Texas Winter 2024-2025

[sphelps8681]

EC hates Houston. 8+ inches snow Tuesday and a low of 12 Wednesday. I need to get up north and reinforce my wall. Encouraging that the ICON went GFS and warmed a good bit, but it didn't do well last event. Canadian remains, well, Canadian. It's forecasting single digits in Houston and below freezing from early Tuesday to maybe Saturday. It's always way too cold for us (thankfully).

How does Beaumont/Lumberton look if you don't mind?

[Ralph's Weather]

All good models are a go for snow up to I20. Outliers are UKMET and ICON but I can live with fringe models like that being outliers. The rest have snow of varying intensity up to DFW and Tyler. Ratios along I20 would be in the 15-20:1 range so instant accumulations and high ratios means whatever falls Tue will accumulate quickly.

I'm north of I20 and east of I35, but pretty far north. Edge of Denton/Grayson. Is this too far for any accumulation at this time?

My best guess would be light snow or flurries maybe a dusting to under an inch.

[Ralph's Weather]

Still wondering if we'll see N/NW shifts/expansion of precip in models by Sunday/Monday...

I expect they will but was hoping the 12Z Euro would join the CMC and GFS on this run with that shift. We are getting close to NAM range, but for now the NAM isn't digging SW as much as other models which I don't love.

NAM actually is digging southwest more so than the other globals (mainly GFS/Euro), its closer to the CMC

Where are you seeing that? Its not a huge difference but NAM looks a bit further NE than the others. Its the end of its run so I'm not concerned by it.

[TheAustinMan]

Models and ensembles have started to key in on the amplification of the shortwave, though it's worth noting that the disturbance responsible for it will only reach the Canadian coast on Saturday, after which it'll be sampled by upper-air balloons for the first time. An amplifying shortwave trough would serve to reinforce cold, especially in the mid-levels (500-700 hPa). That doesn't sound immediately like a big deal, but what it does is sharpen the temperature gradient between the interior Central US and the Gulf coast. Large gradients in temperature in the low to mid-levels means big increases in wind aloft, so that results in a strengthening of the northern stream jet over the Ohio River Valley.

Air accelerating off into the jet results in upper-air divergence, so air needs to be drawn up from the low-levels to replace it. The start of the jet, especially south and east of that area (i.e. the "right entrance region"), is a favored region for air to ascend into. Where this area is depends on the orientation and strength of the trough. The 12z GFS, pictured below, had a stronger, more emphatic jet than the 12z ECMWF, resulting in divergence extending farther north.



Details are yet to be worked out, but the general location of the shortwave is well-suited to draw moisture from the Gulf. We can represent this by plotting potential temperature (theta-E) like an topographical surface, since air tends to maintain constant potential temperature. In this case, the 295K potential temperature level is plotted like terrain, allowing us to visualize the ascent of humid air from the moist Gulf upwards over Texas to feed the jet stream. This translates into vertical motion over Texas, and, provided the air is sufficiently saturated aloft, precipitation:


Key questions determining precipitation location, type, and amount will be:

• How far inland will moisture be able to reach? The 12Z GFS showed the plume of moisture reaching the Red River. The 12Z Euro struggled to reach US-290.
• Will the plume of moisture sustain long enough to permit precipitation before drier low-level air associated with the shortwave trough arrives from the north? (Especially for North Texas)
• How cold will it be throughout the low-levels at the start of the event? Southerly flow inevitably causes warming. Will the resulting warm nose be well above freezing or marginal/below freezing?

[Lagreeneyes03]

If the GFS would just expand slightly north, I would be happy, everybody would get something with that.

Thats exactly what happened last week's storm. Another north trend by 50-75 miles would be great.

[wxman57]

EC hates Houston. 8+ inches snow Tuesday and a low of 12 Wednesday. I need to get up north and reinforce my wall. Encouraging that the ICON went GFS and warmed a good bit, but it didn't do well last event. Canadian remains, well, Canadian. It's forecasting single digits in Houston and below freezing from early Tuesday to maybe Saturday. It's always way too cold for us (thankfully).

How does Beaumont/Lumberton look if you don't mind?

Hard to predict amounts until maybe Monday evening. You could see 2-4" of snow Tuesday, though Maybe more, maybe less.

[Charleswachal]

School closings have begun already

https://www.khou.com/article/weather/ha ... GrVg8s0dyQ

[BigB0882]

School closings have begun already

https://www.khou.com/article/weather/ha ... GrVg8s0dyQ

I don't mean to go too off topic but this blows my mind as someone in education. We still have a lot of time and a lot of changes can happen between now and Mon/Tue. I don't get why a school system would call off school now when they can make the call Sunday.

[WinterMax]

I noticed local Mets here south central Louisiana have sort of flirted with a second event later in the week, although less impactful. They went back and fourth with this idea, and now just call for rain showers, due to a warm up.

But I wonder, if we get higher accumulations on Tuesday, would that possibly keep temps quite a bit colder than forecasted now, due to deeper snow cover on the surface?

[ThunderSleetDreams]

Albedo gets this boards libido raised and temps dropped!

[ThunderSleetDreams]

Models and ensembles have started to key in on the amplification of the shortwave, though it's worth noting that the disturbance responsible for it will only reach the Canadian coast on Saturday, after which it'll be sampled by upper-air balloons for the first time. An amplifying shortwave trough would serve to reinforce cold, especially in the mid-levels (500-700 hPa). That doesn't sound immediately like a big deal, but what it does is sharpen the temperature gradient between the interior Central US and the Gulf coast. Large gradients in temperature in the low to mid-levels means big increases in wind aloft, so that results in a strengthening of the northern stream jet over the Ohio River Valley.

Air accelerating off into the jet results in upper-air divergence, so air needs to be drawn up from the low-levels to replace it. The start of the jet, especially south and east of that area (i.e. the "right entrance region"), is a favored region for air to ascend into. Where this area is depends on the orientation and strength of the trough. The 12z GFS, pictured below, had a stronger, more emphatic jet than the 12z ECMWF, resulting in divergence extending farther north.

https://i.imgur.com/9elxpw4.png

Details are yet to be worked out, but the general location of the shortwave is well-suited to draw moisture from the Gulf. We can represent this by plotting potential temperature (theta-E) like an topographical surface, since air tends to maintain constant potential temperature. In this case, the 295K potential temperature level is plotted like terrain, allowing us to visualize the ascent of humid air from the moist Gulf upwards over Texas to feed the jet stream. This translates into vertical motion over Texas, and, provided the air is sufficiently saturated aloft, precipitation:
https://i.imgur.com/vKB9EZP.gif

Key questions determining precipitation location, type, and amount will be:

• How far inland will moisture be able to reach? The 12Z GFS showed the plume of moisture reaching the Red River. The 12Z Euro struggled to reach US-290.
• Will the plume of moisture sustain long enough to permit precipitation before drier low-level air associated with the shortwave trough arrives from the north? (Especially for North Texas)
• How cold will it be throughout the low-levels at the start of the event? Southerly flow inevitably causes warming. Will the resulting warm nose be well above freezing or marginal/below freezing?

Don’t ever leave us!

[Stratton23]

EPS 12z ensemble mean snow aveage for se texas is 2-4 inches, thats crazy!

[Steve]

School closings have begun already

https://www.khou.com/article/weather/ha ... GrVg8s0dyQ

I don't mean to go too off topic but this blows my mind as someone in education. We still have a lot of time and a lot of changes can happen between now and Mon/Tue. I don't get why a school system would call off school now when they can make the call Sunday.

Monday is a holiday, so probably most schools are closed. Several NWS forecast areas have Tuesday snow/ice "likely." Districts could wait until later in the period (or until the last minute which is how it was when I was a kid when you'd have to turn on the morning news to find out if your school was closed or not). Or they could just go along with the likelihood that it's not going to bust and give parents a chance to organize whatever contingency plans they need to make for school closures. I'm not a teacher, and my kids are all grown now. So I don't have a dog in the fight. But I can see both sides.

[Lagreeneyes03]

School closings have begun already

https://www.khou.com/article/weather/ha ... GrVg8s0dyQ

I don't mean to go too off topic but this blows my mind as someone in education. We still have a lot of time and a lot of changes can happen between now and Mon/Tue. I don't get why a school system would call off school now when they can make the call Sunday.

I think maybe since this is a once in a lifetime event for them, people who may want to leave the area, have ample time to plan.

[sphelps8681]

Closing schools early helps the parents better plan and keep those students who drive to school from being on the road, but also they may have teachers that don't live in the district that are coming from areas that are worse than the area they work in and can't make to work. Meaning trying to find substitutes for those teachers.

[bubba hotep]

Still wondering if we'll see N/NW shifts/expansion of precip in models by Sunday/Monday...

I expect they will but was hoping the 12Z Euro would join the CMC and GFS on this run with that shift. We are getting close to NAM range, but for now the NAM isn't digging SW as much as other models which I don't love.

NAM actually is digging southwest more so than the other globals (mainly GFS/Euro), its closer to the CMC

I think there is probably a lower confidence in models right now than normal. A couple of things to watch: the s/w hasn't moved onshore and into a more dense sampling network. Then, the models struggle with how cold, dense air interacts with the Rockies and oftentimes are too progressive. As the cold air interacts with the Rockies, it can actually cause the trough to slow/dig more than being shown. How these two play out could cause some significant late shifts in the models.

[rwfromkansas]

Albedo gets this boards libido raised and temps dropped!

Now this is funny!

[fendie]

Beautiful column on the GFS for Houston on Tuesday. Moisture, freezing from the surface upward, and a wee bit of lift.



Edit to add source:
http://wxmaps.org/pix/iahgfs.png

[Ralph's Weather]

A nice surprise area of showers and some storms over N TX while it was expected to be sunny.

[txtwister78]

Latest Austin/San Antonio NWS Forecast Discussion pertaining to cold/potential winter precipitation early next week.

Key Messages:

-Hazardous cold occurring early to midweek with very high confidence
(80-100%) in hard freezes each night from Sunday night through
Wednesday Morning.

-Be prepared to protect People, Pets, Plants, and Pipes from the
cold weather.

-Increasing chances for winter precipitation from Monday evening
through Tuesday morning but low confidence on total accumulation
amounts. At least minor travel impacts expected.

-Warming up Wednesday, but monitoring another system towards late
week.

The arctic air will be in place as the period starts on Sunday
morning with area temperatures ranging from the mid 20s across the
Hill Country to the upper 20s and low 30s elsewhere across South-
Central Texas. Factoring in breezy northerly flow with winds around
15 to 25 mph, and higher gusts, wind chills will range anywhere from
10-15 degrees across the Hill Country to 15-25 degrees elsewhere.
This may necessitate a Cold Weather Advisory for a portion of the
region. Mostly sunny conditions are then expected through the rest
of the day on Sunday, allowing for temperatures to climb into the
40s for most locations, and around 50 along the Rio Grande. A
widespread hard freeze is expected Sunday night through Monday
morning, with lows in the teens across the Hill Country and low to
mid 20s for most other locations. While wind speeds will weaken
slightly Sunday night into Monday morning, Cold Weather Advisories
and possibly an Extreme Cold Warning could be needed as wind chill
values range from the single digits to the teens.

In addition to the very cold temperatures, MLK JR Day should start
off with mostly sunny skies but the cloud cover steadily increases
in response to the approaching weather system, which we'll go into
more detail about down below. This cloud cover and increasing
moisture will help to cap afternoon highs in the 30s/lower 40s on
Monday.

While differences are still noted within the latest medium range
guidance, the solutions have narrowed regarding the 500 mb pattern
with the amplification of the shortwave diving south-southeastward
from the Pacific Northwest and the location/strength of the coastal
low/trough off South Texas. The GFS and the GEFS members over the
past 18 to 24 hours have trended toward a slower, more amplified,
and colder/wetter solution than the past runs. While the GFS/GEFS is
still running a tad warmer compared to the ECMWF/EPS and especially
the CMC/GEPS, it's certainly much closer than what prior runs of the
GFS/GEFS had indicated.

This continued trend has necessitated a farther nudge upwards into
the medium chance (40-60%) category for precipitation from the I-35
corridor eastward into the coastal plains. If the recent model
trends continue to hold, then PoPs will likely need to be increased
even more.

Initially, around and soon after the onset of this event, a mixed
precipitation type event may take place near and south of the I-10
and US HWY 90 corridor Monday evening, with modeled sounding
profiles, indicating a weak warm nose aloft. North of this region,
the precipitation should mainly be snow. Forecast soundings show the
column cooling with time across southern areas overnight and through
Tuesday morning with the predominate precipitation type changing to
snow. The precipitation chances are expected to decrease by Tuesday
afternoon across the region as the base of the trough swings through
and then moves east of the area.

While both snow and ice accumulation is looking possible across
portions of the region (30-50% from I-35 eastward for at least half
an inch of snow), it remains difficult to pin down the total amounts
this far out. Additionally, the snow to liquid ratios and shapes
could also become quite tricky, especially as there is the concern
for a very dry layer at least initially, at the more favorable
dendrite growth zone. Again, like the previous discussion had
pointed out, the deterministic runs of the GFS and ECMWF total snow
is on the higher end of it's ensembles. In addition, more
fluctuations in the models are likely, which is why we are showing a
gradual increase upward in PoPs rather than a larger jump. It should
also be stressed to exercise extreme caution when viewing snow or
freezing rain accumulations from any one model or certain apps this
far out. Probabilistic guidance from the Winter Storm Severity Index
continues to show a modest increase in probabilities for minor to
moderate impacts across portions of the region.