766 
FXUS64 KFWD 300435
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
1135 PM CDT Tue Aug 29 2017


.AVIATION...
No changes from previous TAFs with VFR conditions and northeast
winds of 10-20 kts expected through the period. Any lingering 
showers from Tropical Storm Harvey are expected to remain east of
the TAF sites through Wednesday.

-Stalley

&&


.UPDATE... /Issued 859 PM CDT Tue Aug 29 2017/
Nudged PoPs for tonight and Wednesday downward just a little bit,
particularly along the I-35 corridor and the set of counties 
immediately to the east. Latest guidance takes Harvey's center a 
bit farther eastward, and the western edge of the precip shield 
should accordingly lie farther east, closer to the TX/LA border. 
Kept the fairly high pops in place from Van Zandt County southward
to Leon County for Wednesday, but the overnight shift will need 
to consider adjusting these downward if 00z/06z guidance continues
to downplay significant daytime precipitation on the west side of
Harvey. Otherwise, current forecast is on track.

Bradshaw


&&

.SHORT TERM... /Issued 325 PM CDT Tue Aug 29 2017/
(Through Thursday Night)
T.S. Harvey continues to slowly churn 
across the Upper TX Coast early this afternoon. Unfortunately, 
this tropical system continues to be efficient at generating 
copious amounts of rain across the Gulf Coast and looks to do so 
for at least the next 12 to 24 hours. Closer to home---most of 
North and Central TX remains to the northwest well within dry mid 
and low level flow per experimental GOES-16 WV data. The exception
to this is across far eastern and southeastern zones where the 
influence from Harvey will remain over the next couple of forecast
periods. 

For tonight---Afternoon cumulus should subside with the loss of 
daytime heating. Consistent with nocturnal T.S. behavior, I expect
that the precipitation shield will contract leaving a majority of
Central TX dry. I will keep a small sliver of slight chance to 
chance PoPs down across the southeast with just a mention of 
isolated thunder for the overnight time period. Otherwise, it will
be a very pleasant night by late August standards across the 
remainder of North and Central TX with overnight lows dipping into
the 60s and low 70s. There's a low potential that some areas to 
the northwest could dip into the mid to upper 50s. Given that 
925mb flow will remain brisk, AOA 15 knots, I've sided with a 
slightly warmer forecast. 

For Wednesday---T.S. Harvey will become enveloped and eventually
will coalesce with the main upper trough to the east through the
day on Wednesday and Thursday. As it lifts northward, some model 
guidance suggest a very slight jaunt back towards the west 
northwest on Harvey's trek northward. This would mean a large 
swath of precipitation overspreading North and Central TX would be
in play. While possible---I do not believe that this is the most 
probable solution and I've trimmed PoPs downward with just a small
sliver of likely PoPs out across far eastern and southeastern 
zones with slight chance to chance PoPs elsewhere east of I-35. 
While PWAT values across far eastern zones are expected to remain 
near the 2" mark---the potential for widespread, deep moist 
convection here appears low. Given the lower rainfall rates, I 
suspect that the flash flood risk will be low on Wednesday. We 
will continue to advertise a low end minor flood threat, however, 
and monitor radar trends. In addition, thunderstorms that develop 
farther west closer towards the I-35 corridor within the slightly 
drier mid-level air may pose a gusty to strong wind potential, 
especially in the more robust convection. Widespread severe 
weather is not anticipated at this time on Wednesday afternoon. In
general, conditions should be comfortable with temperatures in 
the 80s. If precipitation is more widespread than currently 
forecast, it's possible that forecast highs will be lower than 
currently advertised, especially across eastern zones. Convection 
should diminish quickly after sundown with some lingering 
precipitation out across far eastern zones associated with Harvey.


For Thursday---I've kept just a low chance for showers and
isolated storms across the east on Thursday as there remains some
low level moisture in place. Large scale organized lift appears 
to be lacking, however. Regardless, the late August sun in 
conjunction with remnant moisture should be efficient at 
generating some isolated to scattered convection across eastern 
zones. Again---with large scale lift being scant, I'll only 
advertise 30 to 40 PoPs. Brief bouts of heavy rain and gusty winds
will be possible with the strongest convection. Rain chances and 
the last direct impacts of T.S. Harvey should finally depart the 
region by Thursday evening. 


24-Bain

&&

.LONG TERM... /Issued 325 PM CDT Tue Aug 29 2017/
(Thursday Night through Tuesday) 
The region will continue to see northerly flow prevail in the low
levels through Saturday as Harvey finally exits stage right and a
weak surface high builds into the area. Winds will be light 
during the overnight hours; the clear skies and low dewpoints 
will allow temps to drop below normal. Lows Thursday night and 
Friday night should range from near 70 in the DFW urban heat 
island to the lower 60s in some outlying rural locations. Due to 
the persistent multi-day northerly flow, low level thickness 
values will be unseasonably low and keep high temps only near 90 
despite mostly sunny skies. 

Over the weekend an upper level low will develop over Texas 
(essentially to fill the gap left by Harvey) between 2 strong 
subtropical highs. This upper level low will not have much 
moisture to work with in order to generate convection, but it will
help to turn winds back to a more easterly direction and 
gradually draw some Gulf moisture into the area. This moistening 
process will be slow and will keep just a slight chance of showers
and storms mentioned in the afternoon hours Sunday through 
Tuesday over mainly the southern half of the area. Low 
temperatures will continue to creep upward each night as humidity 
increases, but highs will remain a few degrees below normal.

By early next week, a few of the models remain consistent in 
developing another tropical low in the western Gulf of Mexico. 
Obviously confidence this far out is not high with this feature. 
However, since models are all in pretty good agreement in the main
upper level features, we can say with somewhat higher confidence 
that even if something were to develop it will likely remain 
southeast/east of our CWA as steering flow would favor a north and
northeastward motion. In any case, even if northerly surface flow
doesn't develop as a result of this low, models do indicate a 
true cold front by the middle of next week as a large trough drops
into the midwest bringing cooler/drier air into the region then. 
We'll watch all of these features in the extended with interest.

TR.92

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    71  88  71  90  71 /   5  10   5   5   5 
Waco                70  86  69  89  68 /  10  10   5   5   5 
Paris               70  85  71  84  68 /  10  30  30  10  10 
Denton              67  88  67  88  66 /   5  10   5   5   5 
McKinney            68  87  69  86  65 /  10  20   5   5   5 
Dallas              73  88  71  89  73 /  10  10   5   5   5 
Terrell             71  86  70  86  67 /  10  30  20  10  10 
Corsicana           72  86  70  89  69 /  10  30  30  20  10 
Temple              70  85  69  88  66 /  10  10   5   5   5 
Mineral Wells       63  88  65  88  64 /   5   5   5   5   5 

&&

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

$$

26/66