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

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FXUS64 KFWD 182348 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
648 PM CDT Wed Oct 18 2017


.AVIATION...
Metroplex: VFR conditions will prevail through 06z Friday with
only high clouds moving across the region. South to southeast
winds at 6 to 10 knots will occur.

Waco...Some low clouds and patchy fog may spread into Central
Texas including KACT toward 12z. Have placed a TEMPO 5SM BR
BKN008 for the 12 to 14z period. Otherwise, expect high clouds to
continue to move across the area. Winds will remain south to
southeast at 6 to 10 knots.

58

&&


.SHORT TERM... /Issued 325 PM CDT Wed Oct 18 2017/
Slightly warmer temperatures are expected tonight, with lows
returning to near seasonal normals for most locations. 500 mb
analysis shows that the ridge has flattened out somewhat, with
subtle height falls noted over the South-Central United States
during the past 24 hours. Water vapor satellite imagery shows
mid-level moisture (near 600 mb per El Paso and Tucson soundings)
beginning to approach the area from Northern Mexico. The
experimental GOES-16 Channel 4 "Cirrus" band shows high clouds
already beginning to move into our western counties. These high
clouds should continue to stream into the area overnight. While
the clouds will not be particularly dense across the northern half
of our CWA, they should be enough to reflect back some outgoing
longwave radiation, which will keep overnight lows up a bit. Light
southerly winds of 5-10 MPH will help keep temperatures up as
well by preventing the boundary layer from decoupling completely.
Forecast lows tonight are about 5-10 degrees above where they were
last night, which will bring them to near normal for mid-
October.

Another issue tonight will be the potential for some lower clouds
in the southern and southeastern counties. Model guidance shows
low-level moisture creeping up into these counties, with forecast
soundings showing near saturation in the lower levels of the
atmosphere. With regards to fog potential, opted to keep fog
mention out of the forecast since any fog does not look like it
will be particularly widespread or dense, but this will need to be
monitored during the overnight as some light patchy fog could
develop in our far southeastern zones. At a minimum however,
expect to see increasing low-level cloud cover across the
southern zones, and especially across the Waco/Killeen/Temple area
towards daybreak.

37-Godwin

&&

.LONG TERM... /Issued 325 PM CDT Wed Oct 18 2017/
/Thursday through next week/

The upper ridge currently overhead will shift east on Thursday as
a southern branch upper trough moves into West-Central Texas. An
initial shortwave will lift northeast late Thursday around the
southeast flank of the upper trough, generating weak ascent across
North and Central Texas. Isolated convection will be possible
late Thursday mainly across the western counties where the
stronger lift will occur. However, limited moisture will keep most
areas rain-free.

Moisture will then increase rapidly on Friday as an upper level
trough enters the West Coast, a lee-side surface trough develops,
the pressure gradient tightens and return flow significantly
increases. The West Coast system will kick the southern stream
trough off to the northeast on Friday. Higher amounts of Gulf
moisture will be in place (PWATs around 1.5") and lift will be a
tad stronger as the axis of the southern branch trough passes
overhead. POPs will be maintained and will range from 40 in the
south to 20 in the north for the Friday-Friday night timeframe.

The West Coast system will deepen as it moves into the Plains and
has the potential to become a decent weather maker across the
central part of the CONUS. Strong forcing for ascent associated
with the trough will overspread the Plains with an attendant cold
front providing focus for convection as it pushes southeast with
the upper level system. Thunderstorms will likely erupt along the
cold front Saturday afternoon in the Central and Southern Plains
then spread southeast into North Texas Saturday evening. Shear and
instability will be sufficient for a few strong and possibly
severe storms with damaging winds and large hail the primary
threats. Low level helicity values also hint at a low-end tornado
threat, but these parameters appear to be in place prior to
convective initiation. However, if there are any outflow
boundaries out ahead of the front/main line of storms we would
need to keep a closer eye on the threat for isolated rotating
supercells and a brief spin-up tornado.

Convection will exit the region during the morning hours Sunday with
much cooler and drier air in its wake. Conditions will remain
cool for most of the week due to the arrival of a second push of
cool air on Tuesday. In all reality "cool" will simply be near-
normal temperatures, as normal for this time of year is lows in
the upper 40s to mid 50s and highs in the 70s.

30

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    58  83  63  82  67 /   0   0   5  20  20
Waco                54  84  62  82  67 /   0   0  10  40  30
Paris               52  81  56  80  63 /   0   0   5  10  20
Denton              53  83  61  81  66 /   0   0   5  20  20
McKinney            53  82  60  80  66 /   0   0   5  20  20
Dallas              59  83  63  82  68 /   0   5   5  20  20
Terrell             54  84  59  83  65 /   0   0   5  20  30
Corsicana           57  83  61  81  65 /   0   0   5  30  30
Temple              54  83  62  82  67 /   0   5  10  40  30
Mineral Wells       53  83  61  81  66 /   0   0  10  30  20

&&

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

$$

58



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