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

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FXUS64 KFWD 041739 AAB
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1139 AM CST Sun Dec 4 2016

.UPDATE...
This afternoon is expected to be quiet and dry for most of North
and Central Texas, but periods of light to moderate rain will
remain possible mainly south of a Palestine to Waco to Goldthwaite
line. Rain chances will increase tonight as an upper level low
approaches from the southwest.

Otherwise it will be chilly and mostly cloudy, but there likely
will be some cloud thinning and/or clearing across our northwest
counties and then northern counties this afternoon and evening.
Breaks in the clouds will allow temperatures to creep a little
higher this afternoon despite some continued cold air advection.
However, have kept high temperatures for today in the lower 50s.
Some areas may actually not even reach 50 degrees and remain at
48-49 degrees.

JLDunn

&&

.AVIATION...
/ISSUED 549 AM CST Sun Dec 4 2016/
A few passing light showers will occur through mid morning, then
likely a reprieve in precipitation until later tonight, outside
of some drizzle this morning. Challenges will be cigs as some
subsidence occurs by this afternoon and relatively drier low-level
air entrains slowly in from the north.

.DFW Metro airports...
IFR cigs with mostly VFR visibilities will prevail this morning
and will carry VCSH early on, as well as a TEMPO for LIFR through
mid morning. With subsidence noted above and some modest dry air
entrainment from the north by early afternoon, look for MVFR
cigs to prevail with even a brief possibility of VFR cigs around
mid afternoon, with prevailing north-northwest winds around 10
knots. Winds will veer and weaken as they become northeasterly 5-7
knots. In addition, our next disturbance will bring a mention of
VCSH back to the forecast. In addition, the lower boundary layer
should cool and re-saturate with IFR conditions returning by
midnight/after.

.Waco Regional...
IFR/LIFR cigs should prevail much of the morning with VCSH
continuing as this morning`s disturbance moves across. A brief
period of MVFR cigs should prevail this afternoon and early
evening, before IFR cigs return with a chance of showers once
again. Though isolated thunder is possible, instability is not
great enough and chances are too low for any mention in the Waco
12z TAF. North-northwest winds 5-8 knots will become northerly
around 10 knots, then north-northeast 5-8 knots tonight.

05/


&&



.PREV DISCUSSION... /ISSUED 327 AM CST Sun Dec 4 2016/
Cool and wet weather will continue today as the upper low
responsible for our weather over the past 36 hours continues to
approach the region. Scattered showers and drizzle has developed
from southern KS all the way to South TX as broad ascent ahead of
an upper trough acts upon abundant moisture in the lowest 10 kft
of the atmosphere. The activity across North TX is mostly due to a
northern stream progressive shortwave trough rather than the deep
cutoff low positioned to our southwest. As this trough swings
through this morning, rain and drizzle should come to an end for
North TX as weak subsidence overspreads the area. Low-level winds
will become more northwesterly and the 850mb front that has been
stalled over our forecast area will shift slightly southward,
allowing drier air to build into North TX today. As a result,
there might actually be a bit of clearing across our northwestern
areas this afternoon where a few peeks of sunshine are possible.
This won`t be the case for most of Central TX where better
moisture content and low-level warm advection will cause scattered
showers to continue throughout the day. Have trimmed back PoPs
and shifted the higher chances farther south where the broader
rain shield should be located.

Our final wave of rainfall will develop later this evening and
overnight as the upper low begins lifting northeastward out of
Mexico. Strong warm advection and upper-level divergence should
result in another broad swath of showers across most of North and
Central TX through the day Monday. Some embedded thunderstorms
will also be possible during this time due to the stronger lift
from dynamic forcing as well as better instability than we`ve seen
the past few days. This increased buoyancy will be the result of
cooling temperatures in the mid-levels as the upper low moves
directly overhead. Showers and thunderstorms will taper off from
southwest to northeast on Monday night as the system departs the
region.

While the upper low is ejecting northeastward, another large
trough will be deepening across the western CONUS. One embedded
shortwave within the large scale trough will cause a surface low
to form across the TX Panhandle Monday night. As this low moves
southeastward into south TX, a weak cold front will be pulled
through the forecast area. There won`t be much cold air behind
this front, but it will act to push low-level moisture well to
our south. With little forcing other than the front itself and
very limited moisture available in the first place, am not
expecting any rainfall on Tuesday. However, increased cloudiness
is likely due to saturation within the frontal inversion layer.

The heavily-advertised Arctic blast is still on track to arrive
sometime Wednesday afternoon or Wednesday night, although models
still disagree on the timing. The GFS remains the fastest
solution bringing the front across the Red River Wednesday
afternoon while the ECMWF and Canadian hold off until Wednesday
evening/night. Just ahead of the front Wednesday afternoon, some
weak ascent from WAA may result in scattered showers across parts
of East TX where higher moisture content should be available. Have
continued low PoPs in this area, although instability should be
limited/nonexistent so have not included any thunder mention. Very
strong surface pressure rises behind the front will result in a
sharp pressure gradient and therefore very windy conditions along
and behind the frontal zone (20-30 mph winds with higher gusts are
likely with this frontal passage).

Regarding the temperature forecast, very cold air will surge
southward with this Arctic front and will take up residence across
the forecast area for Thursday and Friday. Thursday will be a
biting cold with lows starting out in the 20s and 30s with
blustery winds still in place. Resultant wind chills will be in
the teens and 20s for a large part of the day and high
temperatures should struggle to reach the 40s. Surface high
pressure will settle into the area Thursday night which will cause
the winds to decrease. Clear skies combined with lighter winds
will allow temperatures to plummet Thursday night as efficient
radiational cooling occurs. Low temperatures on Friday morning
should be in the 20s area-wide with some teens possible in North
TX. Have undercut all temperature guidance, but still may not have
gone cold enough. Raw models and MOS can struggle mightily with
anomalous temperature forecasts like this and we`ll probably get
quite a bit colder than what they`ve been advertising so far.

As surface high pressure shifts east, return flow will resume
Friday night and warmer temperatures and higher dewpoints will
return on Saturday with temperatures bouncing back into the 50s.
Models are suggesting another weaker frontal passage either late
Saturday or Sunday with some low rain chances returning.

-Stalley



&&


.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    54  45  51  43  57 /  10  40  80  20  10
Waco                52  46  51  43  61 /  30  80  90  10   5
Paris               52  43  48  44  56 /  10  30  80  40  10
Denton              52  44  51  41  55 /  10  40  70  20  10
McKinney            53  44  49  42  56 /  10  40  80  30  10
Dallas              54  46  50  44  57 /  10  40  80  30  10
Terrell             53  46  50  43  57 /  10  50  80  40  10
Corsicana           53  47  51  44  60 /  20  70  90  20   5
Temple              53  46  52  44  62 /  60  90  90  10   5
Mineral Wells       53  45  51  41  56 /  10  40  70  10   5

&&

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

$$

25/82



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