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Area forecast discussion
National Weather Service Fort Worth Texas
345 PM CDT sun Oct 20 2019

Short term... /issued 222 PM CDT sun Oct 20 2019/

/this afternoon through Monday/

Forecast trends are in good shape as we expect the main show to
be later this evening and tonight. There is still a slight chance
of convection across the far southeast counties through this
afternoon. Latest satellite image shows the upper level low over
Wyoming and Colorado and the associated cold front extending from
Kansas to southeast Colorado and northern New Mexico. They will
continue east/southeast and move through north and central Texas
later this evening and tonight. Confidence is high that a line of
storms will develop to our northwest by mid-evening, likely
reaching the dfw metroplex around or just after midnight and
moving into central Texas a few hours later.

There is still some uncertainty about the development and the
severity of the storms ahead of the front late this afternoon and
evening. It appears that some of the important ingredients needed
for storms to develop will not be there yet. We will continue to
watch the trends in moisture, instability and lift and will make
necessary adjustment to the pops. For now, we will mention a
chance of storms north and west of the dfw metroplex and across
the south and east to account for this possibility.

In terms of the severe weather risk for North Texas, we still
expect a few strong to severe storms across the area, especially
north of the I-20 corridor. The main threats with the line of
storms will be damaging winds and large hail. If any convection
develops ahead of it or remains cellular, it will increase the
tornado threat. In general, the tornado threat remains low at this
time. We like to remind everyone to stay weather aware tonight
and have a plan if any warning is issued for their location.

After the cold front clears out tomorrow morning, northwest winds
will continue through the day tomorrow. The good news is that high
temperatures on Monday will only reach the 70s area wide under
clear skies.



Aviation... /issued 222 PM CDT sun Oct 20 2019/

/18z taf cycle/

Concerns...widespread showers and thunderstorms tonight as a cold
front moves across the area. Occasional low ceilings due to
heavier precipitation will be possible. South winds shifting to
the north early Monday morning.

For the dfw metroplex taf sites, VFR conditions and south winds
continue this afternoon. We will see an increase in cumulus development
in the next couple of hours with returning moisture. As
anticipated, a cold front will sweep through the area tonight.
Most of the high-resolution guidance agree that a line of storms
will likely develop across the northwest after sunset and move
east/southeast. The arrival time of the storms into the dfw
metroplex taf sites will be around midnight. Ceilings and
visibilities are expected to remain VFR, but occasional and brief
MVFR/IFR cigs will be possible with the heavy precipitation.
Expect frontal passage between 08-09 UTC. Skies will clear just around
sunrise Monday morning, with northwest winds around 10-15 kts
through the rest of the forecast period.

For act, the main difference will be the timing of the
thunderstorms and the wind shift. We expect that the line of
storms will impact Waco 07-09 UTC, followed by the wind shift
around 10-11 UTC. Skies will clear during the early morning hours.



Long term...

/Tuesday through next weekend/

Cool conditions will grip much of north and central Texas to
start the day on Tuesday. With clear skies, low dewpoints and
light winds...ideal radiational cooling is anticipated. NAM MOS
and the previous forecast both appear to encompass the cooler side
of the guidance. With that in mind, i've hedged towards these
cooler solutions which advertise Tuesday morning lows in the 40s
with a few of the sheltered regions in the upper 30s. Some patchy
frost will be possible for locales that dip down into the upper 30s.

Mid-level high pressure will remain in control across our region
during the day on Tuesday and into Wednesday. This will equate to
tranquil weather conditions with high temperatures slowly
moderating both days to above climatological norms. Daytime high
temperatures will climb into the upper 70s to mid 80s by Wednesday
as south to southwesterly breezes develop ahead of the next upper
trough. The warmest conditions are expected near and west of the
US Highway 281 corridor. With the increasing surface pressure
gradient, low level winds should climb into the 20 to 25 miles per hour
range. Given the sufficient boundary layer mixing, wind gusts to
near 30 miles per hour are not out of the realm of possibility on Wednesday
afternoon. Minimum relative humidity values are expected to crater down into the
mid 20s west of I-35. While wetting rains are forecast Sunday
night (tonight) into Monday, 1 and 10 hour fuels---mainly smaller
vegetation types such as grasses and small Timber---dry quickly
under full solar insolation. Given that the drying of fuels is
increasingly likely, it's probable that an elevated fire weather
threat will materialize on Wednesday.

The next weather pattern shift is anticipated on Thursday when an
upper low will detach from the main westerlies and dive south
toward the Lone Star state. If you've been following along over
the past several days, the general model theme persists through
the 12 UTC cycle. The 12 UTC GFS and most of its ensemble members
along with the Canadian remain quick with frontal passage on Thursday across
most of north and central Texas (with frontal passage through central Texas
by 21 UTC thursday). The 12 European model (ecmwf) still remains the slow outlier
as it delays the ejection of the upper trough and front with the
frontal passage not through the entire area until the pre-dawn hours on
Friday morning.

Climatologically speaking, a faster frontal passage would be favored, but
given the uncertainty about the depth/speed of the upstream colder
airmass, i'm reluctant to blindly follow the GFS/Canadian
solutions based on climatology. Moreover, model guidance tends to
struggle with digging upper level troughs and in many instances
their initial solutions prove to be too swift with their
progressions. This would give credence to the slower European model (ecmwf)
solution. What appears to be the most reasonable forecast is for
areas across the northern Big Country to experience frontal passage prior to
peak heating on Thursday. I'll advertise temperatures in mid to
upper 60s here. While the warm sector airmass will likely be
enshrouded with cloud cover, high temperatures may still climb
into the mid to possibly upper 70s courtesy of strong warm air advection. If the
Canadian/GFS are closer to reality, highs may need to be lowered
down into the 60s.

Showers and thunderstorms may Blossom along and behind the front
as it passes southward on Thursday. While deep layer shear will
likely support organized modes, the magnitude of instability is
uncertain. Should the GFS/Canadian models verify, it's likely that
the window for any strong to severe storms will be limited owing
to meager moisture advection. The slower ECMWF, however, would
allow ample time for a better fetch of moisture northward and thus
greater instability over more of the area. We will continue to
refine this portion of the forecast over the next several days.

The forecast difficulty increases significantly as model guidance
remains largely divergent regarding their solutions for Friday
and into next weekend. There is perhaps greater confidence in the
slower solutions given that the Canadian has trended toward the
slower European model (ecmwf). Strengthening 700-850mb warm air advection atop the cooler surface
air---as implied by the Canadian and European model (ecmwf)---should in theory
promote a widespread Post frontal precipitation shield across the
area. While the GFS has shown some run-to-run consistency, it
remains the fast outlier and the latest forecast leans on a blend
of the slower guidance. As such, i've nudged pops slightly above
the GFS-heavy National blended guidance and kept temperatures
below normal as we head into the last weekend of October.



Preliminary point temps/pops...
Dallas-ft. Worth 58 75 47 76 51 / 100 0 0 0 0
Waco 60 76 43 78 50 / 90 20 0 0 0
Paris 59 70 43 72 46 / 100 10 0 0 0
Denton 53 75 40 75 50 / 80 0 0 0 0
McKinney 56 74 42 75 47 / 100 0 0 0 0
Dallas 60 75 48 76 53 / 100 5 0 0 0
Terrell 61 74 44 75 46 / 90 10 0 0 0
Corsicana 63 73 45 77 49 / 100 20 0 0 0
Temple 62 76 42 78 51 / 100 20 0 0 0
Mineral Wells 53 74 40 75 49 / 80 0 0 0 0


Forward watches/warnings/advisories...

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