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

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FXUS64 KFWD 190540 AAB

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
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.



.PREV DISCUSSION... /ISSUED 405 PM CST Sat Feb 18 2017/

Another very warm late winter day is in progress across North and
Central Texas with temperatures climbing well into the 70s and
lower 80s across the region. Earlier cloud cover across the
eastern and northern parts of the CWA has mostly eroded over the
last couple of hours and temperatures have responded nicely in
places like Paris and Bonham. A look outside of the window reveals
some thickening cirrus clouds moving in from the west which is
also noted on visible satellite imagery. This serves as a visual
indication that changes are on the way.

A closer look at surface observation data reveals surface
pressures are falling across much of the Southern Plains with
4.5mb/3hr pressure falls occurring across far West Texas. These
pressure falls are in response to an approaching strong upper
level low which is currently moving into far northwest Mexico.
This system will be responsible for scattered showers and
thunderstorms tomorrow afternoon through tomorrow night.

For tonight...strengthening southerly flow will spread rich Gulf
moisture northward resulting in a rapid moistening of the lowest
2000ft of atmosphere. Widespread low clouds and areas of fog are
expected to develop late tonight through much of Sunday morning.
The deep moisture and initially weak ascent may result in some
areas of drizzle or very light rain through midday.

A large elevated mixed layer will be in place across much of North
and northwest Texas early Sunday and the resulting capping
inversion will initially be quite strong through midday. As we get
into the afternoon hours...much stronger forcing for ascent will
spread into the region helping to lift the inversion. A fairly
well defined warm sector should be in place by mid afternoon with
steep lapse rates aloft associated with the elevated mixed layer.
This should result in surface based instability around 1500 j/kg
Sunday afternoon. All of the available high resolution guidance
...with the exception of the 3km NAM...suggests that
thunderstorms will develop by late afternoon into the evening
hours mainly west of I-35 along an eastward moving dryline. This
initial activity will have the potential to be severe...including
supercells with a hail/damaging wind threat. Deep layer shear
will be strong with 50+kt through 6km...although it will be
unidirectional and feature a veer-back-veer profile. This suggests
that the tornado threat may be somewhat limited...except for
areas where low level flow can remain backed. That threat appears
to mainly be northwest of the Metroplex late Sunday afternoon into
the evening. Given the mainly unidirectional wind profiles this
convective activity should tend to congeal into one or more lines
late Sunday evening into the overnight hours. With waning surface
instability...the severe threat should diminish overnight.

During the overnight hours...the main concern will be locally
heavy rainfall as the whole system progresses eastward. Right now
given the progressive nature of the upstream flow...we don`t
anticipate any stalling of convective elements...although the deep
south to north flow could allow for some training echoes that
could dump 2"/hr in some areas as the main line moves east. This
could cause some localized minor flooding issues across parts of
North Texas.

The whole system is expected to move east of the area on Monday
with precipitation ending from west to east. The remainder of the
forecast will remain dry with above normal temperatures through
mid week. A late week system will send a cold front through the
area on Friday although moisture appears to be too limited for



Dallas-Ft. Worth    59  74  60  73  52 /   5  40  80  30   5
Waco                61  75  59  73  50 /  10  40  80  50   5
Paris               56  75  60  70  52 /   5  20  80  70  10
Denton              57  72  58  74  49 /   5  40  80  20   5
McKinney            57  73  60  73  51 /   5  30  80  40   5
Dallas              60  74  61  73  53 /   5  30  80  30   5
Terrell             58  77  61  72  52 /   5  30  80  60  10
Corsicana           61  77  61  72  53 /  10  30  90  70  10
Temple              61  76  59  73  51 /  10  40  80  50   5
Mineral Wells       55  72  55  76  48 /   5  50  60  10   0




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