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

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FXUS64 KFWD 181614 AAB

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1114 AM CDT Sun Jun 18 2017

The main update to the forecast this morning was to short term
PoPs, temperatures, and wind trends. Went ahead and removed the
mention of thunder this morning and early afternoon across our
northern counties as the ongoing convective complex across eastern
Oklahoma/Arkansas will slide north and east of the region. Our
morning sounding revealed an impressive cap was in place with
nearly +26C air sampled near 850 mb, which has been continually
rejuvenated and bolstered by the advection of an expansive EML
plume along the eastern periphery of the subtropical high to our
west. This plume of warm air just off the surface will
significantly reduce any notable convective chances until later
this evening. As a result, opted to limit thunder chances to
"isolated" through the mid-afternoon hours across our far
northern counties as the cold front approaches.

Surface analysis this morning also reveals that the cold front is
making better progress than previously forecast--likely
encouraged southward a bit quicker by an outflow boundary
deposited by the aforementioned convective complex. The RAP/HRRR
seem to have a decent handle on the ongoing situation, and have
heavily favored their short-term wind trends, which will bring the
front into the Metroplex around 6-8 PM this evening. As is often
the case ahead of incoming fronts, temperatures today may get a
bit of a boost, and have nudged highs upwards by a few degrees. As
a result, we contemplated hoisting a short-fused Heat Advisory
for the Metroplex and portions of the I-35 corridor today.
However, given an abundance of high cloud cover and the potential
for dewpoints to mix out just a hair more today, opted to hold off
on the issuance of an advisory that would be both spatially and
temporally limited. Still, heat index values of 104-106 degrees
will likely be met briefly this afternoon across portions of the
region. Any individuals with outdoor plans on this Father`s Day
should plan accordingly for this level of heat.

The forecast reasoning for late this afternoon and into the
overnight hours remains unchanged, as we still anticipate a
gradual blossoming of convection behind the cold front as just a
hint of upper-level support arrives from the west. Some strong to
severe storms will be possible, mainly for locations north of I-20
late this afternoon and evening.



.AVIATION... /Issued 646 AM CDT Sun Jun 18 2017/
MVFR ceilings had worked their way up through Waco and into the
Metroplex as of 11z. Have placed TEMPO BKN015 in the Metroplex
TAF sites for the 12-15z period. VFR conditions should return to
both the Metroplex and Waco TAF sites by 16z. We will continue to
have some high clouds move across the region. A cold front that
extended southeast of a KTUL-KOKC-KHOB line at 11z is expected to
move slowly southeast and reach a KSLR-KDFW-KGZN line around 02z.
South to southeast winds around 10 knots will become east to
northeast around 10 knots with frontal passage. There will be a
very low chance of a shower or thunderstorm 23-02z in the
Metroplex ahead of the front with better chances along and behind
the front. Have placed VCSH in the Metroplex TAF sites starting at
02z. The front is expected to stall just south of I-20, so
southerly winds will prevail through the period at Waco. MVFR
ceilings are expected to return overnight tonight as indicated by
the BKN/OVC015 in the Waco and Metroplex TAF sites.



.DISCUSSION... /Issued 345 AM CDT Sun Jun 18 2017/
An upper level trough will gradually deepen while shifting east
across the Great Lakes region over the next couple of days. A
series of shortwave disturbances rotating around the upper trough
will assist in deepening the system as it progresses east. One of
these can be seen on WV imagery propagating east across the
Midwest, and is mostly responsible for the widespread storms
across the Plains last night. A second disturbance will drop
southeast across the Southern Plains tonight, then round the base
of the upper trough over the Lower MS and TN Valleys Monday.
Meanwhile, an upper level ridge will remain parked over the Desert
Southwest for the foreseeable future. The resulting upper level
pattern already places North and Central Texas beneath northwest
flow, and this flow will gain a more northerly component as the
upper trough deepens.

Ongoing convection over Oklahoma will need to be monitored as the
deep layer northwest flow drives it southeast towards the Red
River. Storms will likely diminish in intensity and coverage as
they move farther south and away from the stronger forcing. That
said, storms currently north of Oklahoma City are still going
strong and will probably affect northeastern counties after
sunrise before dissipating. POPs will remain in the 20 to 30
percent range this morning for northeast locations including
Paris, Sulphur Springs, Bonham and surrounding areas. Severe
weather is unlikely with the weakening morning convection.

After the morning activity weakens and moves east of the region,
attention will turn to a weak cold front, which is expected to
slowly push south across the Red River this afternoon. The
boundary will serve as focus for a few storms across the northern-
most counties this afternoon, but the lack of any appreciable
forcing should keep activity isolated in nature. The front will
continue to move slowly southward towards the I-20 corridor this
evening. Frontogenetic forcing will intensify north of the front
as the second shortwave drops southeast across the Southern
Plains, resulting in scattered thunderstorm development. Onset
will depend on exactly when the strong forcing arrives, which at
this time appears to be around midnight tonight.

Convection should be elevated in nature and primarily sub-severe,
though instability and shear could be enough for a few severe
storms with large hail and damaging winds. Storms will likely
become somewhat organized overnight while pushing slowly southward
and evolving into an mesoscale convective complex. The main
threat will turn to locally heavy rain during the early Monday
morning hours due to the expected slow movement of the system.
Activity will weaken during the late morning and afternoon hours
Monday as the shortwave and the stronger forcing shift east of the
region. However, a few strong storms could develop (likely
southwest of earlier activity) depending on where any outflow
boundaries may be.

Will keep slight chance POPs in place Monday evening for any
lingering showers or storms, but subsidence will already be on the
increase as the upper ridge expands back towards the east. A nice
break from the heat Monday into Tuesday will come to an end by
midweek as hot, humid and rain-free conditions return. This will
persist through the end of the work week, then another front will
provide at least a slight chance of rain next weekend.



Dallas-Ft. Worth    94  73  90  73  93 /  10  40  40  20   5
Waco                95  76  94  72  94 /   5  10  30  20   5
Paris               87  71  87  67  91 /  30  60  30  10   0
Denton              92  70  88  70  92 /  20  50  30  20   5
McKinney            91  71  88  70  92 /  20  50  40  20   0
Dallas              95  75  90  73  94 /  10  40  40  20   5
Terrell             92  74  89  71  93 /  10  40  40  20   5
Corsicana           93  74  91  73  94 /   5  20  40  20   5
Temple              95  75  93  72  94 /   5   5  20  20   5
Mineral Wells       95  71  89  69  93 /  10  30  30  20   5



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