainfall the past 24 hours was over extreme southeast
Texas, with 6 to 8 inches noted along the Gulf coast from west of
Beaumont to east of Galveston.  Over the coming days, this low
pressure system is expected to bring heavy rainfall to the southern
portions of Texas. Precipitation amounts are expected in the 4 to 6
inch range in isolated spots between San Antonio and Houston. Lighter
amounts of rain are expected over much of central and eastern Texas.
Significant flooding remains possible the next 24-36 hours over
south and southeast Texas.

The upper low will eventually begin moving northward into Colorado
later today and eastward into Kansas by Saturday night. During this
same time, some smaller disturbances embedded within the upper level
flow are forecast to move across portions of southeast Texas...mainly
tonight through Saturday night so rain will continue to fall.
However, drier air will eventually move in from the west, leading to
diminishing rainfall Saturday night into Sunday.

By Monday a ridge of high pressure system will form over Nevada. 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.
Additionally, an upper air disturbance will move eastward across
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, early next week. At this point, heavy
rainfall is not expected during this period.

                    ...PRECIPITATION FORECAST...
For Today into Saturday morning, Mean Areal Precipitation (MAP)
amounts of 0.25 of an inch or more are forecast over much of
eastern and southern Texas into western Louisiana. The heaviest
rain, with MAP amounts of 1.50 to 2.00 inches, are forecast for
portions of south Texas mainly near I-10 from east of San Antonio to
Houston. MAP amounts of 0.25 to 0.50 inch are forecast over
southwest Colorado.   Lighter amounts of MAP are forecast for much
of the WGRFC region...except for west Texas and the southern half
of New Mexico.

For Saturday into Sunday morning, MAP amounts of 0.25 of an inch or
more are forecast over the southeastern third of Texas into Louisiana.
The heaviest rain, with MAP amounts of up to 1.00 inch, are forecast
for extreme southeast Texas and southern Louisiana.  Lighter amounts
of MAP are forecast over the southeast half of Texas, Louisiana,
Colorado, and northern New Mexico.

For Sunday into Monday morning, MAP amounts of 0.25 inch are forecast
for Deep South Texas...mainly from Falcon Reservoir to South Padre
Island. Lighter amounts of MAP are forecast over the southern third
of Texas, most of Louisiana, southern Colorado, and northern New
Mexico.

For Monday into Wednesday morning, MAP amounts of 0.25 to 0.50 inch
are forecast for a good part of south Texas...mainly from Del Rio down
to Brownsville.  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, especially today and Saturday, could produce
some areas of significant runoff. Any flooding would be restricted to
the far east and southern Texas river basins, as well as the
basins along the Gulf coastal region through this weekend.

                     ...HYDROLOGIC DISCUSSION...
...Guadalupe Basin...
...Minor Flooding...
Soils on the lower portions of the Guadalupe Basin and its
tributaries are near saturation.  Expected rainfall Friday should
generate new rises for Sandies Creek at Westhoff (WHOT2), and the
Guadalupe River at Victoria (VICT2) and Bloomington (DUPT2).
Rainfall later in the weekend could generate higher rises.

...Neches Basin...
...Minor Flooding...
The heavy rainfall overnight will put most of the Neches River in
action or minor flood stage.  The upper Neches near Neches, Alto,
and Diboll will all rise or stay in minor flood stage through the
forecast period.  Mud creek rose into action and with the rainfall
over the basin should have a secondary rise into flood stage.
Similar rainfall over the Angelina River will push Cushing bring
flood stage briefly and push downstream to Lufkin.  Attoyac received
a heavy dose of rainfall, but the spread channel may keep the stage
lower than expected but should be in minor over the next few days.
Downstream, already saturated soils responded quickly pushing Sour
Lake into minor flood stage with Beaumont to follow suit in a couple
of days.

...Sabine Basin...
...Minor Flooding...
Heavy widespread 1.5 to 2 inch rainfall caused some new rises and
sustained some already ongoing flooding.  Sites like Kilgore (KLGT2)
and Longview (LONT2) are expected to rise into flood and action
stage accordingly. While Deweyville will remain steady in flood
stage for the forecast period.

...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 for a
few days, and any additional rainfall will cause an increase in
elevation.

...San Bernard Basin...
...Higher Flow Non-Flood Forecasts...
Heavy rainfall over night over the San Bernard basin will cause
local rises at both East Bernard and Boling.  East Bernard should
continue to rise as heavy rain was spread through out the basin and
could reach minor flood stage in a couple of days.  Boling will rise
into action from the local rainfall, than return to action stage
from the routed flow from East Bernard.  Further rainfall will
compound the flooding for the area.

...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 and Normangee are either in action stage or will rise into
action stage over the next day or so.  Easterly will fall rather
rapidly assuming no significant further rainfall while Normangee
will be slightly more prolonged in action stage.

...Remainder of WGRFC Basins...
Southeast Texas and areas along the Gulf Coast will remain under
close watch heading into this weekend.  Areas out west and in New
Mexico are not expected to receive significant rainfall over 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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