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Area forecast discussion...updated 
National Weather Service Fort Worth Texas
1203 am CDT Wednesday Apr 1 2015

Aviation...
/06z tafs/

Concerns...thunderstorm potential...nocturnal stratus.

Storms overnight will be primarily confined to Oklahoma...aided
by a transiting middle-level disturbance. The activity skirting the
Red River will be primarily elevated and non-severe...and will
shift well east of the north departure corridor by morning
operations.

Latest guidance is projecting a low level jet weaker than the fws vwp output
of 40-45kts at 2kft above ground level and up. The Oklahoma storms should sustain
a potent low level jet during the early morning hours...helping to pull MVFR
stratus into all taf sites before dawn. There should be less of a
westerly component than Tuesday morning...enhancing the chances
that this deck is able to blanket the western metroplex airports.
Still expect Dallas/Arlington/Waco will be the last to scatter
Wednesday...in fact...these sites may simply transition from
morning stratus to a broken afternoon stratocu deck.

An impulse with a more southerly track is currently moving through
Chihuahua and The Trans-Pecos. This feature will help to spread
scattered showers/storms across north and central Texas on
Wednesday. For Waco...appears most of the activity will be earlier
in the day...primarily showers. Afternoon thunderstorm chances are
still too low for categorical mention...but will maintain a late
afternoon window of thunderstorms in the vicinity for metroplex sites.

Stratus will return earlier Wednesday night. Have introduced this
into all tafs.

25

&&

Update...
a quick update to trim probability of precipitation to only areas north of Highway 380
between Jacksboro and Sulphur Springs...as the elevated mixed
layer /a scientific name for the cap/ appears stronger with much
drier lower levels at forward compared to oun/S sounding at 00z.
Storms that were out by Abilene are a true indicator to this very
item...though instability above the elevated mixed layer remains
high with lapse rates between 7-8 degree c/km expected through the
overnight across the Red River valley. The boundary layer will
continue to cool and stabilize with any storms near the Red River
counties likely being elevated in nature by the time they reach
our counties. I held probability of precipitation in the chance category for the tail-end
of a possible mesoscale convective system the hrrr and sref have tracking eastward across
south-central OK overnight and through sunrise Wednesday.

Models have been struggling with the environmental parameters all
afternoon and evening long with convective evolution and extent...
but with nightfall upon US they seem to be getting a little better
handle on it...outside of the 18z ttu WRF which already had
storms from Bowie to Sherman by now. I imagine the 00z version
should be better.

Otherwise...I did add a slight chance for thunderstorms into the
overnight period for those parts of central Texas along/west of
I-35 all the way up through our far western counties...as a
shortwave disturbance over Mexico moves northeast toward those
areas. Thunderstorm chances should then spread northeast across
the majority of North Texas on Wednesday...with a few strong
storms containing small hail possible along the northern periphery
of the better chances where steeper middle level lapse rates will
reside...including the dfw metropolitan area into the afternoon hours.

05/

&&

Previous discussion... /issued 334 PM CDT Tuesday Mar 31 2015/
a split flow regime appears to be in place across the Continental U.S. With
multiple progressive weather features potentially affecting North
Texas over the next few days. Northwest flow aloft is currently
taking place in the northern stream from The Rockies into the
central and Southern Plains. Satellite imagery indicates one
shortwave traveling southeast across Arkansas/eastern OK in this
flow with a second disturbance moving into the OK Panhandle. At
the surface...an instability axis resides along and just north of
the Red River where in the vicinity of an old frontal boundary.

Thunderstorms are expected to develop in the next couple of hours
across southeast OK where strong surface heating and lift generated by
the first shortwave should be enough to overcome a cap currently
in place. These storms would likely move east-southeast...with a
few cells affecting the northeast counties around sunset. Given
the impressive instability in place...a few of these storms may be
severe with large hail being the main threat.

Additional convective development will be possible over southwest
OK in the 5 to 8 PM time frame as the second shortwave approaches
from the northwest. These storms would be slow moving and likely
propagate east-southeast. For the rest of the Red River
counties...timing would be later in the evening and into the
overnight hours with this activity. Some of the most recent hi-
res model data is suggestive of upscale growth into multicell
clusters as storms propagate into northwest counties of North
Texas...which should limit the overall severe threat for our
region. An overall weakening trend would take place overnight as
storms approach the I-20 corridor. For tonight...we will indicate
highest probability of precipitation along the Red River...with slight chance along I-20
and little if anything expected across the southern half of the
region.

Additional showers and thunderstorms will be possible Wednesday as
a shortwave trough /currently located over northern Mexico/
traverses the state within the southern stream westerly flow.
There does not appear to be any particular focusing mechanism and
convection will likely remain widely scattered in nature.
Increasing moisture will limit the middle level lapse rates and
marginalize the potential for severe weather....though a few
strong storms will be possible.

Upper level flow becomes conjoined again during the second half of
the week...with a fast moving trough moving east across the
central Continental U.S. Thursday and Friday. The attendant cold front will
push south towards the Red River Thursday while a dryline surges
east towards the I-35 corridor. Shear and instability will be
impressive...but veering winds and a strong cap will likely
inhibit convective initiation. The exception may be near the Red
River along the dryline a few hours prior to sunset when the cap
becomes weakest. We will indicate 20 probability of precipitation in this area Thursday
afternoon and then across the northeast counties Thursday night.

The cold front will dive south through North Texas on Friday with
only low-end chances of showers and storms expected early in the
day along the front. Drier conditions and more seasonal
temperatures are expected Friday and Saturday. The cool air will
remain in place on Sunday. Rain chances are expected during the
day and overnight Sunday night as southwesterly flow aloft
becomes established and overrunning ensues. Embedded thunder will
be a possibility but should remain fairly isolated in nature.
Warmer air will return Monday as the front lifts back to the
north. Storm chances will return area-wide next Tuesday and
Wednesday associated with another progressive upper trough and
another cold front.

30




&&



Preliminary point temps/pops...
Dallas-ft. Worth, Texas 65 81 65 87 66 / 10 30 30 10 10
Waco, Texas 65 78 64 86 66 / 20 30 30 10 10
Paris, Texas 62 79 63 79 65 / 30 30 40 10 20
Denton, Texas 64 81 64 88 64 / 20 30 20 10 20
McKinney, Texas 63 81 64 83 65 / 20 30 30 10 20
Dallas, Texas 66 81 65 87 66 / 10 30 30 10 10
Terrell, Texas 64 81 64 83 66 / 10 30 40 10 10
Corsicana, Texas 64 80 64 82 66 / 10 40 40 10 10
Temple, Texas 64 78 64 85 66 / 20 40 30 10 10
Mineral Wells, Texas 63 84 63 93 63 / 10 20 10 10 10

&&

Forward watches/warnings/advisories...
none.

&&

$$

25/05

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