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

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FXUS64 KFWD 280448 AAA

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1148 PM CDT WED JUL 27 2016

North Central Texas remains caught in a weakness between two areas
of high pressure, and this will ensure continued unsettled weather
through the forecast period. The 28/00Z KFWD sounding reveals a
very moist and unstable profile is in place. As a result, it`s not
surprising that showers continue to develop even at this late
hour in the vicinity of an old outflow boundary just to the east
of the Metroplex sites. At this time, it appears that activity
should remain outside of the TAF sites, but cannot entirely rule
out a stray popup shower during the overnight hours.

The forecast for Thursday will continue to be influenced by
subtle features that makes pinning down the most convectively
active regions and time periods difficult. At this point, decided
to continue VCSH at the Metroplex sites Thursday morning as it
appears convection will re-develop near the Arklatex and
potentially spread westward into the mid-morning hours.

As this activity dissipates, surface heating, in concert with a
weak shortwave aloft, should be sufficient to encourage
additional scattered thunderstorm development during the afternoon
hours. Opted to prevail a short period of VCTS from 20-22Z in the
Metroplex, and a broader window from 17-22Z at Waco as it appears
the Metroplex will be at the edge of the better combination of
lift and instability.

Any lingering activity should then wane Thursday evening, with VFR
conditions and light south winds prevailing at 10 kts or less.



Thunderstorms will continue to weaken through mid evening due to a loss
of heating. We will still keep some chance pops across the
eastern and southern zones and a slight chance elsewhere due to
the numerous outflow boundaries in the area.

The only other changes necessary at this time will be to adjust
the hourly temperature and dewpoint grids where thunderstorms
have temporarily modified the air.



The main highlights for this forecast package will be rain
chances over the next several days and into the early portion of
the weekend. For the latter half of the weekend and into next
week, the upper air pattern favors one that should result in hot
and mostly dry conditions.

For the rest of this afternoon, showers and thunderstorms will
continue as daytime heating and additional convection develops
along outflow boundaries. The main culprits for convection this
afternoon are the mid-level deformation axis as seen in water
vapor imagery and RAP H5 fields across North TX with the main
impetus for convection across Central TX being along modified sea-
breeze outflow lifting northward. The very moist regime, slow
storm motion and weak deep layer shear has resulted in efficient
rain producers across North and Central TX this afternoon.

There have been a few strong convective outflows, but generally
the moist environment makes has made it a bit more difficult to
generate a large amount of negative buoyancy within and below the
convective clouds. That being said, we will maintain a risk for
generally sub-severe downbursts as precipitation loading may
result in winds in the 40 to 50 MPH range. One area that we will
watch will be across southeastern zones where sufficient heating
and a bit more in the way of mid-level dry air exists. This may
promote a slightly higher risk for downbursts across this part of
North and Central TX.

Convection for the most part should wane through the evening
hours before subsiding with the loss of daytime heating. I will
maintain slight chance PoPs (with higher chances across NE zones)
as most of the synoptic models show a shift in the upper air
pattern. This shift places much of the forecast area in northerly
to northwest flow aloft. Most models advertise some DCVA in the
north to northwest flow aloft and given the moist regime, this
warrants at least keeping slight chance PoPs across the area.
Convection is expected to continue Thursday morning across much of
the area as shortwave troughs traverse the north/northwest flow
aloft. The airmass is expected to remain rich and moist and as a
result, instances of minor flooding will be the main risk with
showers and thunderstorms. Similar to today, there will be a gusty
downburst wind threat, but poor lapse rates and generally modest
wind shear should limit overall storm organization.

Rain chances will continue into Friday and Saturday as the swift
north/northwest flow pattern continues. 20-30 percent PoPs were
introduced Friday afternoon into Saturday morning given that a
few lobes of mid/upper level vorticity are forecast to sweep
through the area.

Beyond Saturday, near triple digit heat is expected to grip North
and Central TX. Wind speeds are generally expected to be fairly
light through this portion of the forecast. The weak winds should
prevent deep boundary layer mixing. As a result, relative
humidities will continue to range in the mid-30 to 40 percent
range. While this may limit a larger fire weather concern for
areas that miss out on rain over the next several days, heat
index values will likely climb back into the 102 to near 105
degree range.



Dallas-Ft. Worth    76  94  77  97  78 /  20  40  10  30  20
Waco                77  97  75  99  76 /  30  40  20  20  10
Paris               73  90  73  94  74 /  40  40  20  30  20
Denton              73  93  74  96  74 /  20  40  10  30  20
McKinney            74  93  75  95  75 /  30  40  10  30  20
Dallas              77  94  76  98  79 /  20  40  10  30  20
Terrell             75  93  75  95  76 /  30  40  20  30  20
Corsicana           76  96  75  96  77 /  30  40  20  20  10
Temple              75  96  75  97  75 /  30  40  20  20  10
Mineral Wells       72  94  72  97  73 /  20  40   5  20  10


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