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

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FXUS64 KFWD 171956

Area Forecast Discussion
National Weather Service Fort Worth TX
256 PM CDT Tue Oct 17 2017

Another clear, calm, and cool night is on tap for North and
Central Texas tonight. 500 mb analysis shows northwesterly flow
across the region around the periphery of an upper-level high
centered over northwestern Mexico. Given the subsidence associated
with this high as also seen on water vapor satellite imagery, the
atmosphere over the region tonight will be quite dry, meaning
little to no cloud cover. At the surface, the surface high has
progressed to the east and is currently centered over Appalachia.
This has allowed winds (though light) to turn out of the
southeast this afternoon. Overnight winds should remain calm to
light given the weak pressure gradient across the region. The calm
winds and little to no cloud cover should allow for boundary
layer decoupling and excellent radiational cooling, causing
temperatures to cool to near the dewpoint. The exception will be
in the urban areas of the Dallas/Fort Worth Metroplex where the
urban heat island effect will keep lows as much as 5-10 degrees
warmer than in rural areas.

The bias-corrected CONSShort seemed to have a good handle on
overnight lows, with just a few minor tweaks needed in western
zones where guidance seemed to be a bit warm. Still, lows tonight
should run 5-10 degrees above where they were Monday Night given
the slightly higher dewpoints, warmer afternoon highs today, and
subtle warm air advection. Other than low temperatures, the
forecast was straightforward with clear skies and nil rain



/Wednesday Through Tuesday/
Although temperatures will be a few degrees warmer than today
another pleasant autumn day is expected Wednesday due to light
winds, sunny skies, and low humidity. High clouds will be on the
increase Wednesday night into Thursday and low clouds will
increase thereafter as winds shift around to the south and bring
moisture back to the region. This means high temperatures will
plateau out in the low to mid 80s Thursday and Friday but low
temperatures will continue their warming trend with readings in
the mid to upper 60s by Friday night. With the increasing
moisture, a few showers or isolated storms may be possible on
Friday as an upper level shortwave trough moves across the region.
Surface based instability on Friday will exist across the western
and southern areas of the CWA where an axis of the richest low
level moisture will be positioned. Thus the highest PoPs of 30%
will be restricted to the southwestern zones, with 20% elsewhere,
and no mention of rain potential over the northeast zones.

The moist southerly flow prevails into Saturday with the airmass
continuing to acquire surface based instability. A weak capping
inversion will exist over North and Central Texas during the day
Saturday due to weak subsidence in the wake of the departing upper
level shortwave that moves across late Friday. However a much
stronger upper level trough will approach the region late Saturday
afternoon and strong height falls and frontogenetical forcing
will ensure deep layer forcing for ascent. This will erode any
capping inversion that exists over the region and likely result in
blossoming convective development well ahead of the surface front.
Have increased PoPs over the region Saturday evening and night
due to good model agreement in the upper pattern and high
confidence that moisture/instability will be sufficient for rain
and convection after 3 days of return flow. Additional convection
will likely develop along and behind the front as it arrives into
the region late Saturday night and early Sunday. As far as the
severe weather potential, it may be mitigated by a lack of deep
layer wind shear with 500 mb winds only forecast to range between
20-30 knots by the various models. So the primary convective mode
is likely to be multicell clusters, but due to forecast CAPE
values of 1500+ J/kg, a few storms may be strong to marginally
severe. Otherwise rain and storms should end from northwest to
southeast Sunday morning with cooler and drier conditions
spreading across the region during the day.

Northwest flow aloft is forecast to set up in the wake of the
weekend system which should bring us a multi-day stretch of
pleasant weather. Generally clear skies and dry air will promote
cool nights and mild days. Highs should be in the 70s with lows in
the 40s and 50s.



.AVIATION... /Issued 1220 PM CDT Tue Oct 17 2017/
An upper level ridge will provide clear skies and benign weather
across North and Central Texas for the next few days. With a
surface ridge centered over the Southeastern CONUS, our winds
will fluctuate from south to southeast at 10 KT or less. Will
keep things simple and persist with the one-line TAFs for the 18Z



Dallas-Ft. Worth    54  83  59  83  64 /   0   0   0   0   5
Waco                48  83  56  83  62 /   0   0   5   5  10
Paris               47  79  51  79  57 /   0   0   0   0   5
Denton              47  83  54  81  62 /   0   0   0   0   5
McKinney            47  81  54  81  60 /   0   0   0   0   5
Dallas              55  83  59  83  64 /   0   0   0   0   5
Terrell             48  83  54  82  60 /   0   0   0   0   5
Corsicana           50  82  55  82  62 /   0   0   0   5   5
Temple              45  83  55  82  63 /   0   0   5  10  10
Mineral Wells       45  84  53  82  62 /   0   0   0   0  10



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