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

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000
FXUS64 KFWD 271817
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
117 PM CDT Mon Mar 27 2017

.AVIATION...

MVFR deck that moved in this morning has been slowly eroding, and
will clear all the Metroplex sites by around 19Z. VFR conditions
will prevail through the rest of today but expect the LLJ to pick
up tonight. Moisture will stream northward overnight leading to
MVFR deck moving from south to north. MVFR deck will be moving
into ACT around 06Z Wednesday and into the Metroplex sites by
around 10Z. As the column of air becomes saturated, IFR conditions
are expected, along with a chance of showers.

As the afternoon progresses, instability will increase, and a
potential for thunderstorms exists Tuesday afternoon/evening. Have
opted not to mention it in extended DFW TAF cycle, but will be
evaluated the next TAF issuance.


Hernandez

&&

.UPDATE...
Main update was to temperatures, wx and sky grids. The remainder
of the forecast remains unchanged.

Mid-morning surface analysis combined with hi-res satellite
imagery indicated a weak frontal boundary was near a Mount
Pleasant to Corsicana to Temple line and slowly sliding southward.
There is some concern that a shower or storm could develop down
across southeastern zones in the vicinity of the front, but
warming aloft, as evidenced in forecast soundings, will likely
keep convective chances down to near 20% across this area. Low
clouds also continued to slide southward from Oklahoma in
association with weak cold advection and remnant low level
moisture. The depth of this moisture is quite shallow, so clouds
should slowly erode through the day with daytime heating and
mixing. Weak, but sufficient cold air advection should mean
temperatures will be a little lower than previously thought in the
wake of the front and I`ve nudged temperatures downward by a few
degrees for most locales. The exception will be for locations
along and south of the frontal boundary, which should begin to
stall across Central TX later this afternoon and evening.
Thereafter, the boundary will likely lift back northward, setting
the stage for additional showers and thunderstorms on Tuesday and
Wednesday.

The remainder of the forecast looks to be in solid shape and no
other changes were necessary.

24-Bain

&&

.PREV DISCUSSION... /ISSUED 430 AM CDT Mon Mar 27 2017/
The tail end of a shortwave trough has now passed east of our
area. Although rich moisture remains across much of North and
Central Texas, with an advancing cold front still upstream,
downglide will dominate this morning. Some of the untapped
instability may be realized as the front peels up the buoyant
surface layer, but this should be limited to a few low-topped
showers at best. Northwest winds will invade today, but with
little support aloft to prevent the boundary from stalling across
Central and East Texas, the low-level cold advection will be
limited. The late March sun will push temperatures into the 70s,
and a few locations in the postfrontal air may reach 80F.

Our next storm system is making landfall on the West Coast, and
its downstream jet streak will emerge from the Rockies this
evening. The lee troughing it will create will quickly induce
south winds across the Lone Star State early Tuesday. With Gulf
moisture still draped across Central and East Texas, this buoyant
air will make a rapid return. The upper low will dig into the Four
Corners on Tuesday, helping to create a dryline across West
Texas. Latest guidance suggests this dryline may make a surge down
the high terrain of West Texas early in the day, and with an
initial spoke of lift spreading over the boundary, convective
initiation may occur along it by midday. This activity would head
eastward into a rapidly destabilizing (and uncapped) environment.
MLCAPE values may approach 3000 J/kg across western portions of
North Texas Tuesday afternoon, and as existing updrafts begin
ingesting these parcels, rapid intensification would occur. Large
hail and damaging winds will accompany these discrete cells, which
may reach the I-35 corridor by nightfall. The cap may hold in
areas east of the I-35 corridor Tuesday afternoon, particularly if
morning cloud cover is slow to erode, but a few isolated storms
will still be possible deeper into the humid air.

The dryline may bulge into the Big Country late Tuesday. As
another mid-level impulse arrives Tuesday evening, the boundary
could light up again. This would congeal into a linear MCS that
would race eastward overnight into Wednesday morning, posing a
nocturnal wind threat. This may be the bulk of the rain event for
areas west of the I-35 corridor. Before the atmosphere can recover
during the day Wednesday, a deep mid-level dry slot will shut off
the rain chances, which will be primarily confined to areas east
of I-35 Wednesday afternoon. A reintensification of thunderstorms
in East Texas is likely late Wednesday, with the activity growing
upscale into the Arklatex during the evening hours. This upper low
will have some characteristics of a cut-off, and some guidance is
delaying its departure. But the feature will remain attached to
the polar flow, the progressive nature of which should push it
east faster than the slowest solution (ECMWF) implies. Will
linger some low-end PoPs in eastern zones, but the associated
frontal boundary should end the event by Thursday morning.

Despite extraordinary PW values and the considerable precipitation
efficiency that will result, the system is looking less protracted
with fewer rounds of rainfall at any given location. Event totals
may still exceed an inch in some areas, particularly where storms
occur both late Tuesday and early Wednesday. But this is looking
less like a heavy rain event and more like a typical spring severe
weather event.

Another storm system will arrive in time for the weekend. Although
extended guidance is diverging on the evolution and timing, this
upper low should still have a southerly track similar to the
midweek system. Regardless of which solution you hang your hat on,
the first weekend of April doesn`t look good for outdoor
activities.

25



&&


.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    75  59  80  65  76 /   0   0  30  70  70
Waco                76  61  82  65  78 /  10  10  20  60  70
Paris               72  53  79  63  70 /  10   0  20  50  80
Denton              72  55  78  63  75 /   0   0  30  70  60
McKinney            72  54  78  63  73 /   0   0  20  60  70
Dallas              75  59  81  66  76 /   0   0  30  60  70
Terrell             74  58  82  66  74 /  10   0  20  50  80
Corsicana           78  62  83  66  76 /  10  10  20  50  80
Temple              79  62  84  63  78 /  10  10  20  60  70
Mineral Wells       75  55  77  60  79 /   0   0  40  70  40

&&

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

$$

08



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