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

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FXUS64 KFWD 251152 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
652 AM CDT Tue Jul 25 2017


.AVIATION...
Some additional mid-level moisture is working its way across the
region this morning, and this is resulting in some scattered cloud
cover around FL100. With the heating of the day, additional
cumulus will dot the skies, and bases will rise through FL060. At
Waco, will continue to indicate a brief TEMPO for MVFR cigs as
some occasional low clouds drift across the airfield.

With the increase in mid-level moisture, it`s not entirely out of
the question that a rogue shower or two attempt to develop near
the Metroplex sites later this afternoon. That said, the effects
of increasing large-scale subsidence are clearly evident on our
ascending morning sounding with notable drying and warming
occurring above 500 mb. As a result, any activity that does
develop should be short-lived and too inconsequential to warrant
inclusion in the TAFs. Otherwise, south winds around 9-12 kts will
be the norm today and tonight.

Some additional MVFR stratus appears possible at Waco on Wednesday
morning, but this is just outside the current valid TAF period.

Carlaw

&&


.SHORT TERM... /Issued 316 AM CDT Tue Jul 25 2017/
/Today and Tonight.../

Dewpoint depressions early this morning have dipped to around 0-3
degrees in isolated spots under mostly clear skies. Area VWPs,
however, show 925 mb winds around 20-25 kts, which should keep any
visibility reductions isolated and mainly in excess of 5 miles.

High temperatures today will rise into the middle and upper 90s
across North and Central Texas. At the same time, a notable mid-
level moist axis is forecast to drift overhead near and north of
the I-20 corridor. This will impact today`s forecast in a couple
of ways. First, the increased moisture in the 850-700 mb layer may
actually dampen the effects of diurnal mixing somewhat, resulting
in surface dewpoints only falling to around 70 degrees during the
mid-afternoon hours. The combination of hot temperatures and
locally enhanced humidity will result in heat index values of
105-108 degrees this afternoon from near the Metroplex and
northward to the Red River where a Heat Advisory is in effect.
Isolated locations across Central Texas may briefly approach
advisory criteria, but more efficient mixing should limit the
areal extent of 105+ values.

The second impact of this moist axis will be on any (low)
precipitation potential this afternoon. With convective
temperatures only in the middle 90s, there are signs that a few
parcels may be able to breach their LFCs during peak heating. The
offsetting factor here will be the expanding influence of large
scale subsidence just to our north. As a result, confidence in
convection was not quite high enough to warrant an explicit
introduction of showers/storms in the weather grids, but we`ve
nudged silent PoPs up to 10-15% for the time being.

Carlaw

&&

.LONG TERM... /Issued 316 AM CDT Tue Jul 25 2017/
An upper level ridge will strengthen its grip on the weather
across North and Central Texas Wednesday and Thursday before
shifting westward Friday. Highs will be mid 90s east to around
100 degrees across some areas along and west of the I-35 corridor.
Heat index values of 100 to 108 degrees are expected. Although we
have not done so yet, the Heat Advisory may need to be expanded
south to include areas along and east of the Brazos
River...including the Waco-Temple-Killeen areas. Low level winds
are expected to become a little more southwesterly Thursday which
will result in even warmer temperatures. Highs will range from the
upper 90s to 104 degrees. Dewpoint may be a few degrees lower
along and west of I-35 but with the higher temperatures, all but
the southwestern zones may reach heat index values of 105 degrees
or higher. Some 110+ heat index values will be possible, but at
this time, it doesn`t look like they will be widespread enough to
prompt a Excessive Heat Watch (The criteria for an Excessive Heat
Warning is when conditions are favorable to reach either one of
the following to occur for two consecutive days: 1. Maximum heat
index values of 110 degrees or higher. 2. The actual temperature
to reach 105 degrees.

With the upper high shifting westward, a cold front should move
southward down the Plains reaching the Red River overnight
Thursday night. We will have low chances of showers and
thunderstorms north of the I-20 corridor Thursday night. The
northerly flow along the eastern periphery of the upper ridge will
be conducive for the front to make slow southward progress
through the forecast area Friday and Saturday. Temperatures on
Friday will be cooler along the Red river with mid 90s expected,
but most of the rest of the forecast area will be in the upper 90s
to 102 degrees. Heat index values of 100 to 110 degrees are
expected across the region Friday. With the increase in cloud
cover, temperatures on Saturday and Sunday should be cooler (that
is a relative term). Highs are expected to be in the lower 90s
north to the upper 90s across Central Texas Saturday and Sunday.

Although the GFS, Canadian and ECMWF differ some early next week,
they agree that the upper ridge will remain to our west, with
northwesterly flow across the forecast area. This will lead to
low thunderstorm chances with near seasonal normal temperatures
for the early part of next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    99  79  99  80 102 /  10  10   0   5   5
Waco                99  78  99  78 101 /  10  10   5   5   5
Paris               94  74  95  76  99 /  10   5   0   5   5
Denton              99  77  99  78 102 /  10  10   0   0   5
McKinney            97  77  97  78 100 /  10  10   0   5   5
Dallas              98  79  99  81 102 /  10  10   0   5   5
Terrell             97  75  97  77 100 /  10  10   0   5   5
Corsicana           97  76  96  77  99 /  10  10   5   5   5
Temple              98  76  99  76 102 /  10  10  10  10   5
Mineral Wells       98  75  99  76 101 /  10  10   0   5   5

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon today to 8 PM CDT Wednesday for
TXZ091>095-102>106-117>121-133-134.

&&

$$

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