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

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FXUS64 KFWD 262320

Area Forecast Discussion
National Weather Service Fort Worth TX
620 PM CDT Wed Jul 26 2017

Minimal aviation concerns through the TAF period with VFR
conditions and south winds of 10-15 kts expected. MVFR cigs
should develop overnight across parts of Central TX, but am not
expecting this stratus to reach Waco given a veered and weaker low
level jet than the previous couple of mornings. Diurnal cumulus
6-7 kft AGL will develop again Thursday afternoon.



.DISCUSSION... /Issued 352 PM CDT Wed Jul 26 2017/
The main weather story will be another couple of hot days with a
pattern change arriving this weekend. A cold front will bring a
chance of showers and storms this weekend and some cooler weather
next week. Confidence in the model guidance is very low next week
due to both model disagreements and the fact that every model
solution deviates strongly from climatology.

The heat advisory will continue as is through Thursday. Another
warm and muggy night is anticipated tonight with lows in the mid
70s to lower 80s. Thursday looks like it could be the hottest day
so far this year as winds start the day out of the southwest as a
weak cold front pushes into Oklahoma. These southwesterly winds
could dry out the lower levels during the afternoon with dewpoints
falling a few degrees below what we`ve seen the last couple of
afternoons. On the other hand temperatures would warm up easily
with the drier air and slightly subsident southwesterly flow. So
no matter how you cut it, it will be hot with heat index values
again in the 105 to 110 degree range for the region east of Hwy
281. Any convection tomorrow will likely remain outside of the
CWA, either to the southeast where Gulf moisture is higher or
across Oklahoma near the weak front.

The cold front will likely reach the Red River Friday morning and
there is a slight chance of some showers and storms over the
northern zones during the day Friday. Temperatures will again be
hot and reach the upper 90s to 100 degrees for most areas with
heat indices again reaching the 105 mark across the eastern half
of the region. The heat advisory will likely need to be extended
one more day for parts of the CWA, but some counties in the
current advisory may be discontinued as clouds move in from the
north with the front. This decision will be left to later shifts.

As the upper level high builds in across the western part of the
continent this will result in unusually strong northerly flow
across the Midwest. A strong upper trough and sprawling surface
high will drop south through the Great Lakes region this weekend.
This will all help push the front through North and Central Texas
over the weekend. Along the front an axis of high precipitable
water will exist with values increasing to 2.1 to 2.2 inches.
While these values would be much higher than what we saw with the
last few rain events, upper level temperatures will also be much
warmer so instability and mean layer saturation will not be as
great. Still the airmass will be conducive for scattered
convection to develop both during the overnight hours and daytime
hours. The high moisture and skinny CAPE profile could lead to
locally heavy rainfall, but overall the convective potential will
be limited due to a notable lack of organized lift. Will keep
PoPs in the 20 to 30 percent range for Friday night and into
Saturday. Drier air will move into the region from the northeast
with PoPs tapering off from northeast to southwest Saturday night
and Sunday.

This dry air actually presents a forecast dilemma in next week`s
forecast. On one hand northwest flow aloft sets up which would
certainly open the door for convection to move into the region
from the High Plains, but on the other hand most models show a
lack of moisture and instability for convection to develop Monday
and Tuesday. At this point have kept PoPs in the slight chance
range Monday and Tuesday out of respect for the dynamic setup with
the inclination that there will probably be enough heating and
moisture for some low amount of instability to build up.

By the middle of next week the GFS model diverges from the model
consensus and shows the very dry air lingering (surface dewpoints
in the 50s) with little or no threat of rain. The ECMWF, Canadian,
and NAEFS are indicating more moisture available and a remnant
convectively induced vorticity lobe moving from Colorado slowly
into Texas. These models show generation of widespread convection
with this energy on Wednesday that could potentially bring
significant rainfall to the region. All of that will hinge on the
quality of moisture return by midweek and just how much dry air
moves into the area on the western fringe of the surface high. For
now, it appears that below normal temperatures are a good bet
regardless of whether it rains or not (either due to continued
strong northeasterly low level flow per GFS or rain/convection per
other models). Have indicated highs in the low 90s for most areas
and increased pops to near 40 percent on Wednesday.



Dallas-Ft. Worth    80 101  81 101  80 /   5   5   5  10  20
Waco                77 101  78 102  79 /   5   5   0   5  10
Paris               75  97  77  96  74 /   5   5  20  20  30
Denton              77 100  77  99  76 /   5   5   5  20  30
McKinney            77  98  77  98  75 /   5   5   5  20  30
Dallas              81 101  82 101  81 /   5   5   5  10  20
Terrell             76  99  77 100  77 /   5   5   5  10  20
Corsicana           76  99  78 100  78 /   5   5   0  10  20
Temple              75 100  76 101  77 /   5   5   0   5  10
Mineral Wells       75 101  76 100  75 /   5   5   5  10  20


Heat Advisory until 8 PM CDT Thursday for TXZ091>095-102>107-



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