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

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FXUS64 KFWD 152143

Area Forecast Discussion
National Weather Service Fort Worth TX
343 PM CST Mon Jan 15 2018

/Tonight through Tuesday afternoon/

I will preface this discussion by saying that there have been no
major changes to the current thinking with regards to the expected
winter weather tonight and Tuesday. Therefore, we will continue
with the Winter Storm Warning and Winter Weather Advisory and make
no changes to duration or area of these products.

The Arctic cold front was just north of the I-20 corridor as of
3 PM which is right on schedule. The front will move through the
entire region tonight and result in sharply falling temperatures
and increasing northerly winds along with development of some
light precipitation. The high-res model solutions seem to have
the best handle on the current precipitation moving into northern
Oklahoma as well as the light showers currently developing across
North Texas. However, the HRRR appears a bit too wet with the air
at the top of the frontal inversion and therefore generates quite
a bit of QPF near and just south of the Red River this evening. We
will continue to favor the slightly drier solutions of the TTU
WRF and NAM with regards to precipitation tonight as they seem to
have the best handle on the dry air moving in on the west side of
the upper low. These solutions show scattered light rain
developing early this evening with the precipitation slowly
transitioning to a wintry mix as the lowest layers of the
atmosphere cool below freezing. The period of light freezing rain
will be very brief, but since temperatures will be falling
quickly, light ice accumulations will be likely. A transition to
light sleet and light snow will follow in areas that do see
precipitation. Accumulations across the Winter Weather Advisory
area will be generally less than 1/2 inch of snow and sleet.
Farther south and southeast in the Winter Storm Warning area,
moisture will be more available and amounts will be slightly
higher, generally between 1/2 and 1 inch with some amounts up to 2
inches across the far eastern zones. The northwest zones that are
currently not in an advisory may see some light winter
precipitation as well, but right now we feel amounts will be too
light for significant impacts. However, we will continue to
monitor precipitation trends through the night.

The precipitation will end across the northern half of the region
overnight, but will linger across the south/southeast zones
through mid morning Tuesday before ending Tuesday afternoon.
Again, this setup is not one that typically brings large amounts
of winter precipitation but with the expected cold temperatures,
impacts will be high in areas that see anything. Also, since
temperatures are expected to remain below freezing until
Wednesday, any slick roads could linger for quite awhile.



/Tuesday Night through Sunday/

The main challenge in the long term will be the extreme cold on
Tuesday Night into Wednesday morning. Thereafter, a warmup is
expected, with temperatures likely above seasonal values by the
weekend. Thereafter, there appears to be a chance for showers and
a few thunderstorms during the latter half of the weekend.

Tuesday Night into Wednesday morning should feature one of the
coldest nights thus far in 2018. Skies will gradually clear from
north to south with low level winds diminishing as surface high
pressure settles in from the northeast. The dry airmass in place
will promote ideal radiational cooling. With low temperatures
likely bottoming out into the single digits, a "hard freeze"
appears likely, mainly for areas near and north of the Highway 380
corridor. The previous configuration of the Hard Freeze Watch
looked good, but I went ahead and tacked on a few more counties
where snow/sleet cover may further enhance radiational cooling. If
RAP/HRRR snow depth outputs of 2" of snow/sleet are correct
across more of our East TX counties, it`s probable that a few of
these counties may be added as well in future forecasts. I also
won`t rule out some single digit temperatures in the sheltered
/low-lying areas south of the current Hard Freeze Watch, but for
now will abstain from any wholesale changes as most of these
areas are forecast to fall into the teens to low 20s. Freeze
Watch/Warning or not, it`ll be COLD across all of the area. While
winds will be light, the low temperatures even with the lightest
of breezes will result in single digit wind chill values on
Wednesday morning. During the day, cold conditions will continue
across most of North and Central TX as most areas will struggle to
climb above 32 degrees. Far western zones may be the
beneficiaries of east to southeasterly flow which may limit any
additional CAA.

Thursday and most Friday look to be quiet weather wise as low
level flow finally turns back to the southeast. Most areas should
climb above 32 degrees on Thursday in response to the increasing
southerly winds. There was concern about a brief chance for
winter precipitation down across Central TX, but at this time, it
appears that the track of the upper low may be too far south of
the area to result in any meaningful lift to overcome what should
be a dry airmass. We will keep a close eye on this, but for now,
I`ve pulled the mention of PoPs down here with that reasoning and
after coordination with adjacent WFO`s.

Late Friday into Saturday, there will be a potential for a few
light rain showers, mainly across far eastern zones. At this time,
I don`t have a ton of confidence in the occurrence of this and
it`s likely that this will be mainly sprinkles/drizzle given that
the initial moisture surge will be shallow. The main headline in
the extended will be the noticeable warmup after a cold start to
the week. High temperatures on Saturday will climb into the upper
60s to 70s as southwest winds yield good adiabatic compression off
of the higher terrain to the west.

The forecast becomes challenging on Sunday as model solutions
diverge with regards to the timing of the next front. The general
setup looks to feature a Pacific front/dryline feature that
develops to the west and slides eastward. The progression of this
feature will be largely dependent on the location of the upper
trough. Traditionally, digging upper troughs are not handled well
initially by the synoptic models and these features tend to sag
farther south than forecast. The ECMWF appears to be one of the
slower models with the upper trough and I`ll side with it as it
pertains to temperatures. Low level moisture will have streamed
northward by this time and with strong mid-level flow at 500mb
(in excess of 80 knots), there should be some loose-organization
to the convective mode along the front. At this time, however,
there is still too much uncertainty to advertise any strong to severe
weather potential, but we will keep an eye on this in the



.AVIATION... /Issued 1215 PM CST Mon Jan 15 2018/
The first aviation weather concern this afternoon will be MVFR to
occasional IFR ceilings moving in from the south ahead of a strong
cold front. We expect some temporary MVFR ceilings at the
Metroplex TAF sites through 20Z. Prevailing MVFR ceilings are more
likely in Waco with the low clouds occasionally scattering out
through the afternoon.

A wind shift will precede the cold front and result in a north
wind across the Metroplex TAF sites around 20Z at speeds between
8 and 12 knots. Actual FROPA will occur around 23Z with north
winds increasing between 12 and 18 knots along with some gusts
near 30 knots. The prefrontal wind shift and FROPA will occur in
Waco about 2 hours later than the Metroplex. The strong and gusty
northerly winds will continue at all TAF sites overnight through
Tuesday morning.

Some light rain showers will accompany the cold front with better
precipitation chances arriving a couple hours later around 02Z to
03Z at the Metroplex TAF sites and 04Z to 05Z in Waco. At that
time, temperatures will be falling rapidly and a mix of rain/sleet
and snow will be possible. Any precipitation that develops across
the Metroplex TAF sites should be light but with surface
temperatures falling well below freezing overnight, ground ops and
deicing will be affected. All precipitation should end across the
Metroplex TAF sites between 08Z and 10Z as much drier air moves
in from the north. The winter precip will linger through about
13Z in Waco.

VFR conditions are expected after sunrise Tuesday at the Metroplex
TAF sites but MVFR ceilings will most likely linger in Waco
through the morning hours.



Dallas-Ft. Worth    23  30  12  31  22 /  40  10   0   0   5
Waco                26  32  12  34  20 /  80  20   0   0  10
Paris               18  27   6  31  18 /  60   5   0   0   5
Denton              22  30   8  32  19 /  30   5   0   0   5
McKinney            20  29   9  32  19 /  40   5   0   0   5
Dallas              24  30  14  31  23 /  40  10   0   0   5
Terrell             22  29  11  33  19 /  60  10   0   0   5
Corsicana           24  30  12  32  21 /  80  20   0   0   5
Temple              26  33  16  35  22 /  80  30   5   0  10
Mineral Wells       22  31   9  34  19 /  30   5   0   0   5


Winter Weather Advisory until noon CST Tuesday for TXZ094-095-

Winter Storm Warning from midnight tonight to 6 PM CST Tuesday
for TXZ107-121>123-134-135-142>148-156>162-174-175.

Hard Freeze Watch from Tuesday evening through Wednesday morning
for TXZ091>095-100>107-115>117-123-129.



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