Hydrometeorological Discussion
Issued by NWS West Gulf RFC

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AGUS74 KFWR 171704
HMDFWR
HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE...WEST GULF RFC...FORT WORTH TX
1103 AM CST SUN DEC 17 2017

                VALID DECEMBER 17 THROUGH DECEMBER 22

...ONE PERIOD OF PRECIPITATION IS ENDING, BUT ANOTHER ONE IS
APPROACHING THE WGRFC AREA NOW THROUGH TUESDAY...

                   ...METEOROLOGICAL DISCUSSION...
A deep low pressure system in the upper atmosphere moved from
southeast of El Paso TX to northeast Kansas the past 24 hours.
Moisture was abundant ahead of this low which resulted in widespread
showers and a few thunderstorms across much of Texas and Louisiana.
The heaviest rain fell over portions of southeast and eastern Texas
into northwestern Louisiana.  The heaviest rainfall amounts were
around 3.00 inches in the Tyler area and 2.50 inches near Kilgore.
With the upper low moving further northeast the rainfall has ended
over Texas from this storm this morning.

Meanwhile, a new upper air low has replaced the old low and has
dropped south of Arizona this morning.  As a result a new area of
rain and snow is occurring over southwest New Mexico and
southern Arizona. This precipitation will persist over southern New
Mexico through tonight. By Monday the upper low will move slowly into
southeast Arizona and will finally make its way into New Mexico
Monday night.  Well out ahead of this low some showers will likely
redevelop over much of east Texas and western Louisiana later
Monday. Otherwise the precipitation areas will be confined to
southern New Mexico and far west Texas. By Tuesday this upper low
will begin to accelerate eastward across west Texas, then eventually
across north Texas into Arkansas Tuesday night into Wednesday
morning.  This storm may produce isolated heavy rainfall amounts of
1.50 to 2.00 inches over northeast Texas, and even heavier amounts
over Arkansas.  Although this precipitation will bring some relief to
the dry conditions over portions of the state, the abnormally dry
conditions are expected to remain over most of the region.  While
rises may occur on the east Texas rivers, no flooding is expected
the next 5 days.

Dry weather is forecast from Wednesday morning into Thursday
morning as a surface high pressure system dominates the weather over
our region.  But yet another storm system is forecast to move into
the four corners region Thursday which will bring precipitation to
northern New Mexico and Colorado Thursday into Friday morning.
Further east, some light rain may develop over east Texas and
Louisiana by Friday morning.

                    ...PRECIPITATION FORECAST...
For Today into Monday morning, Mean Areal Precipitation (MAP)
amounts of 0.25 to 0.50 inch are forecast for the southwestern third
of New Mexico into the El Paso Texas area.   MAP amounts of less than
0.25 of an inch are forecast over the southeast quarter of Texas into
much of Louisiana, as well as over far west Texas and southern New
Mexico.

For Monday into Tuesday morning, MAP amounts of 0.25 to 0.50 inch
are forecast over the southeast third of Texas and most of Louisiana.
The largest MAP amounts of 1.00 inch are forecast from near College
Station and Houston TX through the Toledo Bend country into west
central Louisiana near Fort Polk.  MAP amounts of less than 0.25 of
an inch are forecast over most of the WGRFC area except for west
Texas into northern New Mexico and southern Colorado.

For Tuesday into Wednesday morning, MAP amounts of 0.25 of an inch
or more are forecast over the northeast half of Texas and Louisiana.
The heaviest rain, with MAP amounts of 1.50 inches, are forecast for
portions of northeast Texas. Even larger amounts of MAP are forecast
over the Arklatex into southern Arkansas.  MAP amounts of less than
0.25 of an inch are forecast over most of Texas except the far west.

For Wednesday into Friday morning, no significant MAP amounts are
forecast for the WGRFC area.  MAP amounts of less than 0.25 of an
inch are forecast over roughly the southeast third of Texas and
Louisiana, as well as over northern New Mexico and Colorado.

The latest U.S. Drought Monitor for Texas shows the area considered
to be abnormally dry is around 71%, with around 26% of the state
experiencing moderate drought and 12% in severe drought.  In New
Mexico, 89% of the state is having abnormally dry conditions, with
16% in moderate drought conditions (over the western portions).
With the dry weather this fall, a large portion of the WGRFC forecast
area is experiencing some type of abnormally dry or drought
condition.  The heaviest rainfall the next five days will fall in
locations where soils are some of the driest in Texas, specifically
northeast Texas.  Therefore, while minor runoff may occur from the
rain, no significant runoff is expected.

                     ...HYDROLOGIC DISCUSSION...
...Upper Rio Grande Basin...
Water supply numbers are off to a slow pace with snow water
equivalent averages well below seasonal normals.  The weather
phenomenon known as La Nina may be the culprit this water year.

...Sabine Basin...
Toledo Bend continues to release 7000 cfs for 2-3 hours each day for
low flow considerations until further notice.

...Remainder of WGRFC Basins...
All rivers across the WGRFC area are at or below normal flows and are
expected to remain below criteria levels over the next 5 days.  There
could be some nuisance flooding associated with the rains expected on
Tuesday.

              ...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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