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

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FXUS64 KFWD 181955 AAA

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
255 PM CDT Sun Mar 18 2018

/Today and Tonight/

Radar imagery this morning shows a few scattered showers remaining
from last night`s convection continuing to spread east into East
Texas. In the wake of the previous convection, surface winds have
been a little disorganized but a return to east-southeast flow can
be expected through the early morning. The quasi-stationary
frontal boundary remains in place across the northern parts of
the Metroplex from near Breckenridge to North Fort Worth and then
extends east to between Paris and Sulphur Springs. Farther south,
a secondary boundary extends from near Temple to Palestine. South
of this feature, dewpoints are in the upper 60s.

Water vapor imagery over the central and western U.S. shows a
digging trough over southern California with a lead impulse
spreading across Baja California ahead of the main trough. The
latest RAP analysis has a 130 kt upper jet spreading across
northern Mexico and into West Texas associated with this
shortwave. Later this morning, as this disturbance moves eastward
into Texas, stronger height falls will overspread the region
signaling an increase in large scale forcing for ascent.
Initially, some elevated showers and perhaps a few thunderstorms
may develop across west-central Texas associated with a marked
increase in 700-500mb winds and warm advection. This activity
should spread northeast rather quickly through midday. There is
some dry air beneath 700mb associated with an elevated mixed
layer, so stronger convection could have some accelerated
downdrafts, although the boundary layer should remain relatively
stable through late morning which should mitigate any threat for
strong wind gusts.

Attention then turns to later this afternoon, as the main
shortwave trough to the west spreads into New Mexico. This will
allow stronger westerly winds to spread into West Texas
effectively forcing the dryline and Pacific front eastward.
Similar to yesterday, there will be a weak area of low pressure
tied closely to the dryline and nearly stationary frontal boundary
along the Red River. This surface low should be somewhere between
Abilene and Wichita Falls by mid afternoon. To the east of there,
the atmosphere across North and Central Texas will have had ample
time to recover from previous convection and destabilize. Thicker
mid level cloud cover will likely be shunted northeast as the lead
impulse pulls away. This should allow for some sunshine and
temperatures should respond by warming into the mid 70s along the
Red River to the mid 80s in the Metroplex and elsewhere. This
should result in strong instability with surface based CAPE in
excess of 2500 J/kg across parts of North Texas this afternoon,
especially along and south of I-20.

With the main shortwave still trailing to the west, large scale
forcing for ascent will remain present across North Texas through
this evening. Low level convergence should become maximized by mid
afternoon near the surface low with any remaining inhibition being
eroded or lifted between 2-4 pm. This is when more vigorous
convection is likely to develop, somewhere in the vicinity of
Graham to Bowie to Wichita Falls. Convection should rapidly move
east through the evening hours primarily focused in an area near
the quasi-stationary frontal boundary. Highest PoPs will generally
be along and north of I-20 to the Red River this afternoon and
evening. Additional thunderstorms will be possible farther south
into Central Texas given the large area of ascent that persists
into the evening hours, although coverage is expected to be more
isolated farther south off of the frontal boundary.

Concerning severe potential...The atmosphere will become strongly
unstable this afternoon with steep lapse rates between 850-700mb
and strong deep layer shear. This will support supercells with
mainly a large hail and damaging wind threat. There will be a
small tornado threat, mainly near the frontal boundary between
I-20 north to the Red River. This is the area where low level
winds may remain sufficiently backed to support low level
rotation. Otherwise, instability will increase markedly from the
Metroplex southward. There may be a tendency for storms to
initially develop and then turn southeastward into the stronger
instability axis, as is indicated by some of the convection
allowing models. Any storms that manage to move into the stronger
instability farther south would be capable of producing very large
hail into the evening hours.

Concerning fire weather potential...As the dryline moves east into
the area late this afternoon, areas west of I-35 and south of I-20
will see dewpoints drop into the 30s and lower 40s yielding RH
values around 20%. This combined with westerly winds 15 to 25 mph
will result in dangerous fire weather conditions through the
evening hours.

All of the afternoon and evening convection will spread east into
East Texas after dark with rain chances quickly diminishing. Drier
air will continue to filter into the region behind the Pacific
front through the overnight hours as the main shortwave pulls off
to the east.




/Monday through Sunday/

A strong surface low will move east from northeastern Oklahoma
into Tennessee during the day Monday. The resulting pressure
gradient will lead to gusty westerly winds which will become
northwesterly during the afternoon as another cold front moves
through the region. Skies will be mostly sunny and highs will
range from the upper 60s northwest to around 80 degrees southeast.
The combination of 20 to 25 mph winds with gusts over 35 mph at
times, and minimum relative humidities in the upper teens and 20s
will mean critical fire weather conditions across the western
parts of the forecast area with elevated fire weather conditions

Wind speeds will be slow to decrease Monday night with northwest
winds 15 to 25 mph prevailing with some gusts over 30 mph. Lows
will be mostly in the 40s.

An upper level ridge will build across the Rockies early to mid
week and then move into the Plains late in the work week as an
upper level low moves east to off the East Coast by late week. This
will result in dry weather across North and Central Texas for the
upcoming work week. It will be cooler Tuesday with highs in the
60s. As a surface high moves east, moderating temperatures will
occur Wednesday through Friday. Highs will be in the upper 60s to
mid 70s Wednesday, 70s to lower 80s Thursday, and mid 70s
northeast to upper 80s west Friday. Southerly winds will increase
Thursday and Friday and despite increasing humidities, elevated
fire weather conditions may occur across the western counties.

With the continued southerly flow and a weakening upper level
ridge next weekend, there will be low chances of showers and
thunderstorms along and east of I-35 Saturday and most of the
region on Sunday. Warmer than normal weather will continue with
highs mostly in the 80s and lows in the 60s.



.AVIATION... /Issued 1247 PM CDT Sun Mar 18 2018/
/18z TAFs/

Low clouds have been slow to clear this morning, but are finally
showing some signs of improvement as of 18z. The deck of IFR
clouds is beginning to lift/erode from the west as a shortwave
trough approaches while some warmer/drier air arrives from the
southwest. Will continue IFR conditions through 19-20z before
improving to VFR at all TAF sites through the late afternoon.

The next concern is the potential for convection to impact
airports later this afternoon or early this evening. Coverage of
thunderstorms remains in question, as does the most favorable
location for initial development. Stubborn cloud cover has
prevented strong destabilization from occurring thus far, and this
may inhibit the initiation of more widespread convection
throughout the afternoon. Given the presence of the strong
shortwave to our west, still think isolated thunderstorms are in
the cards especially if lift from the shortwave can be aided by
other boundaries present, such as the stationary front draped
through North Texas or the dryline positioned to the west. Will
continue a brief VCTS mention at DFW Metroplex airports centered
around 00z, but will keep rain-free TAFs at Waco for now.
Southerly winds will prevail through tonight.

Overnight, predominantly VFR conditions are expected as a Pacific
front/dryline moves through the area, although a brief period of
MVFR is possible around midnight just prior to the front`s
arrival. Have not included MVFR in the TAFs for now as the
potential looks low. Drier air behind the front will scour all
low-level moisture from the area and VFR conditions will prevail
into Monday.

A crosswind event is likely to occur through the day on Monday as
breezy west winds of 20G30KT are expected. Later in the day, winds
will turn more to the northwest as a cold front arrives, but will
remain breezy through Monday evening.



Dallas-Ft. Worth    56  78  46  65  44 /  20   0   0   0   0
Waco                52  79  45  67  42 /  10   0   0   0   0
Paris               53  73  45  62  41 /  40   0  10   5   0
Denton              51  74  43  65  42 /  20   0   0   0   0
McKinney            51  74  44  63  42 /  20   0   0   0   0
Dallas              56  76  46  66  45 /  20   0   0   0   0
Terrell             53  75  45  65  41 /  30   0   0   0   0
Corsicana           55  77  46  65  43 /  20   0   0   0   0
Temple              51  78  45  69  43 /  10   0   0   0   0
Mineral Wells       50  75  41  65  40 /   5   0   0   0   0


Fire Weather Watch from Monday morning through Monday evening
for TXZ100-115-116-129-130-141>143-156-157.



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