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

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FXUS64 KFWD 151727 AAC
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1227 PM CDT Tue Aug 15 2017


.AVIATION...
/18Z TAFs/

Challenges the next 24-30 hours will continue to be convective
chances off just to the north and west of the DFW Metro airports
and potential for MVFR cig restrictions at all airports early
Tuesday morning.

A weakening cluster of showers and isolated thunderstorm will move
northeast this afternoon and should remain northwest of all Metro
airports. Feel the isolated coverage of showers possible across
DFW are not enough to keep VCSH going in the Metro TAFs.

Another nocturnal West TX cluster of convection this evening will
approach areas northwest of DFW once again late tonight/early
Tuesday morning. A strong southerly LLJ 30-40 knots will help
surge MVFR cigs mostly above FL 020 across all airports by
sunrise. Will also advertise VCSH at DFW Metro airports between
11z-15z.

Otherwise, no convection is expected at Waco throughout the next
24 hours, as the upper ridge keeps the area capped. All airports
will see southerly winds 10-15 knots, with occasional higher gusts
to 20 knots possible.

05/

&&


.UPDATE... /Issued 1056 AM CDT Tue Aug 15 2017/
A weakening complex of showers and embedded tstorms continues to
move progressively northeast across West-Central Texas. This
activity will likely make into our far west/northwest counties and
affect areas mostly north through west of the immediate DFW Metroplex
through this afternoon. In addition, any signs of this morning`s
undular bore is not showing up on surface obs much anymore. However,
that doesn`t mean it`s effects aren`t still present just above
the surface with weak moisture convergence occurring along across
the northwest counties through this afternoon. We are not expecting
anything in the way of strong to severe storms with relatively
skinny CAPE rooted currently above 850mb and deep layer bulk shear
only on the order of 15-20 knots. There could be some localized
and brief heavier downpours with PWATs across this region between
1.75 to 2.00 inches. However, the progressive northeast movement
of individual, small convective rain cores should keep any one
location from seeing any high rainfall amounts.

Outside of raising the rain chances across the west and northwest
counties, moisture within the mid to upper levels should be
persistent enough across the northern CWA to limit insolation
somewhat. I went ahead and lowered highs a few degrees across
the north. Otherwise, south winds 10 to 15 mph will prevail, with
stronger gusts in excess of 20 mph at times where mixing is
stronger and there`s less interruption from remnant outflows from
convective activity.

05/

&&

.DISCUSSION... /Issued 337 AM CDT Tue Aug 15 2017/
Rain chances don`t completely leave the forecast this week with
most of the rain chances along and north of Interstate 20, but the
heat later in the week will make it feel more like the August we
are accustomed to.

A complex of storms in NW Texas continues to make steady progress
east and southeast with aid from a low level jet around 30 kts.
On its current track, this complex would likely move into our
western counties before daybreak. Some gusty winds and brief heavy
rain would be the main hazards. The low level jet will continue
to veer southwest and weaken after daybreak, and we expect the
complex will dissipate by mid morning. Ahead of the complex, some
weak showers and maybe an isolated thunderstorm may occur as
isentropic lift and warm air advection occur with the low level
jet. However, our chances for rain won`t completely be done for
the day for more than one reason. One, this complex may leave an
outflow boundary in the region that could be a focus for
additional showers and storms later today. Two, diurnally driven
convection may occur as a disturbance currently over the TX
Panhandle moves into the Central Plains. With the upper level
ridge centered to our southeast and ample moisture still in place
across the region, most model guidance indicates isolated activity
across the northern half of the region and will keep low PoPs in
that area this afternoon. Temperatures today are likely to remain
near normal values across most of the region (in the mid to upper
90s), but will remain slightly cooler in our northeast counties
that have been inundated with rain over the past few days.

This evening and tonight, our upper level flow pattern will shift
to southwest winds aloft as an upper level trough crosses the
Rockies. Disturbances embedded within this flow are expected to
aid in the development of an MCS across western portions of the
state. Overnight, this complex is projected to move northeast and
east, aided by a 30-40 kt low level jet, bringing rain to our
western counties before daybreak. Severe weather is not expected
but gusty winds and heavy rain will again be possible. Once again
this complex will likely dissipate over northwestern portions of
the CWA, but may bring rain to areas as far east as I-35/35W. Low
rain chances will remain across roughly the northern half of the
region during the day on Wednesday for very similar reasons as
today.

On Wednesday night, as the upper level trough moves across the
Plains, another complex of storms will likely form to our north
along a southward moving front. This front isn`t expected to move
into North Texas, but the complex may and have increased PoPs
north of Interstate 20. A moisture-laden low level jet of 30-40
kts will likely help move the MCS south, but the southern extent
of its track is still challenging and will likely be based on
mesoscale properties of the outflow. Best guess at this time is
this complex will be weakening as it moves into North Texas early
Thursday morning. Low rain chances continue Thursday, and then
another complex of storms may make a run at the region Thursday
night/Friday morning, from the northwest, as another disturbance
moves through the Plains.

Starting Thursday, the upper level ridge will build back west over
the region. Even with the continued rain chances this week, the
heat will make a significant return, and a Heat Advisory may be
needed for parts of the region for several days this week. A
handful of scattered locations may see heat index values of 105 to
106 today, but heat indices will increase starting Wednesday in
our southeast zones where southerly winds will continue to
transport moisture rich air. As the upper level ridge builds back
in and temperatures rise into the upper 90s and around 100
degrees, heat index values of 105 to 110 are possible over much of
the eastern half of the region. Across our western zones, better
afternoon dewpoint mixing is expected, and we will monitor each
day how far east the dewpoints will mix under the influence of the
ridge.

JLDunn

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    96  78  96  79  95 /  20  10  20  20  20
Waco                97  79  99  79  99 /  10  10  10  10  10
Paris               90  73  91  73  90 /  20  10  20  40  30
Denton              95  77  96  77  94 /  30  20  20  20  20
McKinney            94  77  94  77  93 /  20  10  20  20  30
Dallas              97  78  96  79  95 /  20  10  20  20  20
Terrell             95  78  95  77  95 /  20  10  20  10  20
Corsicana           96  78  97  78  97 /  20  10  10  10  10
Temple              98  77  99  78  99 /  10  10  10  10  10
Mineral Wells       95  76  95  76  95 /  30  20  20  20  20

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

05/91



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