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

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910
FXUS64 KFWD 181544 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1044 AM CDT Mon Sep 18 2017


.UPDATE...
Morning satellite and water vapor imagery show a weak disturbance
moving through the southern Plains. This has resulted in some
scattered showers and thunderstorms mainly across parts of
Oklahoma. In its wake, stronger subsidence is noted in the GOES-16
water vapor channels, suggesting that additional afternoon
convection may be more limited in nature and confined to our
east/southeast areas where moisture is a little better. For this
update, we`ll lower PoPs and confine them mainly to our
southeastern counties through the afternoon hours. Subsidence
should overspread the entire area by this evening and have removed
PoPs beyond 00Z. No other changes at this time.

Dunn

&&

.AVIATION... /Issued 629 AM CDT Mon Sep 18 2017/
/12Z TAFs/

Waco Airport: MVFR stratus is much more widespread across Central
and Southeast Texas this morning. This stratus will likely
invade KACT between 1230-16Z. After that, scattered cumulus with
bases between 4-6 kft along with some high clouds will prevail for
the remainder of the day. MVFR, and possibly IFR, stratus will
return early Tuesday morning. Some convection is possible this
afternoon, mainly east of the airport, but confidence and
coverage is not enough to include a VCSH/VCTS mention in the TAF
at this time.

DFW Airports: An outflow boundary pushed through the DFW area
recently resulting in light north winds. The winds will likely
become variable for a few hours before south winds return. VFR
conditions are expected to prevail with scattered cumulus between
4-6 kft along with some high clouds. Some afternoon convection is
possible, mainly southeast of the Metroplex, but confidence and
coverage is not enough to include a VCSH/VCTS mention in the TAFs
at this time.

JLDunn

&&

.SHORT TERM... /Issued 334 AM CDT Mon Sep 18 2017/
/Today and Tonight/

Early this morning, a complex of storms is skirting just north of
the Red River with an outflow boundary stretching south towards
the I-20 corridor. This system will continue moving east-northeast
this morning with isolated to scattered showers and/or storms
across our Red River counties. Severe weather is not expected but
gusty winds may occur. Behind the outflow boundary, breezy
northwest winds and slightly cooler air is being reported. Along
the southern portions of the boundary, lift is weak and very
little if any rain is expected. This complex of rain/storms is
expected to lift farther north of the Red River by mid morning,
but should leave the outflow boundary across the northern
portions of North Texas. This boundary will likely dissolve by
midday.

The upper level ridge will become flattened today as a series of
weak disturbances crosses the Plains. A 300 mb jet on the
southern periphery of the associated weak upper level trough will
move right across the region, and may provide some lift for
isolated to scattered showers and/or storms across parts of the
region today. Several hi-res models are in good agreement that
convection may develop across mainly our southeastern quadrant
beginning later this morning and continuing through the afternoon
hours. This location lines up with the right front quadrant of the
jet, which isn`t always the most preferred location for
convective development, but it appears to also line up with a
possible surge of higher theta-e air into the same area.
Confidence in the quality of moisture return into that area is
not very high due to discrepancies behind the models, and the cap
may hold during the day. However, have increased PoPs to 20-30%
across a large portion of the CWA with the highest PoPs south of
I-30 and east of I-35. An analysis of forecast soundings
indicates the threat for a few strong storms cannot be discounted
but most convective activity will likely occur as "general showers
and storms". Gusty winds would be the main hazard with any
stronger storms. Have carried the low rain chances into the
evening hours, but the overnight period is expected to be dry.

Otherwise, expect mostly to partly sunny skies with highs again in
the 90s, but some locations in our southeastern counties where
cloud cover is expected to be slightly thicker may only reach the
upper 80s. Overnight lows will be in the lower 70s across most of
North and Central Texas.

JLDunn

&&

.LONG TERM... /Issued 334 AM CDT Mon Sep 18 2017/
The upper level ridge will continue to retreat south, becoming
centered over Mexico and the western Gulf on Tuesday. Meanwhile,
a shortwave trough currently located along the coastal areas of
British Columbia will swing east from the Pacific Northwest into
the Northern Plains on Tuesday as well. An attendant surface front
will be forced eastward in the process, and will extend from the
Midwest southwestward into the Texas Panhandle Tuesday afternoon.
With zonal flow aloft, scattered convection should have little
trouble developing along the front to our northwest, and extend
southward across West-Central Texas along a surface trough. The
brunt of this activity will remain west of the region, but slight
chance POPs will be warranted across the western-most counties
where a few storms may occur before convection dies off Tuesday
evening. Similar POPs will continue over the southeast counties
during the afternoon hours Wednesday where isolated sea-breeze
storms will remain possible through sunset.

An even stronger shortwave trough will dig southeastward down the
Northwest Coast late Wednesday and Thursday. Scattered storms are
likely to redevelop in the vicinity of the surface boundary to
our west and northwest Wednesday evening as lift ahead of the West
Coast system increases. Some of this convection will spread into
the western counties again Wednesday night, where slight chance
POPs will once again be in place. The atmosphere across North and
Central Texas will become moist and unstable during this time,
with PWATs around 1.75" in place by Thursday. Outflow from
Wednesday night convection should provide focus for additional
showers and storms during the day Thursday. Low POPs are currently
in place area-wide on Thursday due to the lack of any specific
focus (other than possible outflow) for initiation, and the
expectation that activity will be generally disorganized and
coverage pretty low.

The digging shortwave will generate a large sharp trough extending
from Western Canada to the Desert Southwest Friday through the
weekend. Moist and unstable air will be in place, but the
position of the trough will place North and Central Texas back
into a southwest-flow aloft regime. This pattern usually keeps the
area capped, and convection will likely remain well west of the
area this weekend. The good news is that model ensembles do trudge
the system eastward with time, unfortunately the past few runs
have trended slower. The forecast result is a lack of rain
chances over the weekend, with slowly increasing POPs from west
to east as we head into early next week.

30

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    94  74  94  77  95 /  10   5  10  10  10
Waco                94  74  94  76  95 /  20   5  10  10  10
Paris               91  70  92  73  92 /  10   5  10  10  10
Denton              92  72  95  76  95 /  10   5  10  10  10
McKinney            91  73  94  75  93 /  10   5  10  10  10
Dallas              94  74  95  77  95 /  10   5  10  10  10
Terrell             92  72  93  75  93 /  20   5  10  10  10
Corsicana           93  74  93  75  93 /  20   5  20  10  10
Temple              93  74  93  75  94 /  20   5  20  10  10
Mineral Wells       93  72  95  74  95 /  10   5  10  10  10

&&

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

$$



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