Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX

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FXUS64 KFWD 190926

Area Forecast Discussion
National Weather Service Fort Worth TX
326 AM CST Sun Feb 19 2017

A weak east-west oriented surface boundary near the I-20 area
currently separates cooler and drier air to the north from deeper
moisture and warmer air to the south. This boundary will lift
north this morning as a deep upper level trough approaches and lee
side surface troughing intensifies. This will allow Gulf moisture
to spread north across the entire area mid to late morning as the
boundary lifts north of the Red River, which will set the stage
for a round of showers and storms tonight.

Light showers will be possible this morning as low level moisture
spreads in from the south. This moist air advection when combined
with surface heating will destabilize the atmosphere as we move
into the afternoon hours. Isolated thunderstorms should develop
mid to late afternoon across the western third of the forecast
area as modest lift associated with a lead shortwave develops.
Surface based CAPE is forecast to be at or above 1000 J/KG with 50
KT of bulk shear in place, which should be sufficient for a few
strong to possibly severe storms. Hail and damaging wind would be
the primary threat, though an isolated tornado is possible. Deep
layer meridional flow means that storms will move quickly to the
north-northeast, which should keep activity west of the I-35
corridor during the afternoon and early evening hours.

Stronger forcing for ascent will arrive 9PM to midnight as the
main upper trough axis moves into West Texas. High-res model
solutions are coming into pretty good agreement on rapid storm
development just west of the I-35 corridor during this timeframe.
A window of opportunity may exist during these late evening hours
that may allow for individual cells containing rotating updrafts,
which would keep the severe threat in place through at least
midnight. It appears that storms will quickly grow upscale into a
linear MCS shortly after midnight as forcing continues to increase
and a 30 KT low level jet develops. Individual cells embedded in
the line will be moving rapidly north-northeast while the entire
line shifts steadily eastward overnight. Training storms will
lead to locally heavy rain and flooding of low lying areas, but
the progressive nature of the system should prevent a higher-end
flood threat. Instability will have dropped off significantly
during the overnight hours but will still be enough for isolated
wind damage due to bowing segments along the line.

The line of storms will move east of the forecast area Monday
Morning, with the back edge of lingering stratiform precipitation
ending in the afternoon. The upper trough will then split Monday
night and Tuesday, with the northern half racing off to the
northeast as an open shortwave and the southern half dropping
southeast into the Northwest Gulf as a cut-off low. This will
leave North and Central Texas under the influence of a shortwave
ridge, keeping conditions warm and dry Tuesday through Thursday.
The ridge will break down late Thursday and Friday as an upper
trough sweeps across the Central CONUS, which will send a cold
front through the area on Friday. This will cool things to near-
normal, with conditions remaining dry Friday through next weekend.
Rain chances return by next Monday as a mid-latitude shortwave
and a Pacific cold front affect the region.



/ISSUED 1140 PM CST Sat Feb 18 2017/
A surface trough sank a little farther south into the Metroplex
Saturday evening resulting in winds backing around to the east and
east northeast. This boundary will lift northwards overnight
allowing surface winds to veer around to the southeast before
daybreak. A low level jet developed during the evening and is
advecting Gulf moisture northward. Low clouds that formed over
South Texas early this evening were spreading northward. Expect
MVFR ceilings to spread into the Waco area 06-07z and into the
Metroplex TAF sites 07-08z. As top-down saturation occurs,
ceilings should lower into the IFR category by 11z in the Waco
area and 11-12z in the Metroplex. There may be some scattered
showers and maybe an isolated thunderstorm during the Sunday
afternoon and for now have indicated VCSH in the TAFs starting at
18z. As an upper level low currently over southwestern Arizona
moves east, a dryline is expected to develop over West Texas by
early Sunday afternoon. Scattered showers and thunderstorms along
and ahead of the dry line are expected to form into a broken to
solid line as they approach the I-35 corridor (including Waco and
the Metroplex TAF sites) Sunday evening. This has been indicated
by the TSRA starting at 02z. Some of these storms may be severe
with the potential for large hail and damaging winds. Most of the
storms will move to the east of the TAF sites after 06z Monday so
have just have kept some -SHRA for the 06z-09z extended portion
of the DFW TAF.



Dallas-Ft. Worth    74  61  73  52  76 /  20  60  30  10   5
Waco                75  60  72  51  75 /  20  70  40  10   5
Paris               74  61  69  53  73 /  20  70  50  10  10
Denton              72  59  73  49  75 /  30  60  30  10   5
McKinney            73  61  72  51  74 /  20  70  30  10  10
Dallas              74  62  73  53  76 /  20  70  30  10  10
Terrell             77  62  71  53  74 /  20  80  40  10  10
Corsicana           77  62  71  54  74 /  20  80  50  10  10
Temple              75  60  72  52  76 /  30  70  40  10   5
Mineral Wells       72  56  75  48  76 /  40  60  20   5   5




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