Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX
FXUS64 KFWD 250453
Area Forecast Discussion
National Weather Service Fort Worth TX
1153 PM CDT SAT SEP 24 2016
Complex of showers and thunderstorms continues to make slow east
progress tonight with an outflow boundary now surging to the east.
We should see a general eastward progression of the overall line
of thunderstorms through the overnight hours. Ahead of the
line...isolated convection will still be possible but VFR
conditions will generally prevail for the next few hours. Farther
south at Waco...MVFR cigs are expected to develop and spread north
ahead of the main precipitation areas. Have also included a few
hours of tempo IFR cigs at Waco around sunrise.
For the Metroplex sites...have continued with the VCTS by 10Z and
have included a tempo for TSRA from 11-15Z based on the eastward
progression of the line. Convection should weaken as the outflow
gets ahead of the line but still think there will enough around to
include it in the latest forecast. Otherwise...the cold front will
approach from the north during the afternoon hours and will show a
wind shift by 22Z. Scattered afternoon showers and thunderstorms
will continue through the day across all of North and Central TX.
After the frontal passage...showers appear likely well into the
nighttime hours Sunday night.
No major changes in the forecast this evening, as most everything
is on track. Satellite data continues to show cloud top cooling
with the cluster of storms over the Metroplex, but at least these
storms are moving at a decent clip to the north. As these storms
have lingered, they will at least move through any one spot within
an hour or less.
Attention then turns to the northwest, where the showers and
thunderstorms continue from central Oklahoma down to the Permian
Basin. As expected, the low level winds have increased, with the
VAD wind profile showing 30 knots of wind between one thousand
and four thousand feet. This will help keep the storms going to
the northwest, but will also keep the forward progress of the
storms in check for a while. Still anticipating the line to creep
to the east, making its way into our western counties between 11
PM and 3 AM, and into the I-35 corridor after 3 AM.
.PREV DISCUSSION... /ISSUED 344 PM CDT SAT SEP 24 2016/
A large upper level trough to our west continues to slowly ease
east this afternoon. Although it won`t make it across the Southern
Plains, the impacts from this system on North and Central Texas
will include increasing rain chances, a front, and cooler weather.
This afternoon, showers and thunderstorms have been ongoing from
Northwest Oklahoma to West Texas ahead of the upper level trough.
With the influence of the upper level ridge having been weakened
across North and Central Texas and southerly winds continuing to
provide rich moisture into the region, isolated to scattered
showers and thunderstorms have been developing and moving north
across our area. Lightning and gusty winds to 30 mph have been the
main threats with this activity. We do not anticipate severe
storms through this evening, but an isolated strong storm could
produce winds closer to 50 mph before sunset.
The overnight period is when we expect rain chances will increase
for roughly the northwestern half of the region. A weak shortwave
currently crossing into Texas near the Big Bend area is expected
to continue moving north-northeast this evening, aiding in
additional lift across our western counties. The low level winds
in the 925-850 mb layer are also expected to increase to near 30
kts, providing additional support for convective development this
evening. The area of showers and storms to our west is expected to
move east, reaching our western counties this evening. The models
are quite variable in when the rain will really increase near our
western border, but most of the guidance is indicating between
9-11 pm CDT. By sunrise, the low level winds decrease in speed,
and the shortwave will be lifting northwest of the region. We
should see a weakening of the overall showers/storms and likely a
reduction in coverage through the morning hours. For the overnight
period, will keep the highest PoPs west of a Gainesville to Fort
Worth to Goldthwaite line with PoPs steadily dropping off further
east. Due to potential training of storms, it`s possible some
localized flooding may occur during the overnight period. An
isolated instance of flash flooding is not completely out of the
question depending on rain rates and if training occurs over a
certain area, but flash flood guidance is fairly high in our
western counties, as it is for most of North and Central Texas.
Will encourage the next shift to keep an eye on radar trends and
assess the potential for any Watches overnight and into Sunday.
The most significant changes to expected rain/storm trends comes
Sunday-Monday. An upper level low is forecast to cut-off within
the base of the trough over northern Mexico on Sunday and then
retrograde. In the wake of the departing shortwave in the morning,
and with the best dynamics located well to our west near this
cut-off low, we could end up in a lull in activity late Sunday
morning and into the early afternoon hours until the cold front
arrives later in the afternoon or evening hours. Isolated to
scattered shower and thunderstorm activity ahead of the front is
still expected as heating occurs with rich moisture still in place
and a lack of subsidence over the area. Also, any boundaries that
may be left over from the overnight and morning convection may
become a source for lift. Even in an unstable and uncapped
atmosphere, shear values and lapse rates tomorrow are weak, thus
we do not expect severe storms.
As the front moves in, it should become a focus for additional
shower and storm development. The highest chances for rain will
still be across mainly the western half of the region where we
will keep high PoPs but understand that this is not an indication
it will rain most of the day. We will keep high PoPs overnight as
the front moves through with again the highest rainfall totals
mainly west of Interstate 35. Showers and storms may also occur
behind the surface front as the H850 front lags behind. Lightning
and heavy rainfall will be the main hazards through the overnight
period but rainfall totals are not high enough to warrant a
Flood/Flash Flood Watch at this time. However, minor flooding will
be possible. Rainfall totals through the event are expected to be
less than an inch to the east of Interstate 35, where several locations
may not see rain at all, to 1-3 inches along and west of
Interstate 35. The highest rainfall totals of 2-3 inches are
expected west of Highway 281.
The cold front is expected to push through our southern counties
by early Monday morning. It will continue to push deep into the
Gulf of Mexico early next week with dry air filtering into the
region starting Monday. Some lingering rain may occur on Monday as
the H850 front also slowly moves south, but any leftover rain is
expected to end Monday night. The Gulf of Mexico will remain cut
off from moisture return next week with north and east surface
winds prevailing across the region through the end of the week.
Even as an upper level ridge builds back into the Southern Plains,
temperatures will be very pleasant next week with highs in the 70s
and 80s and lows in the 50s and 60s.
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 77 85 64 76 62 / 50 60 70 30 10
Waco 77 88 66 77 60 / 40 60 70 30 20
Paris 72 88 65 78 59 / 20 30 40 30 10
Denton 73 84 62 73 57 / 60 60 60 30 10
McKinney 73 87 64 77 58 / 40 60 50 30 10
Dallas 77 86 65 77 63 / 40 60 60 30 10
Terrell 73 89 67 80 61 / 30 50 60 30 10
Corsicana 75 89 67 80 61 / 30 50 70 30 20
Temple 75 87 65 76 61 / 30 60 70 30 20
Mineral Wells 73 81 61 70 55 / 70 70 70 30 10