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Area forecast discussion 
National Weather Service Fort Worth Texas
318 PM CDT sun may 24 2015

Discussion...
the upper level trough axis responsible for the most recent round
of rainfall is currently pivoting through North Texas. The strong
forcing ahead of this system has resulted in a second batch of
rain and a few storms over the central County Warning Area this afternoon. But
because the airmass across the region is pretty worked over from
the overnight activity...this convection has been weak and is
expected to remain so into the evening hours as it tracks
northeastward. Will carry just a slight chance of rain over the
west and probability of precipitation of 30-40 over the east this evening. Temperatures
tonight will be in the middle 60s northwest to low 70s southeast as southerly winds
re-establish and bring warmer and more moist air northward.

The moisture return will set the stage for another round of severe
thunderstorms and heavy rainfall tomorrow. Instability is forecast
to become quite high...with surface based cape by midday reaching
2500-3500 j/kg with little convective inhibition. Strong forcing
will spread into the region in advance of a compact and rapidly
moving vorticity lobe that swings across the state during the day.
Thunderstorms should fire from roughly San Angelo to San Antonio
by late morning and grow upscale into a mesoscale convective system or squall line as
they move northeastward into the County Warning Area by early afternoon. Given the
high cape and available shear...severe winds would be possible
with the mesoscale convective system...and several high resolution models are indicating a
Bow echo developing and tracking through the south central and
southeast County Warning Area. However if the storm Mode remains more
cellular...we would become more concerned about the potential for
large hail and perhaps an isolated tornado.

This system will assuredly bring a quick 1-3 inches of rain to
the region southeast of a Comanche to dfw to Paris line where the
severe weather threat is also highest. Obviously continuing the
Flash Flood Watch through tomorrow afternoon for this area is a
given. The heavier rain amounts may spread farther to the
northwest...it is just dependent on how far northwest the return
flow can bring the quality moisture back by tomorrow morning. Due
to this uncertainty and the very saturated grounds that already
exist...will keep the Flash Flood Watch going for the remainder
of the County Warning Area even though it is possible less than a quarter to half
inch may occur tomorrow across the northwest. All of this
convective activity should clear out from west to east during the
late afternoon and early evening hours...making for a quiet and
tranquil evening.

More sunshine is expected Tuesday afternoon and temperatures will
climb into the low to middle 80s. The southerly flow should bring
back low 70 dewpoints into the area again. The middle-upper levels
will feature very steep lapse rates as cold air remains aloft in
the wake of the last two shortwaves. All of this will contribute
to an extremely unstable airmass over the region...with several
models forecasting surface based cape over 5000 j/kg. Upper level
forcing is forecast to be much weaker Tuesday...and a weak cap
will also be present. While this should limit convective
development until the middle-late afternoon hours and keep storm
coverage low...what does develop will have a tremendous amount of
instability to work with. Most of the model guidance is initiating
convection along a dry line that is draped across the western
counties Tuesday afternoon...which raises confidence that
something will probably develop in our County Warning Area. Deep layer shear is
rather limited...but due to the extreme instability it would be
sufficient for supercells with a very large hail...tornado and
locally heavy rainfall threat. Storm motion would probably be
southeast or even south...so will keep the higher probability of precipitation of 30
percent west of I-35.

For Wednesday and Thursday we should be in between systems with
really no organized lifting over the region. Although a few
isolated to scattered showers and storms are possible with
afternoon heating...will keep probability of precipitation at 20-30 percent. High
cape...but very limited shear will keep activity more like
Summer-time pulse convection...so some very localized severe
threat will exist.

The next upper level system arrives in from the west Friday and
Saturday and it will take a couple of days to track through the
area. Rain chances will increase again during this time frame with
a potential for more heavy rainfall. A weak cold front may push
through next Sunday in the wake of the upper system...so will
keep rain chances continuing through Sunday. Northwesterly flow
aloft behind the front will hopefully shunt some of this rich
moisture well offshore...and bring US a break from this rainy
pattern. However I would caution anyone banking on a dry forecast
for early June that northwest flow this time of year is prime
season for mesoscale convective system activity to track in from the High Plains which is
often not forecast well by the global models.

Tr.92

&&

Aviation...
/issued 1235 PM CDT sun may 24 2015/

Another batch of showers will spread across the metroplex
terminals this afternoon. Have not seen lightning in this
activity over the past few hours and decided to exclude and
monitor for needed updates. Expecting this batch to exit the
metroplex around 22z with little or none this evening and
overnight. Another convective complex will develop out west Monday
morning and move across North Texas Monday afternoon...generally
between 18 and 22z. This system again will produce heavy rainfall
and could produce severe thunderstorms as well.

MVFR ceilings and VFR to MVFR visible should prevail this afternoon but
could go VFR before 00z. Expecting MVFR ceilings to return to all
sites tonight by 06z with a lowering into the IFR category around
08-09z. No improvement is expected through midday or early
afternoon Monday. Expecting to see MVFR to IFR visible...and maybe
IFR ceilings as well...during Monday afternoon/S convective system.

75



&&

Preliminary point temps/pops...
Dallas-ft. Worth, Texas 67 80 65 86 68 / 20 70 30 20 30
Waco, Texas 69 80 67 85 71 / 30 90 30 20 20
Paris, Texas 68 80 65 82 67 / 40 70 60 20 20
Denton, Texas 67 80 64 85 67 / 20 70 20 20 30
McKinney, Texas 67 80 65 84 68 / 30 70 30 20 30
Dallas, Texas 69 80 65 86 69 / 20 70 30 20 30
Terrell, Texas 69 80 66 85 69 / 30 80 40 20 20
Corsicana, Texas 71 80 67 84 71 / 30 90 40 20 20
Temple, Texas 69 80 67 86 70 / 30 90 30 20 20
Mineral Wells, Texas 66 78 64 86 69 / 20 70 20 30 30

&&

Forward watches/warnings/advisories...
Flash Flood Watch through Monday evening for txz091>095-100>107-
115>123-129>135-141>148-156>162-174-175.



&&

$$

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