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

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FXUS64 KFWD 181221

Area Forecast Discussion
National Weather Service Fort Worth TX
621 AM CST Sat Nov 18 2017

/12z TAFs/

Main challenges today will be timing the passage of the a pre-
frontal surface trough, then a strong cold front through this
morning. In addition, crosswinds may become a concern for north-
south runways at DFW between 12z-15z between the surface trough
and cold front, as winds shift westerly 15-20 knots.

With 30-40 knot 925mb flow veering quickly, MVFR cigs are no
longer a concern at Waco Regional Airport, though a strong
shortwave will provide plenty of cirrostratus through much of the
daylight hours. An AWW will likely be needed for non-convective
wind gusts in => 35 kts at DFW post-fropa, as strong CAA, strong
3-hourly surface pressure rises, and strong unidirectional mixing
lend to a few gusty to, or possibly in excess of 40 kts by midday
or early afternoon.

DFW Metro airports...
A pre-frontal trough extending from 0F2, KMWL, to KSEP will
arrive into the DFW Metro from the west by 13z and after. This
will result in increasing west winds AOA 15 kts with a few gusts
that could cause minor crosswind issues for 1-2 hours. A strong
cold FROPA will arrive 15z-16z with a rapid shift to the northwest
winds 25-30 kts with gusts 35-40 kts by midday, before coming
down to 20 kts or less by 00z, then 10 knots or less by 03z Sunday
and after. Otherwise, VFR with broken cirrus through much of the
day, before the shortwave aloft departs with skies clearing by 12z
Sun with a surface high pressure ridge settling into the region.

Waco Region Airport...
Similar trends to the boundary passages with respect to the
surface trough, then cold front, but just delayed 2 hours or
slightly more. Threat for MVFR cigs has waned due to strong
veering of 925mb flow which should keep the airport VFR with
similar broken cirrus arriving by midday.



.UPDATE... /Issued 514 AM CST Sat Nov 18 2017/
Despite very strong 3-hour pressures rises with the cold front now
crashing south of the I-40 corridor from Western Oklahoma into the
Panhandles, it appears a frontal passage more toward mid morning
looks imminent for the northwest half of the CWA. As such,
slightly warmer morning highs today across these areas look to
occur and have adjusted highs up a few degrees. The rest of the
CWA still looks on tap for a late morning through midday cold
frontal passage. Otherwise, no other changes were needed.



.SHORT TERM... /Issued 349 AM CST Sat Nov 18 2017/
/Today through Tonight/

We continue to watch a strong surface cold front diving south
across the High Plains and was now just entering the Oklahoma and
Texas Panhandles, as well as far northwestern Oklahoma. The cold
front was being support by a strong upper disturbance moving east-
southeast over the Central High Plains of Eastern Colorado,
Western Nebraska, and Western Kansas. 3-hour pressure rises were a
phenomenal 6-8mb across far Southeast Colorado and far Southwest
Kansas behind the cold front where strong low level cold thermal
advection and tight pressure gradient were being realized.
Otherwise, a low stratus deck was being confined to about the
southeast third of the region with veered low level boundary layer
winds near 35 knots. Elsewhere, high cloudiness was thickening in
advance of the vigorous shortwave exiting across the High Plains
this morning.

As the aformentioned, vigorous shortwave trough moves across the
Central and Southern Plains later this morning and toward the
Missouri and Mississippi Valleys, plenty of upper support and
strong surface pressures rises will help the cold front enter our
far northwest counties just after sunrise. The cold front will
then pass through the I-20/30 corridors around mid morning, before
exiting Central Texas after midday. No convection or rainfall is
expected along and ahead of the front due to strongly veered low
level flow minimizing convergence along with only minuscule
moisture below 850 mb. Our main concerns continue to be the very
strong north-northwest winds of 20 to 30 mph with gusts reaching
40 mph or possibly higher in a few spots. These strong winds will
be driven by both low level cold thermal and surface pressure
advection as noted by earlier 3-hour pressure rises. In addition,
deep mixing of unidirectional strong north-northwest flow 30-45
knot flow should easily occur with the expected momentum

After collaboration with offices to the south and east, I have
added the remaining far southeast counties beginning at 11 am
CST, though they will be on the lower end of advisory wind speeds.
In addition, I have went ahead and extended the advisory through
5 pm, per expected trends in sustained winds and gusts. Per usual
with cold fronts arriving during diurnal hours of the day, a
broad range in highs are expected today from the lower 60s
northwest with an early morning high, to near 80 degrees with
compressional warming in advance of the cold front across the
southeast at midday.

A surface ridge will move into the Southern Plains by this
evening with bulk of the stronger CAA moving off to the south and
east of our area. The very cool and dry air in place will quickly
decouple by nightfall, as skies clear. As such, brisk north winds
near 15 mph will quickly diminish overnight to less than 10 knots
with cold low temperatures by sunrise Sunday in the 30s, to lower
40s southeast and immediate urban areas within the D/FW area. A
few rural areas across the Red River Valley and out west could
briefly dip to freezing for an hour or two, but that`s not
completely certain. We can`t rule out some patchy frost across
protected areas near creeks or bodies of water, however, the
increasingly dry airmass settling should keep much from forming.



.LONG TERM... /Issued 349 AM CST Sat Nov 18 2017/
/Sunday through Wednesday/

Generally tranquil weather conditions are expected through the
entire long term period with a couple of frontal passages. At this
time, the potential for measurable rainfall early in the week
looks. Conditions should be comfortable through most of the long
term period, including Thanksgiving Day.

For Sunday, high pressure will settle in across the region and
after a chilly start to the day, temperatures should range between
the upper 50s and the low to perhaps mid-60s. Rain chances will
remain nil as the airmass will be dry and little in the way of
lift will exist. Skies should be mostly sunny with just a few
passing high clouds. Surface high pressure should slide to the
east, allowing for southerly winds to return and warmer conditions
Sunday night into Monday morning.

On Monday warmer conditions are forecast as temperatures climb
into the mid to upper 60s areawide. While a diffuse upper level
trough will slide through the region, it`s unlikely to result in
nothing more than a slight uptick in the coverage of mid and upper
clouds. Low level moisture will remain confined to the upper TX
coast, limiting the rain potential. Monday should be a breezy day
with surface winds in the 15 to 20 MPH range. A few gusts to near
25 MPH will also be possible.

A more vigorous upper trough will evolve on Tuesday as a conveyor
of 100 knot flow at 300mb extends southward from the Four Corners
region. Attendant to this feature will be another push of colder
air. Ahead of this cold front, however, winds will veer allowing
for even warmer conditions for parts of the area. At this time, it
looks like the cold front will slide through at least North TX
and afternoon high temperatures will be on par with those on
Monday. Across Central TX, however, temperatures may soar into the
upper 70s to near 80 as efficient downsloping occurs ahead of the
front. The veering of the low level flow should also help to
shunt whatever moisture lifted northward during the overnight
hours off to the east. While moisture will be limited, the upper
trough will produce a decent amount of lift. With deterministic
GFS and ECMWF model output remaining dry and GFS and GEFS ensemble
mean QPF trending towards zero, however, I`m inclined to believe
that any precipitation that occurs on Tuesday across southeastern
and southern zones will be nothing more than a few sprinkles.

For the Wednesday through Friday time frame, the weather pattern
looks fairly benign. Aloft, flow will be quite meridional with a
large ridge to the west and deep trough to the east. This should
ensure that the Gulf of Mexico remains shut off and thus no
moisture return northward for rainfall across the region. As a
result, it looks like Thanksgiving Day will be rain-free with
seasonal temperatures. A brief warm up ahead of the next cold
front will be on tap for Friday and potentially into Saturday.
Breezy southwesterly winds combined with decreasing afternoon
humidity and above normal temperatures may raise the fire weather
threat late next week and into the weekend.

The next cold front will slide southward through the area late
next weekend. As mentioned above, limited moisture return
northward will likely limit the chance for any rain and I`ve
maintained a dry forecast through the remainder of the long term
forecast period.



Dallas-Ft. Worth    72  41  62  40  66 /   0   0   0   0   0
Waco                75  36  62  37  66 /   0   0   0   0   0
Paris               72  35  60  36  63 /   5   0   0   0   0
Denton              69  33  62  38  65 /   0   0   0   0   0
McKinney            72  35  60  37  64 /   0   0   0   0   0
Dallas              73  43  62  40  66 /   0   0   0   0   0
Terrell             74  38  62  36  65 /   0   0   0   0   0
Corsicana           73  41  61  38  66 /   5   0   0   0   0
Temple              77  39  63  39  67 /   5   0   0   0   0
Mineral Wells       67  34  61  34  67 /   0   0   0   0   0


Wind Advisory until 5 PM CST this afternoon for TXZ091>095-

Wind Advisory from 11 AM this morning to 5 PM CST this afternoon
for TXZ147-148-162-174-175.



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