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

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FXUS64 KFWD 022153

Area Forecast Discussion
National Weather Service Fort Worth TX
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.



/ISSUED 1215 PM CST Fri Dec 2 2016/
/18Z TAFs/

Much of West Texas is blanketed with MVFR/IFR ceilings, the
eastern extent of which includes Cisco and Comanche. Along the
I-35 corridor, the lowest few thousand feet of the atmosphere
remains quite dry, but westerly flow within the 750-850mb layer
has guided this West Texas moisture in our direction. VFR ceilings
around 7kft AGL will steadily lower as this layer moistens
further, and weak lift within it will allow for a few sprinkles
of light rain this afternoon. However, the first round of rain
showers approaching Austin at midday will take until sunset to
reach the Metroplex. This activity will be free of thunder, and
in-flight icing will be the primary concern. But with better
instability to our west and southwest, there may be some impacts
to west departures and arrivals through the Glen Rose VORTAC.

Showers will be ongoing this evening as a LLJ strengthens, both
processes further lowering ceilings overnight. Another round of
elevated convection will approach from the southwest before
daybreak. With steeper lapse rates aloft, these updrafts may be
of sufficient strength to produce lightning. Supersaturation near
the top of the nocturnal boundary layer will result in IFR
ceilings beneath the convective cells. Although the intensity of
the activity will wane by midday Saturday, showers will continue
during the afternoon hours. Ceilings and visibility will
deteriorate further, and IFR conditions will prevail through the
extended portion of the DFW TAF.

A break in the precipitation may begin Saturday night and continue
on Sunday before the next round arrives Sunday night into Monday.



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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