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

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FXUS64 KFWD 242044
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
344 PM CDT SAT SEP 24 2016

.DISCUSSION...
A large upper level trough to our west continues to slowly ease
east this afternoon. Although it won`t make it across the Southern
Plains, the impacts from this system on North and Central Texas
will include increasing rain chances, a front, and cooler weather.

This afternoon, showers and thunderstorms have been ongoing from
Northwest Oklahoma to West Texas ahead of the upper level trough.
With the influence of the upper level ridge having been weakened
across North and Central Texas and southerly winds continuing to
provide rich moisture into the region, isolated to scattered
showers and thunderstorms have been developing and moving north
across our area. Lightning and gusty winds to 30 mph have been the
main threats with this activity. We do not anticipate severe
storms through this evening, but an isolated strong storm could
produce winds closer to 50 mph before sunset.

The overnight period is when we expect rain chances will increase
for roughly the northwestern half of the region. A weak shortwave
currently crossing into Texas near the Big Bend area is expected
to continue moving north-northeast this evening, aiding in
additional lift across our western counties. The low level winds
in the 925-850 mb layer are also expected to increase to near 30
kts, providing additional support for convective development this
evening. The area of showers and storms to our west is expected to
move east, reaching our western counties this evening. The models
are quite variable in when the rain will really increase near our
western border, but most of the guidance is indicating between
9-11 pm CDT. By sunrise, the low level winds decrease in speed,
and the shortwave will be lifting northwest of the region. We
should see a weakening of the overall showers/storms and likely a
reduction in coverage through the morning hours. For the overnight
period, will keep the highest PoPs west of a Gainesville to Fort
Worth to Goldthwaite line with PoPs steadily dropping off further
east. Due to potential training of storms, it`s possible some
localized flooding may occur during the overnight period. An
isolated instance of flash flooding is not completely out of the
question depending on rain rates and if training occurs over a
certain area, but flash flood guidance is fairly high in our
western counties, as it is for most of North and Central Texas.
Will encourage the next shift to keep an eye on radar trends and
assess the potential for any Watches overnight and into Sunday.

The most significant changes to expected rain/storm trends comes
Sunday-Monday. An upper level low is forecast to cut-off within
the base of the trough over northern Mexico on Sunday and then
retrograde. In the wake of the departing shortwave in the morning,
and with the best dynamics located well to our west near this
cut-off low, we could end up in a lull in activity late Sunday
morning and into the early afternoon hours until the cold front
arrives later in the afternoon or evening hours. Isolated to
scattered shower and thunderstorm activity ahead of the front is
still expected as heating occurs with rich moisture still in place
and a lack of subsidence over the area. Also, any boundaries that
may be left over from the overnight and morning convection may
become a source for lift. Even in an unstable and uncapped
atmosphere, shear values and lapse rates tomorrow are weak, thus
we do not expect severe storms.

As the front moves in, it should become a focus for additional
shower and storm development. The highest chances for rain will
still be across mainly the western half of the region where we
will keep high PoPs but understand that this is not an indication
it will rain most of the day. We will keep high PoPs overnight as
the front moves through with again the highest rainfall totals
mainly west of Interstate 35. Showers and storms may also occur
behind the surface front as the H850 front lags behind. Lightning
and heavy rainfall will be the main hazards through the overnight
period but rainfall totals are not high enough to warrant a
Flood/Flash Flood Watch at this time. However, minor flooding will
be possible. Rainfall totals through the event are expected to be
less than an inch to the east of Interstate 35, where several locations
may not see rain at all, to 1-3 inches along and west of
Interstate 35. The highest rainfall totals of 2-3 inches are
expected west of Highway 281.

The cold front is expected to push through our southern counties
by early Monday morning. It will continue to push deep into the
Gulf of Mexico early next week with dry air filtering into the
region starting Monday. Some lingering rain may occur on Monday as
the H850 front also slowly moves south, but any leftover rain is
expected to end Monday night. The Gulf of Mexico will remain cut
off from moisture return next week with north and east surface
winds prevailing across the region through the end of the week.
Even as an upper level ridge builds back into the Southern Plains,
temperatures will be very pleasant next week with highs in the 70s
and 80s and lows in the 50s and 60s.

JLDunn

&&

.AVIATION...
/ISSUED 1231 PM CDT SAT SEP 24 2016/
Showers and thunderstorms are gradually expanding in coverage
early this afternoon. Coverage is still expected to remain just
isolated to scattered, but on-and-off impacts from thunder are
expected at all of our TAF sites into the mid-afternoon hours. Any
cells will bring with them gusty and chaotic winds and brief MVFR
cig/vis reductions.

The evolution of convective potential late tonight and Sunday
morning remains a bit unclear. Some high-resolution guidance has
aggressively driven an outflow boundary into the Metroplex sites
as early as 06-08Z, bringing with it a brief northwest wind shift
and scattered thunderstorms. However, the environment to our north
and west does not appear to strongly favor the development of a
surging outflow tonight. As a result, I`ve continued to side with
the slower guidance, and will bring VCTS into the Metroplex sites
after 11Z. This timing may be just quick enough to disrupt the
nocturnal development of low clouds in the Metroplex, but an even
slower progression would translate into an increased risk for MVFR
cigs early Sunday morning.

I`ve also attempted to highlight the most likely timing for
thunder in the Metroplex on Sunday. As profiles moisten, activity
may become more showery in nature late Sunday morning.
Thunderstorms may once again re-develop during the mid-afternoon
hours with just a bit of filtered heating. In the DFW extended
TAF, a north windshift will occur with the passage of the actual
cold front around 21Z.

At Waco: after thunderstorms diminish later this afternoon and
evening, MVFR cigs should once again move north late tonight into
Sunday morning. I anticipate the better thunder chances holding
off until towards the end of the valid Waco TAF cycle.

Carlaw


&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    77  85  64  76  62 /  50  60  70  30  10
Waco                77  88  66  77  60 /  40  60  70  30  20
Paris               72  88  65  78  59 /  20  30  40  30  10
Denton              73  84  62  73  57 /  60  60  60  30  10
McKinney            73  87  64  77  58 /  40  60  50  30  10
Dallas              77  86  65  77  63 /  40  60  60  30  10
Terrell             73  89  67  80  61 /  30  50  60  30  10
Corsicana           75  89  67  80  61 /  30  50  70  30  20
Temple              75  87  65  76  61 /  30  60  70  30  20
Mineral Wells       73  81  61  70  55 /  70  70  70  30  10

&&

.FWD Watches/Warnings/Advisories...
None.
&&

$$

90/82


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