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

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FXUS64 KFWD 192013
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
313 PM CDT Thu Oct 19 2017


.SHORT TERM...
/Tonight/
The dry and pleasant weather we have experienced over the past
few days will begin to change overnight as a shortwave trough
over West Texas approaches. An area of abundant Gulf moisture
currently pooled along the Texas Coastal Bend will be drawn
northward over the next few days. PWATs near 1.5" will begin
nosing into the southern counties during the pre-dawn hours
Friday morning. Warm/moist advection showers will be possible as
this airmass moves in and some low POPs will remain across the
southern half of the region for the overnight hours. Low level
moisture will also usher in a layer of stratus, so increasing
clouds can be expected after midnight. More clouds and higher
moisture will lead to warmer overnight conditions with low
temperatures ranging from the upper 50s in the northeast to the
mid 60s across the south.

30

&&

.LONG TERM...
/Friday through next week/
As an upper level trough deepens across the western part of the
continent, 850mb flow is forecast to increase to near 35kt and
will transport Gulf moisture into the region. Precipitable water
is forecast to rise to near 1.6 inches Friday, which isn`t
impressively high, but will be sufficient for some scattered
convection to develop and stream northward through the region.
Shear profiles and instability are marginally favorable for storms
to become strong or possibly severe late Friday afternoon and
evening. However the lack of organized lift and a focus for
convection should mitigate this potential. Convection should
gradually diminish with the loss of heating during the evening
hours Friday. Continued moist southerly flow into the night will
ensure a solid deck of low clouds and unseasonably warm
temperatures with lows near 70.

On Saturday the upper trough will continue to sharpen and move
eastward into the Plains. Increasing cyclonic curvature and
decreasing values in the geopotential height fields across
western Texas are indicative of strong dynamic forcing for ascent
spreading into the region during the afternoon and evening hours.
This lift should help to erode a capping inversion over the
region ahead of an approaching cold front. Because of the cap it
is likely that most of the region will be void of convection
through at least early afternoon Saturday, but some activity may
start to develop and stream northward by mid to late afternoon,
especially east of I-35 within the moisture axis. It`s possible
that some of these storms could become strong or severe, but the
main severe weather potential will likely hold off until Saturday
evening.

As the front impinges upon the increasingly moist and unstable
airmass over North Texas late Saturday afternoon, convection
should rapidly develop along it. At this time North Texas will be
placed in a strongly divergent entrance region of an impressive
south to north 250mb jet max. This should help ventilate the
convection and allow it to grow upscale into a solid line or
complex. While the primary storm mode is expected to be linear
due to the strong dynamics in play and bulk shear vectors oriented
nearly parallel to the frontal boundary, instability and shear is
sufficient for supercells. So we will have to keep an eye out for
any convection that develops ahead of the front within the warm
sector for an isolated tornado threat. Otherwise, the main severe
hazards will be damaging winds and hail up to golf ball size.
Although the entire region has at least some risk of severe
weather, the threat looks highest north of I-20 where there is
the best combination of deep layer shear and instability (shear
values decrease toward Central Texas). Average rainfall will
range from near 2 inches in the northeast CWA where rain is a sure
bet to less than a half inch across the southwestern zones where
rain isn`t a guarantee and the line may be thin with some gaps.
Some isolated locations may receive 3-4 inches of rain, but given
the dry soils, the flash flood threat should remain very
localized.

The latest guidance is mostly keeping the upper trough attached
to the mean flow and has sped up the progression of the convection
and front. The rain should be ending Sunday morning from NW to SE
and we expect clearing skies to occur during the day Sunday.
North winds near 10 mph will result in modest cold advection and
high temperatures will be in the low 70s north to upper 70s
south. The surface high will slide over the region Sunday night
and good radiational cooling will bring lows down into the 40s and
50s.

Dry northwesterly flow aloft will prevail through next week. As a
deep trough drops into the eastern US early next week it will
send a second reinforcing cold front through the region early
Tuesday. Generally clear skies, low humidity, and light winds will
make for a stretch of nice autumn weather. Highs will be in the
70s and lows will be in the mid 40s to mid 50s.

TR.92

&&


.AVIATION... /Issued 1236 PM CDT Thu Oct 19 2017/
Satellite imagery shows the continued approach of a shortwave
trough over West Texas and the cirrus canopy accompanying it. The
atmosphere will moisten up tonight in advance of the system,
which will be evidenced by higher dewpoints and a deck of stratus
spreading north across the area Friday morning. MVFR CIGs have
therefore been introduced at KACT at 20/12Z, then 20/15Z in the
DFW Metroplex. The main issue in the short term is the area of
smoke and haze in the Metroplex which is believe to have
originated from a small controlled burn. There was a pronounced
inversion this morning which likely trapped the smoke near the
surface, but conditions should continue to improve this afternoon
as mixing heights increase.

Friday afternoon has the potential for convection due to increased
moisture from the Gulf and lift associated with the shortwave.
Guidance is mostly conservative with convective coverage due to
the lack of any significant forcing mechanism so TS will be kept
out of area TAFs at this time. The extended portion of the DFW TAF
will, however, include VCSH beginning 20/20Z.

30

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    65  81  71  85  61 /   5  30  20  30  90
Waco                63  81  71  86  64 /  20  40  20  30  80
Paris               57  78  65  80  62 /   5  20  30  40 100
Denton              61  80  69  84  58 /   5  30  20  30  90
McKinney            61  80  69  82  61 /   5  30  20  40  90
Dallas              67  81  71  84  62 /   5  30  20  30  90
Terrell             62  82  68  84  63 /  10  30  30  30  90
Corsicana           63  80  68  84  65 /  20  40  30  30  90
Temple              63  81  70  85  64 /  20  40  30  30  70
Mineral Wells       61  80  67  84  57 /  10  30  20  30  80

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$



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