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

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FXUS64 KFWD 210913
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
413 AM CDT SUN AUG 21 2016

.SYNOPSIS...
The widespread heavy rain potential will be confined to mostly
Central TX for today as drier air slowly invades North TX. Low
level moisture will gradually lift back towards the north late
Sunday into Monday. While large scale ascent will be generally
weak, moisture will be in place areawide to support a low chance
for rain through most of the work week.

&&

.SHORT TERM (Today through Tuesday)...
Surface analysis combined with radar/satellite imagery this
morning revealed that a majority of the convection has been
confined to Central and Southern TX. These areas of convection
were associated with good convergence along remnant outflow
boundaries and lift associated with a couple of MCVs. One decaying
MCV was noted moving through the Piney Woods of East TX while
another one was closer to the Coastal Plain just east of San
Antonio. The departure of the lead MCV has resulted in decreasing
mesoscale subsidence as evidenced by recent radar trends. With
winds on the KGRK VWP veering from the northeast towards the
south, it`s likely that ascent atop remnant outflow boundaries is
instigating new convection. Recent runs of both the operational
and experimental HRRR appear to be doing a decent job with regards
to capturing this evolution and PoPs in the near term have been
adjusted accordingly. The best rain chances today will be confined
to Central TX with lower PoPs towards the I-20 corridor.

With regards to the flash flood potential for today---I have
shaved off a few more rows of counties and the current
configuration includes areas along and south of a Palestine to
Mexia to Killeen line. Areas south of I-20, but north of the
aformentioned line received generally less than 2 inches of rain
on Saturday. While additional rainfall will be possible across
this zone, it`s unlikely that there will be widespread flash
flooding here, especially with slightly drier air working its way
in from the north. Low level moisture will begin to lift back to
the north as broad lee-side troughing resumes, but overall rain
rates should remain below 1 and 3 hr flash flood guidance. Areas
along and south of the Palestine to Mexia to Killeen line still
remain quite saturated from last week`s rain. In addition, FFG
remains relatively lower here and the environment is still
characterized by almost 2" PWAT values. That being said, the
mesoscale ascent responsible for the current convection will
probably not last all day and it`s likely that the remainder FFA
will be cancelled early sometime today. Otherwise, the other
minor concern will be patchy fog for areas generally along and
north of I-20 this morning. Current implications are that despite
wet grounds, clear skies and light winds---enough dry air may
exist near the top of the PBL to mitigate widespread dense fog.
For now, have inserted patchy fog into the worded forecast and
will monitor trends to see if any dense fog related products need
to be issued. Temperatures today will be a little warmer in the
north as the diurnal temperature curve will be quite sharp due to
the presence of dry air and expected sunshine.

Tonight into Monday will see a general increase in both clouds and
moisture as the lee trough gradually draws warm/moist air
northward. There could be some spotty advection fog around tonight
into Monday morning, but for now, will hold off on mentioning any
of this in the worded forecasts as there is some uncertainty with
regards to formation. There will be the threat for some WAA
showers and isolated thunderstorms. Most of the coarser models are
fairly aggressive with the coverage. With most CAMs only implying
isolated to widely scattered coverage, I`ve tapered PoPs down
towards the slight chance/chance category. The highest PoPs were
relegated to western zones along the eastern periphery of the
1000-500mb thickness ridge and along the Red River where low level
convergence may be the greatest along the ill-defined baroclinic
zone.

For Tuesday---I will keep a mention of low rain chances as WAA is
expected to continue across the region. Again, I am not overly
confident in widespread coverage of showers/storms with no apparent
impetus for convection, so I will keep slight chance PoPs across
northern zones on Tuesday morning. Tuesday afternoon should be
mostly dry.


&&

.LONG TERM (Wednesday through Saturday)...
For Wednesday---mostly dry conditions should exist as a portion of
a H5 ridge axis extends a bit further to the east from the
southeast U.S. The 850/925mb reflection of the ridge should help
to tighten the pressure gradient resulting in breezy south to
southwest winds, especially across western zones. Fire weather
concerns will be quite minimal due to the recent rains, but
temperatures may climb back towards the low to perhaps mid-90s due
to the slight adiabatic compression. As a result, have nudged
temperatures a few degrees above guidance. There is a very low
threat that a shower or two may drift southward from convection
along a cold front across OK, but this potential remains low and a
10-20% PoP should suffice for northwest zones.

For Thursday and beyond---low rain chances return for a larger
portion of the forecast area as a cold front should slide
southward towards the Red River. With a fairly amplified trough to
the west, it appears unlikely that this front will make it much
further south than the Red River. Some convection will be possible
along this front and have continued with low chance PoPs across
the northwest. I have also inserted a low chance for rain for
eastern/southeastern zones as the ridge to the east weakens and
potentially opens the door for some sea-breeze convection. Beyond
Thursday, I`ve broad brushed PoPs mainly for diurnal convection.
There is some indication that another frontal intrusion south of
the Red River will be possible during the weekend, but this is
quite some time away and refinements to the long term portion of
the forecast will be made.

24-Bain

&&

.AVIATION...
/ISSUED 1134 PM CDT SAT AUG 20 2016/
Decaying area of rain/storms associated with a departing MCV
continues across parts of Central TX tonight. Additional isolated
showers and thunderstorms have developed in its wake which should
continue overnight with the aid of the low-level jet. This
activity is expected to affect the Waco TAF site for at least a
few hours early Sunday morning but should not progress northward
to the DFW Metroplex sites. As a result, have removed all mentions
of showers from DFW area TAFs and have also backed off on the
amount of time that Waco should be affected based on the latest
trends.

Otherwise, calm surface winds will persist overnight in the
vicinity of the stalled front. At the Metroplex sites, some brief
lowered vsbys due to mist will be possible overnight (and has
already been noted at FWS and CPT), but should not persist long
enough to warrant a mention in the TAFs. MVFR cigs may affect the
Waco site around the time that rain may be occurring, but low cigs
are no longer expected at DFW area airports. Winds will increase
during the morning hours and will initially be out of the
northeast before veering to the east or even southeast by Sunday
evening.

-Stalley


&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    83  72  88  74  91 /  20  20  30  20  20
Waco                82  72  87  74  90 /  70  30  20  20  20
Paris               87  66  85  71  90 /  20  20  40  40  20
Denton              87  69  86  73  90 /  20  20  30  30  20
McKinney            87  70  86  74  90 /  20  20  30  30  20
Dallas              84  73  88  75  90 /  20  20  30  20  20
Terrell             84  72  87  74  89 /  30  20  30  20  20
Corsicana           83  72  88  74  90 /  60  20  20  20  20
Temple              83  71  87  74  90 /  90  30  20  20  20
Mineral Wells       83  69  86  72  90 /  20  20  40  30  20

&&

.FWD Watches/Warnings/Advisories...
Flash Flood Watch through this evening for TXZ147-148-158-
160>162-174-175.

&&

$$

05/24



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