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Area forecast discussion...updated
National Weather Service Fort Worth Texas
605 am CST Tue Jan 17 2017

Aviation...
a quasistationary front has pushed well south of our region, near
the mid- and Upper-Texas coast early this morning. Southerly flow
overtopping the cool near-surface airmass will eventually result
in the development of a widespread area of rain with some
embedded thunderstorms this afternoon and overnight. In the
meantime, VFR cigs should be the rule at area taf sites this
morning with some top-down moistening taking place. Anticipate an
initial wave of showers to push into the region from the south,
impacting Waco around noon, and then into the metroplex a few
hours later. As the low-levels saturate, MVFR cigs should develop,
eventually becoming IFR during the evening with continued bouts
of precipitation persisting overnight.

Have continued to advertise a period of thunderstorms in the vicinity at Waco this
afternoon and evening amidst a zone of higher instability.
Confidence in embedded thunder is a bit lower in the metroplex,
where instability will be in shorter supply. The threat for
thunder may increase late tonight at all taf sites as the mid-
levels cool with the approach of mid-level low pressure. Conditions
will be slow to improve on Wednesday as dry air looks hesistant
to push back into the region, although widespread rain should
quickly come to an end during the morning.

Carlaw

&&



Previous discussion... /issued 406 am CST Tue Jan 17 2017/
an active weather pattern will continue for the next 7-10 days
with several chances for rain. Temperatures will remain above
normal, and there are no signs at this time that another
intrusion of Arctic air is in store for at least the next 7-8
days.

The next in a series of upper level disturbances that will move
through the plains is currently located over Baja California. The
upper level low will dig a little further south this morning, and
then start moving northeast into New Mexico later today and
tonight. Isentropic lift ahead of this disturbance is already
generating showers this morning across our southern and eastern
counties with light rainfall accumulations. Showers and isolated
thunderstorms will slowly spread north today, mainly this
afternoon, as the upper level low starts to move northeast and
warm air advection and isentropic lift increase atop the shallow
cool layer at the surface in the wake of a cold front that moved
through yesterday. Numerous showers and thunderstorms are expected
tonight as the upper level low moves closer to the Southern
Plains, and model guidance suggests some heavy rainfall will be
possible which may result in some flood issues.

Much of the region was already saturated with 1-3 inches of
rainfall Sunday evening, and we know or suspect standing water
remains in many places, including our far southeast counties and
likely along the track of the lone supercell from Coryell County
into the dfw metroplex. Showers and thunderstorms tonight are
expected to be efficient rainfall producers, but will also be
moving at a decent speed that may help to prevent widespread flood
issues. However, we will have to monitor for training of storms
that may result in localized flood issues. The best potential for
heavy rainfall will be in our southeastern counties where hi-res
and ensemble guidance indicate heavy showers and thunderstorms
will occur between roughly 3 am and 9 am. Another 1-2 inches of
rain appears possible tonight into Wednesday morning, especially
in our southeastern counties. At this time, we do not plan to
issue any flood headlines, but will pass onto the next forecast
shift(s) the need to watch the trends.

The rain will shift east on Wednesday as the upper level low pulls
north of the region, and the best lift moves to the east. It will
still be rainy across roughly the eastern half of the County Warning Area
Wednesday morning but most of the rain should clear out by
afternoon. The exception to this will be in our southeastern
counties where weak isentropic/warm air advection lift will
continue and scattered showers will be possible through Wednesday
night. As one more upper level trough pivots around the previous
upper level low, and through the Southern Plains on Thursday,
there may be enough moisture still in our eastern counties for a
few showers east of Interstate 35.

The weather is expected to be quiet and warm on Friday with upper
level ridging moving overhead and south winds already in place at
the surface. Confidence in the forecast beyond Friday is still
low at this time due to differences between the models so kept
pops on the lower end for now. Another strong upper level trough
will dig across the western Continental U.S. Friday and Saturday, quickly
moving across the Southern Plains Saturday night into Sunday.
Another round of rain is possible this weekend, ahead of this
system. Right now, it does not appear there is much of a severe
weather threat, but we will need to keep an eye on this as the
set-up has the potential to produce a severe weather event. The
lift is definitely strong enough, the wind shear looks decent, and
there may be sufficient moisture in place. Storm Prediction Center is already
highlighting an area to our east out ahead of this system.

The upper level trough quickly wraps up into a closed low over the
Southern Plains and gives US a shot of cold rain on the backside
of the upper level low during the day on Sunday, in particular
across our northern and northeastern counties. The h850 and above
temperatures are very cold, and at first glance could suggest
wrap around snow, but sounding analysis indicates the layer below
h850 is significantly warm enough and moist enough to melt any
snow that may fall from a higher level. Wet bulb temperatures are
also forecast to remain well enough above freezing, but again
this small detail may be another thing to keep an eye on.

Jldunn

&&




Preliminary point temps/pops...
Dallas-ft. Worth 55 46 56 45 69 / 50 90 40 10 10
Waco 54 45 58 44 71 / 80 90 50 20 10
Paris 55 45 54 47 64 / 30 100 60 20 20
Denton 54 42 56 41 68 / 30 90 20 10 5
McKinney 54 43 56 43 67 / 30 90 40 10 10
Dallas 55 46 57 47 69 / 50 90 40 10 10
Terrell 55 46 57 47 68 / 50 100 60 20 20
Corsicana 55 48 58 48 69 / 70 100 80 30 20
Temple 54 46 58 46 71 / 80 100 50 30 10
Mineral Wells 53 42 57 43 71 / 60 90 10 10 5

&&

Forward watches/warnings/advisories...
none.

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