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

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314
FXUS64 KFWD 241200 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
700 AM CDT Mon Jul 24 2017

.AVIATION...
Mostly VFR conditions are expected today. A few showers and maybe
a few thunderstorms are possible this morning across North and
Central Texas but the best chances of showers and thunderstorms
will be southeast of a KT35-KTYR line. There will be better
chances of showers and thunderstorms at the TAF sites this
afternoon but the best chances will be south of the I-20/I-30
corridors. Have left VCTS in for the Metroplex TAF sites for the
20z to 00z period and we may be able to remove this later today.
Considered putting a TEMPO TSRA in at Waco for this afternoon, but
decided to just leave VCTS in for now. Outside of the storms,
south winds around 10 knots will prevail.

58

&&


.SHORT TERM... /Issued 359 AM CDT Mon Jul 24 2017/

/Today and Tonight/

The thunderstorm complex that rolled south from Oklahoma Sunday
evening into the overnight hours was dissipating along the I-20
corridor as of 330 AM. The storms did produce a wind gust to 54
knots (62 mph) at Paris Cox Field (Lamar County). Also 2 to over 3
inches of rain fell across parts of Grayson, Fannin, Wise,
Denton, Collin and Tarrant Counties. Farther south, a thunderstorm
downburst Sunday afternoon blew down some trees in the northern
part of Temple (Bell County) and a thunderstorm downburst Sunday
evening broke 3 inch diameter tree limbs and a few power poles in
Poynor (Henderson County).

Isolated to scattered showers and a few thunderstorms are
possible this morning. The focus for thunderstorm development this
afternoon will be outflow boundaries from yesterday`s and the
overnight thunderstorms. Thus have placed the highest PoPs (50
percent) south of a Comanche to Emory line with PoPs trending down
to the 30 percent to the northwest. Cloud cover and whatever
convection that develops may play havoc with today`s temperatures.
Highs are expected to be in the 90s, but some spots along and
west of I-35 could still reach the century mark. Some 105 to 108
heat index values are possible this afternoon along the I-35
corridor. Although organized severe weather is not expected, some
damaging downburst winds are possible again mid afternoon into the
evening hours.

Thunderstorms are expected to decrease in areal coverage after
sunset. Lows will be in the 70s.

58

&&

.LONG TERM... /Issued 359 AM CDT Mon Jul 24 2017/

/Tuesday through Saturday/

The H5 ridge should begin to slowly take hold of much of North
and Central TX by Tuesday, diminishing the threat for additional
rainfall. The one exception will be across eastern zones where
there appears to be a slight weakness in the H5 ridge. The
extended portion of the HRRRx combined with NAM output support
this and I`ve inserted a mention of showers and isolated storms
for mainly eastern zones on Tuesday. Can`t rule out a gusty
wind/heavy rain threat with isolated convection, but the severe
potential appears limited at this time.

Dangerous heat will return Tuesday afternoon through the day on
Friday as the ridge is forecast to be anchored across the Central
and Southern Plains. Afternoon temperatures will likely climb into
the upper 90s and up to 102 degrees with afternoon dewpoints in
the upper 60s and low 70s. With some locations picking up between
1 and 3" of rainfall this morning, it`s possible that we get an
additional flux of moisture into the BL via evapotranspiration,
potentially boosting dewpoint temperatures even a bit more.
Regardless, it appears that heat index values will be well into
the 105 to 110 range and heat headlines will likely be required
during the long term portion of the forecast. While hot, there may
be southerly breezes of up to 15 MPH which could make the heat
*slightly* more tolerable.

Previously, I was a bit pessimistic at the prospects of an
appreciable cool down. Model guidance over the past 24 hours has
provided a glimmer of hope, however, but this is still several
days away. The ECMWF and GFS both still build the ridge back
towards the Intermountain West which in turn should help to
amplify a longwave trough across the eastern two-thirds of the
U.S. This would place North and Central TX beneath brisk northerly
flow aloft. Model progs suggest that a late-season frontal
boundary could slide southward towards North and Central TX during
the day on Friday, but there are some differences thereafter. The
GFS appears to be the aggressor and brings the front to near the
I-20 corridor by early Friday afternoon and slides the boundary
through the rest of the forecast area by Saturday
morning/afternoon. The ECMWF is a tad slower with its progression
of the frontal boundary and does not have the front through all of
North and Central TX until late Saturday. While Friday will
likely be very hot due to southwesterly/westerly winds ahead of
the boundary, Saturday and certainly Sunday appear to be cooler by
at least 5 to 10 degrees. There will also be a threat for showers
and thunderstorms ahead of and near the front. Not too dissimilar
from today, thunderstorms developing in an environment
characterized by what should be nearly 40 degree dewpoint
depressions will have the ability to produce strong downbursts.
For now, will leave PoPs generally broad brushed due to the
discrepancies in timing with values generally ranging between 20
and 40 percent.


24-Bain

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    98  79 100  81 101 /  40  30  10   5   5
Waco                98  75 101  78  99 /  50  30  10   5   5
Paris               92  73  95  75  97 /  30  20  10   5   5
Denton              98  76 100  78 100 /  40  30  10   5   5
McKinney            94  75  99  78  99 /  40  30  10   5   5
Dallas              98  79 101  81 101 /  40  30  10   5   5
Terrell             94  75 100  77  97 /  50  30  20   5   5
Corsicana           96  75 100  77  98 /  50  30  20   5   5
Temple              98  75 100  77  99 /  50  20  10   5   5
Mineral Wells       97  74 101  77 101 /  40  30  10   5   5

&&

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

$$

58/24



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