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Area forecast discussion
National Weather Service Fort Worth Texas
842 PM CDT Fri Oct 18 2019

Update...

Current short term forecast is in good shape with only minor
tweaks needed through the next several hours. Water vapor imagery
shows a mid level shortwave spreading across West Texas this
evening. Strong mid level isentropic ascent associated with this
disturbance is occurring in the presence of ample moisture and has
resulted in widely scattered showers and a few thunderstorms.
Lapse rates will remain sufficiently steep to continue at least a
low threat for a few rumbles of thunder through tonight. The
strongest forcing for ascent is still a couple of hours away for
North Texas but we should start to see an increase in cloud cover
through midnight. Timing of any showers/storms would be between 11
PM and 4 am as the system moves through. The current forecast has
20% pops mainly north of I-20 to the Red River which seems
adequate at this time.

Dunn

&&

Aviation... /issued 645 PM CDT Fri Oct 18 2019/
/00z tafs/

VFR prevails across north and central Texas this evening but a
fast moving disturbance will bring some clouds and perhaps a low
shot at some elevated showers overnight. Water vapor imagery shows
an upper level disturbance spreading into the Texas Panhandle this
evening and it is accompanied by decent moisture. The combination
of lift from the disturbance and this elevated moisture will lead
to some scattered showers later tonight. Dry low levels may limit
the amount of precipitation that actually makes it to the ground,
but turbulence will definitely be possible. Lapse rates will be
sufficiently steep to support a rumble of thunder, but for now
we'll keep vcsh in from 8-11z. As the system moves by early
Saturday morning, winds will gradually shift around to the north
by mid/late morning.

At Waco, similar trends are expected, although any showers should
remain to the north of the Airport. The northerly wind shift will
also be a few hours delayed.

Dunn

&&

Long term... /issued 312 PM CDT Fri Oct 18 2019/
/Saturday night through Friday/

A filling surface low over the arklatex and its attendant
frontolysizing cold front should be draped across central and
southeast Texas Saturday evening. A weak surface high center
should also be moving into the area from the west, allowing for
light surface winds and mostly clear skies to prevail Saturday
night. These conditions will promote strong radiational cooling
making way for a cool morning as you head outside Sunday. Also by
Sunday morning, both the low and cold front should be washed out
and overtaken by southerly flow across the region.

The increased southerly flow across the area Sunday will be a
result of a rather potent upper level system ejecting out of The
Rockies Saturday night into Sunday. This will deepen a low across
the Central Plains with an attendant cold front dipping south into
the OK/Texas panhandles. An active southern branch of the pfj overtop
of the boundary will help to promote cyclogenesis along the trailing
edge of the frontal boundary over the course of the day Sunday.
Southerly flow ahead of this low will will help draw the warmer
and moisture rich airmass pooled along south Texas northward into
central and North Texas -- effectively acting as a warm front and
inducing a triple point across the area with a dry line extending
south across Big Country. Most areas across north and central
Texas will experience a 15-20 degree increase in dew points and
~0.5" increase of precipitable water values between Sunday morning and Sunday
evening. Attm, the Theta-E ridge axis looks to be aligned along
the I-35 corridor, but this could shift east/west as the synoptic
picture comes into clearer focus (more on the significance of this
below).

All of this to say that as the cold front begins making its way
through North Texas, we expect showers and thunderstorms along
the boundary Sunday night with some strong to severe storms
possible. There is small potential for a few isolated storms to
develop in the open warm sector south of the effective warm front
Sunday afternoon, however the potential of this is low at this time since
deep layer moisture and forced ascent will likely be collocated
with the frontal boundary Sunday night. As the stronger cold front
starts pushing into North Texas, strong forced ascent will tap
into the newly advected moist airmass and develop widespread
showers and thunderstorms along the boundary, especially along and
east of the Theta-E ridge axis. Deep layer shear vectors look to
be generally aligned along the boundary, therefore upscale growth
seems likely to take over soon after convective initiation forming
a linear convective system across the area. A relatively quick
moving line of showers and thunderstorms should move through north
and central Texas, clearing the area entirely by mid to late
morning Monday.

This will usher in a much drier airmass across the area with
generally pleasant temperatures remaining in place through the
early to middle parts of next week. Naefs and European model (ecmwf) ensemble
guidance has been indicating a progressive series of troughs
digging into the central and eastern Continental U.S. Mid to late next week.
Confidence continues to grow of another late-week cold front
moving through the area bringing another cool down late next week
into next weekend.

Bonnette

&&

Short term... /issued 147 PM CDT Fri Oct 18 2019/
/today, tonight, and Saturday/

Our postfrontal air mass continues to modify with steady southeast
winds. Despite the unseasonally cool start to the day, dry air and
abundant sunshine will help temperatures reach near normal highs
this afternoon, generally in the 70s.

The warm exception will be in our far western zones, where a
westerly component will push temperatures into the mid 80s. Severe
to extreme drought conditions have stressed vegetation in the
areas that will see these above normal temperatures, and with
relative humidity values dipping below 30 percent, some fire
starts may occur this afternoon. Although the winds won't be
particularly strong, the southerly breeze and dry fuels may
enhance fire spread.

An upper trough will swing through North Texas overnight, well
ahead of an approaching cold front. While moisture will be
limited, the intensity of the lift and the available instability
may allow for a few showers and thunderstorms in areas along and
north of the I-20 corridor. This activity will shift east of the
area before the cold front arrives.

The wind shift will enter our northwest zones before daybreak
Saturday morning. With the parent trough to our east and little
cold advection behind the boundary, the front will make only slow
progress through the County Warning Area over the course of the day. With abundant
sunshine, dry air, and a downslope component to the postfrontal
wind, Saturday afternoon's temperatures will likely exceed
friday's. Despite northwest winds, much of north and central Texas
will top 80f.

25

&&

Preliminary point temps/pops...
Dallas-ft. Worth 61 82 58 88 60 / 20 0 0 10 60
Waco 60 87 56 90 63 / 0 0 0 10 70
Paris 54 77 53 82 58 / 20 10 0 10 80
Denton 58 82 53 88 54 / 20 0 0 10 60
McKinney 58 81 54 87 57 / 20 0 0 10 70
Dallas 62 82 58 88 60 / 10 0 0 10 70
Terrell 58 84 55 88 61 / 10 0 0 10 70
Corsicana 60 84 57 87 63 / 0 0 0 10 70
Temple 60 87 57 89 64 / 0 0 0 20 70
Mineral Wells 58 82 52 91 53 / 20 0 0 0 50

&&

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

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