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

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FXUS64 KFWD 260440

Area Forecast Discussion
National Weather Service Fort Worth TX
1140 PM CDT Tue Apr 25 2017

Breezy south winds will persist overnight with occasional gusts
to around 25 kts or so, and MVFR cigs will prevail at all sites. A
nocturnal bore feature can be seen entering the region on radar
imagery, and recent surface observations from KRPH indicate that a
northwest wind shift accompanies this feature. Should this
move across the Metroplex sites, any wind shift would be brief,
with a quick return to breezy southerly winds.

The main change from the 00Z TAFs was to introduce a mention of
VCTS at all Metroplex sites as it seems likely sufficient lifting
will occur to erode the lingering capping inversion as the main
cold front arrives. Waco looks to remain far enough removed from
the better forcing to preclude an explicit mention of thunder, but
have inserted a brief window of VCSH to account for southwestward
precip development. An abrupt northwest wind shift will accompany
the front, which should arrive between 13-14Z at western sites,
and 14-15Z across the eastern Metroplex sites and Waco.
Convective chances will quickly come to an end by 15-16Z as cooler
and drier air filters in. Cloud bases will then begin to rise,
eventually to VFR Wednesday afternoon.

Winds will then slacken as high pressure builds in overhead, and
airports will likely be able to return to south flow late
Wednesday evening. As winds go nearly calm, there is some
potential for a shallow layer of fog to materialize, but this
potential is too low to include in the TAFs at this time.



Wind speeds have decreased to 15 to 20 mph this evening, thus the
Wind Advisory that was in effect along and east of the I-35
corridor until midnight has been cancelled.



.PREV DISCUSSION... /ISSUED 343 PM CDT Tue Apr 25 2017/
A warm and breezy day is in progress, but a few changes are on
the way in the next 24 hours. A surface low continues to deepen
across western Oklahoma with strong southerly flow being the
result across much of Texas. A cold front is draped westward
through the TX Panhandle with temperatures in the 50s just north
of this boundary. In addition, a dryline is positioned roughly
from Altus, OK to Abilene, TX. An upper trough continues to dig
southward through NM which is causing additional surface
cyclogenesis through western TX. This trough will continue to make
southeastward progress through Wednesday, driving the cold front
through the forecast area Wednesday morning while delivering a
chance for thunderstorms.

Highs today have climbed into the 80s and 90s area-wide, but
widespread cirrus and lingering cumulus have acted to hold
temperatures a few degrees under previously forecast highs. The
dryline is slowly advecting eastward and will enter our western
counties by this evening. This boundary will not be convectively
active due to the strong cap and lack of supplemental forcing.
Moisture continues to increase as a southerly flow regime advects
ample Gulf moisture into North and Central TX. Surface winds will
remain strong through the evening hours until the surface low
approaches from the northwest; a Wind Advisory remains in effect
until midnight.

After midnight, widespread low stratus is expected to
develop across most of the area as the surge of Gulf moisture
continues. The cold front will begin initiating convection across
central OK as it sinks southward and some of this activity may
approach the Red River between midnight and 6am. Much stronger
upper forcing, including a potent PV anomaly, will near the
region between 6am and noon which will aid in the initiation of
convection along the front by lifting the formidable cap. At this
time, we`re monitoring a brief window for some strong to severe
storms mostly across areas east of I-35 from about 10am-2pm when
the lift will be capable of overcoming the cap immediately along
the front as it encounters the highest moisture content. At this
time, storms are expected to initiate near or just east of I-35
across North TX. The southward extent of convection a few hours
later remains uncertain, but a broken line of storms could stretch
as far south as Palestine by the time it exits our forecast area
to the east by mid afternoon. At this time, instability and shear
parameters imply a threat for storms to produce severe winds
and/or hail, especially if they remain discrete along the front.
The tornado threat is low, yet nonzero, but forecast hodographs
are not terribly supportive of a tornado threat. Behind the front,
a few wrap-around showers will be possible, mostly across areas
near the Red River.

As the cold front clears the area later Wednesday afternoon, much
cooler air will filer into the region causing high temperatures
to hold in the 60s and 70s for many locations, but our
southernmost counties may creep into the 80s before the front
arrives. A cool and tranquil Wednesday night will follow.
Southerly flow will quickly return Thursday along with warmer
temperatures as the front returns northward as a warm front.

Another powerful upper trough will begin deepening across the
western US on Friday. A new surface low will form across West TX
on Friday and a frontal zone will become stalled near the Red
River. A dryline will also develop and sharpen just west of the
forecast area. The warm sector ahead of the dryline will be quite
juicy, characterized by 70F dewpoints and temperatures in the 80s.
These conditions will yield considerable instability, especially
as a plume of steep lapse rates aloft is advected eastward above
the warm sector. This would normally result in a stout capping
inversion, but the cap on Friday is expected to be relatively weak
due to strong large-scale ascent (and therefore adiabatic cooling)
from the vigorous upper trough. As a result, there is the
potential for 2 areas of convection on Friday afternoon/evening:
one along the dryline across our western areas, and another near
the stalled front across North TX and into southern OK. Storm
development during this time will hinge on the degree of lift and
ability to overcome the cap. Given the instability and shear, any
storms that would be able to form during this time would likely
become strong or severe.

The thunderstorm threat will continue into Friday night and
through all of Saturday as the upper trough continues pushing east
and we remain situated within a very high-quality warm sector. A
cold front will slowly move through the area during this time and
numerous thunderstorms are expected across most of the forecast
area. While it`s much too early to delve into the mesoscale
details of the forecast, there will be a chance for strong or
severe storms as well as isolated flash flooding across most of
the forecast area throughout this time. The specific timing and
threat locations will continue to change throughout the coming
days as more information becomes available. Those with outdoor
activities on Friday evening through Saturday are strongly
encouraged to keep an eye on the forecast.

This potent system should be exiting the area by around midday
Sunday with cooler conditions following into early next week. A
couple days of quieter weather are expected to prevail through the
first half of next week before another storm system possibly
affects the region around the Wednesday/Thursday time frame.



Dallas-Ft. Worth    70  72  50  82  66 /  20  30   5   0   5
Waco                71  79  49  83  67 /  20  20   0   0   5
Paris               68  69  45  77  60 /  30  70  10   0  10
Denton              66  67  46  78  63 /  20  20  10   0   5
McKinney            68  71  46  77  63 /  20  50  10   0  10
Dallas              71  73  51  83  67 /  20  30  10   0   5
Terrell             70  71  46  80  63 /  20  50  10   0  10
Corsicana           70  77  48  82  66 /  20  40   0   0   5
Temple              70  83  50  84  67 /  20  10   0   0   5
Mineral Wells       64  68  45  85  63 /  10  10   0   0   5




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