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Area forecast discussion
National Weather Service Fort Worth Texas
404 PM CDT Mon Sep 16 2019

Short term... /issued 145 PM CDT Mon Sep 16 2019/
/this afternoon through Tuesday evening/

Easterly low level flow will continue over the next
24 hours as north and central Texas remains wedged between
surface high pressure across the Ozarks and a tropical low now
moving towards the Texas coastal Bend. The tropical low will be
the primary factor in sensible weather across the area.

Clouds will continue to slowly bubble through the rest of the day
as the troposphere continues to slowly moisten. There could be a
few spits of rain beneath the afternoon clouds over the next
several hours, but this potential is too low and sparse to
include in the forecast. Afternoon cumulus will slowly diminish
toward sunset today, leaving mostly clear skies. The exception to
this may be across parts of central Texas were some mid-level
clouds associated with the outer fringes of the tropical low may
attempt to drift northward. Otherwise, it'll be a tranquil
overnight period with low temperatures dipping into the 70s with a
few of the cooler spots across the Big Country falling into the
upper 60s.

Towards daybreak Tuesday, low clouds will slowly creep northward
in the morning---initially across central Texas. These clouds will
then spread northward into North Texas and will keep temperatures
3 to 5 degrees lower than Monday afternoon, especially across
central Texas. There will be some rain and isolated thunderstorm
chances across central Texas during the afternoon hours. With precipitable water
values climbing to near 2" the main weather concern will be for
pockets of moderate to heavy rainfall...along with a risk for
gusty downburst winds due to precipitation loading. For now, i'll
keep pops capped off at 50 across the Brazos Valley as there is
likely to be a tight gradient.



Long term...
/Tuesday night through next weekend/

The aforementioned tropical low should be centered off the Texas
coast Tuesday night, having underwent a process to transition it
from cold-core to warm-core over the course of the day Tuesday.
Some cam guidance has indicated a well-defined circulation
developing and moving onshore between Corpus Christi and Houston
sometime Tuesday afternoon/evening. Regardless of the exact
evolution of the system, favorable moisture trajectories will pump
generous amounts of deep tropical moisture into the southern and
eastern portions of our forecast area through much of next week.
Current naefs ensemble guidance is indicating mean precipitable water values in
the 90th-97th percentile across the area Wednesday through Friday
(generally between 1.75-2"). The European model (ecmwf) ensemble guidance is
painting a similar picture, but a bit more bullish. With the
moisture in place, the driving factor for heaviest precipitation
will be the track of the low as it moves northward.

The current forecast package uses a blend of available guidance,
since it is extremely difficult to pinpoint the evolution of the
system before a well-defined surface low develops. Expect the
precip to be generally concentrated in the vicinity of the surface
low Tuesday night, spreading northward over the course of the day
Wednesday in the form of diurnally driven showers and
thunderstorms. The convective nature of the precip will allow for
localized areas of heavy rainfall and gusty winds south of I-20
and east of I-35 Wednesday afternoon.

The low is expected to slowly track inland across East Texas
Wednesday night and Thursday, with pockets of heavy rain
concentrated around the eastern half of the storm. The exact track
may vary from model run to run, but as of now we are expecting
the heaviest rain to remain east of the I-35 and south of the I-20
corridors Wednesday night through Friday. The low is then
expected to get absorbed into the mean flow Friday, giving one
more day of scattered-widespread precip across north central Texas
Friday. The widespread precip is expected to come to an end Friday
evening, however, our focus will have to transition from the
tropical-low to a more baroclinic system developing across the
Central Plains this weekend. This may drag a weak frontal boundary
across the northern periphery of the forecast area this weekend,
however a dramatic cool-down is not expected.



Aviation... /issued 145 PM CDT Mon Sep 16 2019/
/18 UTC taf cycle/

Concerns---VFR at the metroplex...brief MVFR at Waco Tuesday am.

VFR will prevail at metroplex terminals with east winds of 8 to
10 knots. Afternoon cumulus around fl070 will persist through sunset
with primarily sky clear overnight. More VFR cumulus can be expected Tuesday
afternoon. For brevity sake, will continue to advertise one line
tafs and allow subsequent tafs to address these changes.

At Waco...VFR will continue through most of the outlook, but as
moisture associated with the tropical low swings northward, I
expect a reduction in cigs below fl030 around mid-morning Tuesday
for a couple of hours. VFR is then forecast to return Tuesday
afternoon, but it is possible that MVFR may linger during this
time if low level moisture is greater than currently anticipated.
There is a non-zero chance for intermittent rain showers at Waco, but the
better risk will be beyond the current valid taf cycle as the
tropical low spirals farther inland.



Preliminary point temps/pops...
Dallas-ft. Worth 76 95 76 93 75 / 0 0 0 20 10
Waco 74 93 73 92 73 / 0 20 10 50 20
Paris 73 94 72 92 72 / 0 0 0 10 10
Denton 74 96 74 92 73 / 0 0 0 20 5
McKinney 74 96 73 92 73 / 0 0 0 20 10
Dallas 78 97 76 94 76 / 0 0 5 20 10
Terrell 75 96 74 94 74 / 0 5 5 30 10
Corsicana 73 93 72 91 73 / 5 20 5 40 10
Temple 73 91 72 90 73 / 5 30 20 60 20
Mineral Wells 71 93 71 91 70 / 0 0 0 20 5


Forward watches/warnings/advisories...

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