Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX

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618
FXUS64 KFWD 210301
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
1001 PM CDT Fri Apr 20 2018


.UPDATE...
The upper low continues to move east from the 4 Corners region
this evening. Large scale upward vertical motion continues to
interact with increasing low level moisture to produce numerous
showers and thunderstorms from the Texas South Plains, northward
into Nebraska. The individual storms will continue to move
northeast while the general precipitation area moves east. Linear
extrapolation and some high res models bring the first
showers/storms into the western zones around 08Z with
showers/storms reaching near the I-35 corridor around sunrise or a
bit after. The consensus among the models is that the morning
activity will be relatively weak with the potential for stronger
storms during the afternoon with the cold front. This supports the
ongoing forecast although we will adjust the late evening/early
overnight PoPs down based on the expected timing.

The remainder of the forecast is in good shape for now.

&&


.AVIATION... /Issued 735 PM CDT Fri Apr 20 2018/
/00Z TAFS/

Concerns- Timing of showers and thunderstorms and MVFR ceiling at
all TAF sites.


VFR conditions through tonight. However, flight conditions will
slowly deteriorate during the early morning hours on Saturday. The
anticipated upper low system will approach and showers and
thunderstorms will overspread the area. There`s high confidence
that by 14Z rain showers and isolated storms will impact all the
TAFs sites. Low-end MVFR conditions will accompany this
activity with the possibility of IFR conditions. Some of the
guidances keep it for most of the day, but for now probability is
too low for inclusion. Model trends will be monitored and later
TAFs will include it if necessary.

The challenge continues to be the chance for a second round of
storms during the afternoon hours, likely between 22-00Z as the
cold front surges through the area. We know the lift will be
there, but it will also depend on how the atmosphere can recover
from the morning convection and where instability will be the
greatest. Most of the high-resolution models develop storms along
the front and move them quickly to the southeast, impacting Waco
TAF site later in the evening. For now, kept VCTS in the forecast
for the Metroplex sites, but we will continue to monitor as new
data becomes available. Expect east/southeast 10-15 kts winds
during the day ahead of the front, shifting to the north/northwest
around 00Z for the Metroplex and around 02Z for Waco.

Sanchez

&&

.SHORT TERM... /Issued 332 PM CDT Fri Apr 20 2018/
/Tonight/

Convection has increased across Northwest Texas over the past few
hours in advance of an eastward-moving upper level low pressure
center currently located over the Four-Corners area. This zone of
enhanced ascent will spread east this evening and begin to affect
the northwest counties by midnight. Increasing POPs continue to be
advertised tonight across the northwestern third of the forecast
area, with precipitation approaching the I-35/35W corridor in the
pre-dawn hours Saturday. Severe weather is unlikely with the
overnight convection, but there should be enough elevated
instability for a few strong storms with small hail. Otherwise,
cool and breezy conditions will persist with winds out of the
east-southeast at 10 to 15 MPH and lows generally in the 50s.

30

&&

.LONG TERM... /Issued 332 PM CDT Fri Apr 20 2018/
/Saturday through Friday/

The upper level low currently over the Four-Corners area should
be over southeastern Colorado at 7 AM Saturday. Meanwhile,
a surface low will be over West Texas near Lubbock with a dryline
extending southward and a warm front extending eastward north of
the I-20 corridor. A cold front will extend to the northwest of
the surface low.

With strong isentropic upglide occurring across North and Central
Texas Saturday morning, showers and thunderstorms are forecast to
be on-going west of I-35 before daybreak Saturday. These showers
and thunderstorms will move east across the rest of the forecast
area during the morning into the early afternoon. The storms are
not expected to be severe, but will produce some cloud to ground
lightning and maybe some brief heavy rainfall. There remains a
question about how much the morning clouds and convection will
affect the development of afternoon convection. Some of the
Convection Allowing Models are generating another round of showers
and thunderstorms by mid Saturday afternoon while others are not
so excited. The most likely area for some strong to severe storms
mid to late Saturday afternoon should be across the western zones
where where the strong low level warm advection ahead of the
advancing surface low and dry line will allow temperatures to warm
into the mid to upper 70s. A cold front will overtake by late
afternoon into the evening and sweeps through the forecast area
well overnight Saturday night. The chances of showers and
thunderstorms will end from west to east late evening through the
overnight hours as the upper level low moves across Oklahoma
toward southwest Arkansas.

Cannot rule out a few showers lingering into Sunday morning across
the northeastern zones with some wrap-around moisture from the
upper level low. Otherwise, dry weather is expected Sunday through
Tuesday.

A northern stream shortwave will move southeast across the
northern and Central Plains Tuesday night and Wednesday. This
system and its accompanying cold front will bring chances of
showers and thunderstorms Tuesday night and Wednesday.
Another shortwave in the northwesterly flow aloft, should
allow for other chances of showers and thunderstorms late week,
but the models differ on how they handle this system. For now,
have just placed low PoPs for the Wednesday night through Friday.



58

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    53  66  51  67  51 /  20  80  60   5   0
Waco                53  71  51  70  50 /  20  70  50   5   0
Paris               48  64  51  65  50 /  10  90  70  10   5
Denton              52  64  49  67  49 /  30  80  50   5   0
McKinney            51  63  50  66  49 /  20  80  60  10   0
Dallas              54  66  52  67  53 /  20  80  60   5   0
Terrell             52  66  52  68  50 /  10  70  70  10   0
Corsicana           52  68  53  67  51 /  10  70  70   5   0
Temple              54  72  52  72  51 /  20  60  50   5   0
Mineral Wells       52  69  48  68  47 /  50  70  40   5   0

&&

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

$$



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