Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX

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FXUS64 KFWD 212324 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
624 PM CDT Fri Apr 21 2017

.AVIATION...
Main aviation concerns this evening revolve squarely around
likely convective impacts at the Metroplex terminals, with a bit
more uncertainty at Waco. In addition, a second wave of convection
appears possible after the initial front clears the Metroplex
sites.

Late afternoon satellite and radar imagery reveals a cold front
which presently stretches from near a KBKD-KRPH-K0F2 line. This
front is beginning to make gradual eastward progress, and
convection is attempting to initiate along this boundary. Based
on an earlier 20Z sounding, a stout capping inversion was in
place overhead, but our presently ascending 00Z sounding reveals
this cap is clearly in the process of being lifted and cooled.
Given the current location of the front and the weakening cap,
pushed the TEMPO TSRA mention at Metroplex sites (02-05Z at GKY).
In addition, opted to prevail a mention of VCTS through 22/06Z
given indications that steep lapse rates and ascent will linger
well behind the front. Should additional storms materialize after
the main line (an associated north wind shift), we will need
another TSRA group in subsequent TAFs. Finally, there are hints
that a third round of elevated convection may even materialize
late tonight and towards daybreak on Saturday as another wave of
ascent approaches. Confidence in this scenario, however, is
extremely low and have forgone an additional mention of thunder at
this time.

At Waco, pushed back the initial VCTS mention just a bit to
account for current trends. Thunderstorm morphology is a bit less
clear here, which precludes a TSRA mention at this time. We will
monitor southward development along the front, and amend as
necessary, however.

At all TAF sites, MVFR cigs should invade behind the cold front as
the inversion saturates. Gusty north winds will persist through
the day Saturday.

Carlaw

&&


.PREV DISCUSSION... /ISSUED 355 PM CDT Fri Apr 21 2017/
This afternoon through tonight, we continue to await convective
initiation in the area, but new data suggests the initiation may
be later than previously thought. Data from the FWD 20Z sounding
is arriving now, and it indicates a strong cap remains in place
around the 770 mb level. Water vapor satellite also shows a
stronger EML moving into our western counties. Based on this data,
we still think storms will develop along the front, but
initiation may be a few hours later than we previously thought
when better upper level support crosses the Plains. The best upper
level support will still be north of our area and the Red River,
but forcing along the front, combined with WAA, should be enough
for storms to develop. Any storms that develop this afternoon may
be severe.

Based on the current location of the front, storms may not occur
in our far western or northwestern counties. It still appears the
best rain and storm chances will be generally along and north of
Interstate 20 and east of Highway 281 this evening, with a shift
east and southeast overnight. As the storms progress farther south
into Central Texas, a weakening of the convection and severe
threat is expected as the instability weakens overnight and the
line of storms becomes farther removed from the upper level
support. Any left over rain is expected to end early Saturday
morning, but will retain lower chances for rain Saturday morning
across much of the region until the 850 mb front moves through the
region.

For continued updates on convective trends this evening and
tonight, watch for short-term mesoscale updates, graphicasts,
social media posts and more from the office.

Cool and breezy weather is expected on Saturday in the wake of
the cold front. Lows on Sunday morning will be the coolest we
have had in about 2 weeks with temperatures in the 40s. Dry
weather will occur Sunday through the early part of next week,
despite the progressive zonal weather pattern through the Plains.
Moisture will be scoured out in the wake of tonight`s front and
won`t return until Tuesday. A weaker front will move into part of
the region on Wednesday but quickly return north Wednesday night
in advance of the next strong upper level trough affecting the
region. There are discrepancies between the models on the depth,
evolution and timing of this late week system, and will keep low
rain chances in the forecast starting Thursday. It still looks
like there could be a severe weather threat with this system.

JLDunn

&&



.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    54  68  48  72  50 /  80  20   0   0   0
Waco                57  68  46  72  47 /  60  30   0   0   0
Paris               54  64  45  70  46 /  80  20   0   0   0
Denton              52  67  43  72  48 /  70  10   0   0   0
McKinney            52  65  45  71  48 /  80  20   0   0   0
Dallas              55  69  49  73  51 /  80  20   0   0   0
Terrell             54  67  46  72  48 /  80  20   5   0   0
Corsicana           56  67  47  72  47 /  60  30   5   0   0
Temple              58  67  47  73  48 /  50  30   0   0   0
Mineral Wells       50  67  44  73  47 /  60  20   0   0   0

&&

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

$$


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