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

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855
FXUS64 KFWD 150449
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
1149 PM CDT Sat Oct 14 2017


.AVIATION...
/6Z TAFS/

Main concern in the immediate short term will be the strong cold
front that will move through overnight. Only changes to the
current TAF forecast was to make minor adjustments to FROPA at
area airports based on radar/satellite observations. Timing still
looks like it will be between 830-1030Z in the Metroplex and
around 1030-11Z at Waco. Scattered showers and a few thunderstorms
will likely accompany the front along with an abrupt wind shift to
the northwest. MVFR cigs will also likely prevail for a few hours
through the morning before drier air filters in and cigs scatter.
VFR conditions will prevail Sunday afternoon through the remainder
of the period with gusty north winds diminishing after sunset.

Dunn

&&

.UPDATE... /Issued 1037 PM CDT Sat Oct 14 2017/
No major changes to the current forecast with the front still on
track to move into our area shortly after midnight and through the
Metroplex in the 3-5 am timeframe. It should make it into the
Waco/Temple/Killeen areas near sunrise. Regional radar imagery
shows a line of showers and thunderstorms draped across central
Oklahoma and this should spread south through the night. The front
has accelerated some this evening and is quickly undercutting new
development ahead of the front. This trend will likely continue
and we should see just mainly elevated showers with a few rumbles
of thunder across North Texas. The lack of more robust elevated
instability suggests that any widespread severe weather or hail
threat will be low. An abrupt wind shift will accompany the front
along with a sharp temperature drop. No changes were made to the
current wind advisory although most areas will see at least
temporary wind speeds above advisory level immediately behind the
front. Gradient winds should diminish through the day on Sunday.

Dunn

&&

.SHORT TERM... /Issued 328 PM CDT Sat Oct 14 2017/
/Tonight through Sunday/

After another unseasonably hot day across North and Central TX,
BIG changes are on the way over the next 12 to 24 hours. Surface
analysis at this hour revealed that the culprit for these changes,
a stout cold front, was slowly trudging southward through the
Central and South Plains. Ahead of this feature, shallow low level
moisture was beginning to lift northward with breezy southerly
surface winds in response to the tight pressure gradient. The
expectation is that this front will continue to surge southward
bringing with it a chance for rain and isolated thunderstorms for
at least the northern two- thirds of North and Central TX.

For Tonight---Through midnight, most weather across the area
should be largely uneventful. Afternoon clouds will dissipate with
the loss of daytime heating and surface winds will gradually
subside. With the pressure trough associated with the front, the
nocturnal LLJ should be weaker, limiting additional low level
moisture transport northward. The weaker low level jet, however,
may also foster quicker patchy fog development down across far
southern and southeastern zones and I`ve added a mention of this
where NSSL-WRF visibility products support this idea. I won`t rule
out some patchy dense fog either, but for now, I`ll defer to the
evening and overnight shifts on whether or not this needs to be
mentioned in the forecast.

For Sunday---The cold front should enter northwestern zones
around 1 AM. While the upper trough, currently across southern
Wyoming, will be lifting away, there appears to be sufficient low
level frontogenetical forcing to generate scattered to numerous
convection along the boundary. The time of day isn`t necessarily
favorable for surface based convection and given both the small
amounts of elevated instability AND the fact that convection will
have a tendency to be undercut by the swift moving front, it`s
likely that thunder will be isolated. Severe weather also appears
unlikely given the low amounts of instability (MUCAPE values near
or less than 1,000 J/kg) and weak deep layer shear. That being
said, a strong storm or two cannot be completely discounted, with
the main threat being small hail. The greatest rain chances will
be for areas near and north of a Comanche to D/FW to Bonham line.
Rain chances will continue farther south, but the coverage will
likely be less as winds veer quickly and low-level frontogenesis
weakens. Hi-resolution model guidance depicts this nicely and I`ve
only gone with chance PoPs south of the aformentioned line. Rain
chances should tapper off from north to south through the morning
as drier air filters in from the north.

One big change with the front will be the very windy conditions
in the wake of the front. Impressive surface pressure rises of 3-4
mb/hr in the panhandle coupled with nearly 40 to almost 45 knots
of flow at 925mb in some of the more aggressive guidance supports
sustained surface winds of 20 to 30 MPH across northwestern zones.
With that in mind and after coordinating with surrounding
offices, we`ve hoisted a Wind Advisory that goes into effect at
0800 UTC (0300 CDT) through 1500 UTC (1000 CDT) for areas near and
northwest of an Eastland to Denton to Sherman/Denison line. Winds
in the advisory area may gust closer to 40 MPH out of the north.
It`s possible that some minor alterations to the current wind
advisory may be needed, but for now, I`ll defer to other shifts.
Areas outside of the wind advisory will still be strong with
sustained speeds of 20 to 25 MPH with gusts to near 30 MPH.

The other significant change with the front will be the
noticeably cooler conditions. Pretty stout cold air advection as
evidenced by the rapid decrease in 1000-500mb thickness across the
area should result in high temperatures several degrees below
normal. This coupled with the strong winds will make it "feel"
even cooler. Afternoon high temperatures will likely only climb
into the low to mid 60s for the northwest portion of North TX with
low to possibly mid 70s elsewhere. Mostly cloudy skies in the
morning will yield to partly sunny skies in the afternoon and
surface winds should decrease as the surface pressure gradient
relaxes.

24-Bain

&&

.LONG TERM... /Issued 328 PM CDT Sat Oct 14 2017/
/Sunday Night through Saturday/

By Sunday night the cold front will be pushing into the Texas
Coast with dry conditions and clearing skies filtering across the
region. Wind speeds will diminish to less than 10 mph across North
Texas as the surface high slides into the region from the north.
The pressure gradient will remain a little tighter across Central
Texas, and a stronger breeze of 10-15 mph is expected to prevail
overnight. Overnight lows will be noticeably cooler, but optimal
radiational cooling will likely not occur (despite the drier
conditions and clearing skies) due to 25-35 kt winds in the
925-850 mb layer. Still, overnight lows will fall into the 40s
and 50s.

By most standards, Monday will be a very pleasing fall day with
highs only in the upper 60s to mid 70s, clear skies, and dry
conditions. Good radiational cooling will likely occur Monday
night, and overnight lows across the region are expected to fall
into the upper 30s and 40s. Readings in the upper 30s will likely
be sparse and confined to our west and northwest counties.

Tuesday through Thursday will continue to be dry days with a slow
warming trend. Although technically daytime highs will rise above
average highs for this time of year, readings in the lower to mid
80s will be much more welcomed than the 90 degree weather we have
been experiencing the past 2 weeks. Overnight lows will actually
run below normal, until moisture returns by the end of the week.

The surface high will slide east of the region on Tuesday, and
south winds will slowly return Tuesday into Wednesday, but the GOM
will remain cut off from moisture return until Thursday-Friday.
Near the end of the week, a weak upper level trough is forecast to
traverse the region. With increasing moisture from the southerly
flow in the lower to mid levels of the atmosphere, some rain may
be possible Friday and Saturday, mostly across Central Texas.

Looking a little farther ahead into next weekend, a stronger upper
level trough will move into the Pacific NW on Friday-Saturday, but
the models continue to disagree on the path of this trough. The
path of this system would impact whether another front arrives
next weekend, but for now we will enjoy the pleasant weather
behind tonight`s front and keep a hopeful eye on next
weekend/early next week.

JLDunn

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    62  69  50  73  46 /  80  30   0   0   0
Waco                65  71  49  74  44 /  50  30   0   0   0
Paris               60  69  47  72  43 /  70  30   0   0   0
Denton              58  69  45  72  41 /  80  20   0   0   0
McKinney            59  69  46  72  41 /  80  30   0   0   0
Dallas              62  70  51  73  47 /  80  30   0   0   0
Terrell             63  70  47  74  44 /  50  30   0   0   0
Corsicana           66  71  49  73  46 /  50  30   0   0   0
Temple              66  71  50  74  46 /  40  30   0   0   0
Mineral Wells       58  67  44  72  41 /  80  20   0   0   0

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 3 AM to 10 AM CDT Sunday for TXZ091>093-
100>103-115>117-129.

&&

$$



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