874 
FXUS64 KFWD 160520
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
1120 PM CST Mon Jan 15 2018


.AVIATION...
/06Z TAFs/

Trends being held pretty close to 00z TAF discussion (below this
discussion), though the precipitation, mixed or otherwise is
fairly light due to some very dry surface to boundary layer air 
as noted by the very dry surface dew point temperatures building 
in from the north. Some evaporation is likely occurring and thus 
visibilities continue to be mostly VFR, as are cigs. Precip 
across DFW Metro airports is occasional very light sleet and snow
and now transitioning to mostly light snow or flurries. Only 
light accums are expected, despite temps falling below freezing, 
as road and ground temps vary between the mid 30s-mid 40s. Any 
light wintry precipitation will likely end between 08z-10z and 
before daybreak Tuesday, as the deeper dry air continues filtering
in and the shortwave lifts east away from the area. Otherwise, 
gusty north winds 15-20 knots with gusts to as high as 30 knots 
will continue overnight, weakening with less gustiness during the 
day Tuesday. By late afternoon/early evening Tuesday, clearing 
skies and a very chilly airmass will allow rapid decoupling by 
nightfall with north winds 5-8 knots. 

As for Waco, a little sleet has mixed in at times, but any mixing
with, or transformation to a little light snow will likely hold
off until after midnight and last possibly through daybreak
Tuesday. Otherwise, all other trends are similar with cigs and
winds improving into early Tuesday. 

I have inserted more optimistic vsby and cig conditions at all
airports, despite hit and miss, light wintry precipitation. 

05/

&&


.AVIATION... /Issued 653 PM CST Mon Jan 15 2018/
/00z TAFs/

Concerns: Strength winds both sustained and gusts through tonight
and timing precipitation transition and cig trends. This is a very
complex forecast with regard to winter precipitation with confidence
low on EXACT timing of changeover. I do have better confidence on
cig trends and continued very gusty north winds overnight. 

Currently, a strong arctic cold front was surging into Central
Texas. Strong low level cold advection and increasing mixing of
unidirectional north-northeast low of 35-40 knots below a
deepening frontal inversion were creating gusty north winds.
Sustained winds of 20-25 knots with gusts occasionally exceeding
35 knots were currently occurring, but a look up stream shows they
should soon calm down to around 15-20 knots with gusts to 25 knots
by 06z and after at all airports. Regional radar was noting 
large- scale ascent increasing mostly along and south of the 
I-20/30 corridors. Most of this was still -RA, but some mixing 
with -PL or all over to -PL was starting occur already as far 
south as KINJ. 

For DFW Metro airports...
Have continued to indicate the strongest north winds this evening,
settling down overnight and into Tuesday morning. Any -RA/PL mix 
should occur after 0130z with surface temps remaining above freezing
at least through 03-04z, by which time we would expect a more -PL/SN
transition, going over to all -SN before midnight. After 04z is 
when accums and impacts on tarmacs could start to become problematic
as temperatures continue to plummet. Any sleet accumulations will
be well under a tenth of an inch, with snow accumulations overnight
remaining less than one inch. Low VFR cigs BLO FL035 will fluctuate
at times due to precipitation into MVFR AOA 020 through 08z...before
going VFR ABV FL040 before 12z Tuesday. Any arrival departure
rates tonight and early Tuesday will remain very limited across
the northbound semi-circle and cornerposts from Bowie to Bonham. 

For Waco...
Similar trends to DFW, but more likely a slower transition on the
precipitation as the airmass behind the cold front starts out much
warmer with surface temps currently in the 50s. Transition over 
to a wintry mix likely won't begin until 03z-05z, so a -RA/PL mix 
looks likely before 06z, transition to a -SN or -SN/PL mix through
10-11z, before likely seeing more flurries after daybreak Tuesday
morning. Though you can't rule out a brief pd of -FZRA around 
06z, temperatures still look to hovering around 32-34 degrees and 
would expect a faster transition to -PL as the atmospheric column 
cool. Accumulations of sleet should remain tenth of an inch or 
less, before light snow with accumulations to between 1-2 inches 
occurs toward 12z Tuesday. 

05/

&&

.SHORT TERM... /Issued 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. 


79

&&

.LONG TERM... /Issued 343 PM CST Mon Jan 15 2018/
/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 
extended.

24-Bain

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    19  30  12  31  22 /  40  10   0   0   5 
Waco                24  32  12  34  20 /  80  20   0   0  10 
Paris               15  27   6  31  18 /  60   5   0   0   5 
Denton              16  30   8  32  19 /  30   5   0   0   5 
McKinney            18  29   9  32  19 /  40   5   0   0   5 
Dallas              19  30  14  31  23 /  40  10   0   0   5 
Terrell             20  29  11  33  19 /  60  10   0   0   5 
Corsicana           21  30  12  32  21 /  80  20   0   0   5 
Temple              24  33  16  35  22 /  80  30   5   0  10 
Mineral Wells       17  31   9  34  19 /  30   5   0   0   5 

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon CST Tuesday for TXZ094-095-
104>106-115>120-129>133-141.

Winter Storm Warning until 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.

&&

$$

05/26