NWS Area Forecast Discussion

FXUS64 KFWD 200846

Area Forecast Discussion
National Weather Service Fort Worth TX
346 AM CDT Sun Oct 20 2019

/Today Through Monday/

...The Threat For Severe Weather Increases This Evening With A
Strong Cold Front Bringing Much Cooler Weather On Monday...

A well-advertised, vigorous mid level trough and associated cold
front are expected to impact the region beginning this evening,
before ending across our eastern Central Texas counties early
Monday morning. We`ll actually begin this morning pleasantly cool
and dry with lows in the 50s and lower 60s with a broad ridge of
high pressure draped across the area in wake of yesterday`s cold
front. Residual, richer surface dew point temperatures remain in
the mid 50s to lower 60s across our far eastern counties this
morning and some fog development will be possible across these
areas around sunrise.

The old frontal boundary is now stalled across Southeast Texas but
is expected to lift rapidly back north into Oklahoma and Arkansas
this afternoon; putting our area back into a very warm and
increasingly humid and unstable warm sector. Fortunately, the
moisture surge will initially be shallow in nature outside of our
far southeast counties where a few late day showers and
thunderstorms will be possible. Areas west of a Graham to Gorman
line continue to contain very dry small vegetation and grasses
from lack of rainfall the past month or more. These areas will
also be the slowest to see low level moisture recovery this
afternoon. These antecedent conditions will combine with humidity
values at or below 30 percent and breezy south-southwest winds
today for an increased threat for wildfires. A Grassland Fire
Danger Statement will be issued for locations along and west of a
Graham to Gorman line where humidity values will fall into the
20s. Otherwise, look for very warm temperatures in the 80s to
lower 90s across the western CWA to occur in advance of the
approaching cold front as compressional warming combines with
plentiful sunshine. Forecasted high temps for today are not far
from record values (DFW-95F in 1934, Waco-92 in 2004 and 2005).

A vigorous mid level shortwave is expected to to exit the Central
Rockies and move east-southeast out across the Plains tonight with
a strong cold front dropping southeast across Northwest Texas and
Western Oklahoma this evening. The associated strong height falls
with this system will induce a strong 30-40 knot low level jet by
sunset and beyond. This will draw rich low level moisture north-
northeast across much of the CWA ahead of our advancing cold
front. Initial storm development is expect to occur around or
just after nightfall (mid evening) with the arrival of very
strong large-scale ascent across areas north and northwest of the
immediate DFW Metroplex. A broken line of storms will form fairly
rapidly along the approaching cold front across our far northern
counties as low level southerly wind fields intensify. It is
difficult to diagnose whether any discrete storms are able to
develop out ahead of this line initially with dry and warmer air
occurring aloft within the 450mb-650mb this evening. Environmental
parameters will be conducive for severe weather considering
impressive shear parameters and surface-based instability in
excess of 2000 J/KG from I-20 to the Red River Valley. Regardless
if development remains along the cold front, or if isolated
storms can form well in advance, storms this evening will likely
be supercellular in nature considering Effective Bulk Wind
Difference (EBWD) values of 40-60 knots through late late evening.
All modes of severe weather (including tornadoes) will be
possible this evening.

Storm mode will change more to a broken line of storms, or a
progressive linear MCS as a strong southerly low level jet
continues feeding into the frontal boundary during the overnight
hours. With winds aloft paralleling the line of storms afterward,
the main impacts shift toward localized damaging winds, hail, and
locally heavy rainfall across our eastern counties of 1 to 2
inches and isolated instances of flooding. The cold front and
associated line of strong to severe storms will move quickly into
Central Texas during the pre-dawn hours. The severe weather threat
should begin waning as we approach daybreak Monday as storms
become further displaced from the stronger mid level ascent
moving into the Ozarks and Mid Mississippi Valley. I will linger
low convective chances across eastern Central Texas through mid
morning as the cold front exits the area. Clouds will clear
rapidly across Central Texas leaving a brisk, cooler, and mostly
sunny day across the area for Monday. High temperatures Monday
will be a good 15-20 degrees cooler with most areas warming back
into the lower-mid 70s by afternoon.



/Monday Night through Next Weekend/

Quiet weather will prevail for a few days in the wake of Sunday
night`s cold front, but another storm system is expected later in
the week.

Drier, cooler air and clear skies should allow overnight lows
Monday night/Tuesday morning to drop into the 40s, with a few
locations in the northwest even dipping into the upper 30s. It`s
possible some frost could develop where temperatures drop into the
30s Tuesday morning, but this may be dependent on how much rain
our northwest counties receive tonight. Tuesday will be a pleasant
day with highs in the 70s under (mostly) clear skies. A few high
clouds may pass across the northern half of the region, and the
surface winds will be light as a surface high slides across the
region. Overnight lows Tuesday night/Wednesday morning will be
warmer, but still in the 40s and 50s.

The surface winds will turn to the south on Wednesday as the
surface high moves east of the region. Afternoon wind speeds will
pick up to 10-15 mph in response to the atmosphere responding to a
developing trough to our northwest. Moisture return will begin a
slow progression north, but Wednesday will still be a fairly dry
day, humidity wise, with afternoon highs in the 70s and lower 80s.
The combination of breezy winds and low humidity may cause
elevated fire weather danger to the west of Interstate 35;
especially where temperatures reach the 80s.

A cold front is scheduled to surge into the region on Thursday
afternoon and evening as an upper level trough drops into the
Plains. The longer range models offer different solutions on the
development and track of the upper level trough. The GFS is the
most progressive and farther north of the extended models. The
ensembles do not offer much help, but appear to lean a little more
towards the operational ECMWF and Canadian, where the upper trough
arrives later and drops into West Texas on Friday while developing
a cut-off low. The models are in good agreement that rain will
occur along and ahead of the cold front on Thursday afternoon and
night, but the larger scale lift is still well displaced to the
north at that time, and I do not have much confidence in higher
PoPs and/or the higher QPF amounts produced by the ECMWF and
Canadian. If confidence increases in the ECMWF and Canadian
solutions over the next few days, the PoPs may have to be extended
into Friday and possibly Saturday. The NBM PoPs, which range from
20-40 percent, appear reasonable for now, and I kept rainfall
totals largely below 0.50-1.00" with this system. The forecast
for next weekend will show a dry and warming trend, but this may
change to wetter and cooler conditions depending on the output of
the longer range models over the coming days. The details with
this system will continue to be refined over the next few days.



.AVIATION... /Issued 1134 PM CDT Sat Oct 19 2019/

Main concern over the next 24-30 hours will be the potential for
a line of strong thunderstorms to impact the region Sunday night
as a cold front moves through North Texas. Until then, VFR will
prevail with clear skies and light northerly winds. Winds will
become more southerly by mid morning and increase to 15 to 20 kt
by afternoon. As moisture spreads northward into the evening hours
ahead of a cold front, thunderstorms are expected to develop late
in the evening. We`ll continue a VCTS at 5Z for the Metroplex TAF
sites with a TEMPO TSRA from 6-8Z at DFW. The line of storms
should move through fairly quickly with a wind shift to the north
at 15 to 20 kt and quickly clearing skies.

At Waco, similar trends are expected with timing of thunderstorms
between 8-10Z.



Dallas-Ft. Worth    88  59  74  47  75 /   5 100   5   0   0
Waco                90  61  75  43  76 /  10 100  20   0   0
Paris               81  59  69  43  72 /   5 100  10   0   0
Denton              87  53  74  40  75 /   5  60   5   0   0
McKinney            86  56  73  42  74 /   5 100   5   0   0
Dallas              88  61  74  48  76 /   5 100  10   0   0
Terrell             87  62  75  44  74 /   5  90  20   0   0
Corsicana           88  64  72  45  76 /  10 100  30   5   0
Temple              90  64  75  42  77 /  10  90  30   0   0
Mineral Wells       89  52  73  40  75 /   5  50   0   0   0





NWS FWD Office Area Forecast Discussion