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Area forecast discussion...updated
National Weather Service Fort Worth Texas
1251 PM CDT Wed Jun 28 2017

Aviation...
MVFR stratus moved into Waco area before daybreak today but only
a few fingers of MVFR stratus made it up in the metroplex mid to
late morning. VFR conditions are expected at the taf sites through
08z Thursday. Isolated thunderstorms are possible late this
afternoon and early evening southeast of a kt35-kpsn line but this
activity will remain well southeast of the taf sites. Another
intrusion of MVFR ceilings is expected overnight tonight, moving
into kact around 09z and into the metroplex taf sites around 11z.
Waco may briefly go IFR for a few hours. Ceilings will lift late
morning with VFR conditions returning to the metroplex around 16z
and at Waco toward 18z. South winds 8 to 12 knots will prevail
through the period.

58

&&



Short term... /issued 311 am CDT Wed Jun 28 2017/
/today through Thursday/

The weak upper disturbance responsible for yesterday's scattered
showers and thunderstorms will drift a little farther to the east
today. This should result in fewer showers and storms across our
area with height rises building into North Texas. The only
exception may be our far southeast counties, in closer proximity
to a weak surface trough near the coast, and any sea breeze
convective activity. Otherwise, most areas will be partly cloudy
today with high temperatures climbing into the low to mid 90s.

A strengthening low level jet late tonight may result in a more
expansive low cloud cover by Thursday morning. Low temperatures
will also be a few degrees warmer with most areas in the mid 70s.
Thursday should be dry areawide as the pool of higher precipitable
water associated with the weakness aloft drifts farther into
Louisiana. Increasing influence from the subtropical ridge to the
west will mean temperatures will continue to warm into Thursday.
Highs are expected to climb into the mid and upper 90s.

Dunn

&&

Long term... /issued 311 am CDT Wed Jun 28 2017/
/Friday through Monday/

Friday morning will resemble a pattern more Akin to that of
late Spring. Gulf stratus will be transported northward by a 30-35
knot low level jet across a majority of north and central Texas. The
lone exception may be across far northwestern zones where the low
level wind field is a bit more veered and not as impressive. The
likely breezy conditions during the early morning hours should
result in very mild overnight conditions with temperatures in the
mid to upper 70s. I don't expect a large degree of warm air
advection, so the potential for widespread morning streamer
showers looks low. Thus, i've kept pops generally low during the
morning hours.

Towards the afternoon hours on Friday, a summertime cold front will
make steady progress southward towards north and central Texas. Most
medium and long range guidance remains insistent on developing a
surface low out across southwestern Oklahoma and into western North
Texas. The development of this feature will be an important player with
regards to both the afternoon high temperature and late evening and
overnight pop forecasts. If the surface low develops in line with
GFS, NAM and to a lesser extent the ECMWF, hot and humid conditions
can be expected with heat advisory-like apparent temperatures.
The development of the surface low will back the low level flow
tremendously resulting, maximizing low level convergence---likely
leading to prolific growth of late afternoon and evening
convection across southwestern OK and western North Texas. If the
Canadian is right, however, low level flow will veer rapidly to
the southwest, resulting in deep mixing and a more favorable
downslope component. In response, Max temperatures will easily
approach and exceed the century mark across the northwestern third
of north and central Texas. The Canadian solution would also tend to
delay the onset of convection, until several hours after 00 UTC
Saturday (friday evening). At this time, it's hard to ignore the
consensus of the GFS, NAM and European model (ecmwf) with regards to the
development of the surface low/trough to the west and the longer
term portion of the forecast follows this consensus closely. While
Friday Max t's won't be quite as high as advertised by the
Canadian, I do think that we will see some slight downslope
component to the wind and temperatures across the area will still
range in the mid to upper 90s to near 101/103 out across
northwestern zones. These temperatures, combined with the amount
of low level moisture likely to be in place, will result in
dangerous heat and a heat advisory will more than likely be
required.

For Friday evening and into the overnight hours on Saturday morning,
all medium and long term guidance forecast a complex of storms to
develop along the stalled out frontal boundary near the Red River.
With forcing from the entrance region of an upper jet, sufficient
low level convergence, the solutions forecast by these models
seem plausible, even if some of the quantitative precipitation forecast is a bit on the spurious
side. The complex of storms should generally move from northwest
to southeast initially under the influence of the mid-level
steering flow. With time, however, guidance advertises the
development of a 25-30 knot low level jet and this could allow for
preferred development on the western and southern sides of the
complex. Should this happen, there's a chance that nearly all of
north and central Texas could experience some rainfall and as a
result, i've expanded slight chance pops southward into central
Texas. As one may expect, there will be a severe risk with this
activity as cape values will climb into the 2,000 to 2,500 j/kg
range with deep layer shear on the order of 30 to 35 knots.
Damaging winds will more than likely be the main hazard, but some
near severe hail cannot be discounted given the amount of deep
layer shear present. Rich moisture will also be in place which
will likely Foster heavy rain and some potential flood issues.

The forecast becomes a bit more questionable during the day on
Saturday and will largely depend on the cessation of convection
during the overnight and early morning hours. In general, I feel
that the best chances for showers and storms will be out across
northeastern and eastern zones where the possible mesoscale convective system should be
moving towards the east. Given the uncertainty on the south and
west extent of this MCS, however, i've elected to broad brush a
20 pop back across much of north and central Texas. Given the likely
extensive cirrus canopy and potential for precipitation, i've
nudged afternoon Max temperatures on Saturday downward,
especially across northeastern and eastern zones. The GFS and
European model (ecmwf) offer intriguing output as both models advertise a potential
second complex of storms late Saturday and into Sunday. The areal
coverage of pops associated with this potential storm complex
will be relegated mostly to the Red River given the unknown
magnitude of available instability as well as strength of any low
level jet. Nevertheless, we will have to keep an eye on this. If
it appears more likely that two mcs's will come to fruition, it's
quite possible that there will be some flood//flash flood
headlines required.

For Sunday and beyond---generally quiet weather conditions are
expected with temperatures returning to near seasonal averages as an
500 mb ridge settles in across the region. It appears that this feature
will progress far enough to the east such that any nocturnal mesoscale convective system
activity is confined to The Ark-la-tex and MO valley and for now,
i'll go with a dry forecast.

24-Bain

&&

Preliminary point temps/pops...
Dallas-ft. Worth 93 77 95 80 95 / 5 0 5 0 10
Waco 92 74 94 78 95 / 10 10 10 0 10
Paris 90 72 90 75 92 / 5 5 5 5 20
Denton 91 74 94 77 95 / 5 0 0 0 10
McKinney 90 74 92 77 93 / 5 0 5 0 10
Dallas 92 76 94 79 95 / 5 0 5 0 10
Terrell 90 74 93 77 93 / 5 5 5 0 10
Corsicana 92 70 90 75 95 / 10 10 10 0 10
Temple 92 73 94 76 95 / 10 10 10 0 10
Mineral Wells 92 71 95 74 96 / 5 0 0 0 5

&&

Forward watches/warnings/advisories...
none.

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