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

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542
FXUS64 KFWD 161203 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
703 AM CDT Wed Aug 16 2017


.AVIATION...
Weak ascent continues to the west of the D10 TRACON this morning.
While a few spits of rain will remain possible this morning, it
appears most of this activity will remain to the west of the
Metroplex. The veering low-level flow appears to be guiding the
bulk of the MVFR stratus just east of Metroplex, but a few hours
of lower cigs appear possible, mainly at DFW, GKY, and DAL before
mixing drives any bases above FL030. A similar scenario will play
out at Waco, where we`ll show MVFR cigs in a TEMPO group through
16z. Breezy south winds will prevail today, with occasional gusts
to around 20 kts.

A cold front will move into Oklahoma tonight, and should become a
focus for shower and thunderstorm development. A loosely organized
complex will then drift south towards the Red River. At this time,
it appears that rapidly veering and weakening low-level flow will
considerably limit renewed thunderstorm development along surging
outflow, and an overall weakening trend is anticipated before
activity reaches the Metroplex sites. As a result, have inserted a
period of VCSH in the DFW extended after 17/13z. If it becomes
apparent that convective vigor will be maintained, a mention of
VCTS may be warranted in later TAF issuances.

Carlaw

&&


.SHORT TERM... /Issued 336 AM CDT Wed Aug 16 2017/
/Today and Tonight/

A respectable low-level jet of 35-45 kts per area VWPs is helping
to push a slug of rich Gulf moisture northward at this hour.
Modest isentropic upglide within this moist airmass is
facilitating the sustenance of showers across the Concho Valley,
and expect this activity will continue to head northward through
the morning hours as the best lift shifts across our western-most
counties. The relatively gentle nature of the upglide should help
limit the overall threat for thunder, and have included just
isolated thunder wording through the morning hours. With
plentiful mid and high-level cloud cover expected to hang tough
into the early afternoon hours, elected to cut high temperatures
by a few degrees, mainly across the northwestern quadrant of
counties.

Across the southeast, low clouds will scatter out more quickly,
allowing temperatures to rise into the mid and upper 90s, and heat
index values of 105-108 degrees appear possible roughly south and
east of a Temple to Kaufman to Emory line today. That said, after
coordination with surrounding offices, we have elected to forgo a
Heat Advisory today for a few reasons: (1) some uncertainty
regarding how strongly dewpoints mix out later today with
indications that guidance remains just a bit too moist and (2)
the presence of a decent southerly breeze of around 15 mph, which
should help take some of the edge off the otherwise oppressive
heat. Either way, the rest of the week will be hot, and
individuals should ensure they practice proper heat safety into
the weekend.

Our attention overnight will turn to our north, as a cold front
begins to sag into Oklahoma. During this time, the front will be
losing much of its upper level support as the associated shortwave
begins to pivot northeastward into the Upper Midwest. As a result,
the front`s forward progress should slow during this timeframe.
Convergence along the front, while not incredibly strong, should
be sufficient to initiate at least a broken line of convection
across Oklahoma within a moist airmass characterized by dewpoints
in the lower to middle 70s.

The 16/00z NSSL WRF seems to be keying in on the potential for a
surging cold pool with this activity, and aggressively delivers an
outflow to our Red River counties as early as midnight tonight.
While this solution appears somewhat plausible given relatively
drier air above 700 mb and some DCAPE overnight, am not sure it`s
the most likely scenario given what appears to be rapidly veering
and weakening flow in the 925-850 mb layer overnight. The
implications here are that storm-relative convergence will
gradually diminish as thunderstorm activity approaches the state
line late tonight, and subsequent storm coverage should wane as
well. That said, there`s enough of a signal from guidance to
include 30-40% PoPs roughly along and north of I-20 late tonight.
We do not anticipate severe weather at this time given fairly weak
mid-tropospheric flow, which should limit storm organization, but
gusty winds and locally heavy rainfall will certainly be possible
as PWATs head above 2 inches. We`ll need to keep an eye on our
vulnerable northeastern counties, which are still soggy from this
weekend`s deluge, but the heaviest activity looks to remain
localized enough to temper the overall flood threat.

Carlaw

&&

.LONG TERM... /Issued 336 AM CDT Wed Aug 16 2017/
/Thursday through Wednesday/

Starting Thursday morning after daybreak, a complex of storms may
be weakening across parts of North Texas. Guidance is split on how
fast and how far south this complex moves overnight tonight, but
will keep 30-40 PoPs across our northern two rows of counties in
the morning hours. There is some agreement among hi-res guidance
that this complex may leave a boundary in the region that aids in
afternoon convection. However, where this boundary will be located
remains to be seen and will maintain a broad area of 20% in the
afternoon hours covering all but the far southern counties of
Central Texas.

The upper level ridge will be retrograding into the area on
Thursday and temperatures are expected to start climbing through
the end of the week. Despite some better mixing of dewpoints,
especially across most areas outside of our northeast counties,
heat index values will also be climbing into the 105-109 degree
range along and east of Interstate 35. If the models are overdoing
dewpoints, heat index values may not be as extreme, and we will
continue to monitor for the need for a Heat Advisory some time
later this week into the weekend.

With the upper level ridge expected to remain over the region
through at least the weekend, the only thing that will bring
relief is rain. We will maintain low chances for rain Thursday
night and Friday as another complex of storms may graze our
northern counties. In addition, warm air advection aided by a
30-40 kt low level jet may result in a few showers during the
overnight and morning hours; similar to what we have seen the past
few nights. Again on Friday night/Saturday morning, we may be
monitoring another complex of storms to our north, attempting to
move south, but the influence of the ridge over the region may be
too strong by then. After some low rain chances in the east on
Saturday, rain chances are minimal through Wednesday. However, the
GFS and ECMWF agree on an upper level disturbance/inverted trough
moving west through the Gulf of Mexico that would reach the Texas
Coast by the middle of the week. This may result in at least
isolated convection by Tuesday or Wednesday in our southeastern
counties. This disturbance would nudge the ridge to the west a
little and may allow a front to try and enter the region in the
latter part of next week.

JLDunn

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    94  79  97  79  98 /  30  40  20  20  20
Waco                98  79  99  77  99 /  10  10  20  20  20
Paris               91  75  92  75  93 /  20  40  40  20  30
Denton              93  77  95  76  97 /  30  40  30  20  20
McKinney            93  77  94  76  97 /  30  40  40  20  20
Dallas              94  79  97  80  98 /  30  30  20  20  20
Terrell             94  77  95  76  97 /  20  20  20  20  20
Corsicana           95  78  97  77  98 /  10  10  20  20  20
Temple              97  78  99  76 100 /  10  10  10  20  20
Mineral Wells       93  75  95  74  97 /  40  30  20  20  20

&&

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

$$

90/82



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