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

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FXUS64 KFWD 180455

Area Forecast Discussion
National Weather Service Fort Worth TX
1155 PM CDT Thu Aug 17 2017

Mid level and high level cloud cover remains across North and
Central Texas tonight, but only VFR ceilings are being observed.
Light winds will prevail for most of the night and most of Friday,
with the next shot at scattered thunderstorms moving into the area
Friday afternoon, especially to the north and east of the
terminals. For this forecast cycle, have kept VFR ceilings for the
entire period and do not have enough confidence to carry
thunderstorm restrictions.



.UPDATE... /Issued 1004 PM CDT Thu Aug 17 2017/

With the loss of daytime heating, much of the thunderstorm
activity has greatly decreased. A shrinking area of rain currently
between the Dallas/Fort Worth metroplex and Hillsboro will
dissipate, leaving mostly cloudy skies for the first half of the
night. The thunderstorms did manage to push an outflow boundary
that is now from Athens to Buffalo to Hearne. As the boundary
continues to move south and east, a few short-lived pop up showers
and storms will be possible before midnight.

Did remove the mention of any rain between midnight and Friday
morning due to the heavily worked-over atmosphere currently in
place across most of the area. Low temperatures are expected to be
in the low 70s across the west, and mid to upper 70s across the
south and east. Although not mentioned explicitly in the forecast,
there will be the potential for fog along the Red River east of
Gainesville. Current thinking is that coverage will be isolated
south of the Red River, with better coverage as you cross over to
southern Oklahoma. If guidance suggest a better coverage of fog
during the early morning on Friday, the next forecast package will
reflect it.



.SHORT TERM... /Issued 309 PM CDT Thu Aug 17 2017/
This morning`s thunderstorm complex have resulted in the quite a
temperature gradient across the forecast area this afternoon.
At 3 PM, temperatures were in the mid 70s to mid 80s across the
east and were near 100 degrees at Temple, Killeen and
Breckenridge. Dewpoints were in the mid to upper 70s across parts
the region that received rain this morning. DFW and Dallas Love
Field reached dewpoints of 79 degrees! With temperatures climbing
into the mid 90s across parts of Tarrant County, heat index
values had reached as high as 111 degrees! Isolated showers and
thunderstorms were developing again along and south of I-20.

Expect scattered showers and thunderstorms to continue through
this evening along and south of I-20 with locally heavy rain,
cloud to ground lightning and gusty winds. Will need to keep an
eye on thunderstorm development over the high plains of West
Texas. At this time, am not expecting another complex to move
across North Texas late tonight into Friday morning. I have just
left 20 percent convective chances for the overnight hours. Lows
will be in the 70s area wide with southeast to south winds around
10 mph.



.LONG TERM... /Issued 309 PM CDT Thu Aug 17 2017/
/Friday through the middle of next week/

Friday morning should be quieter than this morning, as convection
across Oklahoma will be delayed while waiting on a shortwave
disturbance coming out of the Rockies. In addition, the low-level
flow in the 925-850mb layer is expected to be more veered and
weaker than what helped generate the slow-moving storms that
produce the localized heavy rains/flooding seen Thursday morning.
The Oklahoma storms will likely produce a weakening outflow
boundary toward the Ark-La-Tex late morning and into the afternoon
hours. In addition, areas east of I-35/35E will be in the axis of
better column moisture with PWATs approaching or exceeding 2
inches once again. That said, without knowing where the outflow
boundary settles and the fact it will be weakening, will only
advertise slight chances for showers/storms across the east for
the morning, then have higher chances just northeast of the
Metroplex for the afternoon hours. If the storm cluster late
tonight across Oklahoma were to be more organized with a strong
cold pool, then rain chances may need to be increased across the
Red River Valley and the east. Though winds through the mid
levels will be weak, instability will be sufficient both at the
surface and aloft for a few strong storms with gusty winds, small
hail, and heavy downpours.

After nightfall Friday evening, it appears things will quiet down
from I-20 south, though a few remnant cells may persist across
the northern tier of counties. Another MCS looks to dive rapidly
southeast and across Southwest Oklahoma that looks to enter our
western Red River counties after midnight, but models rapidly
dissipate this system as it enters weak and veered low-level flow
across the northwest part our area. Similar to early Thursday
morning, if 925-850mb ends up being more backed and stronger,
convective chances will need to be increased across areas along
and west of I-35/35W and north of I-20. Have maintained slight
chances early Saturday morning for any potential old MCS outflow
and storm generation, but this bears watching as well. Though
convection will be weakening, we cannot rule out strong storms
with gusty winds, small hail, and heavy downpours that could once
again produce very localized heavier rainfall and flooding across
areas that have seen heavy rainfall this past 7-10 days.

The remainder of the weekend from late Saturday into Sunday looks
mostly quiet, as the subtropical upper high over Mexico and the
Gulf of Mexico expands northward across much of North and Central
Texas. I still will carry diurnal low chances across the east
where moisture will more than sufficient for a few showers and
storms with strong afternoon heating. We`ll continue to see low
and mostly diurnal chances the first half of next week across our
far east and southeast counties, as an inverted surface trough
sets up near that area with a possible weakness in the upper high.

Where rainfall doesn`t occur, the heat will be on with hot
temperatures each day between 95-100, with the hottest high
temperatures each afternoon across the southwest half of the CWA
where triple-digit readings are highly possible. Problem is, this
is also where the relatively lower dew point readings will occur
from daily mixing. We do see some high heat index values from DFW
to the Red River, but if nocturnal storm complexes are stronger
like today that produce widespread cloud cover and lower temperatures,
then heat index values above 105 degrees may be overdone. We will
not issue any heat highlights today, but will let tonight`s
forecast get another run of models to decipher any storm potential
and changes in dew point temperatures. South-southwest winds will
also play a role in this, as they should sustain at 10 mph or
more if not corrupted by potential future storm outflow. A lot of
players in the game have my confidence too low for any heat
highlight issuance at this time.



Dallas-Ft. Worth    77  98  79  98  79 /  10  20   5  10   5
Waco                74 100  77 100  77 /  70  10   5  10   0
Paris               74  93  74  94  74 /   5  40  20  20  10
Denton              75  98  76  97  76 /   5  20  10  10   5
McKinney            76  96  76  96  76 /   5  30  10  20  10
Dallas              78  97  79  97  79 /  20  20   5  10   5
Terrell             76  96  75  97  75 /  20  20   5  20   5
Corsicana           77  97  77  98  77 /  50  20   5  10   5
Temple              76  99  76 100  76 /  50   5   5  10   0
Mineral Wells       73  97  74  98  74 /  10  20   5  10   5




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