Texas Winter 2017-2018

[Brent]

wow the Euro is so cold... Dallas doesn't get above 40 the rest of the run(close Wednesday) and stays below freezing next Thursday again(after Monday/Tuesday), then barely gets there Friday

[Ntxw]

Thinking we get another cold blast with threat of snow and ice the following weekend. Pretty persistent from the models of Alaskan ridge, more west this go

[South Texas Storms]

Yeah it looks like we will have a lot to track over the next week or two. Really hope all of us get to see some snow with this pattern! It definitely has potential.

[Cpv17]

That means that the coldest anomalies would go more towards us than east of us, correct?

[Ntxw]

wow the Euro is so cold... Dallas doesn't get above 40 the rest of the run(close Wednesday) and stays below freezing next Thursday again(after Monday/Tuesday), then barely gets there Friday

Yeah, as we get closer it's becoming more clear a secondary surge of arctic air moves in later in the week reinforcing the cold already in place. Models have become more bold with this and is no slouch with a 1045+ mb high. And as I posted above not long after another bout of cold in the works maybe. But once again cold air will have already been in place.

[Ntxw]

Thinking we get another cold blast with threat of snow and ice the following weekend. Pretty persistent from the models of Alaskan ridge, more west this go
That means that the coldest anomalies would go more towards us than east of us, correct?

It will be another cold air damming up and bleeding down the Rockies again, maybe even centered further west than next week's blast.

[Brent]

there were some flurries in DFW NYE on the Euro

so at least there's two different storms, NYE is the arctic front actually crossing

[Ntxw]

Getting into range of MOS output now. GFS MOS has DFW down to 15 Monday morning, 13 next Tuesday morning

I'm curious if the NWS will accept the MOS numbers since it is one of their favorite tools for specific site forecasts given its frequent superiority to raw model output close range

[South Texas Storms]

0z Euro control run is very similar to the operational run.

0z Euro Ensemble mean has 0.50 inch of snow across portions of southeast TX. Not bad for a mean 5 days out.

[Brent]

Love the big snow hole over DFW on the EPS control

Bullseye in SE TX

[srainhoutx]

The Updated WPC Day 4 to 5 QPF suggests enough moisture across the Southern half of Texas to raise and eyebrow. There also is a hint of a Coastal trough organizing early New Year's Day into next Tuesday.

[Brent]

NAM has some light snow/flurries approaching DFW Sunday morning

[gpsnowman]

Good morning weather junkies. Good posts overnight, thanks to all. I always enjoy waking up to several fresh pages. Hopefully we keep the trends with increasing snow chances today.

[somethingfunny]

Frankly from where I sit in DFW (I'm a professional driver) I don't mind cold or snow or even rain, but just don't hit me with any freezing rain. Especially on New Year's Eve....

Run-to-run variations in location of precipitation really aren't anything to pay attention to more than a day or two out but the overall pattern has my attention for the possibility we get hit.

[somethingfunny]

Fwd gave us a good discussion this morning:

Most of the model guidance is now showing a weak surface low
developing across Central Texas on Saturday as a shortwave in
northwesterly flow aloft moves across the region. Should this low
form, it would mean that a baroclinic zone (or cold front) would
develop over our CWA during the day Saturday. One impact of this
feature is that it would complicate the high temperature forecast
as cold advection would start across the northern zones Saturday
afternoon (with temps falling into the 30s) while the southern
zones would see strong warm advection and highs pushing 70. The
exact position, strength, and track of the surface low is
uncertain at this time, so have taken a blend of the guidance for
highs. This forecast advertises low 40s along the Red River to the
low 60s in the southern zones. Increasing isentropic lift along
and north of the surface low track would suggest a slight chance
of some weak showers developing during the day. The second impact
of the surface low is that it means the arctic front will be
effectively through the entire CWA by Saturday evening. As
discussed yesterday this arctic front will not immediately bring
the arrival of arctic air and strong winds. Instead it will be a
gradual increase of northerly winds with temperatures getting
progressively colder over many hours.

The arctic airmass will be very shallow, only a few thousand feet
deep Sunday and Sunday night. Above the strongly stable frontal
inversion, the airmass will remain very warm and dry which will
inhibit any significant precipitation and keep QPF at a few
hundredths at best. The cooling of the low level airmass below
the dewpoint will squeeze the excess moisture out as drizzle.
While it`s tempting to look at QPF from the models to make a
drizzle forecast, only models which utilize a complex cloud scheme
(like the NAM and other high-res guidance) are even capable of
parameterizing drizzle. Models which use a simple cloud scheme
(like the GFS, ECMWF, and Canadian) just physically can`t forecast
drizzle, so it`s not that the models don`t agree because their
QPF is different. Instead all models show the same trends of the
temperature/moisture profile as the NAM - but only the NAM is
indicating the telltale signs of a drizzle event in the QPF field.

As surface temperatures drop below freezing during the day Sunday
the drizzle would change to freezing drizzle and create the
potential for icing of bridges, overpasses, and (if it gets cold
enough before the precipitation ends) surface streets. It`s also
possible the drizzle could change to snow flurries before ending.
The main window for any wintry precipitation is during the day
Sunday generally along and north of I-20 and Sunday evening for
areas south of I-20. Due to the brief window and the lack of
significant precipitation any icing that does occur would be
light. That doesn`t mean there won`t be travel issues, but it does
mean we will not have to worry about this event becoming an issue
for downed trees and powerlines. One of the hallmarks of arctic
air is that it is very dry, and those dewpoints Sunday night will
be falling into the single digits. This will shut off any drizzle
from north to south and also serve to subliminate any ice that
did collect on surfaces. This may mean that any icing may be a
non-event or very low impact event...but it`s just too early to
tell at this time.

By Monday, the dry air will help to clear skies over the region,
but continuing cold advection means high temperatures will likely
stay below freezing over almost the entire CWA despite sunshine.
Wind chills will spend New Year`s Eve and New Year`s Day in the
single digits and 20s. Bundle up!

The forecast for Tuesday and Wednesday gets a little more
uncertain. While it`s a guarantee that very cold temperatures
will prevail, the model guidance has some spread on whether
another shortwave will rotate through the region on Tuesday. About
20% of the EPS/GEFS members and the latest operational ECMWF and
Canadian models show this upper level feature. While moisture
would be very limited, it would have the potential to produce some
light snow. Given the low run-to-run consistency and the lack of
a the majority of ensemble member agreement will keep
precipitation out of the forecast but bump cloud cover up. The
increased cloud cover would help to keep our low temperatures
higher Monday night and Tuesday night so I did not lower those
forecasts below consensus numbers. This means as of now, low
temperatures are not expected to be colder than what we saw in
January of 2017, but this cold snap will last much longer than
that one.

[South Texas Storms]

HGX also had a good detailed AFD this morning:

Sunday through Tuesday continues to be a period of the forecast
requiring active monitoring. An Arctic airmass located over the
Northwest Territories of Canada early this morning will become
dislodged later today as an upper level low rotates across the
Canadian prairies and this colder air will ooze south down the
Great Plains over the next few days. A northerly wind shift will
herald the arrival of this much colder airmass during the day
Sunday, with high temperatures for the day likely within a few
degrees of morning temperatures as strong cold air advection
spreads across Southeast Texas. Freezing temperatures are expected
to arrive into the region Sunday evening or night. Weak
convergence along the front during the day Sunday may be able to
generate some light rain, but low confidence still persists on any
kind of winter precipitation for Sunday night.

As the previous forecast package noted, the potential for
precipitation increases when three ingredients align: lift,
moisture, and instability. One way to assess areas of vertical
motion is through isentropic analysis as air parcels flow along
constant potential temperature surfaces. Inspection of the 295K
isentropic surface on the deterministic Canadian, GFS, and
European models all show winds moving towards higher pressures on
these surfaces... which is indicative of descending vertical
motion and continues to limit forecast confidence. However, this
may be overcome by the weak lift along the front tapping into
some elevated instability (3-6 km lapse rates in excess of 6
C/km). There will undoubtedly be enough moisture to lift with
saturated profiles evident on both GFS and European forecast
soundings for Crockett and College Station. The limited alignment
of these three ingredients still indicates that a brief window of
a freezing rain/rain mix may still occur Sunday night into early
Monday morning as surface temperatures fall below freezing, but
may be a smaller window than previously advertised. This window
will likely need to be narrowed further in future forecasts for
areas north of a Brenham to Cleveland line. Little to no
accumulation is expected given the very short time in which
precipitation and sub-freezing surface temperatures will overlap.
Any water left on roadways from rainfall prior in the day Sunday
though will likely freeze overnight and therefore cannot rule out
a few slick spots. Dry conditions are expected inland on Monday as
a result of the aforementioned conditions with high temperatures
only climbing into the mid 30s to lower 40s.

Heading into Tuesday, medium range guidance becomes considerably
inconsistent with precipitation potential for the region. All
drive an upper level trough across the region, increasing
divergence and accordingly lift for precipitation to develop but
are dramatically different when considering the amplitude of this
trough (affecting where the best lift occurs) and the available
moisture (European and Canadian are saturated in the low levels,
GFS is dry). However, even with the inconsistency in moisture
there may be enough dynamic forcing with this upper trough to
result in portions of the atmosphere above the surface to cool to
saturation and provide at least some window for precipitation
during the day. Have pulled low (20%) precipitation chances north
towards Interstate 10 as a result. Thermal profiles during this
time are also somewhat inconsistent between the models and if
precipitation does occur (still not certain)... it could range
from rain to freezing rain to rain to snow. Have kept the
precipitation type only as rain for now given these
inconsistencies but additional refinements to precipitation
type/chances/impacts will be likely over the coming days.

Even if no winter precipitation materializes at all during this
time, there is high confidence that very cold temperatures will
spread across Southeast Texas. Forecast wind chills during the
Sunday night through Tuesday morning time frame fall into the
teens north of Interstate 10 and it may be possible that a Wind
Chill Advisory is needed. (Wind Chill Advisories are issued when
wind chills fall to 13 degrees F or below.) Temperatures are
gradually expected to warm Tuesday into Wednesday as skies begin
to clear.

[stormlover2013]

Lol Gfs once again being the Gfs lol this model flops so much

[WeatherDuck]

In my area of Central Texas the NWS has increased chances of precipitation to 30% for Saturday night through Sunday night.

Will have to see if the cold air arrives earlier than forecast.

[perk]

Lol Gfs once again being the Gfs lol this model flops so much

And it will flips many more times in the coming days.

[stormlover2013]

No doubt but people on here talking about how it was doing and etc, tomorrows runs will be interesting!!!!