Forecast Discussion for Dallas/Ft. Worth, Texas

981
FXUS64 KFWD 220032 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
732 PM CDT Sun Apr 21 2019

.AVIATION...
/00Z TAFs/

MVFR (perhaps IFR) AM stratus. Otherwise, VFR with south flow.

The surface low responsible for our gusty winds on Sunday will
eject northeastward with a passing a shortwave. But it will leave
behind a cold front that will approach from the northwest tonight,
maintaining breezy south winds. This boundary is unlikely to reach
our TAF sites, and fairly uniform surface winds will prevail until
upstream frontolysis Monday evening reduces our wind speeds.

Although the Gulf has been well scoured of moisture by our
previous cold front, our focus instead will be on the Hill
Country where stratus prevailed Easter morning and will quickly
redevelop this evening. The flow above the nocturnal boundary
layer will have a westerly component that will help guide these
low clouds up the I-35 corridor tonight. The deck will be
primarily west of I-35, but all of our TAF sites should be
underneath this blanket by the morning push. Onset times still
look good, but will further assess based on upstream development
this evening. IFR potential is still the greatest across Central
Texas; although a TEMPO should suffice for now at Waco, a
prevailing IFR group may be needed. Late April warmth will lift
the deck, but a stout cap may preclude scattering Monday
afternoon.

An upper low currently over the Great Basin will dig into the
Desert Southwest. The initial convective activity associated with
it may begin to impact west departures and the northwest arrival
corridor Tuesday morning, but showers/storms at our TAF sites is
unlikely until Tuesday afternoon/evening.

25

&&

.SHORT TERM... /Issued 339 PM CDT Sun Apr 21 2019/
/This Afternoon Through Late Monday Afternoon/

Very breezy conditions will continue this afternoon before winds
subside some overnight. Cloud cover will be more widespread on
Monday, but rain and storm chances will likely hold off until the
evening and nighttime hours. Otherwise, it`ll remain mild tonight
with warm and slightly less windy conditions on Monday.

Windy conditions have been a little slower to materialize this
afternoon with most areas near or just below 20 knots. It appears
that vertical mixing may not be quite as efficient as initially
believed. Area radar derived VWPs indicate slightly more veered
flow (winds are more south/southwest) at 925mb while surface obs
report southeasterly flow. Even with that in mind, I`ll hold onto
the Wind Advisory that is set to expire at 1900 CDT as any slight
changes in the surface and/or 925mb wind field could help to
bring more of this higher momentum air down to the surface. Those
with outdoor recreational activities on lakes and rivers should
still use caution this afternoon and through the early evening
hours. Winds and certainly the "gustier" conditions are expected
subside tonight as the boundary layer decouples. The increase in
low level moisture/cloud cover coupled with some remnant
nocturnal breezes will keep conditions mild with most areas only
slipping into the upper 50s and 60s for overnight lows into
Monday.

Cloud cover is forecast to overspread Central Texas initially
after midnight tonight and then through the remainder of North
Texas through the day on Monday. Despite the increase in cloud
cover, southerly flow should maintain decent WAA and allow
temperatures to climb into the 70s and 80s. A front will advance
to near the Red River and could even slip into western North Texas
(towards the Wichita Falls area). This should loosen the pressure
gradient and as a result, it should be a bit less breezy Monday
with sustained wind speeds closer to 15 to 20 MPH. The chance for
rain/storms will increase Monday evening and this is discussed
more in the long term discussion seen below.

Bain

&&

.LONG TERM... /Issued 339 PM CDT Sun Apr 21 2019/
/Monday Night Through Saturday/

A vigorous lead shortwave will lift northeast well out in advance
of an anticipated upper low moving across the Desert Southwest on
Monday night. Meanwhile, a surface cold front will be moving
southward across the Texas/Oklahoma Panhandles and into Western
Oklahoma through midday Tuesday. Strong low level warm advection
provided by 25-35 knot southerly flow in the 925mb-850mb layer
will correlate with increasing ascent within an approaching left
exit region of a 120-140 upper jet maximum over areas in vicinity
of the surface cold front well northwest of our CWA during the
Monday night and Tuesday morning time frame. There will likely be
a capping inversion in the 850mb-700mb layer over the area which
will need to be lifted and moistened before we get much in the way
of showers or thunderstorms occurring in our area. The most
likely area for that to occur will be across our far northwest
counties Monday night, then along and west of I-35 Tuesday morning
where mid level height falls with an assists from the surface
front will be most prevalent. Effective bulk wind
differences(EBWD) and deep layer 0-6km shear will be approaching
40 knots for some organization of scattered, mainly elevated
strong to even a marginally severe storm or two across our western
counties. The increasingly strong kinematic environment will
correlate with steep mid-level lapse rates between 7-8 deg C/km
across the west during this time window.

With time, a cold pool from convective activity that has been
ongoing northwest of our CWA should likely result in a slow
southeastward movement of the surface cold front toward into our
northwest counties late Tuesday into Tuesday evening. Still,
forecasting the cold front`s position is tricky considering the
immense height falls in advance of our approaching mid level
low/trough that will be moving across Northern Mexico and over Far
West Texas. In addition, mid level flow paralleling this surface
feature could potentially counter any assistance from storm
outflow, so it`s anyones guess. With the frontal movement being
somewhat conditional on these mesoscale processes, I continue to
defer to the slightly more aggressive NAM forecast on a more
southern track of the cold front through our western CWA and
eventually tracking toward or across the I-20 corridor Wednesday
morning. Overnight Tuesday night into Wednesday night will be our
wettest period, as the surface cold front is expected to stall
somewhere south of I-20/30 corridors and across Central Texas.
Exactly where is the question.

What`s pretty evident is that widespread rainfall with amounts
between 1-3 inches will likely fall -- with higher amounts with
training convective cells. This will likely occur wherever the
surface front decides to stall. Now that models are coming into
agreement with timing and track of the approaching southern stream
mid level low/trough, I`m fairly confident in this unfolding and
the potential for flooding and possibly isolated cases of flash
flooding wherever training occurs along the surface front across
Central Texas and where better instability will be anchored to the
south of this feature. What`s uncertain is the potential for
severe weather in our Central Texas area due to uncertainty on how
previous convection corrupts the environment and as already
stated, where the front and associated warm sector set up across
our southern CWA. As of now for the mid week period regarding the
severe weather threat, I`m going to bet the warm sector will be
situated either south of Highway 84, or potentially as far south
as the I-14 corridor/Highway 190 from Lampasas and Killeen toward
Cameron and Hearne. We should know more as our upper-air network
and more high-resolution models sample these features more in
real- time.

As the strong upper jet of around 150 knots surges east across
South and South-Central Texas and more downstream of the main mid
level disturbance, I`d expect a more open trough and progressive
west to east movement toward the Central Gulf Coast and Lower
Mississippi River Valley region Thursday morning. When all is said
and done, we expect there will be some residual flooding across
those areas south of I-20/30 if the models solutions remain
consistent with this track. Also, there`s a good bet that some of
the already swollen central and lower parts of the Brazos over to
the Trinity and Sabine basins will also be aggravated from run-
off, so main-stem river flooding could really get problematic the
latter half of the week.

Otherwise, temperatures will not get too overly warm or cool, as
the clouds and expected rainfall keep diurnal spreads fairly low
for this time of year. Highs in the 70s will prevail Tuesday, with
increasing north winds behind the cold front Wednesday into
Thursday resulting in breezy north winds and highs generally 65-75
degrees. As the system continues pulling east away from the
region Thursday night and beyond into the early half of next
weekend, we shall see an increasing abundance of sunshine and with
north winds settling down with the arrival of a broad surface
high pressure ridge. As one would expect in late April,
temperatures will recover well into the 70s to near 80 degrees
Friday, then between 80-85 degrees Saturday just in time for
outdoor activities for many.

05/

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    63  80  65  77  63 /   0   5   5  50  70
Waco                63  80  64  77  62 /   5  10   5  40  40
Paris               58  80  61  76  61 /   0   5  10  20  70
Denton              63  80  63  76  61 /   0   5  10  50  80
McKinney            62  79  63  77  62 /   0   5   5  40  70
Dallas              63  81  65  77  63 /   0   5   5  40  70
Terrell             61  81  63  79  61 /   0   5   5  30  50
Corsicana           61  82  63  77  61 /   5  10   5  20  30
Temple              63  80  65  77  63 /  10  10   5  30  40
Mineral Wells       63  81  61  75  59 /   0   5  10  60  90

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 7 PM CDT this evening for TXZ091>094-100>104-
115>120-129>134-141>145-156>159.

&&

$$

25/30

NWS FWD Office Area Forecast Discussion