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Area forecast discussion...updated 
National Weather Service Fort Worth Texas
1240 PM CDT Friday Jul 29 2016

Aviation...
/18z tafs/

Concerns: shower and thunder potential at the taf sites this
afternoon. Outflow boundary causing wind shifts in the dfw
metroplex.

An outflow boundary from overnight convection in Oklahoma is
slowly moving south through the metroplex, but appears to be in
the process of stalling and possibly diminishing across the
metroplex. With still some little movement to the south, this
boundary may actually stall south of the metroplex but is not
expected to reach kact. Behind the boundary, winds are west and
northwest at speeds less than 10 kts but this is causing some
runway shifts at area airports. Latest thinking is that south
winds will return by 20z as the boundary loses its identity
somewhere within or just south of the metroplex. Southeast to
southwest winds at speeds less than 10 kts will continue through
the valid taf period. Kact will maintain south winds through the
valid taf period. However, for all the taf airports, outflow winds
from any showers or storms may cause erratic wind shifts.

With the outflow boundary stalling across or near the metroplex,
it may become a focus for afternoon showers and isolated
thunderstorms. Will include thunderstorms in the vicinity from 21-01z for this potential
and amend if needed earlier and/or amend to remove if the
convection ends up far enough south. For kact, scattered shower
activity is expected through the afternoon hours but an isolated
thunderstorm could impact the Airport. Have opted to carry vcsh
through 30/00z.

Convective chances beyond this afternoon are minimal but still
bear watching as additional outflow boundaries from storms in
Oklahoma could impact North Texas airports on Saturday. No
convection is mentioned in the taf for Saturday due to low
confidence in any one solution but will be watching convection
across Oklahoma tonight and Saturday morning.

Jldunn

&&

Update...
scattered showers and thunderstorms have formed along the outflow
boundary that has pushed south of the Red River. This activity
developed rapidly and is already showing signs of being undercut.
The scattered showers that developed near the I-20 corridor and
others that developed between Granbury...Palestine and Waco
should slowly weaken as we approach midday. Have increased pops
for this morning for on-going trends. This has also necessitated
adjusting cloud cover and hourly temperatures a little. Updates
have been sent.

58

&&

Previous discussion... /issued 337 am CDT Friday Jul 29 2016/
convective activity ongoing across northern OK and southern Kansas
early this morning will be the main forecast concern for today.
This convective cluster continues to be pushed southeastward by
northwest steering flow aloft of around 40kts. It has been
sustained by a combination of diffluent flow aloft as well as low-
level warm advection and moisture transport which can be seen via
850mb objective analysis. Low level wind fields are stronger
across western OK and the Texas Panhandle and begin to veer and
weaken to the east. This should cause an overall downward trend in
coverage and intensity of this activity as it works southward
toward the Red River early this morning. The hrrr seems far too
bullish on ushering this complex into North Texas and have largely
disregarded its solution in this forecast. However, some remnant
activity from this complex in our northern counties along the Red
River cannot be ruled out thus have continued low pops throughout
the morning and afternoon.

Even if this morning's activity is not sustained into north TX,
outflow boundaries from this convection could set up across our
northern areas this afternoon resulting in new convection. In
addition, a southward-moving boundary from earlier convection
could be vaguely identified on radar and via surface obs draped
roughly from Norman OK to Fort Smith Arkansas as of 3am. This boundary
may also be an additional focusing mechanism for any additional
activity this afternoon. Our area remains under a weakness aloft
today with a deformation axis stretching roughly from del Rio Texas
to Jackson MS. While precipitable water values are less than the past few days,
they will still be above seasonal averages at 1.7-2". Cannot rule
out an isolated shower or storm this afternoon across most of
north and central and have introduced a mention of isolated storms
today given the large scale environment. I should stress that
coverage of thunderstorms today would be far less than what we've
experienced the past few days, should they manage to develop at
all.

Tonight and Saturday morning another complex of storms is expected
to develop across parts of Kansas and OK once again. However, the flow
aloft is expected to become more westerly as the upper ridge
begins to build across Texas. In addition, the most favorable low-
level flow and moisture transport is expected to be confined to
the Texas Panhandle and central OK. These factors would suggest that
convection will stay predominantly out of North Texas Saturday
morning and be confined to areas north of the Red River. Have left
low pops in the forecast for now but they may be able to be
removed if convection allowing models begin following the same
trends as the larger scale guidance.

By Sunday the upper ridge will begin redeveloping directly over
the Southern Plains. This will effectively bring an end to our
rain chances for several days along with a slight warming trend as
temperatures return to the upper 90s and near 100 degrees for
most of the upcoming week. Dewpoints should mix out into the low
to mid 60s for most areas which will keep heat index values under
105. By the end of the week, there is some indication in both the
European model (ecmwf) and GFS that an upper low will become cutoff from the
northern stream flow and will drift across south Texas Friday and
Saturday. This subtle weakness may be sufficient to allow low rain
chances to return to the forecast by late next week and next
weekend.

-Stalley

0



&&



Preliminary point temps/pops...
Dallas-ft. Worth 97 79 98 79 99 / 30 10 10 5 10
Waco 98 77 98 77 99 / 20 5 5 5 5
Paris 95 75 96 76 96 / 40 20 20 10 10
Denton 95 76 97 76 98 / 30 10 10 5 5
McKinney 95 76 96 76 97 / 30 10 10 5 10
Dallas 97 79 98 79 98 / 30 10 10 5 10
Terrell 95 76 97 77 97 / 30 10 10 5 10
Corsicana 96 77 97 77 97 / 30 5 10 5 10
Temple 97 76 98 76 98 / 20 5 5 5 5
Mineral Wells 97 74 98 75 99 / 30 10 5 5 5

&&

Forward watches/warnings/advisories...
none.
&&

$$

82/58

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