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

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FXUS64 KFWD 221142 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
642 AM CDT Sun Oct 22 2017


.AVIATION...
/12Z TAFs/

Concerns...IFR and MVFR cigs this morning, breezy north winds
today.

In the wake of the cold front and line of storms that moved
through earlier this morning, a mix of cigs is being reported
across the region. Sky conditions over the next few hours will
likely bounce between IFR, MVFR and low-end VFR ceilings. However,
by 14-15Z the skies are expected to clear as the main axis of the
upper level trough moves through the region. Once the skies
clear, mixing will occur transporting strong north to northwest
winds to the surface. Wind speeds will prevail for much of the day
in the 15-20 kt range with gusts of 25-30 kts. By sunset, the
winds will subside and fall to less than 5 kts overnight as the
surface high moves into the region. As the surface high moves
south, the winds will back to the west and southwest but remain
light.

JLDunn

&&


.DISCUSSION... /Issued 424 AM CDT Sun Oct 22 2017/
Our linear MCS continues to make steady progress southward into
Central Texas where rich tropical moisture is in place. Although
near the diurnal temperature minimum, dew points remain in the 70s
ahead of the line, and MUCAPE values are still near 2000J/kg.
Showers deeper into the humid air show the nocturnal boundary
layer is capped, but as the line approaches, the mechanical
forcing of the outflow will allow some of this buoyant air to be
ingested into the complex. Despite adequate surface winds nearly
perpendicular to the line, the winds above the surface are already
significantly veered, reducing the depth of the orthogonal
inflow. While there is still extraordinary instability upstream of
the complex, particularly for this time of day, radar imagery
indicates that the leading edge of the line is being dominated by
individual updrafts rather than a meso-beta cold pool. Few of
these updrafts have shown any duration, being quickly separated
from the leading edge. While the updraft strength may be
sufficient for small hail, none of these should last long enough
to approach the size of coins. As the complex travels further from
the better dynamics, the downburst potential will be limited to
precipitation processes, which should keep peak gusts under 40
mph.

The orientation of the flow aloft means the trailing stratiform
rain region (with occasional thunder) will be of greatest duration
in East Texas with a negligible amount near the tail end of the
line in Central Texas. Regardless, all of the rain will come to an
end later this morning. The clearing line is entering our western
zones, and skies will steadily clear today as the convective
complex exits the region. While temperatures will be noticeably
cooler today, particularly with the gusty north winds, the cold
advection will be somewhat offset by the sunshine, dry air, and
downslope component of the wind. Despite how you may feel in the
shade, afternoon temperatures will reach the 70s. However, as the
sun sets, readings will quickly plunge into the 50s this evening.

Even without severe weather, the scale of this MCS has maintained
the strength of its associated jet streak and delayed the
development of a connecting jet segment in the Northern Plains.
This should maintain the oxbow jet long enough to prevent the
upper trough from cutting off until it approaches the Mississippi
Valley. As with any cut-off evolution, guidance has considerable
spread, but the consensus keeps its influence well to our east.
As a result, northwest flow will dominate through the middle of
the week, and dry autumn weather will prevail. Westerly surface
winds should help temperatures reach the upper 70s and lower 80s
on Monday before a reinforcing front arrives. The next warming
trend will push temperatures above normal again by Thursday.

The upper flow is still expected to back late in the week in
response to a Gulf of Alaska low that will charge south out of the
Canadian Rockies. But with unseasonably cool air already plunging
down the High Plains ahead of this system, a cold front should
manage to reach North Texas by Friday. The ECMWF still appears to
be overstating the effect of the flow; but, while delayed, it
isn`t as far behind the GFS/CMC consensus. Will maintain an early
Friday FROPA with some postfrontal rain mainly south and east.
Friday and Saturday look to be the chilliest daytime temperatures
so far this season, but without more precipitation than expected,
highs should still reach the 60s.

25

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    74  52  82  54  72 /   5   0   0   0   0
Waco                76  48  82  52  75 /  10   0   0   0   0
Paris               71  48  78  49  68 /  30   0   0   0   0
Denton              73  46  80  50  71 /   5   0   0   0   0
McKinney            72  47  80  51  71 /  10   0   0   0   0
Dallas              74  53  82  55  72 /  10   0   0   0   0
Terrell             74  48  80  51  72 /  20   0   0   0   0
Corsicana           73  49  80  52  72 /  20   0   0   0   0
Temple              76  47  82  51  75 /  20   0   0   0   0
Mineral Wells       74  46  82  49  72 /   5   0   0   0   0

&&

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

$$

82/25


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