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

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FXUS64 KFWD 141002 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
502 AM CDT Mon Aug 14 2017

.DISCUSSION...
The MCS that congealed in the Texas Panhandle late Sunday dove
south into moist inflow during the evening hours. When its outflow
was too far in advance, it made a left turn toward a strengthening
low-level jet across western portions of North Texas. Initially,
its eastward progression was slow, with deep southwest flow in the
mid and upper levels guiding the updrafts within it. However, as a
30-knot low-level jet was induced downstream in the midnight to
3am time frame, the complex began spilling eastward. With zonal
flow now firmly fixed across North and Central Texas, even our
southern zones are benefiting from the steepening lapse rates as
the impulse aloft approaches. As the low-level jet provided a
boost of warm/moist advection beneath this instability, showers
and thunderstorms developed within Central Texas, well ahead of
the main forcing.

With extraordinary PW values in excess of 2 inches and remarkably
adequate moisture flux for this time of year, expect the MCS will
continue to advance toward the I-35 corridor through daybreak.
Short-range guidance is handling the nocturnal evolution poorly,
but the consensus is strong that as the low-level jet wanes later
this morning, there will be a rapid dissipation. While this may
mean a break in the activity from mid-to-late morning into the
afternoon hours, the convective induced vorticity may see a
rebirth in our northeast zones late in the day. Additional
impulses embedded in the flow may also aid in further development
this afternoon and evening, particularly across the water-logged
northeast. The flow aloft will prevent any downpour from
lingering, but the westerly steering currents may also promote
training. Even without multiple rounds, any heavy rain within
Saturday night`s deluge swath (Sherman/Denison to Sulphur Springs)
will pose a flood threat.

As an upper trough digs into the Desert Southwest tonight, the
flow will back above North and Central Texas. Impulses embedded
in this southwest flow may impact our northwestern zones as early
as Tuesday morning. Additional nocturnal complexes will be
possible Tuesday night and Wednesday night. This stream of
unsettled weather may delay the ridging over the Southeast from
retrograding. As a result, have shaved a few degrees off daytime
temperatures through midweek, more so across our northeastern
zones where evaporation of considerable soil moisture will limit
surface heating. It still appears the heat will gradually return
this week. Heat index values may reach advisory criteria on
Wednesday and Thursday from the Dallas/Fort Worth Metroplex to
Waco and Temple/Killeen and points east.

Extended guidance is in excellent agreement with upper ridging
dominating the region next week. While these week 2 outlooks have
misled us this month, without significant precipitation this week
to disrupt the process, our confidence is growing that August 2017
may finally be able to produce a heat wave.

25

&&

.AVIATION... /Issued 1144 PM CDT Sun Aug 13 2017/
Mostly VFR conditions are expected at the TAF sites through 06z
Tuesday. A Mesoscale Convective System (MCS) that extended from
the Texas Panhandle southeastward to northwest of a line from
KFDR to 60 miles northwest of KABI was moving southeastward. This
system is expected to slowly weaken and move more east-southeast
overnight into Monday morning. Am not confident how much, if any,
of these showers/thunderstorms will reach the Metroplex, but have
placed a VCSH in for the 10-15z period. Generally southeast to
south winds at 6 to 10 knots will prevail, but if we get outflow
from the aforementioned thunderstorm complex, winds could shift to
the northwest for a few hours Monday morning.

58

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    96  79  97  79  97 /  50  10   5  10  10
Waco                99  78  98  80  98 /  20   5   5   5   5
Paris               87  75  93  75  92 /  50  20  10   5  10
Denton              95  78  95  78  96 /  60  10  10  10  10
McKinney            93  78  95  78  95 /  50  10  10  10  10
Dallas              96  80  96  80  97 /  50  10   5   5  10
Terrell             94  77  96  78  95 /  30  10   5   5  10
Corsicana           95  77  97  78  96 /  20   5   5   5   5
Temple              98  77  98  78  98 /  20   5   5   5   5
Mineral Wells       97  77  96  76  96 /  60  10   5  20  10

&&

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

$$

25/82



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