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000
FXUS64 KFWD 171204 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
704 AM CDT Thu Aug 17 2017


.AVIATION...
Earlier showers and and thunderstorms continue to gradually pull
away from the Metroplex sites this morning. The eastern Metroplex
terminals will have to contend with thunder potential for another
hour or so as a few last cells develop behind the southward
sinking outflow, but gradually improving conditions are in store
this morning as VFR conditions return. Northeast winds will become
easterly and then south/southwesterly by mid-morning as the
synoptic flow returns. The outflow boundary from this morning`s
storms should lay up just south of I-20, and could become a focus
for a renewed bout of thunderstorms this afternoon with additional
heating in a moist and unstable airmass. As a result, opted to add
in a period of VCTS at all the Metroplex sites from 21-00z this
afternoon. Gusty downburst winds will be possible with any
afternoon activity.

At Waco, MVFR cigs appear to have been shunted mainly to the south
and east of the airfield, but a few wisps of low cigs may yet
graze Waco Regional before bases lift. VCSH will continue for a
few more hours as activity to the south and west moves
northeastward. High-resolution guidance also suggests that
thunderstorms which develop along the aforementioned outflow
boundary may drift southward an impact the Waco terminal late this
afternoon, and as a result, have also added in a VCTS mention from
23-01z. MVFR cigs tonight look to remain south and east of the TAF
sites.

Carlaw

&&


.DISCUSSION... /Issued 353 AM CDT Thu Aug 17 2017/
A complex of storms has successfully crossed the Red River this
morning and continues moving south and southeast along its well
defined outflow boundary. While new convection continues to
develop along the leading edge outflow, a broader swath of
moderate to brief heavy rain continues behind the outflow as a
30-40 kt low level jet provides lift over the boundary. This
system will continue to progress across North Texas this morning,
but will likely slow down and dissipate before midday as the low
level jet weakens and veers to the southwest. Ahead of the
complex, additional showers and storms are possible this morning
associated with warm air advection with the low level jet.

So far, winds of 20-30 mph have been occurring with the leading
edge outflow and storms. A few strong storms with winds near 40
mph may be possible this morning, and an isolated severe storm
cannot be completely ruled out, but overall, severe storms are
not expected. Gusty winds, lightning strikes, and brief heavy
rainfall will be the main hazards with the morning storms. Minor
flooding may occur, especially in counties near the Red River
where moderate to heavy rainfall falling on still saturated soils
may have trouble running off.

The remnants of the complex are expected to leave a diffuse
boundary across the region. Where exactly this boundary stalls is
yet to be determined, but much of the hi-res guidance appears to
suggest a location near the I-20 corridor, give or take about 40
miles to the south or north. New convection should develop along
this boundary this afternoon and will keep fairly high PoPs across
the middle part of the CWA as a result. Forecast soundings
indicate an uncapped environment this afternoon characterized by
modest instability around 2000 J/kg but with weak lapse rates and
low deep layer shear near 10 kts. This type of environment
usually signifies pulse-type convection very common in the summer
where the main threats will be lightning, downbursts, and brief
downpours due to a slow movement.

Rain chances today are lowest across our far southern counties,
and it is these counties that have the highest threat for
dangerous heat conditions. A Heat Advisory has been issued along
and south of a line from Killeen to Palestine where heat indices
of 105 to 110 degrees are possible. Dewpoints will mix out later
this afternoon, but the highest heat index values are expected
between the hours of noon and 4 pm, before maximum mixing occurs.
With likely a stalled outflow boundary to the north of these
counties, light wind and pooling of moisture may occur, resulting
in the dangerous heat indices. There are 2 caveats: 1) cloud
cover may hang around longer than expected and 2) the boundary
could push farther south than expected with rain this afternoon
near or in the Advisory area. However, based on the latest
expected trends and calculations, did not want to delay
advertising the potential for high heat index values in that area
of Central and East Texas.

The upper level ridge will continue to build into the region over
the weekend and temperatures will climb a little more as a result.
Isolated to scattered afternoon convection is possible across
mainly the northern half of the region on Friday, and then drier
conditions are expected. We will have to monitor for MCS activity
the next few nights, and the latest guidance suggests another MCS
may graze our northern counties Friday night/Saturday morning. The
heat will increase over the weekend as heat index values rise to
near Advisory criteria across most of the area along and east of
Interstate 35. Some showers or storms may be possible in our
southern counties by the middle of the week as an upper level
disturbance retrogrades west across the Gulf of Mexico and into
South Texas.

JLDunn

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    96  78  99  78  98 /  60  20  30  10  10
Waco                99  78 100  77 100 /  40  20  20  10  10
Paris               90  75  94  74  94 /  50  20  30  20  20
Denton              96  76  96  76  97 /  60  20  30  10  10
McKinney            94  76  95  76  96 /  60  20  30  10  10
Dallas              96  79  99  79  98 /  60  20  30  10  10
Terrell             95  75  97  75  97 /  60  20  30  10  10
Corsicana           97  77  99  77  98 /  50  20  20  10  10
Temple             100  76 100  76  99 /  20  20  10  10  10
Mineral Wells       96  74  96  74  98 /  50  20  30  10  10

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon today to 6 PM CDT this evening for
TXZ147-148-158-160>162-174-175.

&&

$$

90/82