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

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FXUS64 KFWD 161800

Area Forecast Discussion
National Weather Service Fort Worth TX
100 PM CDT Fri Mar 16 2018

/18Z TAFs/

Breezy west winds will prevail at the TAF sites through this
afternoon. While a few gusts have exceeded 25 kts, do not expect
these to be prevalent enough to cause prolonged crosswind
concerns. Winds should decrease this evening while becoming a bit
more southerly as the pressure gradient relaxes. Overnight, a
cold front will enter North Texas and stall near I-20. This should
result in a few hours of light and variable winds or even light
north winds at DFW Metroplex airports through Saturday morning. In
the meantime, a surge of very shallow moisture should be moving
northward through Central Texas which may result in some MVFR cigs
at Waco after daybreak which could last through midday. At this
time, don`t expect moisture to be deep enough to result in cigs at
DFW Metroplex airports, although we`ll need to keep an eye on
this and possibly tempo some cigs near 1 kft. The front should
lift back to the north as a warm front by late Saturday morning
and south winds will resume. An increase in mid/high cloud can be
expected into the afternoon. By 3-5 PM, isolated thunderstorms are
expected to develop across parts of North Texas which could
affect some TAF sites and have introduced VCTS in the extended
DFW TAF to account for this potential.



.SHORT TERM... /Issued 347 AM CDT Fri Mar 16 2018/
/Today and Tonight/

Spring appears to be upon us in North Texas with quickly changing
weather conditions including gusty winds, warming temperatures,
and drylines. This morning`s surface analysis shows a deep low
pressure center near Goodland, Kansas where the latest observation
sampled 989 mb. The tight pressure gradient throughout the
Southern Plains has resulted in continued breezy conditions
through the overnight hours.

The strong southerly winds have pulled some moisture northward
into the region and extensive cloud cover is present across most
of North Texas. A band of strong low level isentropic ascent is
also present at this hour across our northwest counties and into
central and southern Oklahoma. There are a few scattered light
showers developing in this region, but most of this activity is
expected to shift to the east rapidly this morning. Outside of a
brief shower this morning, precipitation chances will remain near
zero through the day.

The main concern for today will be the potential for fire activity
across the region, especially west of I-35. As a strong shortwave
trough ejects into the central Plains later today, the
aforementioned surface low over western Kansas will move eastward.
As it does, a Pacific front/dryline will advance eastward into
North Texas. The air behind this dryline is exceptionally dry, and
afternoon relative humidity will likely fall to around 10% across
our far western counties. In addition the pressure gradient,
although weakening this afternoon, will still be sufficiently
tight to keep sustained winds around 15 kt. Temperatures are also
expected to climb into the mid/upper 80s which will aid in rapid
drying of fine dead fuels. We`ll have a Red Flag Warning for parts
of North Texas generally west of a Gainesville to Weatherford to
Eastland line through this evening.

Winds will diminish later today as the main surface low continues
to pull away to the northeast. The fire threat will diminish this
evening as low level humidity begins to recover.

A weak front will also approach overnight from the north and
should cross the Red River sometime after midnight. This front is
likely to slow down and stall near the I-20 corridor overnight.
Low temperatures will range from the mid/upper 40s north of the
boundary to the lower 60s south of it.



.LONG TERM... /Issued 347 AM CDT Fri Mar 16 2018/
/Saturday through next week/

Saturday morning will start off will plentiful low cloud cover
and perhaps some fog across roughly the southeastern one third of
the forecast area as rich Gulf moisture is injected underneath a
strengthening EML plume (capping inversion). At the surface, a
very complex pattern will be materializing as a cold front--left
over from today`s (Friday`s) potent low in Kansas--sinks south of
the Red River. At the same time, Friday`s remnant hybrid
dryline/Pacific front will be retreating northward as an effective
warm front. These two boundaries should meet somewhere in the
vicinity of a Paris to DFW to Comanche line by late in the
morning/early afternoon, give or take about 20-30 miles as a
quasi-stationary front. A weak surface meso-low is forecast to
develop--with very good model consensus--where the aformentioned
dryline begins to drop due south at the triple point intersection
around Eastland-Erath- Comanche counties during the early-
afternoon hours. This feature will be very important to the
eventual evolution of convective chances Saturday afternoon and

Aloft, shortwave ridging will be in place. This is also important,
since the associated neutral or even slightly positive height
tendencies will not add a source of large scale forcing for
ascent on Saturday-Saturday evening, and will in fact result in a
degree of synoptic-scale subsidence across the region.

With all of this in mind, the only real source for lift seems to
be from the locally enhanced convergence in the vicinity of the
aformentioned meso-low/triple point across our western counties.
Forecast soundings across this part of the forecast area reveal
an impressively rapid destabilization through the afternoon as
copious moisture is pumped in behind the warm front. While the
NAM, in typical fashion, may be a bit overzealous on the
instability front, temperatures warming perhaps in the lower 80s
here coincident with dewpoints rising into the upper 50s/near 60
degrees should result in at least modest surface-based instability
for a brief window during the late-afternoon hours. With surface
convective inhibition forecast to nearly completely erode in the
vicinity of these surface features, the local convergence may help
initiate a storm (or two) during the late-afternoon. Any storm
coverage will likely be greatly limited by the ridging aloft.
However, should storm(s) get going here, long and straight
hodographs portend a potential for splitting supercells. In fact,
extended hi-res guidance such as the 3 km NAM and TTWRF show a
similar storm morphology with splitting supercells, which matches
up quite well with our conceptual model.

With this in mind, we`ve focused (but raised) PoPs in a small
corridor from near and just south of I-20 and roughly straddling
the I-35 corridor Saturday afternoon and evening. With such
straight hodographs, any splitting storms (both the left and right
movers) would be capable of producing large hail and damaging
wind gusts, although any left-mover would quickly become elevated
above the cold front, squelching the wind threat. Once again,
while the overall coverage of storms looks to remain quite low
Saturday and into the evening, an isolated large hail and wind
damage threat will exist.

Activity should diminish fairly quickly as subsidence aloft and
nocturnally-increasing inhibition develop. However, there are
signals that very robust isentropic ascent/warm advection will
develop very late Saturday night/early Sunday morning near the
quasi-stationary front in the vicinity of the Red River. The
ECMWF seems to be appropriately responding to this strong lift,
and develops a round of elevated convection just north of I-20 up
to the Red River. While laspe rates aren`t steep through very deep
layers here, at least some elevated instability and 30-40 kts of
effective bulk shear would support a marginally severe hail threat
with any of the stronger storms here. Furthermore, if storms
backbuild just north of the front, then some sporadic hydrologic
issues could develop.

This early-morning activity is forecast to clear the region,
potentially leaving us time to destabilize ahead of the next
intense shortwave for Sunday afternoon and evening. Mid-level
lapse rates are forecast to steepen appreciably as dynamic
cooling spreads overhead, and MLCAPE values may eventually push
1500-2500 J/kg along and ahead of the next Pacific front/dryline.
Lingering capping may be an issue, but with 80-120 m/12 hour
height falls overspreading the region, a few storms could develop
in the warm sector late Sunday afternoon/early evening. These
would also have the potential to become severe, with another hail
and wind damage threat. The tornado potential once again seems to
be on the lower side with relatively weak 0-2 km winds, but any
storms that manage to interact with the warm front near the Red
River may have a somewhat higher tornado potential. There are
still lots of forecast "ifs" for Sunday, but if storm coverage
remains as low as currently anticipated on Saturday, the
atmosphere could be primed for a somewhat higher coverage of
severe storms on Sunday. We`ll get a better idea about this
potential today and tonight as we come in range of some of the
longer-range hi-res guidance.

The next issue is the potential for critical fire weather
conditions on Monday. A Pacific cold front will sweep through
Sunday night, but should do little to impact our high temperatures
for Monday. At the same time, much drier air will advect into the
region on strong northwest winds. Our western counties, which are
already dry and probably won`t receive much rainfall over the
weekend, will be susceptible to the decreasing humidity values
and strong winds as a surface low barrels across northern
Oklahoma. We`ll continue to monitor this potential, but if trends
continue, a Fire Weather Watch may be needed for parts of the
region on Monday.

Another fast-moving disturbance will ripple overhead in northwest
flow aloft on Wednesday, but parched mid and upper-levels will
preclude an introduction of precipitation. Breezy south winds will
return on Thursday ahead of the next disturbance which could bring
shower and storm chances back to the region next weekend.



Dallas-Ft. Worth    86  57  78  59  76 /   0   0  30  40  50
Waco                85  58  83  64  79 /   5   0  50  30  50
Paris               82  54  75  55  68 /  10   0  10  50  70
Denton              85  47  75  55  76 /   0   0  20  50  50
McKinney            80  51  75  56  73 /   5   0  20  50  60
Dallas              84  58  77  60  76 /   5   0  30  40  60
Terrell             85  57  78  61  76 /   5   0  30  40  60
Corsicana           84  62  80  63  75 /   5   5  40  30  60
Temple              88  60  85  64  80 /   5   0  40  30  50
Mineral Wells       86  47  76  57  78 /   0   0  30  30  30


Red Flag Warning until 7 PM CDT this evening for TXZ091-092-



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