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

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FXUS64 KFWD 221809
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
109 PM CDT Sun Oct 22 2017


.AVIATION...
VFR conditions will prevail through the TAF period. Breezy north
winds will continue this afternoon before decreasing to less than
10 kts this evening. Some patchy ground fog may occur early Monday
morning with clear skies and light winds along with moist soils
following last night`s rainfall, but vsby reductions are not
expected at TAF sites. As surface high pressure shifts south of
the area tonight, winds will become light west/southwest
which will persist through Monday afternoon. Have included a
return of north winds in the extended DFW TAF with a dry cold
front expected to arrive late Monday afternoon or Monday evening.

-Stalley

&&


.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    52  82  54  72  48 /   0   0   0   0   0
Waco                48  82  52  75  45 /   0   0   0   0   0
Paris               48  78  49  68  43 /   0   0   0   0   0
Denton              46  80  50  71  45 /   0   0   0   0   0
McKinney            47  80  51  71  44 /   0   0   0   0   0
Dallas              53  82  55  72  49 /   0   0   0   0   0
Terrell             48  80  51  72  44 /   0   0   0   0   0
Corsicana           49  80  52  72  45 /   0   0   0   0   0
Temple              47  82  51  75  46 /   0   0   0   0   0
Mineral Wells       46  82  49  72  44 /   0   0   0   0   0

&&

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

$$

26/91



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