665 
FXUS64 KFWD 020504
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
1204 AM CDT Thu May 2 2019


.AVIATION...
/06Z TAFs/

Challenges: Tracking line of TS with +SHRA currently across DFW
Metro airports southward through 12z Thursday. Cigs...chaotic with
the linear line of TS with patchy MVFR/IFR cigs possible,
especially the Waco Regional Airport area. 

We continue to track a line of TS with +SHRA along and just south
of I-20. Latest CAMs are currently struggling with propagation and
cold pools, so new TAFs will be challenging to say the least. For
now, will time current convective activity out of the DFW airports
in the 07z-08z time frame with lingering showers and N-NE flow
09-12 knots afterward. Flow will gradually back around to the east
or southeast AOB 10 knots as back outflow occurs. 

At Waco, will time in VCTS/CB wording in the 07z-08z time frame, 
as outflow driven, mainly elevated TS arrives into the area with 
occasionally +SHRA. Will have this activity moving out, or 
dissipating across Waco airport by 11z-12z Thursday. 

Some off/on MVFR cigs may rear their heads throughout the day on
Thursday, with redevelopment of TSRA/VCTS at Waco late afternoon
and evening, with just a VCSH wording at DFW airports. All
airports should see E-SE winds around 10 knots at that time. 
It must be stated this is a fairly low confidence forecast beyond
12z Thursday, as daytime heating and uncertainties exist regarding
subtle old outflow boundaries and the next approaching shortwave
late Thursday will dictate convective development and timing.  

05/

&&


.UPDATE... /Issued 1048 PM CDT Wed May 1 2019/
Line of strong storms with heavy rainfall continues to slowly cold
pool it's way southward into the I-20 corridor. As such, counties
north of the main line of storms in Severe Tstorm Watch 118 are no
longer in a threat for severe storms and have been canceled. That
said, localized flooding or flash flooding remains in play so
these areas should not let their guard down. Updates to the watch
and zone forecasts have been issued. 

05/

&&

.UPDATE... /Issued 954 PM CDT Wed May 1 2019/
Though an isolated severe risk for hail may remain across Severe
Tstorm Watch 117, it appears it's evolving more into a linear,
training, heavy rain situation as the nocturnal low level jet
feeds into this line of storms across the watch area.

As such, we'll be allowing Severe Tstorm Watch 117 for our NW
counties to expire at 10 pm CDT. That said, the flash flood risk
may actually increase through/past midnight parts of the watch
area. 

05/

&&

.SHORT TERM... /Issued 313 PM CDT Wed May 1 2019/
/Tonight/

Thunderstorms have erupted across Northwest Texas and Southern
Oklahoma in the vicinity of a weak front and a remnant outflow 
boundary. These storms quickly became severe, which is not 
surprising given how unstable the atmosphere is this afternoon. 
Our 18Z sounding is good evidence of this instability with MUCAPE 
coming in at 4855 J/KG, and it is doubtful that the special 21Z 
sounding we have scheduled will be any different. Anyway, these 
storms are just now beginning to enter the northwest counties of 
the CWA, and this should be the primary area of convection to keep
and eye on as it gradually organizes into a quasi-linear mcs this
evening while progressing southeast across the forecast area. 

That said, isolated thunderstorms will still be possible farther
southeast east late afternoon and early this evening along the 
I-35 Corridor from Temple to Waco to the DFW Metroplex. Though 
isolated in nature, this convection may remain more discrete and 
would be capable of both large hail and damaging downburst wind 
gusts. 

Looking back to the northwest, storms are currently equally
capable of large hail and damaging winds. As time progresses, this
activity should evolve into mainly a damaging wind threat as it 
sags deeper into the forecast area this evening and overnight.

Recent convection allowing model guidance has trended slower with
the overall southward progression of this evening's thunderstorms.
This reinforces the idea that training thunderstorms with heavy 
rain will keep the potential for localized flash flooding going, 
initially from between the Red River and I-20 now through 
midnight, then south of I-20 and east of I-35 during the overnight
into Thursday morning hours. The Flash Flood Watch will remain in
effect for roughly the northeastern half of the forecast area
where the more saturated soils exist. Adjustments to the watch
area could be made in later forecasts depending on where the
heaviest rains occur tonight. Otherwise, low temperatures will 
range from the lower 60s along the Red River to the lower 70s 
across the southern-most counties.

30

&&

.LONG TERM... /Issued 313 PM CDT Wed May 1 2019/
/Thursday through Wednesday/
In the wake of the expected overnight convective complex, odds 
are that the atmosphere will be fairly worked over as a cold front
moves into the region from the northwest. However if the complex 
of storms does not materialize as expected, or instead of moving 
southward into southeast Texas - it heads more east and return 
flow can organize quickly by sunrise, then it's more likely that a
line of showers and storms will develop along the front. Again, 
at this time the odds are that the front should be mostly devoid 
of deep convection in the morning hours due to tonight's activity, 
but it's still possible so PoPs will be set at 40% over the area 
in the morning. This frontal boundary should slow down and stall 
across the heart of the area by the afternoon hours. 

As we head farther out in time, the CAM solutions continue to 
diverge, with some showing vigorous convection along the front in
the afternoon and some guidance keeping things fairly tame 
through sunset. While a moist, unstable, and uncapped airmass will
be in place, the response to the waves of upper level forcing 
rippling through in southwesterly flow aloft will dictate the 
extent of convective activity. The global models
(GFS/ECMWF/Canadian) are in good agreement that a shortwave 
trough will be moving through the region in the morning hours, 
leaving much of the region in subsidence during the afternoon 
hours. Despite the subsidence, the mid and low level flow will 
weaken and therefore we'll see convective initiation following a
more summer-time mode where localized forcing and high buoyancy 
will lead to isolated to scattered storm activity.

By the late afternoon and especially the evening hours, another
strong shortwave will move toward the CWA from the west and 
southwest and organized forcing for ascent will spread across the 
region. It's likely that this shortwave will result in convective 
activity to our west and southwest that will move into the region 
after sunset. The best instability will be south of the front, and
therefore the greatest severe threat will be generally south of 
I-20. The main threat will be damaging winds and large hail with 
the tornado threat being very low due to considerably weaker low 
level flow. This evening convection may evolve into a larger 
complex of storms which could bring the area another round of 
widespread rainfall into Friday. This rain would be heavy in
spots, and could lead to flash flooding and river flooding. The
flash flood watch will remain as is for now, but may be expanded
southward for this round Thursday night and Friday at a later
time. The significant convective overturning should produce a 
large cold pool and push the effective front farther south into
South Central and Southeast Texas Friday. Total additional average 
rainfall Thursday and Friday should average 1-3 inches. 

While a lot of the guidance is still wet for Saturday, the general
thinking is that the front will be farther south than the models
forecast and it's possible we'll salvage the day for outdoor 
activities. Will undercut the guidance PoPs on Saturday and show 
high temperatures a little below normal and in the upper 70s with 
some sunshine and north winds. 

By Saturday evening westerly to northwesterly flow aloft will be
in place over the region. We'll have to keep an eye on convective
potential in the Panhandle as it could form into a complex and
make a run at the CWA by early Sunday morning. The airmass over
North Texas will be more stable, so this activity should weaken,
but will keep some slight chance PoPs in the forecast to the 
west early Sunday. Otherwise Sunday should be a nice day for most
with highs in the lower 80s. Lows Saturday night and Sunday night
should drop into the mid 50s and lower 60s.

The southwesterly flow aloft will return by Monday and Tuesday and
as such the moisture/instability will increase. Subtle
disturbances will likely ripple through early next week so some
chance PoPs will return to the forecast. Otherwise the guidance 
is indicating a stronger trough by midweek that will probably 
bring a more organized threat of heavy rain and severe weather. 
Temperatures will remain warm and muggy Wednesday of next week
with lows near 70 and highs in the mid 80s.

TR.92

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    64  81  64  75  62 / 100  40  60  70  40 
Waco                70  83  64  76  62 /  60  40  60  70  50 
Paris               61  77  63  73  60 / 100  40  70  70  50 
Denton              63  79  63  75  60 / 100  40  70  70  40 
McKinney            63  78  62  74  61 / 100  40  70  70  40 
Dallas              66  82  66  75  62 / 100  40  60  70  40 
Terrell             64  82  66  76  61 / 100  40  60  70  50 
Corsicana           69  82  66  75  61 /  60  50  60  60  60 
Temple              71  83  65  77  62 /  60  40  50  70  50 
Mineral Wells       61  80  62  75  58 / 100  50  70  60  30 

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Thursday evening for TXZ091>095-
101>107-116>123-133>135-146.

&&

$$

05