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

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FXUS64 KFWD 270859

Area Forecast Discussion
National Weather Service Fort Worth TX
359 AM CDT Tue Jun 27 2017

Nearly daily rain chances will continue across some part of North
and Central TX through the weekend. While heavy rain will be a
threat for locales that find themselves beneath a shower or
thunderstorm, the areal extent should be limited. The best chance
for more organized shower and thunderstorm activity appears to be
late in the week and into the early part of the weekend when a
cold front will slide towards the Red River. Unlike last week,
this frontal boundary is expected to retreat back towards the
north into Oklahoma. Otherwise, near to just above normal
temperatures can be expected for most locations.


/Tuesday through Thursday/

Surface analysis this morning indicated that a remnant Mesoscale
Convective Vortex (MCV) across parts of the Hill County was the
culprit for weakly-electrified nocturnal convection across parts
of Central TX. This feature will likely serve as an additional
focus for perhaps some additional showers and thunderstorms on
Tuesday. In addition, tail end of a Great Lakes longwave trough
may provide enough of a spark for some showers across northwestern
zones early this morning. The weak mid and upper level flow
should limit the amount of deep layer shear necessary for storm
organization, but I wouldn`t completely rule out some strong winds
associated with precipitation loading given the moist airmass. In
general, however, most storms should remain below severe limits.
Heavy rain and a potential for flooding will be the primary storm
hazard today given the tall narrow CAPE and 9 to 10kft warm cloud
depths. The best potential for "more" widespread shower and storm
activity will be across Central TX, closer to the location of the
MCV. One potential caveat for more widespread activity will be the
interaction of the aformentioned longwave trough. If this feature
can provide additional lift, there could be a higher coverage of
storms than what is currently reflected. Most hi-res guidance
doesn`t support this potential, so I`ll keep PoPs on the
conservative side. With that in mind, I`ll also side with the
warmer guidance which advertises afternoon high temperature in the
upper 80s to low 90s across much of the forecast area.
Temperatures will be slow to fall during the evening hours, but most
shower and storm activity should diminish rapidly after sunset.

For Wednesday---By Wednesday, the MCV should essentially be very
ill-defined and located across southeastern zones as southerly
low level flow intensifies and likely destroys what remains of
this feature. While not truly subsident, there shouldn`t be too
much to force additional convection across much of North and
Central TX. The exception will be across far southeastern zones
where there could be re-development along the modified sea-breeze
front. There should be enough instability for a storm or two, but
the coverage will likely be isolated. The threat for severe
weather will remain low given the weak wind shear, but a the gusty
wind potential will exist given that afternoon temperatures will
continue to moderate with most areas experiencing high
temperatures in the low to mid 90s. Similar to Tuesday, most
convection should wane quickly with the loss of daytime heating.

For Thursday---Low rain chances will continue on Thursday, mainly
across East TX and parts of Central TX. While little in the way of
inhibition is evident in forecast soundings, it`s likely that
model QPF is a tad aggressive as most models saturate the boundary
layer quite quickly with widespread stratus more likely than
precip on Thursday morning. The airmass will remain moist and
afternoon heating should in theory encourage afternoon
convection. With that reasoning in mind, I`ll go with a low chance
for showers and a few storms mainly during the afternoon and early
evening hours across the climatologically favored areas of East
and Central TX. Temperatures will continue to moderate with upper
90s possible out across western zones with low to mid 90s
elsewhere. Heat index values may near the century mark across most
areas. Breezy southerly winds on Thursday should make conditions
not feel as oppressive, however. South winds of 10 to 20 MPH with
perhaps some gusts to near 30 MPH will be possible as the surface
pressure gradient tightens in response to lee cyclogenesis to the


/Friday through Monday/

For Friday---Friday should feature hot and humid conditions. A
swift moving upper trough should slide eastward through the
Central Plains. In response, it will send a quick moving cold
front to the south. As the front nears the Red River, it`ll likely
lose a bit of its push. As is typical with these summertime
fronts, the air in their wake isn`t too terribly cold and thus
pressure rises are generally quite weak. The cold front should
near the Red River late Friday before stalling. Longer range
guidance is in fair agreement with the placement of this boundary
on Friday. Prior to the front arriving, however, it appears that
there will be enough of a nocturnal LLJ to transport Gulf stratus
northward through the morning hours. Morning breezes should
subside with the surface pressure gradient loosening in response
to the approach of the front later in the day. With less wind on
Friday afternoon, conditions will likely feel more uncomfortable
compared to Thursday, even though temperatures may only be a
degree or two higher. Heat index values do creep up towards the
103-105 degree range and we will have to monitor the potential for
a Heat Advisory on Friday.

Similar to Thursday, I think model QPF during the morning hours
is a tad overdone across the east. While the boundary layer will
be moist, the depth of moisture doesn`t appear overly conducive
for widespread rainfall. With this in mind, I`ll carry a mention
of a 20 PoP across eastern zones. Towards the late afternoon and
evening hours, most models do convect along the slow moving frontal
boundary as broad upper level troughing grazes the Red River. It
is interesting to note that models develop a surface wave across
SW OK/western NTX. Should this come to fruition, low level flow
would likely back and would maximize convergence along the surface
front, leading to widespread convection, mainly along the Red
River. Given the mid-level flow, it`s likely that this activity
would move parallel to the front, leaving much of Central TX
precipitation-free. The backed surface winds may also mean that
temperatures don`t sky rocket as there wouldn`t be much of a
downslope component.

At this point, I`m not overly confident in the model`s depiction
of the strong open wave along the front given that the stronger
flow aloft necessary for cyclogenesis will be to the north. This
combined with the occurrence in the forecast (day 4/5), I`ll
simply advertise a 50 PoP along the Red River where there should
be some convergence along the front to promote the development of
showers and storms. In addition, I`ve nudged temperatures a few
degrees above guidance as winds may become more southwesterly. If
the good model agreement remains and it appears more likely that
a strong surface wave will develop, higher PoPs may be warranted
and temperatures will need to be lowered. In addition, the
strength of the jet entrance region forcing will have to be
monitored as well.

For Saturday---Models diverge some on how quickly the front lifts
on Saturday and this lowers confidence for this portion of the
forecast. The GFS quickly lifts the front towards the north,
resulting in little in the way of precipitation on Saturday,
except maybe along the Red River. This would result in warmer
conditions. The ECMWF, on the other appears to be hair slower and
paints a large swath of precip across the northern half of the
forecast area. The resultant precip and cloud cover would support
cooler conditions. For now, I`ll side with a persistence forecast,
GFS and model consensus which all support a faster retreat of the
front. Thus, there`s a low chance for showers and storms along
the Red River early in the day with afternoon temperatures closer
to the warmer guidance. Trends in model output will need to be
monitored, however, as the varying solutions offer about a 10
degree spread in high temperatures on Saturday.

For Sunday and Monday---Sunday and Monday appear quite similar
with mostly precipitation-free conditions. Mid-level ridging does
appear to try to make a return with the faster flow to the north.
For now, I`ll advertise a rain-free forecast across all of North
and Central TX towards the latter half of the weekend and into the
early portion of next week.



.AVIATION... /Issued 1145 PM CDT Mon Jun 26 2017/
/06Z TAFs/

DFW Airports: VFR conditions are expected through Tuesday night.
Few-Sct clouds with bases between 3-4 kft may occur overnight,
and a few patches of MVFR cigs could occur after daybreak Tuesday.
Generally light and variable winds will occur through Tuesday
morning, becoming southeast by midday but remaining below 10 kts.
Some pop up afternoon showers or storms are possible again Tuesday
afternoon, but the confidence and threat is too low at this time
to include a VCTS mention. For the extended portion of DFW, MVFR
cigs are likely to return early Wednesday morning.

Waco Airport: As one boundary continues moving north, approaching
KACT, a few showers will be possible before 06Z. Otherwise, the
remainder of the overnight period is expected to be dry but there
may continue to be isolated showers in Central Texas overnight. VFR
conditions with light and variable winds are expected overnight,
and then MVFR stratus will likely return between 13-16/17Z. Some
pop up afternoon showers or storms are possible again Tuesday
afternoon but the confidence and threat is too low at this time to
include a VCTS mention.



Dallas-Ft. Worth    91  74  92  77  96 /  20  20   5   5   5
Waco                92  72  91  75  95 /  30  30  10  10  10
Paris               88  71  89  72  89 /  20  10   5   5  10
Denton              89  72  92  74  95 /  10  10   5   5   5
McKinney            89  72  91  74  92 /  20  20   5   5   5
Dallas              92  74  94  76  95 /  20  20   5   5   5
Terrell             89  72  89  74  91 /  20  20  10  10  10
Corsicana           91  70  91  71  92 /  30  30  10  10  10
Temple              88  71  92  73  95 /  40  40  10  10  10
Mineral Wells       89  70  92  72  97 /  10  10   5   5   0




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