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

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FXUS64 KFWD 220032

Area Forecast Discussion
National Weather Service Fort Worth TX
732 PM CDT Sun May 21 2017

Moisture appears to be surging north in advance of a shortwave
trough over South-Central TX. A swath of rain with occasional
embedded thunderstorms has moved into the southern-most counties,
warranting an increase to likely POPs for the 00-06Z time across
the southern few rows of counties. Clouds and precipitation have
kept temperatures down across the southern half of the forecast
area and hourly temp grids have been adjusted accordingly. The
south-to-north POP gradient will be kept for the overnight hours
with likely POPs across the south decreasing to slight chance near
the Red River. A break in the precip is expected during the day
Monday, then another disturbance will bring a chance of storms
(some possibly severe) Monday evening.



/ISSUED 658 PM CDT Sun May 21 2017/
/00Z TAFs/

Concerns...Convection this evening and overnight. MVFR and IFR
cigs returning. More convection Monday afternoon and night.

A large area of rain and storms continues to spread into Central
Texas this evening with isolated to scattered convection also
developing east of this area. For the Waco area, will prevail -SHRA
VCTS through the evening and overnight hours, but the rain activity
likely won`t become more continuous until 01Z. For the Metroplex
TAF sites, some of this rain could spread into the Metroplex by
03Z. The chance for thunder will increase in the Metroplex after
midnight as an elevated front moves north. It appears this wave of
rain will end at all the airports by 12-14Z as the responsible
shortwave moves east of the region. As we monitor trends, we will
make adjustments to the TAFs and TEMPO groups as needed.

Overnight, MVFR and IFR cigs are expected to spread north as a
warm front moves across the region. MVFR cigs are expected at KACT
around 09Z with IFR cigs possible between 12-17Z. MVFR cigs are
expected at the Metroplex airports beginning around 14Z. However,
rain trends overnight could interrupt the ceiling trends and
timings. MVFR cigs are expected to prevail through Monday, but a
period of VFR may occur late in the afternoon and/or evening
hours. Generally, northeast to east winds are expected, but may
become more southeast Monday evening.

Additional convection is possible Monday afternoon and more likely
Monday evening/night. One complex of storms is forecast to develop
in the Panhandle tonight and move southeast. However, most
guidance weakens this complex as it moves across southern
Oklahoma during the day. We will have to monitor for any outflow
boundaries that this complex leaves behind. Models are hinting
that another shortwave could provide lift for additional showers
or storms in the region Monday afternoon and will maintain VCSH
starting at 21Z. Then, another complex of storms is expected to
arrive Monday evening from the northwest, quickly moving southeast
across the region. Will include a VCTS mention in the extended
KDFW TAF for this trend.



.PREV DISCUSSION... /ISSUED 333 PM CDT Sun May 21 2017/
After a round of morning strong to severe storms in the vicinity
of the 850mb front and steep lapse rates aloft, a quiet period has
settled across the CWA in between shortwave disturbances. A
strong shortwave trough in the southern stream was seen on water
vapor imagery moving out of West TX and over the Upper Rio Grande
Plain and southern Hill Country as of this afternoon. Meanwhile,
the old surface cold front was draped along the I-10 corridor.

The surface cold front will remain south of the area through this
evening, before both it and the 850mb front begin their trek back
north as a warm front with the approach of the subtropical branch
shortwave over Southwest TX. Convective rain chances will increase
across our Central TX counties very late this afternoon and through
this evening. Thunderstorms, some possibly strong to marginally
severe will then expand north up through the I-20/I-30 corridors
later tonight through Monday morning, as the southern branch
shortwave trough moves across Central TX and enhances isentropic
ascent and elevated WAA above the frontal slope. A brief reprieve
is expected later in the morning and into mid afternoon Monday, as
this shortwave exits the area to the east. We will then await an
amplifying northern branch shortwave arriving from the northwest
later in the afternoon and even, at which time a second round of
storms will move southeast toward our northwest counties. There
will be the potential for strong to severe storms with large hail
and damaging winds. Any morning severe weather will likely be
associated with hail due to the elevated nature of convection with
the surface front to the south of the CWA. However, this surface
front will move north during the day and allow the area to be in
the warm sector by afternoon and add the damaging wind threat to
the equation.

By later Monday night/Tuesday morning, a cold front will move
into the region from the northwest, as yet another strong and
progressive shortwave disturbance arrives. Scattered showers and
storms will likely occur both in advance and behind the cold front
for another round of at least some strong storms. The environment
becomes more unclear at this point due to previous rounds of
convection and how much the atmosphere has been contaminated and
if re-charging can take place. We will continue to refine threats
for the late Monday night/Tuesday time period in future forecasts,
as it`s totally possible the morning MCS could really play a role
in evolution of frontal convective activity and the thermodynamic
environment during the afternoon hours Tuesday.

Afterward, convective chances come to an abrupt end on Tuesday
evening, as both the cold front and shortwave disturbance shift
southeast of our area. Brisk north winds will occur Wednesday,
before diminishing Wednesday evening with surface high pressure
settling in. Morning lows will be cooler with values in the 50s,
however, with the bulk of CAA remaining northeast of our area,
strong late May insolation will help heat the dry airmass in place
and allow for highs to rebound into the 70s to lower 80s.

Temperatures are expected to modify and warm up readily with the
arrival of shortwave ridging aloft and a return to southerly winds
Thursday through Saturday, especially the western half of the
region where low-mid 90s will make a return to the area. A broad
Western CONUS trough organizes next weekend, but bulk of the
stronger energy appears to remain north of the area. That said, a
few shortwave disturbances will move southwest to northeast across
the area during the Memorial Day Weekend into early next week. I
have have added low confidence slight rain chances through the
period. Either way, the modest west-southwest flow aloft will
likely enhance a relatively strong EML (cap) over the area than
even the medium range models are realizing, not to mention the
normal bias of these models being too weak and progressive with
the longwave trough to west and northwest. We should see better
upper-air sampling of this system as the week progresses, which
will help in refining the forecast with more confidence.



Dallas-Ft. Worth    64  79  63  77  57 /  40  30  50  30   5
Waco                64  78  62  79  55 /  70  50  40  40  20
Paris               59  75  60  73  52 /  20  40  40  30  10
Denton              59  78  61  75  51 /  30  40  50  30   5
McKinney            60  77  60  75  54 /  30  40  50  30   5
Dallas              65  78  64  78  57 /  40  30  50  30   5
Terrell             62  75  62  76  55 /  50  40  40  30  10
Corsicana           64  77  63  78  55 /  60  60  40  40  20
Temple              64  78  62  79  55 /  70  60  40  40  20
Mineral Wells       59  78  60  74  51 /  30  30  50  30   5




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