NWS Fort Worth, TX wrote its last area forecast discussion before the first event at Dec 31, 10:55 PM CST, 1 hour 5 minutes earlier.
Area forecast discussion, Dec 31, 10:55 PM CST, 1 hour 5 minutes before
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1055 PM CST Sat Dec 31 2016
.AVIATION...
/06Z TAFs/
Concerns...IFR conditions at the Metroplex airports Sunday
morning. MVFR/IFR conditions at all the airports Sunday evening
and night. Low threat for thunder Sunday morning, but higher
potential for thunder late Sunday night into Monday morning.
Metroplex airports...IFR cigs and fog are expected to spread across
the Metroplex airports late tonight as low-level moisture increases
from the east. Deteriorating conditions are expected to start
between 10-12Z and persist through at least midday. We will have to
monitor for possible LIFR/VLIFR conditions with visby AOB 1/4
mile and cigs below 500 feet for a period of time. As south winds
return across the region in the late morning hours, models
indicate an improvement to VFR at the Metroplex airports, but
there is a low chance the airports remain in sub-VFR conditions
through the afternoon hours. MVFR and IFR cigs are expected to
return north across the airports Sunday evening and night ahead of
a line of thunderstorms.
Showers with a low potential for an isolated thunderstorm will cross
North Texas Sunday morning, most likely between 12-18Z. For now,
will continue with VCSH as lapse rates appear a little too weak for
thunderstorms and the best lift will be north of the region. Better
rain chances are late Sunday night into Monday morning as widespread
thunderstorms, likely in the form of a squall line move across the
region. These storms could be severe.
Waco airport....A stalled front to the east of Waco is expected to
keep the low cigs and fog east of KACT. Therefore, VFR conditions
will prevail with north-northwest winds tonight becoming
southeasterly by midday Sunday. MVFR, or possibly IFR, cigs are
expected to spread north into KACT early Sunday evening. It is
possible a stray shower could move across the airport Sunday
morning. Better rain chances are expected Sunday night into Monday
morning as widespread thunderstorms, likely in the form of a
squall line, moves across the region. These storms could be severe.
JLDunn
&&
.UPDATE...
Another update here to include the Dense Fog Advisory, which is in
effect for locations east of a Sherman to Rockwall to Hearne line
from 11 PM CST to 10 AM CST on Sunday. Surface observations across
Eastern Texas reveal steadily lowering visibilities late this
evening. As surface winds continue to veer towards an easterly
direction across our eastern counties, this moisture will be
steadily ushered into the region which will result in
deteriorating visibilities through the overnight hours. Confidence
in the western terminus of the dense fog remains a bit uncertain,
and as a result, have left Tarrant, Dallas, and our I-35 Counties
out of the advisory. We will continue to monitor observations, but
would not be surprised if the Dense Fog Advisory needs to be
expanded westward by a county or two.
Carlaw
&&
.PREV DISCUSSION... /ISSUED 336 PM CST Sat Dec 31 2016/
Quiet, warm, and breezy weather was occurring this afternoon, as
weak cold front continues to slide southward through our
northwest counties. The current front will likely stall across
Central Texas by midnight, then lift gradually northward through
the morning hours in response to height falls associated with a
shortwave trough currently over NW New Mexico. The brief low level
warm advection and lift from the shortwave, along with forcing
with the warm front will likely produce scattered showers and
isolated thunderstorms late tonight and potentially across parts of
the area later Sunday morning. No severe weather is expected with
this system Sunday morning. In addition, moisture convergence
near and just southeast of the stalled frontal boundary will
likely result in patchy to areas of fog, mainly across the eastern
half of the area where low level dew points are higher. Localized
dense fog may occur southeast of a Sulphur Spring-Corsicana-Waco-
Killeen line, but for now, will let the evening shift determine any
need for an early morning dense fog advisory on Sunday.
After the next shortwave departs the area New Years Day/Sunday
afternoon, the warm front will have surged north of the Red River
with North and Central Texas back into the warm sector. Currently
advertising mid 60s north to lower 70s south due to lingering cloud
cover. That said, if we partially clear out and get any insolation
going, my highs may be too low for New Years Day/Sunday. With the
area in between disturbances, have decreased previous rain chances
Sunday afternoon into Sunday evening.
I will advertise better chances for warm advection showers with
isolated thunderstorms across the far eastern counties later
Sunday evening as we await our more vigorous shortwave trough now
located over San Francisco, California. This disturbance will move
over far West Texas and the High Plains of the Texas Panhandle
during the evening hours, before lifting east across our area
overnight Sunday night and Monday morning. Models have shown this
system to be a tad deeper and further south in its track, meaning
our confidence for severe weather has increased, especially along
and south of the I-20/I-30 corridors. These areas will have the
richest dew points, especially across our Central Texas counties,
where SBCAPE values 1000-2000 J/KG will exist with elevated lapse
rates approaching 7-8 Deg C/KM. Throw in southwesterly 0-6km bulk
shear on the order of 40-50 knots and we're looking at a set up
for severe storms, most likely in the form of a QLCS moving
readily east across the area. Though severe storms with large
hail, damaging winds, and possibly a book-end vortex type of
tornado or two, the best threat for severe storms will be from
D/FW south where the better instability will reside for deeper
and stronger updrafts. The current Slight Risk area looks situated
in the appropriate area and would not be surprised parts of
Central and South-Central Texas are put in a higher category if
model track and trends continue on all these parameters. Be
prepared for some rocky weather to begin the new year 2017. The
main window appears to be 2 am to 9 or 10 am Monday morning due to
the deeper/slower nature of the shortwave disturbance. The
progressive nature of this system should keep any hydrologic
concerns brief and minimal.
The severe threat will remain over the eastern counties later
Monday morning. before shifting east of the area for the afternoon
hours, as a pacific cold front moves out of the area. That said,
plenty of insolation and west winds should allow highs Monday
afternoon to warm well into the 70s. The mild conditions will
continue Monday night with lows mostly in the 40s to lower 50s
with light west-southwest winds continuing into Tuesday morning.
The next item of concern is an arctic cold front that is expected
into the area during the day Tuesday, as flow aloft remains mostly
zonal with most energy rippling through remaining north of the Red
River Valley. Even so, much colder and frigid temperatures more
conducive for January area expected late Tuesday and through the
end of the week. With MOS Guidance and model guidance not being
cold enough, even with shallow arctic outbreaks, I have decided to
cut highs and low under MOS Wednesday through Friday. Regarding
wintry weather, have toned down the latter half of the week to
either a slight chance of very light rain/sleet or a few flurries
or sprinkles. As noted previously, better forcing will remain to
the north. In addition, moisture quality does not look very good,
especially the potential for ice nuclei to seed lower level
moisture. The main theme for the first week of January will be the
bitter cold temperatures.
The arctic air will begin shifting gradually east of the area by
next weekend, with a slow modification of temperatures back toward
normals for this time of the year, but not quite. Lows will be
mostly in the 30s with highs 45 to 55 degrees. No concerns for
rain next weekend as of this writing.
05
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 46 67 59 71 49 / 10 30 80 60 0
Waco 46 69 58 73 45 / 10 30 80 60 0
Paris 47 64 57 70 48 / 5 30 70 90 5
Denton 40 66 55 71 47 / 20 30 70 50 0
McKinney 43 65 57 71 46 / 10 30 70 70 0
Dallas 48 67 60 73 49 / 10 30 80 60 0
Terrell 47 68 59 73 47 / 10 30 70 80 0
Corsicana 48 70 62 73 48 / 10 20 70 80 0
Temple 46 70 59 72 47 / 20 30 80 60 0
Mineral Wells 39 68 52 71 44 / 20 30 80 20 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM CST Sunday for TXZ093>095-104>107-
120>123-135-147-148-162-175.
&&
82/90