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

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FXUS64 KFWD 050223 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
823 PM CST Sun Dec 4 2016

.UPDATE...
Main update was to reconfigure PoPs/Wx grids for the overnight
hours. Otherwise, the remainder of the forecast remains unchanged.

IR satellite imagery in combination with the latest suite of upper
air observational data reveals that a wedge of dry air has slipped
south of the Red River. The 00 UTC FWD RAOB sampled some of this
dry air with a PWAT falling to just above half an inch (compared
to a PWAT of just above one inch this morning). The drier air`s
southern progression should be limited somewhat tonight as the cut
off low across northern Mexico lifts northwards towards the region
and deeper Gulf of Mexico moisture is transported northward. The
northerly winds aloft will eventually become more easterly and
ultimately southeasterly. The subsequent isentropic ascent along
the 305K theta surface is expected to be confined to Central TX
before this conveyor of ascent spreads northward towards I-20
around daybreak Monday. With this in mind, I`ve re-configured and
limited PoPs to areas generally along and south of a line from Breckenridge
to Sagner to Paris. Locations further north of this line may still
be under the lingering influence of the the aformentioned dry air
and I think chances for measurable precip is low. With ascent
still forecast to occur here, however, I`ll include a mention of
drizzle...especially as shallow low level moist advection is
injected into the dry air at the surface. I won`t rule out a
rumble of thunder or two down across extreme southern/southeastern
counties where there does appear to be some elevated instability,
but light rain showers are expected to be the primary convective
mode.

The remainder of the forecast elements appear to be on track.
Updated products have been transmitted.

24-Bain

&&

.AVIATION...
/ISSUED 600 PM CST Sun Dec 4 2016/
/00Z TAFS/

Extensive low cloud cover again prevails across most of North and
Central Texas this evening. Water vapor imagery shows the large
upper low spinning over northern Mexico. This system is expected
to move across North Texas during the day Monday. In the
meantime...widespread MVFR cigs are expected to prevail through
late evening. There is some drier air moving in aloft from the
north and we`ve seen a gradual north to south erosion of the lower
clouds over the last several hours...however most of the short
term guidance suggests that the southward push of drier air will
be short lived. Latest thinking is that it will not make it into
the Metroplex so have kept MVFR cigs in through the late evening.

Later tonight...widespread light rain is expected to fill in
across most of the area. This will help cigs to continue lowering
through the early morning hours. Expect IFR cigs by sunrise with
reduced visibility in light rain. The light rain will continue
into the early afternoon hours before a rapid west to east shift
in precipitation brings things to an end. While the rain is
expected to end and drier air aloft will move into the
region...there will still be abundant moisture in the lowest 1000
feet of the atmosphere which will likely result in areas of
fog/drizzle with IFR conditions continuing into Monday night.

Dunn


&&



.PREV DISCUSSION... /ISSUED 350 PM CST Sun Dec 4 2016/
North and Central Texas have experienced a break from the rain
and drizzle that plagued the region yesterday, but another round
of rain is expected tonight through Monday evening as an upper
level low moves across the region. The upper level low is
currently located just east of southern Baja California. It will
start moving northeast tonight and cross North and Central Texas
tomorrow afternoon and evening.

Large scale lift ahead of the upper low will result in another
round of widespread showers with isolated thunderstorms on Monday.
Rain is already expanding in coverage from the Hill Country back
into northern Mexico. As this rain approaches our Central Texas
counties this afternoon, it is working against some cold air
advection that is dissipating most of the rain activity. However,
isentropic lift is expected to increase across our southern
counties tonight, and we expect to see some rain spreading south
to north overnight tonight. The rain may move into our far
southwest or southern counties this evening, and will carry the
highest PoPs south of Interstate 20 after midnight tonight.

The rain will continue to expand in coverage on Monday, and then
gradually end from west to east Monday afternoon and evening. The
best chances for rain will be across the southeastern half of the
CWA. We anticipate just about everyone will receive rainfall but
it is possible locations in our far northwest could miss out on
this last round of rain. Rainfall totals will vary from less than
a 1/4 inch in the northwest to near 3/4 of an inch in the
southeast. With more convective activity expected with the added
lift from the upper level low, pockets of heavier rainfall can be
expected within thunderstorms, but widespread or significant
flooding is not expected. Very localized nuisance flooding may
occur where some of the heaviest rains occur, but antecedent soil
conditions are likely to handle the rainfall without much problem.

As the upper level low moves northeast of the region on Tuesday,
a weak front will drop into the region. This front will bring
drier air to the region but warm air advection will bring some
limited moisture back to the region Tuesday night and Wednesday in
advance of our strong cold front. We may see a few showers in our
eastern counties Wednesday and Wednesday night ahead of the front,
but forecast soundings indicate a strong cap will likely suppress
any attempts at rain. Instead, we may see some drizzle in our
eastern counties if the isentropic lift is decent enough.

The front will come blasting through Wednesday evening and night
with strong north winds of 15-20 mph. These strong winds will
continue into Thursday morning. Temperatures will drop quickly and
most of the region will fall into the mid 20s to mid 30s Thursday
morning. However, with the wind, it will feel like the teens and
lower 20s. On Thursday, temperatures will only recover into the
mid 30s to lower 40s. With the wind, it will feel like a bitter
cold day by Texas standards. A surface high will slide into the
region Thursday afternoon and night, decreasing the wind speeds.
With clear skies and light winds, temperatures will plummet
Thursday night and Friday morning into the 20s, with wind chill
readings in the teens and lower 20s.

Temperatures will still be winter-like on Friday but a warming
trend will begin Friday night. At that time south winds will return
to the region as the surface high slides east and a weak low
pressure system develops in the Plains. Another front now looks
like it will arrive early next week instead of next weekend.

JLDunn



&&


.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    46  50  43  56  43 /  40  90  30  10   5
Waco                47  51  43  60  43 /  80  90  10   5   5
Paris               43  48  44  55  43 /  10  90  60  10   5
Denton              45  51  42  55  41 /  20  90  30  10   5
McKinney            45  50  43  55  42 /  20  90  40  10   5
Dallas              46  50  44  57  44 /  40  90  30  10   5
Terrell             46  50  43  58  44 /  50  90  40  10   5
Corsicana           49  50  44  59  45 /  80  90  20   5   5
Temple              47  51  45  62  44 /  90  90  10   5   5
Mineral Wells       45  50  41  55  41 /  30  90  20  10   5

&&

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

$$

91/24


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