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

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FXUS64 KFWD 280839

Area Forecast Discussion
National Weather Service Fort Worth TX
339 AM CDT Fri Jul 28 2017

Present on the surface charts this morning is a cold front, which
appears to have made its way south of Frederick, Oklahoma, and
just south of the I-40 corridor. With little in the way of
convection to its north and limited cold advection/pressure rises
noted, this front will only inch southward this morning before
slowing even further this afternoon as diurnal mixing ensues.
Modest isentropic ascent is present along and behind the front at
the nose of a 30 kt low-level jet, so a renegade shower or two
appears possible this morning near the Red River. However, with
moisture along the 310 K surface in short supply, wouldn`t
anticipate much more than this.

The main story today will once again be the oppressive heat on
what may very well be the hottest day of the year so far for many
of us. There are still some questions regarding the degree of mid-
and high-level cloud cover that gets thrown our way, but latest
indications point to just some passing high cloud cover and
percolating high-based cumulus with the heating of the day. As
lower-level winds veer out of the west ahead of the front, drier
and warmer air will advect into the region, and guidance continues
to indicate H85 temps warming to around +25 C in the prefrontal
thermal ridge. The implication here is that temperatures will
rocket towards the century mark and just above this afternoon.
Local research supports highs in the Metroplex as warm as 104-106
degrees given the H85 temperatures and westerly/southwesterly
winds. We`ve undercut these numbers just a hair with the
expectation of slightly filtered sunshine, but are advertising 103
readings across the Metroplex and at Waco. The one consolation
here is that vigorous mixing should allow dewpoints to fall into
the mid and upper 60s, resulting in heat index values in the 105
to 110 degree range as opposed to 115+. A Heat Advisory remains in
effect east of a Killeen to Mineral Wells line, and south of
Denton to Sulphur Springs. It`s possible the sites immediately
along the Red River briefly flirt with the 105 threshold, but
slightly increased cloud cover there precludes a northward
extension of the current advisory.

During the afternoon and evening hours, the front will finally
start sinking south of the Red River. With such vigorous mixing
today, it appears that any instability of significance will
actually be displaced behind the front where dewpoints will be
higher. As a result, we`ve confined low (20%) PoPs to our
immediate Red River counties this afternoon. Dewpoint depressions
of 30 degrees (+) will support a downburst wind threat if any
isolated convection is able to develop.

Tonight, weak upglide along the front may support the development
of a broken band of showers and thunderstorms across our
northeastern counties, but the combination of limited deep
moisture and subsidence overhead will keep PoPs capped at 30%.
Popcorn convection then appears possible pretty much area-wide
during the afternoon on Saturday. With high temperatures in the
99-102 degree range forecast across Central Texas, heat index
values of 105-108 degrees are possible, mainly near the region
bounded by the I-35 and I-20 corridors. Given uncertainties
regarding cloud cover on Saturday, however, we have not extended
the heat advisory at this juncture. If storm/cloud coverage
continues to look limited, a one-day extension of the heat
advisory would be warranted.

By Sunday and Monday, drier and more stable air will have worked
its way through the eastern half of the forecast area, relegating
any low shower/storm chances to west of I-35. Monday actually
looks--dare we say it--rather comfortable for the last day of July
with highs in the lower to middle 90s and low 60s dewpoints.

During the middle and end of next week, moisture will gradually
return to the region with north/northwesterly flow aloft
continuing as the subtropical high consolidates across the
Intermountain West. With a mean trough looking to set up across
our area, several decent shots at showers and storms appear
possible through this period. This will provide the added benefit
of keeping temperatures in check through the end of the week.



.AVIATION... /Issued 1133 PM CDT Thu Jul 27 2017/
VFR conditions and south winds will prevail through Friday
morning. As a cold front approaches North Texas, winds will veer
to the west and eventually become light and variable by late
Friday afternoon. A prefrontal trough will eventually cause winds
to shift to the northeast Friday evening around 04z, and they will
remain out of the north or east through the upcoming weekend. The
northerly wind shift will not occur at Waco within the valid TAF
period, and south winds will prevail into Saturday. With limited
low-level moisture, no low-level cigs are expected to accompany
the frontal zone.

Have kept dry TAFs at all airports through the period although
there could be a couple showers or storms in North Texas Friday
evening through Saturday morning. The potential for convection at
any airport is simply too low to include in the TAFs at this time.



Dallas-Ft. Worth   103  80  97  77  94 /  10  20  30  10   5
Waco               103  79 102  77  96 /   5  20  20  20  20
Paris               96  76  92  70  89 /  20  30  20   5   5
Denton             101  77  95  75  93 /  10  20  30  10   5
McKinney            99  76  94  73  91 /  20  30  30   5   5
Dallas             103  80  97  77  94 /  10  20  30  10   5
Terrell            100  77  96  74  93 /  10  20  30   5   5
Corsicana          100  78  97  75  93 /  10  20  30  10  10
Temple             102  77 102  77  97 /   5  10  20  20  20
Mineral Wells      101  76  97  73  94 /  10  20  30  10  20


Heat Advisory until 8 PM CDT this evening for TXZ103>105-107-



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