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

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642
FXUS64 KFWD 230038 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
738 PM CDT THU SEP 22 2016

.UPDATE...
Quick update to remove thunderstorm chances across the southeast
through early evening. There are a couple of showers approaching
College Station and these will continue to move northwest as
strong low level moisture advection continues...but overall
intensity should wane over the next hour or so. Otherwise...
strengthening southerly flow will help moisture spread rapidly
northward. Dewpoints will increase into the lower 70s by morning
and should be accompanied by an increase in low level cloud cover.
No other changes at this time.

Dunn

&&

.AVIATION...
/ISSUED 705 PM CDT THU SEP 22 2016/

DFW Metroplex TAF sites can expect VFR conditions to continue
through the night with southeast winds at 5 kts. MVFR ceilings
will be possible 13Z-16Z as Gulf moisture streams northward.
Stratus deck should scatter out after 16Z with southerly winds at
around 10 knots.

For Waco, VFR conditions will continue through 10Z Friday. After
10Z, a stratus deck is expected to move in reducing CIGs to around 1500
FT. Guidance is beginning to suggest a short period of IFR
conditions between 12Z and 14Z with ceilings below 1,000 FT and
patchy fog leading to reduced visibility. Stratus should scatter
out after 16Z, leaving VFR conditions. There is the possibility
of convection developing in the afternoon, but have opted to leave
it out of this TAF cycle due to the low confidence in it affecting
KACT.

Hernandez


&&



.PREV DISCUSSION... /ISSUED 332 PM CDT THU SEP 22 2016/
The first day of astronomical fall certainly doesn`t feel like
it. Temperatures this hour are running in the lower to middle 90s,
some 6 to 9 degrees above our climatological norms for this time
of year. It`ll start feeling more like fall in a few days,
however. More on that below. For the rest of this afternoon and
into the early evening, I`ve decided to add in a small sliver of
isolated thunder (10%) wording across our southeastern most
counties (Milam, Robertson, and Leon) where the cumulus field is
showing a bit more in the way of vertical development. This lines
up with recent objective analysis, which shows MLCAPE steadily
increasing as dewpoints in the 70s are being ushered into the
region. Any activity that manages to sneak into our CWA will
dissipate around sunset. We`ve also added in some patchy fog to
the forecast, roughly south and east of an Athens to Cameron line,
overnight and into tomorrow morning as moisture advection
continues and temperatures cool.

Tomorrow, a robust trough and associated upper-level low
currently diving into the Great Basin will emerge out onto the
High Plains. Stout upper divergence in association with the exit
region of a 100 kt jetstreak will encourage lee cyclogenesis
during this time, which will act to further increase the northward
transport of moisture across our region. Large-scale forcing for
ascent will, however, remain displaced well to the north and west
of North Central Texas tomorrow, so any showers and storms should
remain diurnally driven and isolated to scattered in coverage.
I`ve expanded some low 20% PoPs northward across our western
counties to coincide with progged deeper low-level moisture. A
well-mixed boundary layer with DCAPE values pushing above 1000
J/kg will mean any of the stronger storms will be capable of
producing some gusty downburst winds during the afternoon and
evening hours.

The upper-trough will nudge slowly eastward on Saturday and a cold
front will begin dropping southeastward across Kansas. Several
weak mid-level perturbations may graze our western zones and weak
warm advection/isentropic ascent will act to produce scattered
convection across our region. The highest PoPs (50%) are painted
across roughly the western half of the CWA, coincident with the
best upper-level dynamics and moisture content. Some strong storms
will be possible during the afternoon on Saturday, primarily
across our northwestern counties, where wind shear will be
maximized.

The forecast from Sunday and beyond remains in a state of flux,
with considerable uncertainties regarding the pertinent large-
scale features. That said, recent runs of ensemble systems from
the NAEFS (a combination of the GEFS and Canadian ensembles) to
the EPS (ECMWF ensemble) seem to be locking onto a scenario in
which a low cuts off from the mean flow and hangs back across the
Desert Southwest/northern Mexico as the main trough continues
east across the Upper Midwest. Given enough support from the
ensemble systems, we`ve started to trend the forecast gradually
towards the Euro`s cutoff solution in this afternoon`s forecast
package. As a result, the highest PoPs are painted during the
Sunday through Monday period, coincident with the arrival of a
surface cold front. I`ve then continued at least low-end chance
PoPs now through Tuesday as the frontal boundary may linger across
our CWA. If trends continue, these chances may need to be raised
in subsequent forecasts.

While we`re not prepared to bite off wholesale on the ECMWF
solution at this point, the potential exists for a fairly drawn-
out episode of wet weather across the region into next week. With
PWAT values approaching +2 SD and individual cell motions largely
paralleling the surface front, flooding--at least on a localized
basis--will be a concern from Sunday into Monday, and potentially
lingering through Wednesday. Along with the rain, much cooler
temperatures look to arrive this weekend and next week.

Carlaw



&&


.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    76  93  76  91  75 /   5  10  10  40  50
Waco                74  94  76  90  74 /   5  20  10  50  40
Paris               71  92  73  90  72 /   0  10  10  30  50
Denton              71  92  74  89  73 /   0  10  10  40  60
McKinney            72  92  74  90  73 /   0  10  10  40  50
Dallas              76  94  77  91  75 /   5  10  10  40  50
Terrell             73  93  74  91  73 /   5  10  10  40  40
Corsicana           74  93  75  90  74 /  10  20  10  40  40
Temple              74  92  74  89  74 /  10  30  10  50  40
Mineral Wells       71  92  73  89  71 /   5  20  10  50  60

&&

.FWD Watches/Warnings/Advisories...
None.
&&

$$



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