Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

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

Aviation update...
/1400 UTC/

Scattered showers are developing across the metroplex this morning
within an area of mid level instability. Have amended the tafs to
include a vcsh mention with a tempo for rain showers. Any showers over an
Airport may produce slightly gusty winds and temporarily reduced
visibilities due to moderate to heavy rainfall.

In addition, an outflow boundary is moving rapidly south through
southern Oklahoma from a complex of storms that formed overnight.
The complex of storms is dissipating across Oklahoma but the
outflow boundary is still steadily moving south and nearing the
Red River. 30 kt winds behind the outflow boundary support the
likelihood that this boundary will reach the metroplex airports
around 1600-1630z but the wind speeds behind the boundary should
be less by the time it reaches the metroplex. North winds around
15 kts can be expected behind this boundary for about 1-2 hours
before southeast winds return across the region. Additional
showers may develop along the boundary as it moves into North

At this time, confidence is not high enough to amend kact but
will monitor the progression of the outflow boundary. The boundary
will likely dissipate before reaching kact as daytime mixing works
against it.


../previous aviation discussion/...
An mesoscale convective system over Oklahoma is expected to gradually weaken as it pushes
south towards the Red River this morning. Outflow from the
diminishing complex should come close to the Dallas-Fort Worth
metroplex later this morning and may kick off a few showers around
midday. The main change with this forecast set was to move up the
timing of vcsh based on the extrapolation of the approaching
outflow boundary.

At this time, the latest high resolution guidance for the most
part indicates significant weakening and only spotty
redevelopment with the outflow. There is a slim chance for thunder
later in the afternoon and early evening, but coverage is expected
to be less than the past several days due to increasing
subsidence from the ridge overhead, and thus feel the probability
is too low to mention in area tafs.




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

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



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


Forward watches/warnings/advisories...



National Weather Service Glossary of Abbreviations