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

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FXUS64 KFWD 210459 AAC

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1159 PM CDT Fri Oct 20 2017

MVFR ceilings have been spreading northward late this evening
and had moved into much of the Metroplex as of 0430z. Ceilings
may lower to IFR for a few hours at Waco so have placed a TEMPO
BKN007 between 09z and 13z. Southeast winds around 15 knots will
prevail and some gusts over 25 knots will be possible late
Saturday morning through the afternoon hours. Some isolated
showers/thunderstorms are possible during the day Saturday but
the cap is expected to keep this activity very limited, so
SHRA/TSRA has not been mentioned in the Metroplex TAFs. A line of
strong to severe thunderstorms are expected to develop ahead of a
strong cold front Saturday night. Thus have placed a VCTS in the
Metroplex TAFs starting at 05z. Have included a TEMPO 5SM TSRA
BKN025CB in the extended portion of the DFW TAF and shown a wind
shift to the north at around 17 knots at 09z Sunday.



.UPDATE... /Issued 950 PM CDT Fri Oct 20 2017/
A strong low level jet is setting up this evening in response to a
trough moving across the Rockies. Southeasterly winds have picked
up to 15 to 20 mph with some gusts over 25 mph this evening
across parts of North Texas. Thus winds speeds have been bumped up
for the rest of tonight. Isolated to scattered showers are
possible before daybreak along and east of the I-35 corridor, so
have left some 20 percent POPs there.

Have also bumped up the winds a bit across areas along and west of
the I-35 corridor tomorrow where some gusts over 25 mph are



.SHORT TERM... /Issued 327 PM CDT Fri Oct 20 2017/
Moisture continues to slowly increase within the southerly flow
regime across the southern US. This has led to a partly/mostly
cloudy day for much of the area along with a few showers and
isolated storms. Without sufficient ascent to overcome the capping
inversion around 750 mb, these precipitation trends will continue
to be the story through the remainder of the afternoon and
evening. The upper trough has remained too far west to provide
significant lift across North Texas while the strongest warm
advection is positioned off to the east/southeast. Overnight,
only isolated showers are expected as moisture continues to
increase, thus have included low broad PoPs without a mention of
thunder for the overnight period.

With increasing clouds expected during the overnight hours and
winds remaining around 10-20 mph, low temperatures should stay on
the warm side and be relatively uniform across the area in the
upper 60s and low 70s. Dewpoints will continue to slowly increase
to the upper 60s and even low 70s across parts of the forecast
area by daybreak which will set the stage for some stronger storms
late Saturday as discussed below.



.LONG TERM... /Issued 327 PM CDT Fri Oct 20 2017/
/Saturday through Friday/

Saturday will start out warm and muggy across the region as low
level southerly flow continues to pull moisture northward. Outside
of some scattered warm advection showers, most of Saturday should
be precipitation free. Forecast soundings from around North Texas
suggest that most of the area will remain capped well into the
afternoon hours as southwesterly flow between 800-700 mb
strengthens to around 30 kt. Beneath the capping inversion will
be a warm moist boundary layer with surface based instability
climbing to 2500-3000 j/kg. The capping will become weakest in
areas east of I-35 during the late afternoon, although this will
be the area of weakest synoptic forcing. Long story short, if any
storms can break the cap well ahead of the cold front tomorrow
afternoon and early evening, they will have the potential to
become supercells with all modes of severe weather. This potential
right now is about 20% or less.

Later Saturday evening into the nighttime hours as stronger height
falls overspread North Texas, thunderstorms are expected to be
ongoing along and ahead of the cold front across parts of
Oklahoma. These storms will continue to rapidly develop southward
along the front and will be developing in an unstable
environment. Given the available instability and strong forcing
for ascent, thunderstorms should be able to maintain vigorous
updrafts rooted in the warm sector. This suggests that a well
organized squall line accompanied by a damaging wind threat
should develop and be in progress prior to midnight across parts
of North Texas. Low level shear will be sufficient for a few
bowing segments and possibly a few QLCS tornadoes well into the
late evening and overnight hours. Hail will be a threat especially
in the evening hours on Saturday and with initial thunderstorm
development, but the main threat should transition into a damaging
wind threat later into the evening hours.

Precipitation should end from west to east early Sunday morning as
the front continues east. We`ll have PoPs confined to areas mainly
east of I-35 Sunday morning with all rain chances ending during
the afternoon hours. Next week looks really nice with a
reinforcing shot of cooler air moving through on Monday night.
This front should come through precipitation free. We`ll see a
slight warm up through mid week, then a much stronger front will
move through the Plains on Thursday evening. This could mean a
significantly cooler weekend next weekend.



Dallas-Ft. Worth    71  85  60  73  52 /  20  20 100  20   5
Waco                70  86  63  75  50 /  20  20  90  30   0
Paris               67  80  61  70  49 /  20  20 100  50  10
Denton              70  86  58  73  49 /  20  20 100  20   5
McKinney            70  83  60  72  50 /  20  20 100  30   5
Dallas              71  86  62  73  53 /  20  20 100  30   5
Terrell             70  85  61  73  48 /  20  20 100  40   5
Corsicana           69  83  63  72  50 /  20  20  90  40   5
Temple              69  86  62  76  50 /  20  20  80  30   0
Mineral Wells       69  86  55  74  48 /  10  20 100  10   0




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