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

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FXUS64 KFWD 201155
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
555 AM CST Fri Jan 20 2017

.AVIATION...
/12Z TAFS/

VFR conditions are expected to prevail areawide although in the
immediate short term we will be watching IFR cigs/vis approach the
Waco area from the south. The best moisture is expected to remain
east of there but if northward trends continue...we`ll add a TEMPO
for these for a few hours this morning.

Otherwise...a couple of strong shortwave troughs will swing
through the Southern Plains over the next 36 hours. The first one
will swing through this afternoon spreading some lift across North
Texas. This may be sufficient with the available moisture for a
few isolated thunderstorms this afternoon/evening across southeast
Texas. Most of this activity should stay east and southeast of the
major airports. Surface winds will gradually become more
southwesterly and should generally be 240-250 degrees around 15
kt this afternoon.

Another stronger disturbance will move across the Plains late
Saturday. This system will spread some lift across the region as
early as tomorrow morning although most of the moisture will be
located in the mid/upper levels. Given the strength of the system
we do expect scattered showers and possibly a few thunderstorms to
develop during the day Saturday. These showers or storms will be
high based and will pose a downburst wind threat. For now we have
introduced a VCSH at DFW for the extended portion of the TAF and
will update timing through the day today. By Saturday
night...surface winds will become westerly and increase to 15 to
20 kt which will introduce some crosswind issues. These winds will
gradually continue to shift to the northwest by Sunday morning.

Dunn

&&


.PREV DISCUSSION... /ISSUED 347 AM CST Fri Jan 20 2017/
An energetic and active weather pattern will continue through the
next week across the CONUS, although precipitation chances across
North and Central Texas look to remain confined primarily to this
weekend.

Currently, pressure falls across the Texas Panhandle signal
ongoing cyclogenesis associated with the left exit region of a
100+ kt jet streak this morning. What appears to be a pseudo-
dryline structure--really just a remnant low-level moisture
boundary--currently bisects our CWA from north to south. To the
east and south of this boundary, low clouds and some patchy fog
have materialized, but stout advection of dry air means we will
not see a repeat of widespread dense fog across our region. Today,
dry air will continue to punch eastward as the aforementioned low
pressure system races northeastward into Kansas and Nebraska. The
combination of drier air and breezy west-southwesterly winds mean
a warm day is on tap. Sided with the higher end of guidance today
for temperatures, which will likely top out in the mid and even
upper 70s across the region.

This evening, a subtle disturbance embedded within the
southwesterly flow aloft is expected to scrape our
southeasternmost counties. While coarse-resolution guidance does
not seem too keen on producing precipitation in our region, there
are signs that isentropic ascent around the 305 K surface,
combined with just of hint of mid-level moisture and instability
may result in the development of showers and storms across parts
of our area as this wave skirts by. Several members of the NCAR
ensemble and a handful of other hi-res CAMs show this potential
and, as a result, added a sliver of isolated thunder wording south
and east of roughly an athens to Groesbeck to Cameron line.

For tonight, added patchy fog to the forecast south and east of a
Cameron to Palestine line. This region will remain in a zone of
higher-moisture air, and forecast soundings indicate a rapid
increase in dewpoints just off the surface here. Otherwise,
tonight will feature some increase in mid-level cloud cover and
mild temperatures in the upper 40s and 50s.

Saturday and Sunday look quite interesting from a weather
standpoint. A very strong 130+ kt jet streak will overspread the
Southern Plains on Saturday, which will result in rapid lee
cyclogenesis across the Oklahoma/Texas Panhandles. Models suggest
a potentially sub-990 mb surface low will then track eastward
across southern Oklahoma and near the Red River into Saturday
night. While overall output QPF is on the light side from the
global models, this impressively dynamic system will likely be
able to tap into what would otherwise be pretty paltry moisture--
PWATs generally under three quarters of an inch. Some of the
longer range hi-res guidance seems to be keying into this,
developing what will likely be high-based showers and some
thunderstorms Saturday evening and overnight. Increased PoPs
Saturday afternoon slightly, but I suspect these may still be too
low. While surface-based instability will be in short supply,
some strong storms cannot be ruled out, especially east of I-35
where a bit more moisture will be present. Furthermore, forecast
soundings from some model output indicates deep inverted-Vs up to
around 650-700 mb. Any precip (even light precip) falling and
evaporating through this deep layer may actually pose a strong and
gusty wind threat across our area.

Strong west/northwest winds will also descend upon the area this
weekend. It looks like we could potentially see wind advisory
criteria speeds across our far western counties as early as
Saturday afternoon, with even stronger winds on Sunday. These
strong winds and falling humidity values may result in an elevated
fire threat across parts of our area, especially with several
days of anomalous warmth and westerly breezes curing fine fuels.

Dry weather is in the forecast Monday and beyond. A reinforcing
cold front is slated to move through on Tuesday night, but very
dry air in place mean it will come through sans precip.

There are some uncertainties regarding the evolution of potential
precipitation chances Wednesday night into Thursday. The GFS
indicates the presence of quite a bit of isentropic upglide
through a pretty deep layer during this time frame, while the
ECMWF remains dry. Given the time range and uncertainties, have
left the forecast dry for now. We`ll need to keep tabs on this,
however, as surface wet bulb temperatures will be flirting with
the freezing mark across our northwestern zones.

Carlaw

&&



.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    76  51  73  49  65 /   5   5  30  40  10
Waco                76  47  74  49  67 /   5  10  30  30   5
Paris               70  49  70  46  62 /   5  10  30  50  30
Denton              74  48  72  46  62 /   5   5  30  40  10
McKinney            74  49  71  47  62 /   5   5  30  40  20
Dallas              76  53  73  50  63 /   5   5  30  40  10
Terrell             74  50  73  48  64 /   5  10  30  40  10
Corsicana           75  52  72  49  66 /   5  10  30  40   5
Temple              76  49  74  49  65 /  10  10  20  30   5
Mineral Wells       76  48  73  46  63 /   5   5  30  30   5

&&

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

$$



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