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

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FXUS64 KFWD 151643 AAA

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1143 AM CDT Thu Mar 15 2018

North and Central Texas is currently situated between a surface
high pressure ridge over the northeastern Gulf and a strengthening
cyclone in lee of the Rockies. The resulting pressure gradient is
generating gusty south winds across the region. The most recent
guidance continues to keep velocities just below advisory
criteria, and a wind advisory is not expected at this time.

Gulf moisture will be on the increase this afternoon and overnight
and most areas should be covered in stratus by morning. A few
showers will be possible early tomorrow along and ahead of a
dryline, then all activity will push east as the dryline moves
through. Warm and dry weather is still expected tomorrow afternoon
with elevated fire danger the main weather concern for Friday.



.AVIATION... /Issued 723 AM CDT Thu Mar 15 2018/
/12z TAFs/

Breezy south winds will develop this afternoon in response to a
deepening area of low pressure across Colorado. Some occasional
gusts to 30 kts are possible. While VFR conditions are expected to
persist for the next 12 to 15 hours, a surge of Gulf Moisture will
result in the development of MVFR cigs early this evening. Waco
will be the first to experience deteriorating cigs around 16/01z,
followed by the Metroplex sites a few hours later. At this time,
the signal for IFR cigs is too low to warrant a mention in the
TAFs, but there may be a small window of opportunity--mainly at
Waco--for this to occur late this evening.

Winds just off the surface will quickly veer late tonight and into
Friday morning, quickly ushering the low cigs east of the I-35
corridor by 16/14z, perhaps even a few hours sooner. As this
occurs, surface winds will also start to veer as a dryline/cold
front heads eastward. Surface winds on Friday afternoon will
likely favor a 240-260 direction around 15-20 kts, and this will
result in moderate crosswind issues on N-S and even NW-SE oriented



.SHORT TERM... /Issued 420 AM CDT Thu Mar 15 2018/
/Today and Tonight/

Today will be a breezy and warm day across North and Central
Texas, with high temperatures headed into the upper 70s and lower
80s. This will be occurring as lee cyclogenesis begins over
eastern Colorado, which will tighten up the surface pressure
gradient. Wind speeds today look to remain safely under Wind
Advisory criteria (which is sustained winds at 25 mph), but we`ll
still probably manage some 30-35 mph gusts at times as higher
momentum air is mixed down today. While our winds will remain more
southerly today, minimizing/eliminating any downsloping component,
filtered sunshine should still allow temperatures to warm quickly
today, and have sided with the warmest guidance for highs.

With the very warm temperatures and breezy conditions expected
today, an elevated fire weather threat exists north and west of a
Bowie to Mineral Wells to Eastland line.

As warm advection increases later this morning in response to the
aformentioned cyclogenesis, some showers may develop and move out
of the Trans-Pecos region. This activity should diminish as it
spreads eastward into a drier environment, and will keep PoPs at
10 percent or less across our western zones this afternoon.
Another batch of showers and thunderstorms may initiate in the
vicinity of a burgeoning dryline across far West Texas late this
afternoon and evening, but this activity should also decay as it
heads eastward and away from any of the more meaningful low-level
moisture and instability this evening.

As the surface low heads north and eastward tonight, some streamer
showers may develop under a strengthening capping inversion, and
we`ve painted some low (20%) PoPs generally along and east of I-35
tonight to account for this. Above this cap, fairly steep lapse
rates (nearing 8 C/km) will exist as warm advection/isentropic
ascent persists, generally around and just above 700 mb. At this
time, it appears that this upglide will not coincide with enough
moisture to produce any meaningful signals for convection, but
we`ll need to keep an eye on this as the lift is actually fairly
robust. If mid-level moisture increases more than currently
anticipated, then some thunderstorms would be possible overnight
mainly east of I-35 and north of I-45.



.LONG TERM... /Issued 420 AM CDT Thu Mar 15 2018/
/Friday through next week/

There continues to be a severe storm threat on Saturday, and
potentially on Sunday, too. A cold front will sweep across the
region Sunday night and Monday, and then dry weather is expected
through at least next Thursday.

On Friday, as a shortwave disturbance lifts northeast through the
Central Plains, it will drag a dryline across the region. Some
light showers may occur across our eastern counties Friday
morning, but any rain is expected to end by midday. A rumble of
thunder cannot be ruled out, but hi-res radar model output
suggests only light rain or shower activity. Behind the dryline,
west-southwest winds of 10 to 20 mph will occur, and afternoon
high temperatures are expected to be in the 80s across nearly all
of North and Central Texas. Elevated to near critical fire weather
conditions are expected roughly along and west of Interstate 35
in the afternoon due to the combination of warm temperatures,
breezy winds, and humidity values in the teens and lower 20s.

The dryline will stall across our east and southeast counties
Friday night, and then begin a slow retreat from southeast to
northwest starting late Friday night. This will result in a
fairly dramatic low temperature difference across the region.
Forecast soundings show a strong cap remaining in place in the
925-850 mb level with very dry air above the cap, so removed PoPs
for the overnight period; although some drizzle may be possible
underneath the cap in the southeastern quadrant of the CWA. By
daybreak Saturday, an upper level disturbance will be approaching
the region from the west, and this is where things start to get

The dryline will continue to slowly retreat north and west during
the day on Saturday, but its extent of progression north is still
uncertain. The upper level disturbance will quickly advect mid
level moisture into the region which will result in mostly cloudy
skies for most of the area due to a combination of mid and high
level clouds. By the afternoon, the dryline is expected to be
stalled west of Interstate 35, and despite the mostly cloudy
skies, we are anticipating at least some storm initiation along
the dryline. The upper level disturbance moving across the region
during the day and a 80-90 kt upper level jet will provide the
necessary lift for convection. Breaks in the clouds should allow
for sufficient heating of the lower atmosphere. The mid level
wind fields aren`t too impressive, but there is some increase to
the 700 mb winds during the afternoon hours. The models are
developing a surface low along the dryline, and we will need to
watch where this develops as initiation will likely be near this
triple point. At this time, the most likely area for initiation is
somewhere west of I-35 and along or south of I-20, and the most
likely timing for initiation is in the afternoon hours. However,
we could begin to see convection or convective attempts during the
morning hours. Forecast soundings show a weakening or erosion of
the cap with surface based CAPE values of 1000-1500 J/kg in the
warm sector. With 0-6 km shear values near 60 kts, this would
support supercell development with a main threat for damaging
downburst winds and large hail.

As storms develop, the mean motion is expected to be east and/or
northeast, so trended PoPs towards that direction for the
afternoon and evening hours. For now, due to uncertainty in storm
coverage, have kept PoPs at 20-40 percent, but as we get into the
timeline of the hi-res models, we should be able to refine these
details. In the evening hours, the forecast soundings show the cap
rebuilding over the region which may act to quickly weaken the
ongoing activity before midnight, but this isn`t the end of rain
chances Saturday night.

On the backside of the departing upper level disturbance, with a
strong jet stream still overhead, strong isentropic lift in the
300-305K layer suggests additional elevated convection may develop
after midnight along and north of Interstate 20. This would be
near the northern portions of the old dryline that may have
transitioned into a retreating warm front. There may be a threat
for hail with these elevated storms due to strong shear and decent
lapse rates.

The dryline isn`t expected to progress east Saturday, and it will
likely retrograde west Saturday night as it waits for the next
disturbance on Sunday. An upper level trough will be moving into
the Four Corners area Sunday morning and will move into the Plains
Sunday night. Embedded weaker disturbances ahead of the main
trough will likely provide lift for shower and storm development
beginning Sunday morning near the dryline to our west, then the
upper level trough will spread additional lift (noted by
increasing height falls) in the afternoon hours. The dryline will
be slow to move east during the day, and may only be near the
I-35 corridor by sunset on Sunday. Isolated to scattered showers
and thunderstorms will be possible all day along and east of the
slowly advancing dryline. Forecast soundings do not appear too
favorable at this time for another round of severe storms, but
this may be dependent on if the atmosphere can recover from
Saturday`s storms. If coverage of storms is not too great on
Saturday, the atmosphere may be primed for severe storms on
Sunday. Right now there are too many IFs to make a better
distinction, so our message is we will not discount the severe
storm threat for Sunday and will continue to refine this time

A cold front will quickly sweep across the region on Monday
resulting in cooler and drier conditions for the next several
days. The ECMWF is attempting to develop low rain chances next
Wednesday as another upper level trough swings through the region,
but the lower levels will should still be too parched for any
precipitation to reach the ground. Temperatures should start to
warm late in the week.



Dallas-Ft. Worth    78  61  84  54  80 /   5  20  10   5  20
Waco                76  61  86  60  82 /   5  20  10  10  40
Paris               73  59  81  55  76 /   0  20  20   5  20
Denton              78  59  83  49  78 /   5  10   5   5  20
McKinney            75  60  82  51  78 /   5  20  10   5  20
Dallas              77  61  86  57  80 /   5  20  10   5  20
Terrell             75  60  83  58  79 /   0  20  20  10  20
Corsicana           77  61  84  61  81 /   5  20  20  10  20
Temple              76  61  86  59  83 /   5  20  10  10  40
Mineral Wells       80  57  84  49  80 /   5  10   5   5  30




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