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

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773
FXUS64 KFWD 200844
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
344 AM CDT Sun May 20 2018

.SHORT TERM...
/Today/

Showers and thunderstorms are ongoing across the region, mainly
west of Interstate 35 and north of Interstate 20 early this
morning. Gusty winds have been the main hazards with these storms,
but some of these storms have also produced heavy rainfall. To
our southwest, a small mesoscale rotation developed earlier in the
night, and this feature may persist for a few more hours,
regenerating some rain across our southwestern counties. The
other feature of interest for today is the outflow boundary
associated with the complex of storms in our northwest counties.
Hi-res model guidance continues to track this outflow boundary
east and southeast today, generating scattered to numerous
convection across the region all day. This scenario is very
plausible as we maintain southwest flow aloft with embedded
disturbances providing necessary lift. Forecasted CAPE values of
1500-2500 J/kg ahead of this boundary will support thunderstorm
development in an uncapped environment. Deep layer wind shear
values decrease throughout the day to values less than 20 kts this
afternoon which doesn`t usually support a severe weather threat,
but where the better lift and instability align today, a few
strong or severe storms may be possible. The most likely location
for strong or severe storms is southeast of a DFW to Lampasas line
this afternoon. Damaging winds and hail around 1" are the most
likely threats.

JLDunn

&&

.LONG TERM...
/Tonight Through the End of the Week/

Today`s thunderstorm activity will have effectively stabilized
much of the region, and tonight will likely be a corresponding
lull for much of North and Central Texas. However, the next
impulse embedded in southwest flow aloft will emerge from
Chihuahua this evening. Remarkably moist upslope flow should aid
in the development of another nocturnal complex near the Pecos
River Valley. While the flow would guide this to the northeast, a
stalled frontal boundary should limit its northward progress. If
it is able to sustain itself into the early morning hours Monday,
it may be able to take advantage of the moist fetch to the east,
turning right toward our southwestern zones. While possible, this
appears unlikely, and even if it were to occur, these storms would
not be strong/severe.

Morning low clouds will slow the recovery of the boundary layer
Monday, particularly across Central and East Texas. However, with
sufficient surface warming and quality low-level moisture in
place, the largely uncapped instability may be realized Monday
afternoon. Weak surface flow may preserve some of the convective
boundaries from the previous day, but without a well defined
surface focus, these diurnally driven convective elements should
be rather disorganized. Although a strong storm could result, the
weak shear environment should limit this potential while reducing
the duration of any storms that do develop.

As an upper low digs into the Southwest, the troughing currently
in the Central Plains will be absorbed into the vigorous flow over
the Great Lakes. While the upper low will maintain southwest flow
over West Texas, increasingly disorganized mid-level flow will
dominate North and Central Texas during the middle of the week. As
early as Tuesday, weak subsidence may nose into the region from
the southwest, potentially capping the surface layer the remainder
of the week. But for areas east of the I-35 corridor, where rich
low-level moisture will remain beneath the weakness aloft, the
potential for diurnally driven showers and thunderstorms will
continue.

This pattern will also allow showers and thunderstorms to flourish
in the Gulf of Mexico. Although guidance varies with the intensity
of the convectively driven trough that results, the consensus is
that this deepening will occur with a corresponding impact on the
upwind flow across our region. In other words, a gradual
transition to northwest flow late in the week is looking more and
more likely. By that time, the energy associated with the Southwest
trough early in the week will have become a deep, late season low
over the Prairie Provinces. This feature will remain well south of
the polar jet, which remains displaced well poleward for this early
in the year, but the low will still be able to tug unseasonably
cool air south of the border. The resulting cold front will surge
down the High Plains, reaching the Texas Panhandle on Friday,
before surging into North Texas on Saturday. While certainly
nothing extraordinarily cool for late May, it could make for a
more tolerable Memorial Day weekend.

25

&&


.AVIATION... /Issued 1157 PM CDT Sat May 19 2018/
A cold front extended southeast of a KEND (Enid, OK) to KCDS
(Childress, TX) to KROW (Roswell, NM) line as of 0430z. Showers
and thunderstorms along and ahead of this boundary were generally
moving northeast but storms west of KJTS (Jayton) had already
started to move southeast as cold pool develops. Meanwhile, there
was another band of showers and thunderstorms farther to the
northwest along the 850 mb front. There was also an area of
showers and thunderstorms from just south of KABI (Abilene)
southward to Cotulla. Satellite imagery indicates that cloud tops
have been warming on the activity and radar trends have been
showing a weakening of the cells.

Showers and thunderstorms will continue to affect the northwest
cornerpost (UKW) through 09z. Have kept VCSH in the Metroplex TAF
sites starting at 08z with a TEMPO SHRA for the 09 to 13z period.
This may need to be updated to VCTS/TSRA with later updates. An
outflow boundary from the showers/thunderstorms may bring a wind
shift to the northwest for a few hours at the Metroplex. Some MVFR
ceilings are also expected to spread north into the area around
08z and hang in through 16z. VFR conditions are expected to return
16-17z Sunday. Additional thunderstorm development could occur
late afternoon into Sunday night, but that is dependent on the
morning activity and confidence that it will occur is too low to
include in the TAFs at this time.


58

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    83  69  88  71  90 /  70  30  30  10  30
Waco                84  68  88  69  91 /  70  30  30  10  20
Paris               85  67  87  68  88 /  60  20  30  10  30
Denton              81  66  86  69  89 /  80  30  30  10  30
McKinney            82  67  86  69  88 /  60  20  30  10  30
Dallas              84  71  88  73  90 /  70  30  30  10  30
Terrell             84  69  88  70  89 /  70  20  30  10  30
Corsicana           86  69  89  70  90 /  70  30  30  10  30
Temple              85  68  88  68  90 /  70  30  30  10  20
Mineral Wells       79  66  86  67  89 /  80  30  30  10  30

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

82/25



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