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000
FXUS64 KFWD 170942
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
442 AM CDT Fri Aug 17 2018


.AVIATION UPDATE...

A quick 09Z TAF update was done to account for an earlier arrival
of morning showers, and late afternoon thunder potential.

Isolated thunderstorms nearing the Bowie corner post will drift
slowly south through the morning. Activity may arrive a bit
earlier than previously forecast, but current indications are
that it will weaken and affect areas west of DFW. Will keep VCSH
in the forecast from 15-18Z but remove the VCTS/CB for now.

Additional storms that form along the Red River late this
afternoon will also move south. Coverage will be higher, and
northern portions of DFW TRACON may begin to be impacted by late
afternoon. Recent guidance suggests that storms may push a little
farther south than earlier progs, so have added a VCTS for the
22-02Z timeframe.

The probability of direct impact to DFW remains fairly low, but we
will continue to monitor trends this morning and fine tune the
TAFs at the 12Z issuance as needed.

30

&&


.SHORT TERM... /Issued 412 AM CDT Fri Aug 17 2018/
/Today and Tonight/

The axis of a shortwave trough extends from the Great Lakes to
the Southern Plains and continues to generate convection north of
the region early this morning. This feature is weakening the
northeast flank of the upper ridge centered over West Texas,
which will leave the northern counties of North Texas vulnerable
to additional convective development this afternoon.

For this morning, isolated elevated thunderstorms still remain
possible along the Red River due to added lift from a 30 MPH low
level jet, but coverage should remain low and POPs limited to 20
percent. Better chances of development are expected this afternoon
and evening on either side of the Red River as stronger ascent
associated with the shortwave arrives during peak heating hours.
This warrants chance POPs along the Red River with slight chance
extending south to the I-20 corridor. Shear and instability will
be sufficient for some strong storms with gusty winds and
frequent lightning, with an outside chance of a damaging wind gust
or two. Storm motion will remain southerly, and any storm that
attempts to push south of the I-20 area will likely be diminished
by stronger subsidence and a strengthening capping inversion. Heat
indices will again approach 105 in a few locations along and east
of the I-35 corridor this afternoon, but convection and
associated loud cover should keep conditions just below advisory
criteria.

Another disturbance rolling out of the southern Rockies will
generate additional showers and thunderstorms to our northwest
tonight. Activity will weaken as it moves southeast, but
probabilities of storms lingering into the area are high enough to
keep slight chance POPs going into the overnight areas. Otherwise
warm and humid conditions can be expected with lows in the mid
and upper 70s.

30

&&

.LONG TERM... /Issued 412 AM CDT Fri Aug 17 2018/
The upper ridging that brought an end to our rain event earlier in
the week will continue retrograding into the Desert Southwest this
weekend. The northerly flow that will result will allow the
unsettled weather that has so far been confined to areas north of
the Red River to spill south into North Texas. The rain chances
Saturday will be primarily north of the I-20 corridor where
convective debris may shave a few degrees off afternoon
temperatures. However, across Central Texas, the summer heat will
continue unimpeded, and some locations may reach the century mark
on Saturday afternoon. In areas east of the I-35 corridor, where
dew points may still be in the upper 60s or lower 70s at peak
heating, the heat index could approach 105.

A nocturnal MCS may make a charge at North Texas early Sunday
morning, but the veered flow may keep the bulk of the activity
within Oklahoma. Regardless of its southern extent, if the
resulting outflow boundary is able to survive the day, it could be
the focus for renewed development Sunday afternoon. However,
intensifying lee troughing should enhance the southerly winds
across North and Central Texas, reducing the likelihood that the
boundary remains into the afternoon hours. The best forcing will
remain well to our north, associated with a deepening upper low
over the Central Plains, but strong surface heating and rich
boundary layer moisture could allow for a few strong storms late
Sunday afternoon.

The tail end of a potent shortwave will swing through North Texas
early Monday with an attendant cold front. The main event will
likely be focused from the Ark-La-Tex and points northeast, but
our radar scope may still be busy Sunday night into Monday
morning. With the departing trough, the front may lose its
southward push, particularly if the associated convection isn`t
particularly widespread. If the boundary stalls through Central
and East Texas, Monday afternoon/evening may be the main event for
those areas. Intensifying northerly flow aloft should finally
surge the boundary through all of Central and East Texas on
Tuesday. This is still August, and with abundant sunshine,
postfrontal temperatures will be in the 90s along and south of the
I-20 corridor. However, the reduction in humidity will make the
middle of next week noticeably more comfortable.

The rain-free period may end late next week, but with considerable
divergence among extended guidance, confidence is low in returning
rain chances. While there is the typical ensemble spread at day 7,
the GFS members overwhelmingly favor a Desert Southwest upper high
rather than the ECMWF`s more August-like Southern Plains ridging.
For now, will keep the end of the 7-day forecast dry, but with
this afternoon`s package, low PoPs may need to be introduced for
Friday next week.

25

&&

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

$$

30/25