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

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FXUS64 KFWD 191816 AAB
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
116 PM CDT Tue Sep 19 2017

.AVIATION...
/18Z TAFs/

Nocturnal convection across West Texas has survived the morning
though it is beginning to weaken as it invades western portions of
North Texas. The activity remains elevated, but if the updrafts
are able to begin ingesting surface parcels this afternoon, there
could be a reintensification near the western edge of our CWA.
With more zonal flow across North Texas and the cells` inclination
to turn right toward the deeper moisture across Central Texas, the
activity is more likely to aim toward Waco than the Metroplex TAF
sites. Regardless, with the loss of daytime heating, the activity
should dissipate this evening long before reaching the I-35
corridor.

Similar flow tonight might suggest a repeat of IFR ceilings
Wednesday morning, but the moisture looks to be more focused
across Central and East Texas. Will maintain prevailing ceilings
at FL010 for Waco. The Metroplex will likely require a TEMPO, but
it is too early to introduce that at this time.

25

&&

.SHORT TERM... /Issued 312 AM CDT Tue Sep 19 2017/
Our streak of above normal temperatures will continue today with
highs once again expected to climb into the 90s for most of the
forecast area. Although these temperatures are several degrees
above normal, they won`t come close to reaching record values
which are over 100 degrees at both DFW and Waco. With slightly
higher dewpoints than the past couple of days, heat index values
will climb near or slightly above 100F for many locations this
afternoon. However, an increasing south wind with occasional gusts
of 20-25 mph should keep the heat from feeling too oppressive.

With the aforementioned increase in moisture comes some low rain
chances once again this afternoon and evening. Locally higher PWs
of 1.5-1.7" will be in place across our southeast zones this
afternoon, and we`ll probably see a few convective attempts in
this area during peak heating that may amount to a few showers or
an isolated storm. Have maintained some 20% PoPs and expect
minimal coverage. Later this evening, we`ll need to monitor the
potential for a batch of decaying thunderstorms to enter our
forecast area from the west. This activity should initially
develop in West TX along a vague dryline feature as a subtle upper
disturbance passes overhead in increasingly zonal flow aloft. Any
storms that develop should grow into a convective cluster in
vicinity of San Angelo to Abilene. From there, the chance of any
of this convection making it into our western zones will be
dependent on cell redevelopment along its outflow, since steering
flow alone probably won`t be strong enough to nudge this activity
into our forecast area. Either way, the strength of any convection
should be on the downtrend the farther east it moves, although it
would still be capable of producing some strong winds or small
hail through the early evening west of HWY 281. With fairly low
confidence in this convection making it into our western counties,
have opted for only 20-30% PoPs at this time.

-Stalley

&&

.LONG TERM... /Issued 312 AM CDT Tue Sep 19 2017/
/Wednesday through Tuesday/

Wednesday...A shortwave embedded in zonal flow will be exiting the
region on Wednesday leaving subsident conditions in its wake. The
subsidence in combination with southwest winds in the lower layers
of the atmosphere above the surface will contribute to a hot day
across the region with highs in the 90s, reaching near 100 degrees
in some of our western counties. Heat index values will be 100-105
degrees mainly along and west of the I-35 corridor.

At the surface, a dryline will be located across NW Texas and
could approach our western counties in the late afternoon hours.
Some models develop convection along the boundary in the
afternoon, but with subsidence and weak ridging aloft occurring,
confidence in convective development is low. If convection does
occur, despite a lack of significant large scale forcing, forecast
soundings indicate storms could be strong with a threat for
strong winds and hail. Forecasted MUCAPE near 3000 J/kg with
decent mid level lapse rates and shear near 20 kts means a severe
storm cannot be ruled out. Due to low confidence in development
and expected low coverage, have kept PoPs at 20% along and west
of a line from Bowie to Mineral Wells to Goldthwaite. Have also
maintained a low chance for rain in our far southeast counties
where ample moisture may combine with the departing shortwave to
produce some diurnally driven convective activity.

Thursday through the weekend...The upper level ridge will build
back across the region as an upper level trough amplifies to our
west. Dry weather is expected for all of North Texas and most of
Central Texas. On Thursday, kept a slight chance for rain in our
far southeastern counties again for possible seabreeze convection.
Despite the influence of the upper level ridge, high temperatures
will actually lower a tad in part due to drier air in the lower
and mid levels advecting into the region from the east; around
the south/southeastern side of the upper level ridge. For most of
the weekend, highs will largely be in the lower to mid 90s, and
overnight lows will also lower into the mid 60s to mid 70s. This
drier air will also contribute to the lower rain chances.

Monday and Tuesday...For early next week we continue to monitor
the potential for a cold front approaching the region. On Monday,
the main disturbance that was located in the upper level trough
to our west moves northeast into the Northern Plains. This helps
to advance the front into Northwest Texas, but the models are
hesitant to advance it much further south with the main energy
moving farther north. By the middle of the week, the front may get
another push to bring it into North Texas. For now, will keep the
front outside of North Texas through Tuesday and maintain low
rain chances in our northwestern counties.

JLDunn

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    95  77  96  77  95 /  10  10  10  10  10
Waco                94  76  96  76  94 /  10  10  10  10  10
Paris               91  74  92  74  92 /   5  10  10  10  10
Denton              95  77  95  75  94 /   5  10  10  10  10
McKinney            93  77  93  74  92 /   5  10  10  10  10
Dallas              95  77  96  77  95 /  10  10  10  10  10
Terrell             93  76  93  74  93 /  10  10  10  10  10
Corsicana           93  76  94  75  93 /  10  10  10  10  10
Temple              94  74  95  75  93 /  10  10  10  10  10
Mineral Wells       95  75  97  73  94 /  10  20  10  20  10

&&

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

$$

25/05



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