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

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FXUS64 KFWD 190256 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
956 PM CDT Wed Apr 18 2018


.UPDATE...
The forecast is in pretty good shape with only minor tweaks to
hourly temperature and sky grids.

Upper level high clouds continue to stream in from the southwest
and this is expected to persist through the overnight hours. I did
increase sky cover a little across Central Texas to account for
these trends. Winds have and will continue to subside with the
onset of nocturnal cooling and boundary layer decoupling. While
temperatures have been a little slower to fall than previously
thought, it`ll still be cooler tonight compared to previous
nights with the dry airmass and lower wind speeds. As a result,
the current forecast with lows in the 40s and 50s seem
reasonable.

24

&&


.AVIATION... /Issued 655 PM CDT Wed Apr 18 2018/
00 UTC TAFs

Concerns---None. VFR with north to northeast winds.

VFR will prevail at all TAF sites in the wake of the cold front
today. High pressure will build across western North Texas
ensuring that northerly winds will remain in place. Surface wind
speeds, however, will decrease during the overnight hours to
around 8 to 10 knots. Winds will slowly turn towards the
northeast through the day tomorrow and and will increase to around
10 to 12 knots. A sct to bkn deck of high level clouds (above
FL250) will continue to stream in from the west/southwest this
evening and through the TAF period.

For the 24 to 30 hour portion of the D/FW TAF...winds will take on
an increasingly easterly component and this may allow for the
transition to a south flow. Mid-level clouds will also invade
from the southwest with heights around FL150.

24

&&

.SHORT TERM... /Issued 332 PM CDT Wed Apr 18 2018/
/Tonight and Thursday/

With today`s cold front successfully shunting low level moisture
to the south/southeast, expect patchy high clouds through the
night as a plume of slightly higher moisture content moves from
west to east. The gusty winds experienced during the day today
will slowly decrease around sunset as the bounday layer decouples
from the higher wind speeds just above the surface.

Overnight, temperatures will range from the 40s and 50s with wind
speeds between 5 and 10 mph out of the north/northeast. The
surface high will continue moving to the east through the day on
Thursday, leading to a gradual easterly wind shift by late
Thursday afternoon. High temperatures will likely be in the upper
60s to around 70 along the Red River, low to mid 70s along the
I-20 corridor and mid 70s across Central Texas. Cloud cover will
be on the increase Thursday afternoon as the subtropical jet
begins to usher in better Pacific moisture ahead of the
approaching upper level low.

Hernandez

&&

.LONG TERM... /Issued 332 PM CDT Wed Apr 18 2018/
/Thursday night and Beyond/

Surface ridging across the area will diminish Thursday night and
into Friday as the associated high pressure cell builds across
the Great Lakes. Our low-level winds will begin to veer in
response and will return to favor a southeasterly direction
through the day on Friday. The initial moisture return associated
with the renewed southerly flow will be feeble, and dewpoints will
likely only rise into the 40s Friday afternoon. Guidance suggests
that mid and high-level moisture will stream in as Pacific
moisture is ushered overhead. As a result, trimmed a few degrees
off high temperatures for Friday given the somewhat decreased
insolation.

By Friday evening, a potent upper-low will be ejecting out onto
the Central Great Plains. As the attendant 120 kt jet streak
overspreads the Texas Panhandle, lee cyclogenesis will begin
within the favored left exit region across southeastern Colorado.
A burgeoning dryline will also be setting up across far West
Texas during this time, which should become a focus for one area
of vigorous convection during the late-afternoon/early-evening. A
second area of showers and thunderstorms may also materialize to
the east of the surface dryline, possibly stretching from the
Trans-Pecos and into the Texas Rolling Plains. This activity will
be associated with robust warm advection/isentropic ascent above
the re-invigorated EML plume/capping inversion. At this time,
the model consensus is good that all of this initial precipitation
will remain west of our CWA during the day on Friday. We`ll show
some low (20-40%) PoPs west of I-35 during the evening hours as
remnants of this elevated activity may leak into our western
zones after sunset. Any elevated instability will be minimal (at
best), so we`re not anticipating strong or severe storms Friday
evening and overnight.

The main focus of this forecast package continues to be on the
Saturday-Saturday night time frame. Model guidance (both
deterministic and ensemble) remains in very good agreement
regarding the general evolution of the pertinent large-scale
weather features through this period, which leads to confidence in
the PoP (precip probability) part of the forecast. Mid-level
heights will be falling through Saturday morning as the core of
the potent upper-low barrels towards southern Oklahoma. This
increasing large-scale ascent will lead to the development of
widespread showers and thunderstorms Saturday morning. The highest
precip chances (at least through noon) should be along and north
of the I-20 corridor. Forecast soundings show any storms during
the morning hours would be elevated in nature. Extremely skinny
MUCAPE profiles do not portend a strong-severe thunderstorm
threat, even amidst an environment characterized by increasing
mid-level wind speeds.

During Saturday afternoon, a cold front will likely seep south of
the Red River and towards the I-20 corridor, while a dryline mixes
somewhere into our southwestern counties. The greatest
precipitation chances will shift to roughly along and east of the
I-35 corridor during this time frame. Given the anticipated
widespread cloud cover and precipitation through the day, the
potential for severe weather during the afternoon and evening
hours is in question at this time. If breaks in the clouds can
develop between the eastward-mixing dryline and southward-
surging cold front, then a localized severe threat could
materialize south of I-20 and west of I-45 as 750-1500 J/kg of
MLCAPE are realized. The main hazards would be from quarter-sized
hail and damaging wind gusts. The low-level wind field looks
quite weak, which would help to limit the tornado potential unless
any surface-based storms interact with outflow from earlier
precipitation. Once again, the severe threat is far from certain
and looks to be tempered a good deal by morning activity.

Locally heavy rainfall will also be a threat with this storm
system, but widespread flooding/flash flooding is not anticipated
given this storm`s fairly progressive nature. Still, individuals
north of I-20/I-45 can expect to pick up 1-2 inches of rain
(locally higher) through Sunday night. High temperatures will also
be tricky for Saturday, and have trended these downwards today
with the indications of pervasive clouds and storms. It`s possible
our zones near the Red River struggle to even get out of the 50s,
while locales closer to the Concho Valley warm into the upper
70s/near 80 degrees behind the dryline.

Precipitation will clear out of all but the far eastern portions
of the area Sunday morning, leaving a breezy and cool day behind.
Temperatures will gradually moderate into early next week, but
look to remain below climatological normals through Wednesday as
another weak/reinforcing cold front slips into the area.

Carlaw

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    51  73  50  70  53 /   0   0   5   5  20
Waco                48  74  48  71  53 /   0   0   5  10  20
Paris               45  69  45  68  50 /   0   0   0   5  10
Denton              44  72  46  70  51 /   0   0   5   5  30
McKinney            45  71  46  69  51 /   0   0   5   5  20
Dallas              52  73  51  71  53 /   0   0   5   5  20
Terrell             47  72  47  70  51 /   0   0   0  10  10
Corsicana           48  72  48  69  52 /   0   0   5  10  10
Temple              48  75  50  71  54 /   0   0   5  10  20
Mineral Wells       46  74  47  70  51 /   0   0   5  10  40

&&

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

$$

24/79


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