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Area forecast discussion
National Weather Service Fort Worth Texas
103 PM CDT sun Mar 26 2017

concerns: thunderstorm potential this evening, MVFR/IFR cigs
overnight into Monday morning.

Breezy southerly winds continue to pull in Gulf moisture to the
region. Later this afternoon, isolated strong/severe
thunderstorms are expected to develop near/north of Interstate 20
and move eastward across North Texas. This activity will likely
impact Bowie and Bonham cornerpost arrivals as well as northward
departures throughout the evening hours. High-res models are
still somewhat inconsistent on how far south to initiate
thunderstorms, but it is possible that a severe storm affects
airports within the immediate dfw area after 00z. Frequent
lightning, large hail, and strong winds will all be possible with
these thunderstorms. Have maintained a mention of thunderstorms in the vicinity but have
delayed it from previous taf issuance based on latest guidance;
have elected not to include a prevailing ts mention yet due to
uncertainty. The threat for thunderstorms in the dfw area will
decrease after 04 or 05z. The potential for a storm at the Waco
taf site is too low to include in the taf as coverage is expected
to be limited farther south. The highest storm chances will
continue to be located near/along the Red River.

A cold front will be approaching the area late tonight and early
Monday morning. In advance of this front, widespread MVFR and IFR
stratus should develop and cigs below fl015 are likely at all taf
sites beginning around midnight. Post-frontal stratus will likely
be an issue throughout Monday morning with cigs falling below 1
kft immediately along the front. Winds will turn to the
northeast and decrease in speed as the front moves through. Waco
may experience several hours of IFR cigs tomorrow morning
including some at or below 600 ft. Conditions should begin
improving by late Monday morning with VFR conditions expected at
all airports by Monday afternoon.



only changes to the short term forecast through this afternoon was
to raise pops along the Red River and adjust them westward a tad
based on latest high-resolution guidance. The dryline is still
located to the west of Sweetwater but winds have begun to veer
ahead of it suggesting that eastward progression is continuing.
All of the guidance seems to handle this fairly well moving the
dryline across our far western counties by mid afternoon. To the
east...low level moisture has begun to surge northward with 60
degree dewpoints into the metroplex and mid-60s to the south. This
initial surge of low level moisture is shallow and some mixing is
expected through afternoon. The latest runs of the hrrr show this
well and generally keep dewpoints in the 60-62 degree range
through late afternoon, which seems reasonable. There is some high
cloudiness spreading in from the west which could somewhat limit
vertical mixing, so moisture quality remains the biggest question.

The severe weather setup is typical of a Spring event with
forecast soundings showing around 2000 j/kg of MLCAPE with large,
clockwise curved hodographs in the lowest 2 km, and steep mid
level lapse rates. This suggests all modes of severe weather will
be possible. As of this afd, the threat for very large hail
remains the biggest concern, especially with the initial
development. The tornado threat will be dependent upon the quality
of moisture return through the afternoon. If extensive mixing
occurs, keeping dewpoints in the upper 50s then the threat for
tornadoes would be somewhat lower given the higher storm bases. If
moisture return is more robust and limited mixing occurs, then
the tornado threat would increase. We will send up an extra
balloon this afternoon to assess this potential. Either way, there
will be a threat for tornadoes with this event well into the
evening hours. This threat should be highest along the Red River.

Concerning timing...all of the high-res guidance is clustered
around 22z (5pm) for initiation across our northwest counties
(montague/Jack/wise areas). Highest storm chances through the
evening hours will generally remain north of I-20. Lower storm
chances are expected south of I-20.

Additional info...we will be sending out further mesoscale
discussions through the afternoon concerning the next 12 hours
with detailed info on storm environment and updated threat areas.



Previous discussion... /issued 502 am CDT sun Mar 26 2017/
a rather cool and dry air mass is in place across North Texas
early this morning. However, dew points in the mid to upper 60s
are just to our south. As a shortwave emerges from The Rockies,
this Mt air mass will surge northward as an effective warm front.
Initially, there may be some mild reductions in visibility as the
dew points upstream currently exceed the surface temperatures
across our area, but no significant fog is expected. The evening
shift was keen to notice the depth of the moisture in south Texas
is greater than earlier progged. This is improving our confidence
in the quality of the boundary layer moisture that will be
available at peak heating this afternoon. A cap will likely
prevent convective initiation until late in the day when both
surface heating and arriving lift aloft gradually erode it. While
this may delay (or prevent) thunderstorm development, it will also
limit the depth of the mixing today. This will maintain ample
boundary layer moisture, and with temperatures soaring into the
80s with full sun, will result in MLCAPE values in excess of

Another player in our thunderstorm game is the dryline, which may
struggle to penetrate the unstable air within North Texas. The
boundary will initially develop as return flow creates a moisture
discontinuity on the High Plains of West Texas this morning. With
the deepening low in Kansas, the mid-level flow will be most
favorable for dryline propagation farther north. This will focus
the best moisture convergence within Oklahoma this afternoon. To
our west, the boundary may only progress about 100 miles between
mid-morning and late afternoon. It is unlikely to reach our
southwestern counties at all (at least until the front arrives
Monday morning). While surface heating may allow for isolated
cells deep within the unstable air late in the day, the portion
of the dryline within western North Texas may be inhibited by
greater heating on the dry side. Some guidance is impressed enough
with the instability and the forward motion of the boundary that
it can't help but convect, but the consensus among mesoscale
guidance is for the initiation to be primarily across Oklahoma
with perhaps a few rogue cells south of the Red River late this

While this event remains conditional on the extent of the
development within North Texas, any storms that develop may
quickly become severe. Supercell structures will be favored, and
although the greatest hail growth potential will be farther north
where the mid-level air closer to the cyclone will be quite cold,
our rotating updrafts would be of such intensity that they could
produce very large hail in excess of 2 inches in diameter. The
tornado threat may increase into the evening hours as a low-level
jet in excess of 40 knots ensues and the best forcing aloft
arrives. Additional development may occur after the traditional
peak heating time period. The Richer moisture may result in lower
LCLs, which will only fall further as the boundary layer cools.
With the dryline unlikely to make any additional progress after
sunset, buoyant (likely untapped) air will remain across much of
North Texas. The best forcing will be north of I-20, but as a cold
front eventually overtakes the dryline late tonight into Monday
morning, additional development will be possible farther south
within our County Warning Area. The intensity of the convection will likely wane
after midnight as the boundary layer instability further
diminishes and the best forcing passes to the east. This will also
slow the surface boundary, which may never actually exit the County Warning Area.

This will keep the Gulf moisture right on our doorstep. And as the
next more powerful system digs into The Four Corners, this
moisture will surge back across North Texas. As large-scale
forcing for ascent begins arriving on Tuesday, some showers and
thunderstorms may develop, particularly across western portions of
North Texas. In addition, dryline convection across West Texas
Tuesday afternoon will race eastward into the Richer moisture.
This activity could impact our western zones late in the day into
the evening hours. A very unstable boundary layer and steepening
mid-level lapse rates will help the cells maintain their intensity
with large hail and damaging winds the primary threats late
Tuesday. If a sufficient cold pool is able to develop, a linear
mesoscale convective system with an attendant wind threat may travel deep into North Texas
late Tuesday night into Wednesday morning. This could disrupt the
evolution of the activity the remainder of the day, or this
complex may blend seamlessly with additional rounds of heavy rain
and thunderstorms. Deep tropical moisture flux within and above
the boundary layer will provide a continuous supply of fuel as
subsequent rounds of lift arrive during the day Wednesday.
Precipitable water values approaching 2 inches, extraordinary
precipitation efficiency, and training echoes will all increase
the likelihood for areas of heavy rainfall and the potential for
flooding issues. Precipitation deficiencies in recent weeks may
reduce the flooding impacts, but this event has the potential to
produce some of the highest 24-hour rainfall totals we have seen
in 2017.

The rain chances will end on Thursday, but again, the interlude
between systems will be short. Another deep low will dig into the
Desert Southwest late in the week, taking a similar southerly
track to its predecessor. This may ruin outdoor plans for the
first weekend of April, but the Spring rainy season has clearly



Preliminary point temps/pops...
Dallas-ft. Worth 84 59 80 57 81 / 30 30 5 0 20
Waco 84 60 83 60 81 / 10 20 10 5 20
Paris 80 59 76 54 78 / 10 60 20 0 10
Denton 82 56 78 54 79 / 40 30 5 0 20
McKinney 81 59 78 54 79 / 30 40 10 0 20
Dallas 84 61 81 59 81 / 30 40 5 0 20
Terrell 83 62 79 57 81 / 20 40 10 0 20
Corsicana 84 62 81 61 81 / 10 30 10 0 20
Temple 85 61 84 60 82 / 10 20 10 5 20
Mineral Wells 87 53 80 55 79 / 20 10 0 0 30


Forward watches/warnings/advisories...

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