Forecast Discussion for Dallas/Ft. Worth, Texas

FXUS64 KFWD 181219 AAA

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
719 AM CDT Tue Jun 18 2019

/12 UTC TAF Cycle/

Concerns---Brief MVFR vsby at Waco this morning. Convective
chances through the entire TAF cycle.

A decaying complex of showers and storms will continue to dive
southeastward this morning. While the core of the more robust
convection is expected to miss most TAF sites, I cannot rule out a
rogue lightning strike in the the large rain shield as it nears
FTW...AFW and D/FW. As MVFR BR dissipates across Central
Texas...there will be a threat for TS INVOF Waco, but have opted
to leave mention out at this juncture as instability wanes near
the I-35 corridor and the current trajectory would take the
complex south and west of the airfield. Trends will be monitored.

VFR should persist after 1500 UTC today through the remainder of
the TAF with another round of storms expected near and just before
0600 UTC Wednesday. The complex should gradually decay, but not
before it produces a few lightning strikes at D/FW...FTW and AFW
where instability will be the greatest. For DAL and GKY, I have
included a mention of VCSH, but if instability is greater than
currently expected...a mention of VCTS will be warranted. There
may be another window for storms during the Wednesday morning push
as a complex dives southward out of Oklahoma. While confidence is
too low this far out in the forecast to explicitly mention TS in
the TAF, impacts to the Bowie and Bonham cornerposts as well as
north and east bound departures appear probable.



.SHORT TERM... /Issued 346 AM CDT Tue Jun 18 2019/
/Today and Tonight/

Several challenges exist in the short term forecast period...all
revolving around the storm potential. There will be a risk for
strong to possibly severe-caliber winds associated with this
potential this afternoon and tonight. Confidence in storms
occurring somewhere across North and Central Texas over the next
24-36 hours is high, but the exact locations where things will
unfold remains uncertain at this time.

Morning radar observations indicated an area of storms ongoing
across the northern Big Country. The eastern flank of this small
complex is expected to only graze areas near and west of the US
HWY 281 corridor where I have placed 50-60 PoPs. East of this
line, the airmass appears much more stable and void of any
meaningful instability and thus rain/storm chances decrease
drastically east of a Jacksboro to Stephenville to Lampasas line.
Severe weather is unlikely this morning, though some strong
thunderstorm winds are possible. Exactly how far east convective
outflows travel this morning will dictate 1) The potential for
re-development of convective cells this afternoon and 2) The
afternoon high temperatures. With regards to the potential for
afternoon re-development, this threat looks largely conditional
given the strong capping that will be in place and as such, I feel
that most areas will remain rain/storm free after noon. However,
mesoscale ascent may be sufficient to overcome the layer of warmer
air aloft and I`ve painted some slight chance PoPs west of a
Bowie to Stephenville to Goldthwaite line which should be INVOF
the outflow boundary. If this boundary is shunted eastward, PoPs
may need to be increased closer to the I-35 corridor. High
temperatures are lowest across the Big Country where mid/upper
level clouds, coupled with convective outflow should keep things a
little "cooler". Still, with the high sun angle, temperatures
even behind the outflow should still climb into the mid to upper
80s. Elsewhere, highs will climb into the low 90s.

Tonight, confidence wanes in the location of convection, but there
are two areas I`m focusing on for rain/storms. The ill-defined
upper air pattern (though slightly more northwesterly aloft)
coupled with uncertainty in afternoon/evening convective
initiation (CI) results in a tricky forecast for the first area
(mainly the Big Country), but some higher resolution guidance
seems to be on the right track with CI across the Big
Country...likely near convective outflows. For now, I`ll highlight
a 30-40 PoP across the west (particularly south of I-20 and west
of I-35). Deep layer shear is marginal, but instability may
support strong updrafts...which may pulse and decay rapidly
yielding a damaging wind risk. Activity may attempt to organize
along a congealed cold pool and move south/eastward. Instability
decreases markedly with eastern extent south of I-20 and thus a
weakening trend is probable as showers/storms move
east/southeastward. It is possible, however, that storms could
track a bit more east/southeast than currently advertised. If this
pans out, alterations to increase PoPs for more of the area will
be needed.

There is slightly greater model agreement that convection will
develop across Oklahoma and track southeastward toward North Texas.
Given modest 850mb flow, portions of this complex may attempt to
build back towards the south/southwest into North Texas...mainly
along and north of US HWY 380. I`ve nudged PoPs upward to near 50
percent here given that 850mb flow increases to near 30 knots.
Similar to the potential convection across the Big Country...there
could be a strong to severe wind threat across the area. In
addition, heavy rain may aggravate any flooding of creeks, rivers
and lakes with a low, but non-zero threat for flash flooding
especially for areas that receive multiple rounds of rainfall.



.LONG TERM... /Issued 346 AM CDT Tue Jun 18 2019/
/Wednesday through Monday/

Thunderstorms should be ongoing early Wednesday morning well to
the northeast of our area as a low amplitude shortwave moves
through the Central Plains. A trailing mid level wave will extend
all the way westward across the Texas Panhandle during the morning
hours. As thunderstorms to the northeast diminish in intensity
through the morning, it`s remnant outflow or a weak cold front
will slide south through eastern Oklahoma. By afternoon, we should
become strongly unstable across North Texas with temperatures in
the low to mid 90s with dewpoints in the low to mid 70s as the
boundary to the north pushes into our area. As the trailing
shortwave spreads across the Red River during the late afternoon,
thunderstorms should fire along the southward moving boundary. As
previously mentioned, we`ll be quite unstable by afternoon with
MUCAPE >4000 J/kg and non-trivial mid/upper level flow. Low level
winds will veer out of the southwest early in the day, but 35-40
kt flow at 500 mb and an 80-90 kt upper jet along the Red River
should provide sufficient support for at least some organized
clusters of thunderstorms. Damaging winds would certainly be a
threat Wednesday afternoon and evening, but some hail will also be
possible given the potential for sustained updrafts. PoPs will be
highest along the boundary which should extend from the Paris
area southwestward into the Metroplex by mid afternoon.
Thunderstorms should move east with time into the evening and
we`ll have the highest PoPs east of I-35 during that time.

The other concern on Wednesday and into Thursday will be the heat
and humidity, particularly south of I-20 into the Brazos River
Valley. Highs are expected to top out in the mid to upper 90s in
this area with afternoon dewpoints progged to be in the lower 70s.
This would yield heat indices as high as 107 degrees both
afternoons and may necessitate the issuance of a Heat Advisory.
We`ll assess this in a little more detail later today as concerns
over potential cloud cover from overnight convection and
thunderstorm chances on Wednesday could result in cooler
temperatures than currently forecast.

Thursday should be dry areawide, but it will be hot and muggy as
850 mb temps climb to +27C across our western counties. Moisture
will linger across the region through the upcoming weekend and
with an upper pattern that features continued troughing over the
western U.S., we`ll see periodic disturbances that are able to tap
into the available moisture resulting in continued rain/storm
chances. Thunderstorms may develop along a dryline across West
Texas on Friday evening and spread into our western counties. The
GFS is most aggressive with this scenario, but other guidance also
shows some potential. We`ll have generally low PoPs west of I-35.
Low storm chances will continue areawide on Saturday with better
chances arriving on Sunday as another decent shortwave moves
through the Plains. Most of the activity Friday and Saturday
should be diurnally driven and will be more typical of summertime
thunderstorms, while the storm chances on Sunday may have a little
better organization to them. There will be at least a low threat
for severe weather through the weekend.



Dallas-Ft. Worth    92  74  94  76  95 /  10  30  30  40   5
Waco                92  76  97  77  98 /  40  20  10  30   5
Paris               87  71  90  71  90 /  10  50  40  50  10
Denton              91  73  94  74  95 /  10  40  20  30   5
McKinney            91  74  94  74  94 /  10  40  40  40   5
Dallas              94  75  94  76  96 /  10  30  30  40   5
Terrell             90  74  95  75  94 /  10  30  40  50   5
Corsicana           90  73  93  75  94 /  10  20  20  40   5
Temple              91  74  97  77  97 /  40  20   5  20   5
Mineral Wells       90  72  95  72  97 /  40  40  10  20   5





NWS FWD Office Area Forecast Discussion