Forecast Discussion for Dallas/Ft. Worth, Texas

472
FXUS64 KFWD 181806
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
1206 PM CST Mon Feb 18 2019


.AVIATION...
/18Z TAFs/

Concerns for this TAF cycle are centered on the arrival of low
CIGs/VSBYs on Tuesday. Until then, expect generally
north/northeasterly flow around 10-15 kt (with isolated gusts to
15-20 kt) this afternoon into the overnight. A thick canopy of
cirrus (around 250-300) is expected to persist into this evening
across Metroplex sites, although KACT may clear some aloft by late
afternoon.

Winds remain out of the northeast to east/northeast after 00Z
tonight. By 09-12Z, MVFR CIGs are forecast to rapidly build
northward from Central Texas to North Texas. In fact, CIGs around
020 could reach sites 1-2 hours ahead of what`s indicated in
respective TAFs. Rain and IFR CIGs are forecast to spread north
during the morning hours, with confidence high enough to show -RA
and OVC007 prevailing at all sites by late morning. In fact, given
strength of warm-air advection aloft and forecast thermodynamic
profiles, some deeper convection appears possible around mid-day.
While confidence is too low to include a TS mention in TAFs,
decided to TEMPO 2SM in locally heavier rain. Potential TS impacts
will have to be monitored closely.

IFR CIGs likely continue beyond 18Z. Some potential for IFR VSBY
in -DZ/-RA as well, but think such VSBY restrictions will be
generally delayed til after 00Z (beyond the KDFW 30-hour TAF).

Picca

&&


.SHORT TERM... /Issued 355 AM CST Mon Feb 18 2019/
/Today Through Tuesday/

A relatively quite and cool forecast is expected through this
evening, as we await our system arriving Tuesday/Wednesday. Brisk
northeast winds 10-15 mph are expected today with fast west-
southwest flow aloft creating an extensive mid-high cloud canopy
across all but our far northwest counties. Temperatures will
remain on the chilly side despite some pockets of sunshine. After
a chilly start, look for temperatures to only warm into the 40s
north, with a few readings in the 50s across parts of Central
Texas, as warm advection begins in earnest just above the shallow
cool airmass at the surface.

Isentropic ascent/upglide on the order of 30+ knots and
impressive pressure advection on the 290K-300K surfaces(basically
the 850mb-700mb layer) really gets going late tonight and Tuesday
morning in response the approaching system across the Desert
Southwest states. This will lead to quick saturation of the
atmospheric column across Central Texas after midnight with
increasing chances of rain just before daybreak Tuesday. In
addition, mid level lapse rates steepen across the region to near
7 deg/C with MUCAPE values between 500-1000 J/KG across Central
Texas during this time with a chance for some embedded rumbles of
thunder, as our main upstream mid level trough shifts east across
New Mexico/Far West Texas. Temperatures are expected to be between
35-40 degrees across Central Texas where precipitation starts
late tonight, thus we do not expect any wintry precipitation to
affect areas around freezing across our far northwest counties
until later Tuesday morning.

A widespread, cold rain will advance northward and encompass much
of the CWA by midday Tuesday and continue on through the day. I
had initially contemplated putting in a slight chance for a few
sleet showers across our far northwest counties and along the Red
River along and west of I-35 with the increasing lift and very
limited instability well aloft. However, after looking at
frontogenetical forcing and thermal profiles aloft, it appears
warm advection in the precipitating layer between 5-15 kft will be
too warm for supercooled drops to freeze before making it to the
surface later Tuesday morning. In addition, I expect latent heat
release from the increasing rainfall later Tuesday morning to help
moderate those temperatures in the northwest from freezing into
the mid-upper 30s pretty quickly. As such, it will be miserably
wet and cold across the entire CWA, but do not expect any frozen
or freezing precipitation on Tuesday. Lastly, the expected rain,
lack of insolation/radiation under cloudy skies, and any warm
advection aloft transitioning to the surface will likely result in
a very low diurnal warm up regarding high temperatures, as low
level flow from the surface-925mb transitions more easterly at
5-10 mph. After much collaboration, temperatures closer to the
colder NAM12 numbers was agreed upon versus the warmer national
blend numbers with many areas only seeing highs from the mid 30s
north to the lower-mid 40s across our Central Texas counties on
Tuesday.

05/

&&

.LONG TERM... /Issued 355 AM CST Mon Feb 18 2019/
/Tuesday Night Onward/

By Tuesday night, the main source of lift will be moving off to
the northeast as the upper level trough in the Western CONUS
becomes slightly modified with the exiting shortwave. There may be
just enough instability prior to midnight to continue any ongoing
thunderstorms across the Brazos Valley and East Texas. Drier air
will push in from the west as the departing low pressure system
moves eastward, helping to oust most of the moisture out of North
and Central Texas. Lows Wednesday morning will range from around
freezing in the northwest to around 40 degrees in Central Texas.

Wednesday and most of Wednesday night will be precipitation-free,
as the aforementioned dry air settles across the region. Westerly
winds will be in place for much of the region, but with a rather
dense cirrus deck, temperatures will struggle to climb out of the
50s Wednesday afternoon. Given the high clouds are expected to
remain through the night, lows will likely stay above freezing
across all of North and Central Texas.

Rain chances will increase around sunrise Thursday, initially
across Central Texas as moisture once again returns to the region.
Rain should gradually spread northward, but the highest PoPs will
remain across East Texas in the afternoon. Instability appears to
be lacking during the day, but as lapse rates steepen and
instability increases overnight, some isolated storms will be
possible across Central Texas.

With continued warm air advection Thursday night, low temperatures
will be in the upper 30s across the northern counties and upper
40s across the Central Texas. As the atmosphere becomes more
unstable through the day, the chance for thunderstorms increases
across North Texas as well. Highs will range from the middle 50s
to middle 60s. Thunderstorms on Friday will have limited instability
to work with, keeping them mostly below the strong category.

A potent shortwave will be making its way eastward from New Mexico
Saturday, overspreading impressive height falls area-wide. With
plenty of moisture to work with and up to ~1800 J/Kg of MUCAPE in
place, we will need to keep an eye on Saturday for the possibility
of a few strong to severe thunderstorms, mainly east of I-35. It
is yet too early to nitpick at the details this far out, and
several adjustments to the forecast are expected.

A cold front Saturday afternoon will end all precipitation
changes from west to east as high pressure builds in. Post-frontal
windy conditions are expected, with latest model guidance
suggesting winds could be between 25-30 mph, with higher wind
gusts. This will need to be watched closely on both the fire
weather front with dry air filtering in, as well as the aviation
side as north-south oriented runways may see impacts due to
crosswinds.

As we finish out this week and start the next, expect a gradual
shift in the upper level pattern, keeping most of the active
weather north of the region. Temperatures will likely remain
slightly below normal, but the absence of a good source of lift,
conditions appear to be dry Sunday and Monday.

Hernandez

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    46  36  40  35  58 /   5   0  90  20   0
Waco                48  38  41  36  60 /   0  20  90  30   5
Paris               47  35  38  35  55 /   0   0 100  40   5
Denton              46  35  39  33  56 /   0   0  90  20   0
McKinney            46  35  39  34  56 /   0   0 100  30   0
Dallas              47  37  41  36  57 /   5   5  90  30   0
Terrell             48  37  41  36  57 /   5   5 100  40   5
Corsicana           50  38  42  38  58 /   5  20  90  40   5
Temple              50  38  43  37  61 /   0  20  90  30   5
Mineral Wells       47  34  38  33  58 /   0   0  80  20   0

&&

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

$$

11/24

NWS FWD Office Area Forecast Discussion