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

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FXUS64 KFWD 081156 CCA
AFDFWD

Area Forecast Discussion...CORRECTED
National Weather Service Fort Worth TX
556 AM CST Thu Dec 8 2016

.SYNOPSIS...
An arctic front was continuing to move through North-Central
Texas this morning. Despite north winds occurring all the way to
the I-10 corridor, the leading edge of the wind shift was actually
a pre-frontal trough. The frigid air was now crossing the Red
River and entering areas north of the I-20/30 corridors. The
freezing line was fast-approaching the Red River Valley as we
speak. Meanwhile aloft, an upper low was noted over Ottawa Canada,
with a detached upper trough and associated shortwave extending
southwest across the Plains and into the Southwest CONUS and
Mexico. Mid level frontogenetical forcing was noted in advance of
the shortwave along the Mexico/Southern AZ border per cooling
cloud tops (cirrus) on water vapor imagery across the Southern
High Plains. A few flurries or spotty drizzle/light rain were
occurring along/south of I-20 as we speak per clear-air mode/VCP
31 on area radars. However, there was nothing of significance with
regard to precipitation rates or amounts at this time.

&&

.DISCUSSION...
We only made minor tweaks to the ongoing forecast, as progress of
events with the shortwave to our west appear to be on track. As
the frontogenetical forcing aloft continue to slowly sink southeast
with time today, felt the mixture of drizzle, freezing drizzle, or
light sleet was appropriate per environmental analysis on forecast
soundings. Though a snow flurry or two can`t be ruled out, seeding
from cirrostratus aloft will be minimized due to a significant dry
layer between 800mb and 550mb. As such, do not feel the need to
add an insignificant weather element to an already complex weather
forecast. Basically, no snow accumulation is expected. As noted
the past few days, any minor impacts will be across our southwest
counties on elevated surfaces toward daybreak and through this
morning where temperatures can fall close to 30 degrees. Some
lingering forcing is expected across eastern parts of Central
Texas. However, temperatures will warm to above freezing this
afternoon, so will only advertise a slight chance for light
rain/drizzle, possibly mixed with a snow flurry or two.

The shortwave responsible for the possible, very light wintry mix
across Central Texas this morning will exit stage right this
evening. Subsidence with dry arctic air entraining into the area
will result in a gradual decrease of clouds from north to south
through the duration of the night. Despite the clouds, will continue
to advertise chilly low temperatures Friday morning from the upper
teens to the mid 20s, as clouds, and even insolation during the
daylight hours usually have little influence on very dense and
cold airmasses like the one we`ll be experiencing. That said for
Friday after a very cold start, I was hesitant to want to go more
than a 20 degree diurnal range with the highs being that models
tend to scour out arctic airmasses too quickly. For now, I`ll
only undercut guidance a few degrees and go with highs 40 to 45
degrees, though I have my reservations despite some weak return
southeast winds during the afternoon hours.

With strong zonal flow aloft for the weekend, continue to expect
strong lee cyclogenesis to occur with increasing southerly winds
and warm advection. This should put temperatures back up to near
seasonal normals for Saturday in the 50s and in the 60s for
Sunday. In addition, another shortwave moves east across the
Southern Plains late Saturday into Sunday. For the late Saturday
into Sunday morning period, it appears most of the moisture per
forecast soundings is contained below 850mb, thus per coordination
with surrounding sister offices this morning (thank you all),
we`ll only advertise low chances for a very light rain or drizzle
with very dry air above 850mb. By Sunday afternoon, the approach
of another shortwave will help to moisten the column up higher and
allow for some steepening of the mid level lapse rates that low
convective chances across our eastern counties Sunday afternoon
appear reasonable. We will NOT be worried about any wintry precip
over the weekend due to the strong warm advection expected.

Next week looks to remain primarily dry and cool to start off
with Monday into Tuesday, before what appears to be another
possible arctic air intrusion either Tuesday afternoon or Tuesday
night. The GFS is deeper with the cyclonic flow aloft versus the
Euro or Canadian models(which suggest a more shallow push of this
airmass). Either way and again with much collaboration (thank you
all again), we will use a raw blend of the model fronts and winds
and lean with an initial push into our northern counties Tuesday
afternoon, before moving through the entire area Tuesday night.
Did undercut guidance values for highs Wednesday and Thursday
considering the cold air with this airmass. I would not be
surprised if both low/high temperatures need to be lowered even
more for the latter half of next week. Luckily, it appears no
impacts at this time with a dry frontal surge expected, though the
Euro does show a potential low chance for precipitation next
Thursday. With my confidence wavering that far out in time,
prefer to lean with the dry forecast for now.

05/

&&

.AVIATION...
/ISSUED 1126 PM CST Wed Dec 7 2016/
North winds of 15-20 KT and MVFR conditions will be the norm
overnight in wake of the strong cold front, which was pushing
into the Waco area during the past hour. Recent hi-resolution model
data was indicating the potential for some light precipitation
across Central Texas Thursday morning so we will keep -DZ at KACT
during the 9-15Z timeframe. At this time it appears that
temperatures will remain above freezing if and when any
precipitation falls. Conditions are expected to improve to VFR
during the morning hours Thursday. Winds will eventually fall
below 10KT after sunset Thursday.

30


&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    38  25  42  32  52 /  10   0   0   0   5
Waco                40  24  44  31  51 /  20   5   0   0  10
Paris               38  20  41  29  46 /  10   0   0   0  10
Denton              38  19  41  30  50 /  10   0   0   0   5
McKinney            38  22  40  30  48 /  10   0   0   0   5
Dallas              38  25  42  32  51 /  10   0   0   0   5
Terrell             38  23  42  30  49 /  10   5   0   0  10
Corsicana           39  25  43  31  51 /  10   5   0   0  10
Temple              40  25  44  32  51 /  20   5   0   0  20
Mineral Wells       38  20  42  29  53 /  10   0   0   0   5

&&

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

$$

/05



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