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

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570
FXUS64 KFWD 221642 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1042 AM CST Fri Feb 22 2019


.UPDATE...
Though a couple of rural sites were still reporting visibilities
of a quarter of a mile, most locations have improved to half a
mile or more and the Dense Fog Advisory was allowed to expire.
Areas of fog and drizzle will still produce visibilities between
half a mile and a mile in some areas today with only minor
improvement expected this afternoon.

Recent guidance has keyed on another quick-moving disturbance
moving northeast across the region today, which is already
generating isolated storms along and east of I-35. Occasional
lightning and possibly some more pea-sized hail may accompany the
stronger storms this afternoon, but severe weather still appears
unlikely. Activity will move off to the northeast this evening,
followed by another quick round of showers and storms (again
mainly along and east of I-35) overnight tonight as a Pacific
front and an upper level low pressure system Traverse the Southern
Plains. Otherwise, Saturday still looks dry and windy behind the
front.

30

&&


.AVIATION... /Issued 604 AM CST Fri Feb 22 2019/
/12Z TAFs/

Relatively unpleasant flying conditions will persist through today
and into tonight, with continued IFR or lower CIGs and VSBY
restrictions.

A re-invigoration of warm-air advection across the region has
lowered CIGs to LIFR levels early this morning, along with a slow
reduction in VSBYs. CIGs are unlikely to improve much today, and
they will likely struggle to even reach 010. Less confidence in
the VSBY forecast, but periods of IFR to MVFR are forecast this
morning. Occasional showers will be possible as well through mid-
day so maintained the TEMPO group through 16Z. Additionally, a
couple storms could develop across North and Central Texas through
early afternoon, but confidence is too low for any mention in
TAFs. This potential will need to be monitored accordingly.

While TAFs explicitly forecast MVFR/4SM by afternoon, some
potential exists for VSBYs to fall below 3SM at times this
through early evening. Thereafter, expect a more notable
reduction in flight categories area-wide after 00Z, and a return
to prevailing LIFR CIGs and IFR or lower VSBY.

Conditions will rapidly improve around/after 10-12Z Saturday
following the passage of a sharp Pacific front. Winds will veer
from the southeast to the west and become gusty behind the front,
especially once deeper mixing ensues by mid morning Saturday.
Therefore, indicate gusts to 30 kt in the 30-hour KDFW TAF.
Indeed, isolated gusts up to 35 kt will be possible.

Picca

&&

.SHORT TERM... /Issued 411 AM CST Fri Feb 22 2019/
/Through Saturday/

Periods of fog, drizzle, a few thunderstorms, and then fairly
vigorous winds during the short-term period -- a little something
for everybody!

A cool, moist air mass remains solidly established beneath a stout
elevated mixed layer (noted in our 22/00Z sounding) currently.
With another shortwave impulse approaching our region at present,
further saturation of low levels should bring about increasing
drizzle, shower activity, and some fog, especially for areas
along/west of the I-35 corridor through mid morning. While
residual T-Td spreads have kept fog from becoming dense on a
widespread scale, aforementioned saturation may decrease
visibilities sufficiently for more areas of dense fog towards
daybreak, and this will be monitored accordingly.

Through morning and into the afternoon hours, this low-amplitude
system will lift northeast across North Texas. Forecast soundings
(and the observed steep mid-level lapse rates from our 00Z
sounding) suggest positive theta-e advection and implied
isentropic ascent may support isolated thunderstorm activity ahead
of this wave. Given fast convective-layer flow and steep mid-
level lapse rates, especially towards Central Texas, small hail in
the strongest cores will be possible once again.

Behind this system, fog and drizzle may decrease some during the
afternoon, before likely re-developing during the evening and
overnight hours, owing to light surface winds, moist conditions,
and weak warm advection. Areas of dense fog will be possible.

This fog is expected prior to the glancing influence of a very
compact mid-level low over the southern High Plains. As one
vorticity lobe rotates around this cyclone tonight, the closed
low will eject northeast, forcing a Pacific front east across
North and Central Texas. The front should enter western North
Texas after 3am and clear eastern areas towards 9am. Convergence
along the front and the mid/upper low should offer enough ascent
for at least a few thunderstorms. However, maintenance of cool
surface air across most, if not all, of North and Central Texas
and dry air aloft may significantly limit convective activity
through daybreak, especially given that the core of the strongest
height falls will only glance richer boundary-layer theta-e air
(focused towards East Texas). Still, we will have to monitor the
potential for at least a few elevated hailstorms east of the 35
corridor towards sunrise. Additionally, any substantial northward
advance of unstable surface air would yield a threat of damaging
winds as well. However, the NAM and several CAMs indicate that
this cool, moist low-level air mass, albeit shallow, will yield
little ground through tonight. This evolution seems quite
reasonable, relative to the more aggressive scouring of stable air
shown by medium- range/global guidance. In turn, while some
severe potential cannot be discounted (especially the elevated
hail threat), continue to think that a more notable threat will be
confined east of our area.

Lastly, Saturday will be quite windy, initially from the west
behind the Pacific front and then eventually the northwest behind
a stronger cold front. Ample momentum and deeper mixing could
support sustained winds as high as 30-35 mph, especially west of
I-35 and north of I-20. Also sided with the warmer side of
guidance for highs, which will be boosted by a strong downslope
component. Some fire-weather concerns will likely exist as a
result, and this is discussed in greater detail in the Fire-
Weather Planning Forecast.

Picca

&&

.LONG TERM... /Issued 411 AM CST Fri Feb 22 2019/
/Saturday Night Through Next Week/

Following the late week weather event, generally zonal flow will
ensue and prevail throughout much of the upcoming week. A rex
block in the Pacific around Alaska`s longitude will prevent any
similar southern stream cyclones into early March. However, subtle
ripples in the flow will bring periodic rain chances and
subsequent cold fronts during the final week of February.

Following a remarkably mild day on Saturday, cP air will filter
into North and Central Texas in the wake of the departing storm
system. Despite sunny skies and dry air, temperatures will only
peak in the 50s Sunday afternoon. A warming trend will begin the
workweek with seasonal highs in the 60s both Monday and Tuesday.
Low-level moisture will gradually return, more vigorously into
East Texas. But when a weak wave swings through late Tuesday into
Tuesday night, a strengthening inversion may effectively cap the
boundary layer. As a result, will only carry some low-end PoPs in
the east.

A mistimed cold front will arrive on Wednesday, free of
precipitation. A more substantial shortwave will arrive on
Thursday, but guidance differs with respect to the moisture
profile above the chilly boundary layer. This is not a favorable
setup for overrunning precipitation, the hallmark of postfrontal
days in February, but a few elevated showers may result in some
sprinkles into the cool surface layer.

25

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    54  49  68  37  57 /  60  60  40   0   0
Waco                54  49  71  39  59 /  60  60  40   0   0
Paris               52  48  70  36  56 /  60  70 100   0   0
Denton              52  47  66  35  56 /  60  60  40   0   0
McKinney            53  49  66  36  56 /  60  60  60   0   0
Dallas              54  50  70  38  58 /  70  60  50   0   0
Terrell             54  49  68  37  57 /  70  60  70   0   0
Corsicana           54  50  68  39  56 /  70  60  70   0   0
Temple              55  48  72  39  59 /  60  50  40   0   0
Mineral Wells       54  46  69  33  57 /  50  50  20   0   0

&&

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

$$

30/91



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