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

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FXUS64 KFWD 202050

Area Forecast Discussion
National Weather Service Fort Worth TX
350 PM CDT Sun May 20 2018

/Through Tonight/

Showers and thunderstorms are currently in progress across the
southeastern quadrant of the forecast area this afternoon where
they will persist through early evening. There remains a threat
for a couple strong or marginally severe storms southeast of a
Cameron to Athens line where the atmosphere is uncapped and
moderately unstable. The two limiting factors and reasons for the
lack of widespread severe storms is the absence of strong large
scale lift, as most new convection is being initiated by previous
thunderstorm outflow, as well as modest deep-layer shear to
support organized storms. Strong winds and some small hail remain
possible with more robust convection over the next few hours.
Otherwise, we`ll continue monitoring the potential for isolated
instances of flooding where prolonged heavy rainfall occurs. A
plume of high PWs approaching 2" is centered across our
southeastern zones where we`ve received reports of rainfall around
1.5-2" per hour. Fortunately, these areas are in need of rainfall
(like much of the region for that matter) and have been able to
handle the welcome rain without much issue thus far. This area of
showers and thunderstorms will continue a southeastward push
through this evening and exit the forecast area by midnight.

Otherwise, we continue to watch a low potential for redevelopment
along the diffuse frontal boundary that has stalled from roughly
Abilene to Cisco to Gainesville. Afternoon satellite imagery
depicts a rather stable cumulus field that has developed along
this boundary where weak low-level convergence is occurring.
Models continue to disagree on the potential for redevelopment
along this boundary over the next 2-4 hours as this area has
slightly destabilized after some clearing and heating this
afternoon. However, given what seems to be a largely subsident
airmass over North Texas and the lack of vertical growth on
cumulus, this potential still appears to be quite low. Have only
included some 20% PoPs for areas northwest of the Metroplex
through the rest of the evening on the off chance that an
isolated shower or storm manages to develop.

Overnight, am expecting generally a lull in any rain/storm
activity as convection continues south of the forecast area along
the effective front/outflow. Winds are expected to become
relatively light overnight, which may favor the development of
some patchy fog given the recent rainfall. This potential will be
conditional on whether skies clear out, which remains uncertain at
this time. Due to uncertainty regarding if/where sufficient
clearing may occur, have not included a mention of fog in the
forecast at this time, though it will need to be monitored



/Monday Through the End of the Week/

An upper level low will continue diving southward across the
Pacific coast during the day on Monday as the parent trough
continues to amplify. With a constant stream of disturbances
making their way across the region the next several days, low rain
chances will remain in the forecast every day through next weekend.

There will be enough low level moisture during the day on Monday
to maintain a low chance of showers and storms across most of the
region. Forecast soundings continue to show a largely uncapped
atmosphere, but with very little environmental shear, any
thunderstorm that develops will likely be short-lived. These
storms will likely produced outflow boundaries, aiding in the
development of additional storms. A ripple in the atmosphere will
move in from the west late Monday night into Tuesday across West
Texas. Unfortunately, the southwesterly flow aloft will likely
keep all showers and storms well to the west/northwest of the
region. With little modification to the air mass on Tuesday, rain
chances will once again increase during the afternoon. For areas
west of Interstate 35, slightly drier air will likely inhibit the
development of any convection. Areas east of Interstate 35,
however, will remain in a moist environment with little to no
capping inversion aloft. Shear will once again be missing across
the area, but enough instability will be in place for non-severe
convective development.

Wednesday and Thursday`s rain and storm chances will be confined
to areas east of Interstate 35 where the highest concentration of
moisture is expected to remain. Temperatures will be on the rise
throughout the week, with low to mid 90s by Friday. As we move
into Memorial Day weekend, there remains many forecast
uncertainties with regards to precipitation and temperatures.
Temperatures will be dependent on the strength of the trough that
digs down across the Midwest. A cold front may be able to slip
down across the Central Plains, reaching North Texas by Saturday.
If this is the case, temperatures next weekend may be slightly
cooler than currently forecast. If a cold front is not able to
reach the area, temperatures may have to be adjusted upward.
Precipitation chances will also depend on whether or not a low
pressure system slides into the Mississippi River Valley from the
Gulf of Mexico. For now, have kept 20-30% PoPs across the eastern
portions of North Texas.



.AVIATION... /Issued 1240 PM CDT Sun May 20 2018/
/18z TAFs/

Morning showers and thunderstorms have mostly exited the DFW area,
although occasional light rain will be possible through the early
afternoon at DFW, DAL, and GKY before all activity shifts
eastward. Numerous thunderstorms continue to impact the Waco TAF
site which will persist for another ~2 hours before exiting to
the east. Behind this activity to the west, the environment is
quite worked over and widespread subsidence appears to be in
control. As a result, additional development along the stalled
frontal boundary located northwest of the area seems fairly
unlikely this afternoon. Because of this, have maintained rain-
free TAFs following the departure of the current activity.

One of the biggest challenges through the morning has been the
wind direction, which has been highly variable in light of the
widespread showers/thunderstorms, outflow boundaries, and other
mesoscale influences. However, winds have finally begun coming
around to the east across the DFW area where I`ve prevailed them
through the afternoon. At Waco, northwest winds will likely
continue until thunderstorms subside, with a return to southeast
winds later this afternoon.

VFR conditions are expected overnight with continued light
southerly winds. Monday morning, there is a low chance for MVFR
cigs to develop across the area, and have introduced some brief
mentions at all TAF sites to account for this fairly low
potential. Also, if skies clear out more than anticipated
overnight, some patchy fog may also develop. We`ll have to monitor
this potential into the morning hours. Improvement to VFR is
expected at all TAF sites by midday Monday.



Dallas-Ft. Worth    68  87  71  89  72 /  10  20  10  30  10
Waco                68  88  68  90  69 /  20  20  10  20   5
Paris               67  86  68  88  69 /  20  20  10  30  10
Denton              65  86  68  89  69 /  10  20  10  30  10
McKinney            66  86  68  88  70 /  10  20  10  30  10
Dallas              68  88  72  90  73 /  10  20  10  30  10
Terrell             68  87  69  89  70 /  20  20  10  30  10
Corsicana           68  87  69  89  70 /  20  20  10  30  10
Temple              67  87  68  89  68 /  30  20  10  20   5
Mineral Wells       66  85  67  88  68 /  10  20  10  30   5




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