National Weather Service Raw Text Product

Displaying AFOS PIL: AFDFWD Received: 2019-01-12 23:52 UTC

FXUS64 KFWD 122352

Area Forecast Discussion
National Weather Service Fort Worth TX
552 PM CST Sat Jan 12 2019

/00Z TAFS/

Cloud cover continues to plague the region this evening and will
likely linger through much of the overnight hours. There's not
much in the way of upstream drying and low cloud cover actually
extends all the way northward to the Canadian border. We'll likely
have MVFR cigs tonight with heights around 2500 ft, then see some
improvement through the mid/late morning hours on Sunday.
Northwest winds will become more northerly overnight. No
precipitation is expected.



.SHORT TERM... /Issued 331 PM CST Sat Jan 12 2019/
/Through Tonight/

A blanket of postfrontal stratus has separated areas that peaked
in the 40s from the sunnier spots that climbed into the 50s this
afternoon. The southern edge has invaded Central Texas, but the
thinner/higher ceilings suggest it should make little additional
progress to the south. Dry advection on the western periphery of
this cloud bank will steadily erode it this evening, but the 
considerable cloudiness trapped beneath the frontal inversion 
upstream will help to reinforce the cloud deck overnight, 
particularly in areas north and east of the Dallas/Fort Worth 
Metroplex. The wind will subside this evening, but the proximity 
of a departing surface low will keep a brisk northerly breeze 
across North Central and Northeast Texas into the early morning
hours Sunday. Across our western zones, where clear skies will 
combine with the lightest winds, morning lows will reach freezing 
for the first time since last weekend.



.LONG TERM... /Issued 331 PM CST Sat Jan 12 2019/
/Sunday into Next Weekend/

The primary forecast concern in the extended period is the arrival
of a strong cold front early next weekend, with a related 
possibility of some winter precipitation across parts of the area.
Regardless of the precipitation potential, next weekend looks
quite cold. More on that below.

In the meantime, cyclonic 500mb flow will continue shifting east
from the Mississippi Valley towards the Atlantic Seaboard 
tomorrow. Heights aloft will be relatively neutral over Texas,
however, and the resultant surface pattern will be characterized
by a ridge anchored to our north. In turn, the influence of
continued northerly boundary-layer flow and some low-level cloud
cover will offer another cold day across North and Central Texas. 

Weak anticyclonic flow and building heights aloft overspread 
Texas Monday into Tuesday. Subsequent eastward evolution of an 
expansive surface ridge will place the southern Plains under 
southerly return flow, although this regime will be unimpressive 
with regard to initial moisture return. A considerable warming 
trend will be underway, though, and highs should reach the 60s to 
near 70 during the second half of the week.

A pair of weak shortwave impulses embedded within the zonal flow
pattern overhead could offer a couple of upticks in our rain 
chances here locally. The first will translate across Texas 
Tuesday into Tuesday night, but its low amplitude and meager 
antecedent moisture should preclude rain chances. A second system
then approaches on Thursday, and its ascent should work in tandem
with richening moisture profiles to promote at least isolated rain
showers Thursday into Friday, primarily east of the I-35 corridor.

The most noteworthy potential of the extended forecast exists
Friday night into next Saturday. By most indications, a Hudson Bay
vortex will deepen during the first half of the week, while
heights will build from Alaska towards the North Pole. Resultant
cross-polar flow will dislodge very cold surface air southward
into southern Canada and the northern Plains by mid/late week.
Meanwhile, medium-range deterministic and some ensemble guidance
suggest a Pacific impulse will undercut the aforementioned western
ridge and cross the Plains through the day Saturday. As an
attendant surface cyclone develops across the south-central US,
strengthening northerly flow behind the wave will draw this cold-
air reservoir southward over Texas.

Of higher confidence is an expectation that temperatures will
become quite cold on Saturday, with some locations perhaps
remaining in the 30s during the day. Indeed, the potential exists
for highs to be lower than what is currently advertised, but did
not want to be too aggressive with the forecast at such an
extended range.

As for any winter-weather potential, large uncertainty exists with
the spatial and temporal evolution of the broader mid/upper trough
and the associated surface low. Most guidance indeed indicates a
positive tilt with the passage, suggesting any substantial
deepening and related mass response (impacting precipitation
potential) will be highest to our east. However, the ECMWF has
been trending towards a somewhat deeper solution and farther
southward advance of the synoptic trough, which would increase
winter weather potential, especially towards the Red River.
Meanwhile, the GFS and a notable number of its ensemble
counterparts maintain a slightly more progressive, less amplified
system, with rapid drying in its wake, ending any light 
precipitation well before snow/sleet is possible.

So what's a meteorologist to do with this conundrum? Well, a
slightly more amplified system (e.g., the ECMWF portrayal) does 
not seem unreasonable, especially given the thrust of cold air and
baroclinicity that will be present. However, the antecedent 
synoptic pattern will be characterized by relatively fast, zonal 
flow ahead of this wave, which would favor a quicker eastward 
cyclogenetic evolution that would be drier for North and Central 
Texas (e.g., the GFS solution). Given that the answer most likely
(but still with low confidence) lies somewhere between those two
solutions, and also considering the very complex upstream/Pacific
pattern impacting the approaching wave, think it is too soon to 
introduce any winter weather into our forecast. Therefore, have 
maintained only low chances for rain showers Friday into Saturday,
before conditions dry out (with higher confidence) Saturday 
night. Regardless, keep checking back for updates, as the forecast
will change (and that's a 100% confidence forecast).



Dallas-Ft. Worth    35  45  31  50  36 /   0   0   0   0   0 
Waco                34  46  30  51  34 /   0   0   0   0   0 
Paris               34  43  29  48  33 /   0   0   0   0   0 
Denton              33  44  28  50  34 /   0   0   0   0   0 
McKinney            34  43  29  48  34 /   0   0   0   0   0 
Dallas              35  45  33  50  36 /   0   0   0   0   0 
Terrell             35  45  30  50  34 /   0   0   0   0   0 
Corsicana           36  46  33  49  36 /   0   0   0   0   0 
Temple              35  47  32  51  35 /   0   0   0   0   0 
Mineral Wells       33  44  29  49  34 /   0   0   0   0   0