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

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FXUS64 KFWD 272038
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
338 PM CDT Thu Jul 27 2017

.DISCUSSION...
It is another hot and humid afternoon again with temperatures
reaching the mid 90s to 102 degees and heat index values between
100 and 107 at 3pm. Warm and muggy conditions will prevail again
this evening with temperatures only falling into the lower 80s in
the urban areas with mid to upper 70s elsewhere.

Meanwhile a cold front is making slow progress across the Plains
and at this time is casually draped across Oklahoma. The front
will make its way to the Red River Valley overnight and may
contribute to a few high-based light rain showers across the
northern zones by morning. The main impact the front will have
will be an increase in mid level cloud cover and a veering low
level wind profile. Both of these impacts will have major
implications on the high temperature forecast, but both will try
to pull high temperatures in opposing directions. With the low
level westerly winds, it will drag much warmer air in from the
higher terrain to the west and put 850 mb temperatures near 25C
in the heart of a thermal ridge that gets situated along the I-20
corridor. Historical data and pattern recognition would argue for
forecasting high temperatures near 105 degrees at DFW. However
this value could be out of reach should cloud cover inhibit max
insolation. Will not be as aggressive as history suggests but will
forecast the hottest day so far this summer across all but the
northern zones where more cloud cover should win out. The heat
advisory will continue for most of the eastern 2/3rds of the CWA
with the exception of the northern zones.

Due to the southwesterly winds, low level moisture will be limited
ahead of the front which means any threat of daytime convection
should stay immediately north of the frontal boundary where
dewpoints will remain near 70 degrees. While the chance of
convection looks low due to weak forcing and the upper level high
remaining planted over North Texas during the day, any convection
that does develop could produce microbursts so this will need to be
monitored. The front will gradually move southwest across the
area Friday night and Saturday morning and precipitable water
values will surge to above 2.1 inches. Again instability and lift
will be rather limited during the overnight hours, but it is
possible some high-based rain showers or storms could form Friday
night and Saturday morning. This time period likely represents the
best chance for rain with the front, but still only 20-30%.

A strong upper level trough will drop through the Great Lakes
region and cause a large sprawling surface high to drop into the
Midwest and cover the eastern CONUS. So while the upper high will
remain overhead, the cold front will receive a push southwestward
Saturday from the surface high. The low level thermal ridge of hot
850 mb air will be being shunted into central Texas by the
afternoon. Again high temperatures depend on the amount of mid
level cloud cover but it is likely they will exceed 100 degrees
again on Saturday across the southwest and southern zones. Across
the northeastern zones cooler and drier air will begin to move in
with highs only in the lower 90s. Isolated thunderstorms are
possible near the front during the heat of the day which could
lead to another risk of microbursts during the afternoon hours.
Synoptic lift will remain limited beneath the upper ridge so
coverage should stay isolated.

The upper level ridge will begin to weaken over Texas and will
intensify over the western CONUS Sunday and Monday. This will put
North Texas in northwest flow aloft. Meanwhile moisture will get
depleted as drier air from the northeast continues to filter into
the region from flow around the surface high. So while, normally
we would be concerned about the potential for High Plains
convection to impact the region early next week, it looks like the
airmass will be too stable...especially in the eastern zones. It
does look like a good setup for rain across the western part of
the state, and will keep slight chance PoPs going across the
western zones in case some of this activity survives long enough
to impact those areas. Otherwise highs next week will be below
normal and in the low to mid 90s. Humidity will also be lower than
normal and low temperatures will drop into the 60s in outlying
areas. So certainly a good way to start August.

By midweek moisture should increase which will likely allow for
some convection or remnant convectively induced vorticity centers
to move into the area from the northwest and fire off additional
activity. Most models are advertising an upper level trough
taking hold over the state by Wednesday or Thursday. This would
likely result in good chances of scattered showers and storms and
continue to keep highs in the lower 90s.

TR.92

&&


.AVIATION... /Issued 1231 PM CDT Thu Jul 27 2017/
/18Z TAFs/

The only concern this TAF cycle will be veering winds associated
with an approaching surface cold front on Friday. Otherwise, VFR
conditions are expected with a few diurnal CU this afternoon and
broken cirrostratus leftover from MCS anvil debris across eastern
Oklahoma and the Ozarks.

S-SW winds around 10 knots will persist through tonight, though
they could briefly back SE this evening. As the cold front moves
slowly into North TX later on Friday, winds will veer westerly
by 15Z Friday, then eventually shift NW 5-10 knots by 21Z Friday.
A lot will depend on the timing of shortwave support in weak north
flow aloft over the area. Convective chances look too isolated
and uncertain for any VCTS mention in the TAFs at this time.

05/

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    81 102  80  97  77 /   5  10  30  30  10
Waco                77 102  79 101  76 /   0   5  20  30  20
Paris               75  96  75  92  69 /  10  20  30  20   5
Denton              76 100  77  95  74 /  10  10  30  30  10
McKinney            77  98  77  94  73 /  10  20  30  20   5
Dallas              82 102  80  97  77 /   5  10  30  30  10
Terrell             76  99  77  95  74 /   5  10  30  20   5
Corsicana           77 100  78  98  75 /   5  10  20  30  10
Temple              74 102  78 103  76 /   0   5  10  20  20
Mineral Wells       74 102  76  97  73 /   5  10  20  30  10

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT Friday for TXZ103>105-107-117>123-
131>135-144>148-157>162-174-175.

Heat Advisory until 8 PM CDT this evening for TXZ091>095-102-106.

&&

$$


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