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

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FXUS64 KFWD 201128 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
628 AM CDT Sun May 20 2018

.AVIATION...
/12Z TAFs/

Concerns: Storm potential today and wind shifts.

DFW Metroplex TAFs: A cluster of thunderstorms is approaching from
the southwest and will impact all DFW TAF airports between 12-15Z.
Gusty west winds and brief heavy rain are the main hazards.
Another round of convection is possible later this morning and/or
into the afternoon hours, but there is considerable uncertainty
with this next round. However, have decided to include a VCTS from
18-21Z which lies in the middle of model guidance, but this may
have to be removed or adjusted once we see if convection
redevelops to our west along the cold front.

An outflow boundary is moving through the DFW area at this time,
resulting in north winds around 15 kts. In the wake of this first
round of storms, north winds may continue to prevail, eventually
becoming more easterly. Some MVFR cigs are expected this morning
with the precipitation.

Waco Regional Airport: MVFR cigs are already occurring at the
airport but may be interrupted in a few hours by north winds
behind an outflow boundary. Isolated to scattered showers may move
across the airport early this morning with better chances for
convection late this morning into the afternoon hours. Convective
trends are challenging today and adjustments to timing may be
needed. Gusty winds will be the main hazard with any storms but
hail up to 1" may occur in stronger storms this afternoon. North
winds may prevail for most of the morning hours, but will
eventually become more easterly or light and variable after the
convection ends.

JLDunn

&&


.SHORT TERM... /Issued 344 AM CDT Sun May 20 2018/
/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... /Issued 344 AM CDT Sun May 20 2018/
/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

&&

.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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