000 
fxus64 kfwd 171152 
afdfwd 


Area forecast discussion 
National Weather Service Fort Worth Texas 
652 am CDT Fri Aug 17 2018 




Aviation... 
elevated storms in the vicinity of the Bowie / ukw cornerpost 
will continue to drift slowly south over the next several hours. 
Activity may become close to the northwestern fringes of the 25nm 
dfw range ring before the low level jet abates and storms 
dissipate. Since it still appears that convection intense enough 
to produce lightning will remain just beyond the 25nm threshold, 
will forego the mention of thunder for this morning but continue 
to indicate vcsh for the 15-18z time frame. 


Additional thunderstorms are expected later this afternoon along 
the Red River where a lingering surface boundary will provide 
focus for development. The southward movement of this activity 
may bring some storms within the vicinity of the dfw area taf 
range rings this evening, and will therefore include thunderstorms in the vicinity for the 
00-04z time. It's possible that this evening's activity will also 
diminish before arriving, but the current feeling is that overall 
coverage will be better, and outflow will have a better southward 
push, which increases the probability of a few storms invading 
the metroplex area. All activity is expected to remain north of 
the kact area for the duration of this taf cycle. 


Otherwise, VFR conditions and south to southwest winds around 10 
knots are expected at all locations. 


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 miles per hour 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 mesoscale convective system 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 


&& 


Preliminary point temps/pops... 
Dallas-ft. Worth 97 78 97 78 95 / 20 20 10 20 20 
Waco 99 76 100 78 99 / 5 5 5 5 5 
Paris 94 73 94 75 91 / 30 40 30 50 40 
Denton 97 76 96 77 95 / 20 20 20 20 20 
McKinney 97 76 96 77 94 / 20 20 20 20 20 
Dallas 98 79 98 80 95 / 20 20 10 20 20 
Terrell 96 76 97 77 95 / 20 20 10 20 20 
Corsicana 97 77 99 77 97 / 10 10 5 10 10 
Temple 99 75 99 76 98 / 5 5 5 5 5 
Mineral Wells 97 74 97 75 97 / 20 10 10 10 10 


&& 


Forward watches/warnings/advisories... 
none. 



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