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

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000
FXUS64 KFWD 011136
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
636 AM CDT SAT OCT 1 2016

.AVIATION...
/12Z TAFs/

Light and variable winds at the start of the TAF period will
become light southerly in a few hours. Wind speeds will remain
less than 7-8 kts through the period with the wind direction
varying between southeast to southwest. BKN mid and high level
clouds will persist for much of the period. As a shortwave
translates across the region today, a few sprinkles may be noted
at times but measurable precipitation is not expected.

JLDunn

&&

.SYNOPSIS...
Pleasant and warm weather will be the norm for the first few days
of October. Towards the middle of next week, the chance for rain
will increase ahead of an approaching dryline and cold front. The
passage of the front should usher in cooler and drier air beyond
the mid-week time frame.

&&

.SHORT TERM (Today through Monday)...
The short term time period should be mostly dry with afternoon
high and evening low temperatures moderating each period. IR
imagery this morning revealed a widespread mid/upper level cloud
canopy, likely ahead of a shortwave trough sliding eastward
through the southern plains, continued to overspread nearly all of
North and Central TX. While cumuliform in nature, these clouds should
only produce an occasional sprinkle or two given their high based
nature and sufficient dry air down at the surface per regional
RAOBs.

For Today---It should be a partly sunny day across much of the
forecast area, with the exception being across far western zones,
where more sun than clouds are expected late. Daytime high
temperatures will be hampered somewhat by cloud cover, but most
areas should still top out in the upper 70s to low 80s. Despite
clearing skies, tonight should feature slightly warmer conditions
as light south winds develop in response to weak lee-troughing to
the north and west.

For Sunday---Mostly sunny skies are expected as Saturday`s upper
trough departs the region and is replaced with a more subsident
airmass aloft. Temperatures should be a degree or two warmer than
Saturday with the relatively clearer skies and sinking motion
associated with the ridge. Light south winds may transport a small
amount of moisture northward, but all in all, it should be a very
nice day on Sunday.

For Monday---Monday will be very warm with above normal
temperatures as the spine of the ridge axis will be oriented directly
on top of North and Central TX. High temperatures will climb into
the mid to upper 80s, and it`s not out of the question that some
areas could near 90 degrees across far southern zones. Our
attention will turn towards the west as a potent upper trough will
amplify some across the intermountain west and four corners
region. As more impressive height falls overspread the central
Plains, a broad lee trough should develop. This lee trough will
start to draw moisture from the western Gulf of Mexico northward.
A few areas of cumulus may develop across far southern and western
zones, but the forecast will remain dry with the ridge still
overhead.

&&

.LONG TERM (Tuesday through Friday)...
For Tuesday---The forecast remains challenging during this time
period as discrepancies between models remain. What is certain,
however, is that lee troughing will aid in the development of a
sharpening dryline across eastern portions of the TX panhandle
late Monday and into Tuesday. This feature should gradually mix
eastward towards the Big Country and may even near far
northwestern portions of the CWA. With 700-850mb flow veering, a
decent cap should be in place just east of the dryline. Current
implications are that a bulk of the forcing for ascent will remain
to the north and west of North and Central TX. As a result, a good
portion of the day on Tuesday will likely be dry. Late in the
afternoon, heating, weak ascent at the tail end of the upper jet
and perhaps some mesoscale circulations along the dryline may be
enough to erode the cap sufficiently for a few storms to develop.
How close the dryline mixes towards our area will dictate the
coverage of convection. The latest ECMWF has pulled the
position of the dryline a bit back to the west than the previous
runs (which would support a drier forecast) and the GFS brings it
nearly to Young County (which may be a result of the GFS`s
tendency to quickly mix). With those differences, I feel that a
20-30 PoP should suffice across far western zones, but it`s
possible that this may be overdone if the cap becomes more
formidable than currently thought and/or the 00 UTC ECMWF
solution verifies. In addition, I`ll keep some low PoPs along the
Red River Tuesday night into Wednesday as any nocturnal convection
(though likely not surface based) may persist with a strengthening
low level jet. If convective chances on Tuesday afternoon continue
to dwindle, it may be necessary to remove rain from this part of
the forecast as well. Questions regarding overall moisture
quantity still remain given the most recent frontal intrusion into
the Gulf of Mexico. While lee-side cyclogenesis will certainly
help a rapid surge of moisture northward, it`s likely that the
initial moist tongue will be shallow in nature. If moisture can be
lifted northward and enough instability is generated, convection
will develop in an environment characterized by 30-40 knots of
deep layer shear. This would set the stage for some strong to
severe storms on Tuesday afternoon, mainly across northwestern
portions of the forecast area.

For Wednesday---With the location of the upper trough to the
north, its plausible that the dryline will slosh back towards the
west during the overnight time period before mixing back towards
the east during the day. This is where model solutions diverge
greatly and generally lowers confidence in the forecast. The ECMWF
remains aggressive with continued amplification of the longwave
trough to the west. By midday Wednesday, it suggests that a potent
shortwave trough will rotate around the base of the larger trough
and provide enough lift across southern OK and northern TX to
produce convection. With an additional day of moisture return,
instability across North TX should be a bit better with some
values in excess of 1500 J/kg possible. Deep layer shear values
will be on the order of 30 to 35 knots which should easily support
organized storm modes and thus a threat for strong to severe
storms. The ECMWF (faster progression of the front and deeper
trough) appears to have most of its QPF tied to the southward
surging cold front with perhaps a few storms along the dryline.
The GFS (much slower progression and broader trough) develops
convection mainly along the dryline. Again, given the ECMWF`s
consistency, I`ve sided with its solution for now. We will
continue to monitor the evolution of model output over the next
several days.

For Thursday and beyond---The latest GFS has latched onto the idea
of a cold front sliding southward through the forecast area,
though it still lags the ECMWF by 6 to 12 hours with its timing of
FROPA. However, if the GFS solution is correct, temperatures on
Thursday will be much warmer over a larger area of North and
Central TX than is currently forecast. While I do think that the
ECMWF is correct in its faster progression, it`s possible that
some of our Central TX counties will still remain to the south of
the cold front during peak heating, and I`ve nudged max
temperatures upwards across these locations.

With the front sliding through most of the forecast area on
Thursday, there should be some decent rain chances given the
amount of low level moisture in place and focused ascent along the
front. Winds should ramp up a bit more than advertised by model
blend output given the good pressure rises after FROPA. These
winds should usher in cooler and drier air in its wake. Dry
conditions and cooler temperatures are expected as high pressure
settles in across the region. It will certainly feel like fall in
North and Central TX by the end of next week.

24-Bain

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    81  63  84  65  87 /   0   0   0   0   0
Waco                82  57  84  62  89 /   0   0   0   0   0
Paris               81  56  84  58  87 /   0   0   0   0   0
Denton              80  57  83  59  85 /   0   0   0   0   0
McKinney            80  57  82  60  84 /   0   0   0   0   0
Dallas              82  64  84  64  88 /   0   0   0   0   0
Terrell             81  59  84  61  87 /   0   0   0   0   0
Corsicana           81  59  84  62  88 /   0   0   0   0   0
Temple              81  58  84  62  87 /   0   0   0   0   0
Mineral Wells       81  58  84  59  88 /   0   0   0   0   0

&&

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

$$

82/24



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