AFD's like this 1) give me optimism about the possibilities and 2) also show some of the things the NWS looks at in the model outputs beyond the simplistic things that I do. Yeah my condensation pressure deficits were way off...
Things start to get interesting (and perplexing) on Sunday.
Another shortwave trough will move out of the Rocky Mountains, but
this time, at a lower latitude than the one on Saturday. This
shortwave trough will act to amplify a longwave trough that will
be in place over much of the CONUS. The result at the surface will
be a deep intrusion of arctic air across the interior CONUS,
including here in North/Central Texas. This synoptic pattern is
shown by both the GFS and ECMWF, but with significant timing
differences. The ECMWF is faster, and perhaps a bit stronger than
the GFS. The ECMWF also shows more widespread precipitation
developing within the cold air, whereas the GFS is on the drier
side. A closer look at the GFS however shows that parcels are near
saturation with condensation pressure deficits generally less than
25 hPa. This means that it would not take much more synoptic-scale
ascent than is being advertised by the GFS to result in the
development of precipitation (it is no surprise that the ECMWF
shows larger height falls, and has the more widespread
precipitation). Given the "qualitative" assessment of the synoptic
environment, we are inclined to lean a little bit towards the
ECMWF. Some of the features within the synoptic setup include the
aforementioned height falls, large PV anomalies around the 500 mb
level, a 120+ knot jet streak, and conditionally unstable lapse
rates. All of this is to say that there should be lift, and there
should be cold air. The only question is will we have enough
parcel saturation to get precipitation processes started.
It is certainly too early to get too deep into the weeds with
respect to precipitation type (let alone amounts), but a quick
glimpse at forecast soundings suggests that some wintry
precipitation will be possible, with the greatest chances being
the farther north one goes. It needs to be stressed that there is
significant uncertainty right now given the aforementioned
disagreements between the GFS and ECMWF, and the uncertainty in
the antecedent conditions (i.e. how cold will we get on Saturday
before the "better" cold air moves south). The takeaway message
should be that the "big picture" suggests a possibility of winter
weather beginning Sunday morning and lasting through Monday
morning for portions of our county warning area, but amounts,
types, and the precise locations of where this winter weather will
occur remains highly uncertain at this time. Interests in North
and Central Texas are advised to check the forecast as the week
progresses, and to be wary of anything out there (particularly on
social media) that makes big claims about winter weather next
week. The truth is, the science is simply not good enough to know
exactly what we will be looking at during the Sunday/Monday
timeframe, but we should get a better handle on things later this
week.
Godwin
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or 
