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

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FXUS64 KFWD 030330 AAB

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
930 PM CST Fri Dec 2 2016

The inherited forecast remains in good shape this evening. This
update is mainly to re-trend the near-term weather elements and
to make a few tweaks to the PoP grids.

An initial wave of showers continues to progress through the
region at this hour, with the bulk of the activity now moving into
central and western Oklahoma and East Texas. Precipitation has
been light, with amounts generally under a tenth of an inch. With
the strongest isentropic ascent now moving north of the Red River,
we`ll see a short-lived reduction in precip coverage for the next
few hours.

The next batch of rain and thunderstorms is currently congealing
across Coahuila and the Middle Rio Grande Valley as substantial
upper-level divergence offered up by a strengthening 130+ kt jet
streak overspreads western Texas. This area will blossom
overnight, and envelop all of North Central Texas with widespread
rainfall early Saturday morning and through much of the afternoon
and evening. The focus for the heaviest axis of rainfall continues
to be along a strong low-level theta-e axis which will set up
from roughly Athens to Waco to Killeen. Enhanced convergence and
moisture transport should result in widespread rainfall totals of
2-3 inches in this region. Some high-resolution guidance, such as
the NCAR ensemble, suggests localized amounts through Saturday
evening of 4+" are not out of the question. We continue to believe
antecedent dry soil conditions across the region will largely be
able to handle this steady rainfall, precluding the need for a
Flash Flood Watch, although localized minor flood issues may
arise. Rainfall totals and soil/river responses after this next
batch will largely dictate the need for a Flood Watch during the
Sunday night into Monday timeframe as the last wave of rain moves
into the area.



/ISSUED 558 PM CST Fri Dec 2 2016/
/00Z TAFS/

Conditions will continue to deteriorate through late tonight as
areas of light to moderate rain overspread North Texas. Right
now...very light rain has spread as far north as DFW although the
air beneath the rain producing clouds is still sufficiently dry
for most precipitation to evaporate. This should result in only
very light rain or sprinkles for the next few hours. As these
lower level rapidly saturate...widespread showers are expected
through the overnight hours. Ceilings are expected to drop rapidly
later tonight becoming BKN/OVC030 before midnight and IFR during
the overnight hours.

Persistent cool east-northeast winds at the surface will be
accompanied by warm moist flow above the surface through the day
Saturday. IFR conditions are expected to prevail areawide through
Saturday with periods of rain. There does appear to be a window
for isolated thunderstorms early Saturday morning into the early
afternoon hours across the region. No severe weather is expected
but lightning will be a threat. Otherwise...there may be a brief
period where precipitation diminishes in coverage Saturday
night...but IFR cigs/vis are still expected to prevail. Rain
chances will continue on and off well into Monday.



.PREV DISCUSSION... /ISSUED 353 PM CST Fri Dec 2 2016/
Our anticipated rain event is now underway as showers are
currently spreading north through Central Texas and into our
western counties. The rain is being generated by increasing
isentropic lift ahead of an upper level low currently crossing
Arizona into northwest Mexico. The isentropic lift will continue
to increase into the overnight hours, and so will the rain
coverage and intensity. For the remainder of the evening hours,
the coverage of rain will increase from south to north with
widespread showers expected overnight and Saturday morning.

Isolated thunderstorms will be possible due to a limited amount
of elevated instability, but severe weather is not expected. The
main hazard through Saturday morning will be the potential for
locally heavy rainfall across roughly the southeast third of our
CWA. This is where we expect the highest rainfall totals with
totals of 2-3 inches generally southeast of a Waco to Van Zandt
line. This rain will fall over an area currently experiencing
D0-D2 drought conditions which should provide relief. At times,
the rain may be heavy across our southeast counties, especially
within thunderstorms. We considered the need for a Flood Watch at
this time, but with the current dry conditions experienced across
much of the region (especially in our southeast), in addition to
the more steady nature of the rain through the night, we expect
most of the region will not be significantly impacted by flooding
through Saturday morning. It`s definitely possible there may be
short-term minor flood problems in some areas, in particular in
the southeast, but we feel most of the region will fair okay with
this first round of rainfall. It is the next rounds of rain that
may result in some flood impacts depending on how much rain falls
tonight through Saturday morning.

The first wave of rain is expected to move east Saturday
afternoon and evening with a break in the overall coverage and
intensity Saturday afternoon through the evening hours. Scattered
rain showers can still be expected but the lower coverage of rain
may allow for outdoor activities to continue Saturday evening. The
next wave of rain is expected Saturday night into Sunday morning
but minor discrepancies between the models challenge the coverage
and how much rain is expected during this period. Weak upper
level ridging over the region during the day on Sunday is expected
to result in less rain coverage on Sunday. The best rain chances
Saturday night and Sunday are south of Interstate 20 across our
Central Texas counties. Rainfall amounts in this time period do
not look quite as high, but could exacerbate any ongoing flood
problems remaining from the first round of rain. We will further
evaluate the need for a Flood Watch with the second and/or third
wave of rain.

Our final wave of rain is expected Sunday night and Monday as the
upper level low moves across the state. The rain will end from
west to east Monday afternoon and evening. In the wake of the
upper level low, broad cyclonic flow will continue across the
country through at least Thursday. Under this pattern, an arctic
front will arrive around the middle of the week bringing winter-
like temperatures to the region. Unfortunately the GFS and ECMWF
differ on the timing of the arctic air, because they differ on
the strength and timing of the upper level trough. The GFS, which
has support from the Canadian for now, brings the front through
on Wednesday while the ECMWF blasts it through as a strong front
Wednesday night. There will be a chance for some showers and
storms ahead of the front Wednesday and Wednesday night across
our eastern counties. Behind the front, there are hints of what
appear to be light winter precip but as of right now the timing
and temperatures do not align for confidence in this possibility so
will continue with a dry forecast for now. It is more likely we
will be too dry for precip behind the front.

Rainfall totals through Monday are forecast to be 1-5 inches with
the highest totals in our southeast counties. Isolated locations
in the southeast could potentially receive closer to 6 inches of
rainfall over the multi-day period.

Temperatures the next few days will remain in the 40s to mid 50s due
to the cloud cover and rain. We will warm on Tuesday but highs in
the 40s and overnight lows in the 20s and lower 30s can be
expected behind the front. A hard freeze is expected Thursday
and Friday mornings in many areas of North and Central Texas.



Dallas-Ft. Worth    48  50  44  54  45 /  90 100  60  40  60
Waco                48  50  45  52  45 / 100 100  80  70  80
Paris               46  47  42  51  42 /  80 100  90  30  50
Denton              46  48  42  54  43 /  80 100  60  30  60
McKinney            47  48  43  53  43 /  90 100  70  30  60
Dallas              49  50  44  54  45 /  90 100  60  40  60
Terrell             47  50  44  53  45 /  90 100  80  40  70
Corsicana           48  50  44  52  45 / 100 100  90  60  80
Temple              48  50  44  51  45 / 100 100  80  80  80
Mineral Wells       46  48  42  53  42 /  80 100  70  40  60




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