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

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391
FXUS64 KFWD 221820
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
120 PM CDT Fri Jun 22 2018


.AVIATION...
/18z TAFs/

VFR conditions will prevail through tonight. Outflow from
convection along the Red River caused winds to shift to the north
at DFW Metroplex airports briefly this morning, although they`re
beginning to become light and variable and will turn back to the
south in the next couple of hours.

Late tonight, a complex of storms is expected to take shape in
southern Oklahoma and may affect parts of North Texas after
midnight through daybreak Saturday. While I haven`t included a
VCTS mention in the Metroplex TAF sites at this time, it may be
necessary in future TAF issuances to account for this potential.
At a minimum, another outflow boundary from this convection may
cause a wind shift in the DFW area early tomorrow morning.
Otherwise, some MVFR cigs are possible at Waco around daybreak
where I`ve introduced a Tempo group. VFR conditions and
predominantly south winds at 15-20 kts will prevail into Saturday.

-Stalley

&&


.SHORT TERM... /Issued 356 AM CDT Fri Jun 22 2018/
/Today and Tonight/

Hot but breezy conditions are expected across much of the region
today with a few showers and storms possible in our north and
northeast counties. A warm night is expected as a complex of
storms moves through Oklahoma and potentially grazes our northern
counties.

A front can be tracked on regional radars and surface observations
moving south through Central and Eastern Oklahoma early this
morning. A few showers and storms have developed ahead of the
front across Southeastern Oklahoma, and nighttime satellite is
showing a growing area of ACCUS expanding into our northern
counties. Most model guidance keeps these storms to our east and
northeast, but as the front continues to move south this morning
we may see a few showers or storms in our northeastern counties.
Have maintained low PoPs through the morning hours along and
northeast of a Bowie to Sulphur Springs line as heating later this
morning may generate some elevated convection. The complex of
storms that is taking shape in the TX Panhandle at this time is
expected to weaken before reaching North Texas this morning but
should spread high cloud cover into the region.

An upper level ridge will remain anchored to our west today and
tonight with northwest flow aloft continuing. The front should sag
into part of our CWA this morning but may not make it any farther
south than the northern row of counties. This front should be a
focus for convection this afternoon with the help of peak heating.
The instability this afternoon will be greatest in our northeastern
counties where CAPE values near 3500 J/kg are forecast in an
uncapped environment. Deep layer wind shear values between 15-25
kts and decent mid level lapse rates support a potential hail and
damaging wind threat, but without a more significant mid-level
shortwave, the forcing may not be strong enough to utilize this
energy. We cannot discount a severe storm threat this afternoon
but coverage of storms may be isolated at best. The area that may
see isolated to scattered storms this afternoon is roughly along
and east of a line from Bonham to Athens.

Otherwise, today will be hot and breezy south of the front. A
plume of hot H850 temperatures is expected to spread across our
western counties with the help of west to southwest winds this
morning. Afternoon highs around 100 degrees will be common along
and west of Interstate 35/35E with highs in the mid to upper 90s
east of Interstate 35/35E. Even though they will be from the west-
southwest, 10-15 mph winds will provide some relief. Heat Index
values across most of the region are calculated to remain below
105 degrees, but some areas across Central Texas where the
humidity is higher will reach 105-107 degrees for a little bit
this afternoon. At this time, we do not plan to issue a Heat
Advisory as the breezy winds will likely reduce the heat stress
factor, but that doesn`t take away from the fact that dangerous
heat conditions will occur today. In addition, slightly elevated
fire weather conditions may exist this afternoon west of Highway
281 where temperatures near 101 degrees, southwest winds 10-15 mph
and humidity values near 25 percent are expected.

Overnight, the winds will back to the south but remain breezy in
response to a surface low moving southeast through the Texas
Panhandle. This surface low will be associated with a shortwave
trough moving through the Plains and is expected to foster the
development of a MCS to our northwest. Steering flow winds move
this system east across Oklahoma, but part of this system could at
least clip our northern row of counties along the Red River. The
low level jet will increase to 35-40 kts overnight from the south
and southwest, helping fuel this complex which could result in
part of the system moving southeast towards our CWA. For now, will
maintain PoPs along and north of an Olney to Sulphur Springs
line. Forecast soundings are in good agreement the region will
remain capped tonight, but gusty winds may be possible, even if
the storms remain elevated. Overnight lows will range from the
mid 70s to around 80 degrees in the DFW Metroplex.

JLDunn

&&

.LONG TERM... /Issued 356 AM CDT Fri Jun 22 2018/
/Saturday through the End of Next Week/

The remnants of an MCS over Oklahoma may bring an area of
weakening convection to the Red River early Saturday, but activity
should dissipate by midday. Meanwhile, lee-cyclogenesis will be in
full swing as a shortwave drops southeast through the Great Basin.
The resulting increase in surface winds (which will have a more
southerly component compared to Friday) combined with lingering
cloudcover may keep temperatures a couple degrees below Friday`s
expected temps. It will still be a hot one, with highs ranging
from the mid and upper 90s along and east of I-35 to triple digits
west.

Zonal flow aloft will be in place Saturday with a lead disturbance
racing eastward across the Southern Plains in advance of the Great
Basin upper low. This should ignite another round of showers and
storms in the vicinity of a stationary front, which will likely
remain draped somewhere near the Red River. An unstable
environment including a couple thousand J/KG of MUCAPE and mid
level lapse rates not all that far below dry adiabatic presents
the possibility of a few severe storms with any convection that
develops. The caveat may be that a decent capping inversion will
be in place, but a 40KT low level jet should help storms get going
above the cap.

The most likely location for severe storms would be along the Red
River Saturday evening with large hail initially being the
primary threat, especially if any storms are able to rotate. Storm
mergers will eventually interrupt the rotation of any discrete
cells, shifting the primary threat to damaging winds later in the
evening. Activity should be in a weakening phase around or shortly
after midnight as convection approaches the I-20 corridor, the
fast-moving wave exits to the east and subsidence from a ridge
aloft becomes too strong to overcome.

Another hot one can be expected on Sunday, and the possibility of
a heat advisory comes to mind as the potential for heat indices to
reach or exceed 105 degrees for consecutive days will exist. The
likely areas would be along the Trinity and Brazos River Basins
where the hottest conditions will occur, which includes a good
portion of the I-35 corridor. We will likely wait until later
today or tonight to make the decision on whether or not to issue
the advisory as changes in the evolution of tonight`s and Saturday
night`s convection may alter the temperature / heat index
forecast.

The upper ridge aloft will break down a little late Sunday and
Monday as the Great Basin shortwave trough crosses the Plains. A
few storms associated with the trough will be possible on Monday,
but with 500MB heights in excess of 590DAM and the presence of a
good cap in place, will keep POPs in the slight chance category
at this time. Mid range model data further strengthens the ridge
from Tuesday on, meaning above-normal temperatures and dry weather
in the forecast for mid to late next week.

30

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    98  79  99  79  98 /  20  10   5  20  10
Waco               100  77  98  78  98 /   5   5   0   5   5
Paris               90  75  93  75  94 /  50  30  20  30  20
Denton              95  79  99  78  98 /  30  20  10  30  10
McKinney            94  76  97  76  97 /  30  20  10  30  10
Dallas              98  80  99  79  98 /  20  10   5  20  10
Terrell             97  77  97  78  96 /  20  20   5  20  10
Corsicana           98  76  97  76  95 /  10  10   0  10   5
Temple              98  76  98  76  96 /   5   0   0   5   5
Mineral Wells       99  78 102  77  99 /  10  10   5  20   5

&&

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

$$

26/91



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