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

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FXUS64 KFWD 130916
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
316 AM CST Wed Dec 13 2017

.SHORT TERM...
/Today and Tonight/

We`ll continue our ride on the temperature roller coaster today as
highs are expected to warm into the lower to mid 70s across a
sizable chunk of the region ahead of the next cold front.
Temperatures will get an additional boost from a bit of adiabatic
compressional warming as winds will favor a west-southwesterly to
southwesterly orientation ahead of the surface pressure trough,
and we`ve continued to side with the warmer guidance as a result.
The "coolest" parts of the CWA will actually be across our
southeastern-most counties where increasing upper-level moisture
will manifest in an increasing canopy of cirrus.

The main weather focus today will be on the elevated to near-
critical fire weather threat across most of the region. As
vertical mixing ensues later this morning, momentum transfer will
result in breezy conditions with occasional gusts to around 20-25
mph. Quickly warming temperatures, combined with dewpoints falling
into the 20s will also result in relative humidity values dropping
into the teens across the northwestern half of the CWA, and
between 20-30 percent across the south and east. These atmospheric
conditions, combined with the extremely parched vegetation, will
create an environment conducive to the quick spread of grassfires
if proper precautions are not taken. As a result, a Grass Fire
Danger Statement has been issued today for locations north and
west of a Temple to Corsicana to Athens line.

A reinforcing shot of cooler air will arrive this evening as a
dry cold front slips through the region.

Carlaw

&&

.LONG TERM...
/Thursday through Wednesday/

Thursday will be a noticeably cooler day with a 10-15 mph north
breeze and high temperatures in the mid 50s to lower 60s. Wind
speeds will relax overnight enough for radiational cooling
(despite some high clouds) to result in overnight lows varying
from the upper 20s to mid 30s.

An upper level trough begins to move across the Southern Plains
Thursday night-Friday morning and spreads large scale lift across
the region. The set-up appears very similar to the pattern that
produced light sleet in North and Central Texas last week, and we
will have to closely watch the observations and forecast soundings
for this time frame. Forecast soundings do show some possible
moisture within the H600-H450 layer, but the depth of the moisture
looks minimal and not as saturated as previous events. At this
time, there is also a lack of isentropic lift aiding in saturation
within that mid level layer. Therefore, will have silent 10 PoPs
in the forecast with no weather mention.

As the positively-tilted upper level trough moves through the
Southern Plains on Friday, the base will detach into a closed low
over Mexico. With the main branch of the upper level trough still
passing, Friday will also be a chilly day with high temperatures
mainly in the 50s. The upper level low over Mexico will rapidly
move northeast Friday night and Saturday ahead of another
approaching upper level trough. South to west winds are expected
to return in the lower and mid levels Friday night, and the models
subsequently produce a rapid return of moisture above the surface
Friday night and Saturday. At the surface, a low pressure in the
western Gulf of Mexico looks to keep moisture return limited
until later on Saturday, but even this rapid moisture transport
looks questionable with dewpoints increasing nearly 20 degrees in
about than 12 hours. GFS and ECMWF soundings instead indicate that
top-down saturation will eventually allow precipitation to reach
the ground, and due to consistency, have increased PoPs Saturday
afternoon and Saturday night. Thunderstorms will be possible but
strong or severe storms are not expected due to limited
instability. At this time, the highest rainfall totals are
southeast and east of Central Texas but rainfall totals up to a
quarter of an inch are possible in our southern and eastern
counties. Locations northwest of DFW may miss out on the rain all
together or only receive very minimal rainfall. Otherwise, expect
a cloudy, breezy and chilly Saturday across the region. Due to a
combination of breezy winds and low humidity values, locations
west of I-35 may experience elevated fire weather concerns
Saturday afternoon, but this also depends on the speed of the
moisture return and rainfall coverage.

A front will pass Sunday night into Monday but temperatures will
warm a little each day through at least next Wednesday. The models
are showing another strong front arriving late next week, possibly
bringing arctic air to North and Central Texas. However, as to be
expected, there are differences in the upper air patterns between
the models late in the week. Based on raw model output (mostly
from the GFS), talk is already being generated about a possible
wintry mix around Christmas. As a reminder, it is much too early
to predict with confidence if any winter precipitation will occur
around the holiday. However, we will closely be watching this
potential in the models over the next 7-10 days and changes are
likely to occur.

JLDunn

&&


.AVIATION... /Issued 1121 PM CST Tue Dec 12 2017/
Light southwest winds will continue through daybreak before
increasing to around 15 kts for most of Wednesday. Later
Wednesday evening, another dry cold front will move through the
area, causing winds to turn to the north. While the front should
clear the DFW Metroplex before 06z, it likely won`t reach Waco
until closer to 09z which remains outside of the current TAF
period. VFR conditions will prevail through the period with only a
few high clouds present.

-Stalley

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    75  40  57  36  55 /   0   0   5  10   5
Waco                71  37  61  34  56 /   0   0   5  10   5
Paris               70  37  53  30  52 /   0   0   5  10   5
Denton              72  35  56  30  54 /   0   0   5  10   5
McKinney            71  35  55  31  53 /   0   0   5  10   5
Dallas              74  41  58  38  55 /   0   0   5  10   5
Terrell             70  37  58  32  54 /   0   0   5  10   5
Corsicana           70  39  60  35  55 /   0   0   5  10   5
Temple              70  39  61  34  56 /   0   0   5  10   5
Mineral Wells       76  35  57  30  54 /   0   0   5  10   5

&&

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

$$

82/90


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