Hydrometeorological Discussion
Issued by NWS West Gulf RFC

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AGUS74 KFWR 181650
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HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX
1049 AM CST SAT FEB 18 2017

                VALID FEBRUARY 18 THROUGH FEBRUARY 23

...LARGE STORM SYSTEM TO AFFECT TEXAS AND LOUISIANA LATER THIS
WEEKEND INTO EARLY NEXT WEEK...

                   ...METEOROLOGICAL DISCUSSION...

A low pressure system moved across Texas and Oklahoma into Arkansas
the past 24 hours. This low produced some rainfall across the eastern
third of Texas and western Louisiana the past 24 hours.  Outside of
the Texas upper Gulf coast region the amounts were light (under 0.50
inch).  But along the coast the rain was heavy at times, with the
locations around Galveston and La Marque receiving 2 to 3.25 inches.
Since this low has pushed northeast of our region the rainfall ended
last night.

A ridge of high pressure now extends along the Texas/New Mexico
border and is expected to dominate the region temporarily today and
tonight, and as a result warm and dry conditions are expected.

A significant heavy rainfall event is shaping up for early next
week (Sunday/Monday). The most favored area for heavy rains appears
to be across east Texas and western Louisiana.  A large elongated
trough of low pressure is along the California coast now.  This
storm will be moving eastward and should be centered over southern
Arizona by Sunday morning.  Thereafter, this long trough will be
moving slowly eastward across the WGRFC area, and by Tuesday morning
it will extend across eastern and southern Texas.  Precipitation
is expected to develop Sunday afternoon into Sunday evening, mainly
for areas along the I-35 corridor.  Precipitation is then expected
to spread eastward into the overnight hours Sunday night into Monday.
The heaviest rain should focus along a surface boundary where the
atmospheric moisture will be deepest over east Texas and western
Louisiana.  The upper trough will continue to move slowly over Texas
and should eventually move east of the WGRFC area on Tuesday. At
this time, maximum rainfall amounts of 6.00 inches are possible
for areas across east Texas. Widespread amounts of 2 to 4 inches
can be expected for primarily the eastern half of Texas and Louisiana
during this event. Since this storm is still a day or two away we
will need to monitor any changes in the movement of this storm and
adjust the expected impacts accordingly.

A ridge of high pressure is forecast to bring dry weather conditions
to most of the WGRFC area by Tuesday evening and continuing into
Thursday morning.  However, the next storm system may begin to
spread some snow into the higher elevations of northwest New Mexico
and southwest Colorado Wednesday night into Thursday.

                    ...PRECIPITATION FORECAST...
For Today into Sunday morning, no significant Mean Areal
Precipitation (MAP) amounts are forecast for the WGRFC area.  MAP
amounts of less than 0.25 of an inch are forecast over parts of
south Texas, as well as over western New Mexico into western
Colorado.

For Sunday into Monday morning, MAP amounts of 0.25 inch or more are
forecast for the eastern two thirds of Texas, as well as over
northern New Mexico into southwest Colorado.  The heaviest rain, with
MAP amounts of up to 3.00 inches, are forecast from near the
Bryan/College Station area to near Palestine TX.  MAP amounts of less
than 0.25 of an inch are forecast over most of the WGRFC area of
responsibility.

For Monday into Tuesday morning, MAP amounts of 0.25 inch or more
are forecast for the eastern third of Texas into Louisiana.  The
heaviest rain, with MAP amounts of up to 3.00 inches, are forecast
over portions of extreme east Texas between Nacogdoches and
Henderson, as well as over western Louisiana just east of the
Sabine River.  MAP amounts of less than 0.25 of an inch are forecast
over the eastern half of Texas.

For Tuesday into Thursday morning, no significant MAP amounts are
forecast for the WGRFC area.  MAP amounts of less than 0.25 of an
inch are forecast over parts of southeast Texas, most of Louisiana,
as well as over northwestern New Mexico into western Colorado.

In spite of recent rainfall, the latest U.S. Drought Monitor for
Texas shows the area considered to be abnormally dry is at 12%.
Also, 4% of Texas is experiencing moderate drought conditions and 1%
is in severe drought. In New Mexico the drought monitor shows around
12% of the state experiencing abnormally dry conditions, with 2%
remaining in moderate drought. The rainfall forecast the next 5 days
will likely result in runoff.  Significant runoff will occur over
those basins over east and southeast Texas which receive heavy rain
in short durations, which will likely result in minor to moderate
mainstem river flooding.

                     ...HYDROLOGIC DISCUSSION...
...WGRFC Basins...
Rivers are near baseflow, but the soils do remain saturated along
the Gulf Coast.  More rainfall in the forecast over these basins
could generate flooding early next week.  Similar amounts over the
same area will have higher responses than last week due to the
current soil conditions.

              ...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/wgrfc/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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