Heavy Snow in Texas, January 3, 2019

Area Forecast Discussion
National Weather Service Norman OK
1111 PM CST Wed Jan 2 2019

.DISCUSSION...

&&

.AVIATION...
For the 06z TAFs:

A challenging forecast with regards to where the greatest chance
of snow with significant visibility reductions will occur, and
precipitation type/transition leading up to this. The general
trend is for MVFR ceilings and light freezing rain possibly mixed
with sleet to gradually transition to snow in the morning at most
sites. There will likely be a band where snow will significantly
reduce visibility at least briefly, and this is most likely around
LAW/OKC/OUN and just south from late morning through mid
afternoon. Temperature profiles aloft are marginal for snow and
some sites may see rain/freezing rain continue as the dominate
precip type through much of the day tomorrow. IFR or lower
ceilings should improve toward the very end of the TAF period and
precipitation will begin to shift east by then. Expect several
amendments through this event based on trends in the observations
and short term guidance.

&&

.PREV DISCUSSION... /issued 919 PM CST Wed Jan 2 2019/

UPDATE...
Challenging forecast continues this evening as we continue to
closely look at trends in both models and observational data.

Have raised precip chances overnight, but kept precip types
similar to prev forecast. Still with much of the area hovering
near the freezing line, both at the surface and aloft, precip
types are a challenge.

Latest thinking is that potential for heaviest snow amounts will
be from portions of southwest into south central Oklahoma on
Thursday with a tight gradient near the I-40 corridor of central
Oklahoma, including the OKC metro. Could also see a transition
back to rain across parts of western into central Oklahoma
Thursday evening as colder core of upper low transitions east into
northeast Texas.

Updates to forecast have been sent. No changes to headlines at
this time.

30

PREV DISCUSSION... /issued 547 PM CST Wed Jan 2 2019/

DISCUSSION...

AVIATION...
For the 00z TAFs:

Precipitation type, and timing of intermittent waves is the
primary forecast challenge. First wave of freezing rain and sleet
mix should end or at least lessen over the next hour at OKC, and
the same at OUN within a couple of hours. Another round may be
more freezing rain than sleet given thermal profiles, arriving at
southwest TAF sites (SPS, LAW, and possibly CSM) first by mid-late
evening, and then late evening or closer to midnight for OKC and
OUN. Ceilings during this time should be MVFR and could briefly
scatter out, especially at CSM and OKC. Precipitation type should
transition to mostly snow tomorrow morning with the potential for
IFR or lower ceilings and significantly reduced visibilities
depending on where the heaviest band sets up. Will refine and
possibly lower once confidence increases.

PREV DISCUSSION... /issued 404 PM CST Wed Jan 2 2019/

DISCUSSION...
Very challenging forecast through Friday morning as the upper low
currently over NM/AZ moves eastward, tracking generally along the
Red River. This track is climatologically favorable for heavy
snowfall near the I-40 corridor, but uncertainty remains regarding
where exactly the heaviest band of precipitation may develop to the
north of the upper low track, and what the temperature profile will
look like.

For the rest of today and tonight...continued weak isentropic ascent
will allow for areas of mostly freezing drizzle and light freezing
rain, although some sleet may be possible as well. Expecting this
ascent to increase over southern into central OK overnight, which
should gradually increase coverage and intensity of precipitation.

By tomorrow morning... the upper low and associated colder mid level
temperatures will introduce snow as the dominant precip type across
SW OK and portions of western north Texas. This area of snow will
advance north and east during the day as models depict a deformation
band developing to the north of the upper low, but still disagree
with its exact location. The ECMWF is furthest north and east with
this band, and is colder in the mid-levels than other models. This
would put the heaviest totals right along the I-44 corridor from
Lawton to OKC. Other models are further south with this band and
slightly warmer, suggesting southwest into south-central OK would be
favored for the highest totals. Did not go as far north as the ECMWF
with this forecast, but trends in the high-res models will need to
be watched closely in regards to where this heavy band will
eventually set up. Most areas outside this band will likely warm
above freezing by noon tomorrow, meaning we should be dealing with
just a rain or snow scenario by that point in time. The band of snow
should begin moving out of the area by tomorrow evening, tapering to
some light rain or snow.

Currently have a swath of 3-6 inches of snow over portions of
southwest, south-central, and central OK, along with portions of
our western north Texas counties. This includes most areas east of
I-44 and south of I-40, with the exception of our far SE counties
where near surface temps may be warm enough for more rain to mix
in. As mentioned there is still a great amount of uncertainty, and
there will likely be a sharp gradient outside of the heavy snow
band of lower snow accumulations. Likewise, it is possible for
some locally higher totals to occur within the band.

After this system clears the area, a pronounced warming trend with
most areas well into the 50s on Friday, with the exception of
areas that receive heavy snowfall, where snow cover should keep
temperatures in the 40s. By the weekend everyone should be in the
mid to upper 50s as the next system approaches Monday. This system
currently does not look like a major precipitation producer but
will bring a chance for some showers across mostly eastern
Oklahoma.

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  34  30  33  23 /  20  70  70  60
Hobart OK         37  29  33  22 /  20  70  60  40
Wichita Falls TX  36  31  33  23 /  30  90  80  50
Gage OK           40  29  44  27 /   0  20  10  10
Ponca City OK     36  25  45  25 /  10  20  20  20
Durant OK         37  32  34  28 /  60  70  90  60

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Winter Weather Advisory until 6 AM CST Friday for OKZ013>022-
     033>036-047-048-050>052.

     Winter Storm Warning until 6 AM CST Friday for OKZ023>032-
     037>046.

TX...Winter Weather Advisory until 6 AM CST Friday for TXZ083>085-087-
     088.

     Winter Storm Warning until 6 AM CST Friday for TXZ086-089-090.

&&

30/12/12

Hazardous Weather Outlook...UPDATED
National Weather Service Norman OK
824 PM CST Wed Jan 2 2019

OKZ004>048-050>052-TXZ083>090-040230-
Harper-Woods-Alfalfa-Grant-Kay-Ellis-Woodward-Major-Garfield-
Noble-Roger Mills-Dewey-Custer-Blaine-Kingfisher-Logan-Payne-
Beckham-Washita-Caddo-Canadian-Oklahoma-Lincoln-Grady-McClain-
Cleveland-Pottawatomie-Seminole-Hughes-Harmon-Greer-Kiowa-Jackson-
Tillman-Comanche-Stephens-Garvin-Murray-Pontotoc-Coal-Cotton-
Jefferson-Carter-Johnston-Atoka-Love-Marshall-Bryan-Hardeman-
Foard-Wilbarger-Wichita-Knox-Baylor-Archer-Clay-
824 PM CST Wed Jan 2 2019

This hazardous weather outlook is for portions of northern...
western...central...and southern Oklahoma...and western north
Texas.

.DAY ONE...Through tonight...

.Winter Weather...
Periods of light freezing rain and sleet will continue to move
across portions of central and southern Oklahoma and western north
Texas this evening resulting in light ice accumulation and some
travel impacts. Snow is expected to mix with the sleet across
southwest Oklahoma and western north Texas overnight with some
light snow accumulations expected in those areas by morning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday...

.Winter Weather...
A winter storm will move across Texas Thursday and Thursday night.
This will result in snow, sleet, freezing rain and rain,
especially across the southern half of Oklahoma and western north
Texas. At this time, portions of central into southern Oklahoma
and western north Texas may receive 3 to 5 inches of snow with
lighter amounts across far west central, northern and southeast
Oklahoma.

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