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

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FXUS64 KFWD 241203
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
703 AM CDT Sun Mar 24 2019


.AVIATION...
/12z TAFs/

Challenge and concerns: Timing increasing TS-severe threat by this
evening and in/out MVFR cigs at KDAL/KACT through mid morning,
with a return of MVFR at KACT after 06z Monday.

All airports should remain TS-free through 00z, though isolated
activity could develop with max heating late this afternoon N-NW
of DFW airports. With high-res models differing on timing a cold
FROPA in later tonight and subsequent TS development, I have
leaned toward the middle and remain consistent with the previous
forecast of a 4-hour VCTS window from 01z-05z this evening. It`s
quite possible this window will need to be adjusted on the 18z,
21z, and 00z Monday TAFs.

MVFR cigs are beginning to shift east of most airports sans
KACT/KDAL this morning, as the 35-45 knot LLJ has veered
southwesterly the past 3 hours. MVFR should prevail at KACT
through 15z, but KDAL will be in/out through 15z as they remain on
the western periphery of the stratus field. Otherwise, VFR
conditions will prevail at all DFW Metro airports through tonight,
despite the arrival of a cold FROPA late this evening. With FROPA
expected to be around 12z Monday at KACT, will introduce MVFR cigs
back into the forecast after 08z. FROPA timing here is tricky as
some models are near 11z Monday, while others are after 12z. I`ll
let later TAFs refine cold FROPA timing at KACT with the
uncertainty.

Lastly, regarding veering surface winds just ahead of cold FROPA
later this evening at DFW and DAL, the window should be limited to
1-2 hours with speeds below 10 knots -- thus, minimal to no
impacts are expected with regard to crosswinds just in advance of
FROPA.

05/

&&


.SHORT TERM... /Issued 336 AM CDT Sun Mar 24 2019/
/Today Through Tonight/

Another active weather day, possibly more so than Saturday, is
expected late this afternoon into tonight, as a strong shortwave
trough rotates through progressive westerly flow over the area and
south of the main mid level trough lifting east from the Central
Plains into the Mid Mississippi Valley by tonight. Scattered to
numerous showers and thunderstorms will form along and east of the
I-35/35W corridor and ahead of a southward advancing cold front
arriving this evening. Storm coverage will be more isolated in
nature farther west, which is away from the better large-scale
ascent and where surface convergence along the cold front will be
the primary forcing mechanism.

South winds through this morning, will veer more southwesterly
across the western half of the area. The veering low level flow
should result in compressional warming off the higher terrain just
ahead of the cold front and during time of max heating. Western
areas should see some partial sunshine by this afternoon. As such,
this will be our warmest day with highs in the lower-mid 80s.
Where cloud cover and moisture is higher in the east, highs of
around 75-80 appear reasonable. The warm temperatures will lead to
MLCAPE/SBCAPE values between 1500-2000 J/KG ahead of the cold
front late this afternoon and through sunset this evening. Mid-
level lapse rates near 7 deg C/km aloft will allow for ample
elevated instability within the prime hail growth zone. The
combination of lift and instability with west- southwest deep
layer and effective shear forecast around 50 knots will be more
than sufficient for strong-severe thunderstorms once development
occurs later this afternoon and through midnight. The main concern
will be large hail and damaging downburst winds. Though the
tornado threat would be non-zero, rapidly veering 0-1km flow
should limit the tornado threat, though any discrete storms
intersecting localized outflow boundaries will need to be watched
for any brief spin ups.

The cold front should see an increase in forward momentum and
southward progression late this evening and overnight, as it
becomes more supported aloft with the strong shortwave moving
southeast across the Ark-La-Tex region into the Lower Mississippi
Valley area by Monday morning. This will push the better coverage
of showers and thunderstorms to areas south of I-20/30 and east
of I-35 overnight. Coverage of severe activity will begin to wane
as the instability decreases somewhat and the surface-boundary
layer continues cooling. Nevertheless, an isolated risk of severe
weather will continue across our southeast counties through sunrise
Monday. North-northeast winds of 10 mph or a little more will
usher in cooler air, though the bulk of stronger low level cold
advection should remain confined well northeast of our region.
Lows Monday morning will see wide variability from northwest to
southeast, as our area will be in transition with the cold front.
Lows will range from around 50 degrees across the far west and Red
River Valley, to the upper 50s and lower 60s in much of Central
Texas.

05/

&&

.LONG TERM... /Issued 336 AM CDT Sun Mar 24 2019/
/Monday through Saturday/

A few lingering showers and thunderstorms are possible on Monday
morning as a cold front continues to sweep southward through East
and Central Texas. Monday through Wednesday are expected to be
rain/storm free with mild conditions. Thursday and into next
weekend will be more active as another upper level trough will
result in another threat for rain and thunderstorms.

By 12 UTC Monday, the cold front should be across the Brazos
Valley. Storm activity should be on the decline as 850mb flow will
weaken and veer. Despite the passage of the cold front, Monday
should largely be a pleasant day, albeit a bit breezy. Highs are
still expected to climb into the upper 60s along the Red River to
low to mid 70s elsewhere. The dry airmass in place coupled with
clearing skies should help to facilitate a large diurnal range
as low temperatures Monday night into Tuesday fall into the 40s.
Some parts of Central Texas may remain in the low 50s.

Warm conditions will continue into the day on Tuesday and
Wednesday. As noted yesterday, some of the model blends suggest
that Tuesday may be a little cooler, but mostly sunny skies and
the dry airmass will likely be enough to offset any lingering CAA.
Winds on Tuesday will also become easterly and ultimately
southerly by days end, essentially shutting of any additional CAA.
We will need to watch a compact upper wave rippling through the
Ozarks which may send another surge of cooler air southward,
however. Wednesday will remain warm, but we will see more in the
way of cloud cover from Pacific moisture ahead of a longwave
trough to the west. This may temper warming some, but highs in the
upper 60s to mid 70s still look reasonable. Southerly winds will
also increase with speeds in the 10 to 20 mph range.

On Thursday, we will see our first little surge in low level
moisture. The GFS remains the most aggressive with moisture
transport northward with low 60s degree dewpoints. Given that
moisture will be somewhat scoured southward by Sunday/early
Monday`s front...and will likely be shallow in nature and
susceptible to vertical mixing, I feel that the ECMWF and
Canadian solutions are much more plausible with low to mid 50s
dewpoints advancing northward in response to southerly flow. I`ll
only advertise a 15 PoP with showers in lieu of thunderstorms as
instability will be low given those aformentioned dewpoints from
the EC/Canadian forecasts. With the surface pressure gradient
magnitude increasing breezy south winds are anticipated.

Friday into next weekend will see a return to a more active upper
air weather pattern. Most of the synoptic guidance advertises a
stout upper level trough with upper tropospheric winds nearing 100
knots. In response, surface cyclogenesis will commence across
southwest Kansas. This will allow for a larger breadth of moisture
return northward. A dryline is progged to mix eastward through the
Big Country and could be a focus for convection. I`ve reoriented
the highest PoPs a little further west given the expected position
of the dryline. With sufficient shear and instability in place and
given the time of year, we may have to contend with a round of
strong to severe storms Friday and possibly into Saturday. Details
regarding capping and mesoscale influences this far out are a
little unclear, so we`ll be reevaluating this portion of the
forecast in the coming days. Nevertheless, `tis the prime season
for strong to severe storms, so stay tuned.

The front should sweep southward through the area by midday
Saturday, and model guidance is insistent on post-frontal rain
chances. Given that there`s a little bit of run-to-run consistency
in the ECMWF and now better agreement from the GFS, I`ve elected
to keep low rain chances through the end of the weekend.
Instability appears low at this time, so I`ll leave thunder out
for Sunday and Monday. Model solutions have also slowly converged
towards cooler conditions on Saturday and Sunday. I`ll nudge high
temperatures down, but if GFS numbers are correct, highs in the
40s and 50s may be all most areas can muster next weekend. For
now, I`ll continue to lean on blended guidance which advertises
below normal temperatures in the low to mid 60s.

Bain

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    82  55  72  47  72 /  30  60   0   0   0
Waco                81  59  76  48  73 /   5  20   5   0   0
Paris               76  52  69  45  68 /  40  80   0   0   0
Denton              81  52  72  45  71 /  30  40   0   0   0
McKinney            80  53  72  46  70 /  30  70   0   0   0
Dallas              82  57  73  48  72 /  30  60   0   0   0
Terrell             78  57  73  47  70 /  20  60   5   0   0
Corsicana           79  60  73  48  71 /  10  60  20   0   0
Temple              80  61  75  50  74 /   5  20  10   5   0
Mineral Wells       83  50  73  45  74 /  20  20   0   0   0

&&

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

$$

05/24


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