FXUS64 KFWD 141723

Area Forecast Discussion
National Weather Service Fort Worth TX
1223 PM CDT Tue Aug 14 2018

Regional radar imagery shows the bulk of the precipitation lifting
to the northeast at this time. Stronger isentropic ascent
associated with the slow moving upper low over the Plains should
continue to spread northeast into the evening hours resulting in a
gradual decrease in precipitation coverage through the afternoon.
Only changes to the forecast at this time are to narrow the
corridor of precipitation this afternoon and evening to areas
mainly north and east of the Metroplex and to lower high
temperatures a few degrees in areas where thick cloud cover is
likely to persist.



.AVIATION... /Issued 706 AM CDT Tue Aug 14 2018/
/12Z TAFs/

Enhanced by the nocturnal low-level jet beneath it, a narrow
corridor of mid-level lift has brought showers to the Metroplex
TAF sites early this morning. Despite the rain, the veered flow
beneath the cloud bases has been unable to effectively saturate
the deep sub-cloud layer, and VFR will prevail. There is a sharp
southern edge to the shower activity, beyond which the surface
layer has been able to radiate sufficiently for another MVFR
stratus intrusion. This deck has been tenuous but will dominate
at times through mid-morning at Waco. As the low-level jet weakens
later this morning, the shower activity should diminish, gradually
shifting to the northeast as the associated forcing aloft is
tugged away with a departing upper low in the Central Plains.
Aided by convective downdrafts, some of the momentum from the
stronger flow aloft may reach the surface, resulting in gusts
approaching or exceeding 20kts. Otherwise, wind speed/direction
will have minimal variation through the valid TAF periods. An
additional line could be added to remove VFR ceilings, but with no
other significant changes, this is operationally insignificant.



.SHORT TERM... /Issued 345 AM CDT Tue Aug 14 2018/
/Today and Tonight/

Satellite imagery shows the the upper low responsible for the
past several days of rain currently lifting northeast across
Kansas. A zone of upper diffluence in advance of the system
continues to generate a persistent area of showers and
thunderstorms from the Red River region northeastward through
eastern Oklahoma and Arkansas. Showers and isolated thunderstorms
were confined to the Red River counties during the overnight
hours, but we are already seeing an increase in activity farther
south as we move through the early morning hours due to enhanced
ascent associated with a 35KT low level jet. Likely POPs will
remain along the Red River this morning with chance POPs extending
south to the I-20 corridor. Coverage should be lower than the
past several mornings due to more veered low level flow and the
fact that the strongest lift has shifted northeast.

A few spots will probably deal with nuisance street flooding from
the DFW Metroplex northward. The Red River counties will have the
highest potential for receiving locally heavy rainfall and will
be monitored for localized flash flooding potential. Precipitation
will end from southwest to northeast this afternoon, with the
exception of the immediate Red River counties where redevelopment
will be possible during the peak heating hours. The potential for
redevelopment farther south this afternoon appears unlikely as the
upper level low continues to shift north and east, along with the
lift associated with the system.

The temperature forecast will once again have a north-south
gradient with highs in the 80s across the north and 90s across the
south. A few showers will be possible overnight across the far
north, but most areas that have been experiencing overnight rains
will finally receive a break as forcing for ascent shifts north
and east of the area.



.LONG TERM... /Issued 345 AM CDT Tue Aug 14 2018/
/Wednesday through Early Next Week/

The upper low will transition into an open shortwave and move
eastward across the Mississippi Valley Wednesday and Thursday.
This will allow a ridge to spread in from the west and deliver
subsidence and a return to typical Summer weather for mid to late
week. High temperatures in the mid and upper 90s coupled with
dewpoints in the lower 70s will yield heat indices in the 102-105
range for areas along and east of the Interstate 35 corridor from
Wednesday through the weekend. There will be some low-end
opportunities for storms across the far northeast counties during
this period, where northwest flow may allow a few thunderstorm
complexes to skirt the area.

Better chances for precipitation will return early next week as
an unseasonably strong upper trough swings east across the Plains
and sends a cold front southward into the area. Pops have been
increased for the late Monday-Tuesday timeframe, but still remain
below guidance because of model uncertainty this far in advance.

Both the GFS and ECMWF have consistently indicated the development
of the upper trough and the arrival of the front, but have shown
run to run changes regarding the timing and strength of both. A
weaker system would only bring a slight chance of rain, while a
stronger one would bring better chances and a break from the heat,
so it will be something to watch as we move through the week.



Dallas-Ft. Worth 89 76 94 78 97 / 70 10 5 10 5
Waco 96 76 95 76 97 / 10 10 5 5 5
Paris 86 74 93 74 95 / 80 20 20 20 20
Denton 88 75 94 77 97 / 80 10 10 20 10
McKinney 88 75 94 76 97 / 70 10 10 20 10
Dallas 89 77 95 79 97 / 60 10 5 10 5
Terrell 89 76 93 77 95 / 30 10 5 10 5
Corsicana 94 76 94 76 96 / 10 10 5 10 5
Temple 97 75 95 75 97 / 10 10 5 5 5
Mineral Wells 85 73 95 74 96 / 70 10 5 10 5



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