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

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FXUS64 KFWD 251555
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
1055 AM CDT WED MAY 25 2016

.UPDATE...
Morning visible satellite loops show extensive cloud cover across
much of the region associated with 70+ kt subtropical jet streak
analyzed by the recent RAP. At the surface, a cold front arcs to
the southwest from a surface low near Dodge City, Kansas and into
the Texas Panhandle with a dryline extending to the south across
the eastern Trans-Pecos region. Regional soundings show a very
stout capping inversion in place with steep mid-level lapse rates
of near 8 C/km atop moist low levels characterized by dewpoints in
the low to mid 70s.

Point forecast soundings across our far western zones show a
continual lifting and weakening of the aforementioned cap through
the day in the vicinity of the eastward-mixing dryline. Cloud
cover continues to gradually thin west of a Bowie to Abilene line,
which will foster more diabatic heating--possibly enough to raise
temperatures to near 90 F. In addition, HRRR dprog/dt plots show
a strong signal in developing thunderstorms in this region later
this afternoon. Based on all of this, raised PoPs into the 30%
range out west after 21Z to account for the possibility of a bit
more convective coverage out there. With MLCAPE values on the
order of 3000-4000 J/kg and effective bulk shear values
approaching 30 kts, any storms that do develop with have the
potential to produce localized severe hail/wind. We will also need
to watch for convection entering our CWA later this evening and
tonight as it moves out of the Concho Valley.

Finally, updated the grids to raise cloud cover and nudge
temperatures down a few degrees based on current trends.

Carlaw

&&

.AVIATION...
/ISSUED 647 AM CDT WED MAY 25 2016/
/12Z TAFs/

Gusty south winds have prevented any significant reductions in
visibility and have kept ceilings above FL010. MVFR ceilings will
dominate this morning, becoming VFR around midday. Peaks of sun
this afternoon will help temperatures soar to near 90 degrees,
which will result in considerable instability. This heating may be
enough for surface parcels to overcome a formidable cap, which
would result in intense thunderstorms. The favored area for
development would be west of the I-35 corridor, but even there,
the prospects are slim.

A better chance for showers and thunderstorms will be during the
day Thursday. Have introduced VCSH into the extended portion of
the DFW TAF. If the precipitation is both widespread and of long
duration, low MVFR ceilings may prevail throughout the day.

25


&&



.PREV DISCUSSION... /ISSUED 405 AM CDT WED MAY 25 2016/
A very warm and muggy day is anticipated today as our southerly
fetch of moisture continues under a warm advection regime.
Afternoon dewpoints will be in the low to mid 70s, and when
combined with temperatures in the upper 80s to near 90, will
result in heat index values in the upper 90s area-wide this
afternoon. These conditions will also yield abundant instability,
over 4000J/kg of MLCAPE in most areas this afternoon, but a strong
cap and little to no forcing should prevent thunderstorms from
developing today. However, the latest two runs of the HRRR (06Z and
07Z) are a bit concerning for the afternoon hours today. The HRRR
seems to be generating convection in our western areas, roughly
from Comanche to Graham by mid afternoon, which appears to be solely
due to buoyancy. If enough breaks in the clouds occur to the west,
strong diabatic heating may allow very isolated breaks in the
capping inversion. A RAP sounding at Cisco this afternoon shows
nearly 6000J/KG of SBCAPE, no CIN, and 40 kts of 0-6 km shear,
which is why the HRRR is depicting isolated supercell storms on
the latest runs. This potential seems very low, and have only
included 20 PoPs this afternoon, but if any storm manages to
develop in this area, it would quickly become severe.

Morning water vapor imagery depicts a swath of Pacific moisture
beginning to overspread much of TX as it is ushered in by a 100+
kt upper- level jet ahead of the main upper trough axis. Although
low clouds will likely go broken or scattered today, mid and upper
level clouds should be on the increase as some top-down saturation
occurs. These features will help to set the stage for increasing
rain and thunderstorm chances on Thursday and Friday, which will
be the main focus of the forecast.

A lead shortwave will move across south Texas tonight and early
Thursday morning, resulting in our first batch of showers and
thunderstorms. At this time, expect a broad swath of rain with
some embedded thunderstorms to move northeastward from south TX
and the Hill Country late Wednesday night and early on Thursday
morning. The areal coverage of this activity remains unclear. A
strong cap will still be in place so this first wave of activity
will primarily be elevated showers and a few storms. This activity may
act to initially reduce the amount of instability in place by
lessening lapse rates aloft as latent heat release occurs and
temperature profiles become closer to moist adiabatic. Most of
North and Central TX should receive at least some rain from this
initial wave of activity on Thursday morning.

We may see a bit of a lull in activity late Thursday afternoon or
evening, but widespread redevelopment of thunderstorms is
likely thereafter as the main trough axis nears and strong forcing
for ascent impinges on the area. Redevelopment seems likely across
southern parts of Central Texas where the environment may have
time to recover from the morning`s activity, as well as across
the Hill Country and West TX. With the upper-forcing arriving
along with the associated speed max aloft, increasing wind shear
means this round will have a higher potential for strong to severe
storms. At this time, would expect numerous thunderstorms and/or
potentially an MCS to traverse most of our area late Thursday
night and Friday morning. With very high PW values at or in excess
of 2SD above normal and sufficient instability, rainfall will be
very efficient. Should any training of storms occur during this
time, flooding issues will be of concern. A Flash Flood Watch may
be necessary at some point for the Thursday/Friday time frame, but
would prefer to hold off until a clearer picture of thunderstorm
evolution comes into focus. Redevelopment of thunderstorms will be
possible through the day on Friday, but the strong to severe storm
threat is unclear until we can get a better handle on the
evolution of the events of Thursday through Friday morning.

Activity should taper off from west to east Friday evening and
early Saturday morning. Subsidence should prevail for most areas
beginning by midday Saturday in the wake of the departing
shortwave trough. Have cautiously cut back on PoPs for Saturday
despite the 6000J/kg of CAPE that models continue to advertise
with very warm and moist conditions still in place. Subsidence and
a strong CAP should limit thunderstorm potential on Saturday, but
it will not take much forcing at all to initiate a thunderstorm in
those conditions. This portion of the forecast will need to be
monitored, especially if any outflow boundaries from Friday`s
convection still exist across our area, which may be sufficient to
generate an isolated thunderstorm.

Rain and thunderstorm chances will begin increasing again on
Sunday as broad upper troughing resumes across the western CONUS.
Large scale upper-level diffluence near the nose of an 80 kt jet
streak should support widely scattered showers and storms across
much of the southern Great Plains for the second half of the
Memorial Day weekend. Any outdoor events on Sunday should not be a
washout, but Monday is looking rather soggy at this time and
should be the wettest day of the weekend. An overall sloppy
weather pattern will continue through much of next week with
little organization and broad, weak forcing. A weak front may
encroach on North TX around midweek, which would act to increase
rain chances further. While showers and thunderstorms seem
possible nearly every day again next week, the severe threat may
be tempered by the lack of strong dynamic forcing and relatively
weak wind shear despite favorable thermodynamics.

-Stalley



&&


.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    86  75  84  72  81 /  20  20  50  60  70
Waco                86  75  83  72  83 /  20  30  60  60  70
Paris               84  72  80  69  79 /  20  10  50  50  70
Denton              86  74  82  70  80 /  20  20  50  60  70
McKinney            86  73  82  71  79 /  20  10  50  50  70
Dallas              87  75  84  72  81 /  20  20  50  60  70
Terrell             86  73  83  72  81 /  20  10  50  50  70
Corsicana           87  74  81  72  80 /  20  20  50  50  70
Temple              87  74  82  71  82 /  20  40  60  60  70
Mineral Wells       86  73  82  70  84 /  30  20  50  70  60

&&

.FWD Watches/Warnings/Advisories...
None.
&&

$$



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